WO2024034193A1 - Laser processing device and laser processing method - Google Patents
Laser processing device and laser processing method Download PDFInfo
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- WO2024034193A1 WO2024034193A1 PCT/JP2023/015987 JP2023015987W WO2024034193A1 WO 2024034193 A1 WO2024034193 A1 WO 2024034193A1 JP 2023015987 W JP2023015987 W JP 2023015987W WO 2024034193 A1 WO2024034193 A1 WO 2024034193A1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
- B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
- B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
Definitions
- One aspect of the present invention relates to a laser processing device and a laser processing method.
- a laser processing device that forms a modified region on an object by irradiating the object with laser light (for example, see Patent Document 1).
- Such a laser processing device includes, for example, a support part that supports an object, a light source that emits laser light, a spatial light modulator that modulates the laser light emitted from the light source, and a spatial light modulator that modulates the laser light emitted from the light source. and a condensing section that condenses the laser beam.
- the modulation pattern set in the spatial light modulator is set based on, for example, simulation, and is optimized through actual processing.
- the modulation pattern is optimized by the above method, it may not be possible to perform desired laser processing using the modulation pattern due to various factors.
- One aspect of the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a laser processing device and a laser processing method that can perform desired laser processing.
- a laser processing apparatus includes a support part that supports a wafer having a first surface and a second surface, a light source that emits laser light, and a spatial light modulator that modulates the laser light that is emitted from the light source.
- a light-concentrating section that focuses the laser beam modulated by the spatial light modulator onto the wafer from the first surface side of the wafer; a moving part that moves relative to the first surface; an imaging part that acquires a captured image by detecting light propagated through the wafer via a light condensing part;
- a first process that controls the moving unit to move relative to the first surface; and a second process that controls the light source so that the laser beam is continuously emitted while the first process is being performed.
- a fourth process of acquiring an optical axis profile which is a profile image of the laser beam along the optical axis direction, by combining a plurality of captured images sequentially acquired in the third process. and a control unit.
- laser light is irradiated while moving the light condensing part in the optical axis direction, and the light reflected on the second surface of the wafer is detected to continuously produce a plurality of captured images. is obtained.
- a plurality of captured images are combined to obtain an optical axis profile that is a profile image of laser light along the optical axis direction. In this way, while moving the focal point of the laser beam in the optical axis direction (in the depth direction of the wafer), the reflected light from the second surface, which is the back surface of the wafer, is detected, and the above optical axis profile is obtained.
- the irradiation state of the laser light along the optical axis direction for example, the position and intensity of the condensing point
- the irradiation state of the laser light along the optical axis direction for example, the position and intensity of the condensing point
- the convergence state of the laser internal processing can be grasped without actually performing laser processing on the wafer (before laser processing), and optimization of the modulation pattern can be realized. be able to.
- control unit may further execute a fifth process of adjusting the modulation pattern of the spatial light modulator based on the optical axis profile acquired in the fourth process.
- the modulation pattern can be optimized in consideration of the optical axis profile, and desired laser processing can be performed more appropriately. That is, the information on the focused state of the laser internal processing that has already been obtained can be fed back to the modulation pattern generation, and the desired laser processing can be performed.
- the wafer is configured to include a birefringent material
- the control unit determines the focal point related to the ordinary ray and the extraordinary ray based on the optical axis profile.
- a modulation pattern is created so that the intensity of light at one of the two identified focal points increases and the intensity of light at the other focal point decreases. May be adjusted.
- these incident lights are divided into ordinary rays and extraordinary rays, but the extraordinary rays do not follow Snell's law and propagate at a different angle of refraction than the ordinary rays.
- the P-polarized light component and the S-polarized light component are focused at different positions in the depth direction of the wafer.
- This branching of the focal point in the depth direction causes a plurality of unintentional focal points to be formed on the wafer, resulting in the formation of inappropriate cracks. This may reduce the quality of processing such as slicing.
- the modulation pattern based on the optical axis profile so that the intensity of one focal point becomes large and the intensity of the other focal point becomes small, the plurality of focal points described above can be adjusted. It is possible to suppress deterioration in processing quality due to the formation of .
- the control unit may cause the control unit to control, in the fifth process, the intensity of the light at the focal point on the side closer to the second surface of the two focal points increases, and
- the modulation pattern may be adjusted so that the intensity of light at the focal point on the far side becomes smaller.
- the intensity ratio of the two focal points can be changed by adjusting the modulation pattern, one of the focal points cannot be completely eliminated. For example, if you mainly use the light convergence point on the side far from the second surface and minimize the intensity of light at the light convergence point on the side close to the second surface, then is set at the processing target height, and there is a focal point near the second surface, although it is weak.
- the device Since a device is provided on the second surface, it is conceivable that the device may be damaged due to the influence of the focal point on the side closer to the second surface.
- the light convergence point on the side closer to the second surface is set at the processing target height, and the light is focused on the second surface side. Since no light spot exists, damage to the device on the second surface can be reduced. Note that even for a wafer in which no device is provided on the second surface, damage on the second surface can be reduced by providing the laser processing apparatus with the above configuration.
- the control unit adjusts the modulation pattern using a slit pattern that blocks some polarized components of the laser beam. good. According to such a configuration, the intensity of light at any focal point can be easily reduced.
- the control unit changes the spherical aberration conditions determined by the modulation pattern and performs the first processing, second processing, The third process and the fourth process are carried out, and in the fifth process, the maximum values of the brightness values of the laser beams indicated by the optical axis profiles acquired under each condition are compared with each other, and the optical axis having the maximum brightness value is
- the modulation pattern may be adjusted to meet the spherical aberration conditions related to the profile. According to such a configuration, appropriate spherical aberration correction can be performed, for example, even for a wafer whose refractive index is unknown.
- the control unit compares the optical axis profile acquired in the fourth process with comparison data that is a profile image for comparison, If the difference between the compared data is within a predetermined range, the optical axis profile is determined to be normal; if the difference is outside the predetermined range, the optical axis profile is determined to be abnormal, and the determination result is output.
- a sixth process may be further executed. According to such a configuration, by setting a profile image when the laser processing device is normal as comparison data, it is possible to detect whether any abnormality occurs in the laser processing device based on the comparison between the optical axis profile and the comparison data. It can be easily determined whether the Then, by outputting the determination result, it becomes possible to adjust the laser processing apparatus in consideration of the determination result. As described above, according to the configuration described above, desired laser processing can be performed more appropriately.
- the control unit controls the light source in the second process so that a laser beam with a lower output than the output during wafer processing is emitted. May be controlled. Thereby, an optical axis profile can be obtained without performing actual laser processing.
- the optical axis profile may be three-dimensional data obtained by combining a plurality of two-dimensional captured images.
- a laser processing method includes a condensing section that condenses laser light modulated by a spatial light modulator onto a wafer from a first surface side of a wafer having a first surface and a second surface. a first step of moving in the optical axis direction that is perpendicular to one surface; a second step of continuously emitting a laser beam while the first step is being executed; and the second step is executed. a third step of continuously acquiring a plurality of captured images by detecting the light reflected on the second surface in a state where the A fourth step of acquiring an optical axis profile which is a profile image of the laser beam along the optical axis direction.
- the laser processing method may further include a fifth step of adjusting the modulation pattern of the spatial light modulator based on the optical axis profile acquired in the fourth step. good.
- the wafer includes a birefringent material, and in the fifth step, based on the optical axis profile, a focal point for ordinary rays and a focal point for extraordinary rays are determined. Even if the modulation pattern is adjusted so that the intensity of light at one of the two identified focal points increases and the intensity of light at the other focal point decreases. good.
- the intensity of the light at the focal point on the side closer to the second surface increases among the two focal points, and the intensity of the light on the side farther from the second surface increases.
- the modulation pattern may be adjusted so that the intensity of light at the light spot is reduced.
- the modulation pattern in the fifth step, may be adjusted by a slit pattern that blocks part of the polarized component of the laser beam.
- the laser processing method described in any one of [E10] to [E15] above compares the optical axis profile acquired in the fourth step with comparison data that is a profile image for comparison, and a sixth step of determining that the optical axis profile is normal when the difference is within a predetermined range, determining that the optical axis profile is abnormal when the difference is outside the predetermined range, and outputting the determination result; may further include.
- the optical axis profile may be three-dimensional data obtained by combining a plurality of two-dimensional captured images.
- desired laser processing can be performed.
- FIG. 1 is a configuration diagram of a laser processing apparatus according to an embodiment.
- FIG. 2 is a cross-sectional view of a portion of the spatial light modulator shown in FIG.
- FIG. 3(a) is a diagram illustrating continuous imaging along the Z direction
- FIG. 3(b) is a diagram illustrating an optical axis profile obtained by combining captured images.
- FIG. 4(a) is a cross-sectional view showing an optical axis profile represented by two-dimensional data
- FIG. 4(b) is a diagram showing an optical axis profile represented by three-dimensional data.
- FIG. 5 is a flowchart showing the optical axis profile acquisition process.
- FIG. 1 is a configuration diagram of a laser processing apparatus according to an embodiment.
- FIG. 2 is a cross-sectional view of a portion of the spatial light modulator shown in FIG.
- FIG. 3(a) is a diagram illustrating continuous imaging along the Z direction
- FIG. 3(b) is a diagram illustrating an optical
- FIG. 6(a) is a diagram showing an optical axis profile of a wafer including a birefringent material
- FIG. 6(b) is a diagram illustrating damage to a device due to light leakage.
- FIGS. 7(a) and 7(b) are diagrams illustrating focal points depending on the birefringent material.
- FIG. 8(a) is a diagram showing an optical axis profile of a wafer including a birefringent material
- FIG. 8(b) is a diagram showing a modulation pattern in consideration of the optical axis profile shown in FIG. 8(a). It is a figure which shows the optical axis profile when adjusted.
- FIG. 9(a) is an image of the focal point when no countermeasures are taken, and FIG.
- FIG. 9(b) is an image of the focal point when the intensity of the front surface side focal point is increased.
- c) is an image of the focal point when the intensity of the focal point on the back side is increased.
- FIG. 10(a) is a diagram showing the intensity ratio in the case without a slit pattern
- FIG. 10(b) is a diagram showing the intensity ratio in the case where the slit A is provided.
- FIG. 11(a) is a diagram showing the intensity ratio when the slit B is provided
- FIG. 11(b) is a diagram showing the intensity ratio when the slit C is provided.
- FIG. 12 is a flowchart of modulation pattern adjustment processing.
- FIG. 13 is a flowchart of error state identification processing of the laser processing apparatus.
- FIG. 14(a) is a diagram showing the optical axis profile when a wafer with an unknown refractive index is processed with an inappropriate modulation pattern
- FIG. 14(b) is a diagram considering the optical axis profile shown in FIG. 14(a).
- FIG. 4 is a diagram showing an optical axis profile when a modulation pattern is adjusted by adjusting the modulation pattern. It is a figure explaining spherical aberration adjustment. It is a flowchart which shows spherical aberration adjustment processing.
- the laser processing apparatus 1 includes a support section 2, a light source 3, an optical axis adjustment section 4, a spatial light modulator 5, a condensing section 6, a moving section 7, and a visible imaging section. It includes a section 8 (imaging section) and a control section 10. Note that the imaging unit may be an infrared camera.
- the laser processing apparatus 1 is an apparatus that forms a modified region 12 on the wafer 11 by irradiating the wafer 11 with a laser beam L.
- three mutually orthogonal directions will be referred to as an X direction, a Y direction, and a Z direction, respectively.
- the X direction is a first horizontal direction
- the Y direction is a second horizontal direction perpendicular to the first horizontal direction
- the Z direction is a vertical direction.
- the support section 2 supports the wafer 11 having a front surface 11a (first surface) and a back surface 11b (second surface).
- the support section 2 supports the wafer 11 by adsorbing a film (not shown) attached to the wafer 11 so that the surface 11a of the wafer 11 is perpendicular to the Z direction.
- the support portion 2 is movable along each of the X direction and the Y direction, and is rotatable about an axis parallel to the Z direction.
- the light source 3 emits laser light L.
- the light source 3 emits the laser beam L using a pulse oscillation method.
- the laser beam L is transparent to the wafer 11.
- the optical axis adjustment unit 4 adjusts the optical axis of the laser beam L emitted from the light source 3.
- the optical axis adjustment unit 4 adjusts the optical axis of the laser beam L while changing the traveling direction of the laser beam L emitted from the light source 3 so as to follow the Z direction.
- the optical axis adjustment section 4 is composed of, for example, a plurality of reflecting mirrors whose positions and angles can be adjusted.
- the spatial light modulator 5 is placed inside the housing H.
- the spatial light modulator 5 modulates the laser beam L emitted from the light source 3.
- the laser beam L that has traveled downward along the Z direction from the optical axis adjustment unit 4 enters the housing H, and the laser beam L that has entered the housing H is directed in the Y direction by the mirror M1.
- the laser beam L is reflected horizontally at an angle to the mirror M1 and enters the spatial light modulator 5.
- the spatial light modulator 5 modulates the thus incident laser light L while horizontally reflecting it along the Y direction.
- the spatial light modulator 5 of this embodiment is a reflective liquid crystal (LCOS) spatial light modulator (SLM). As shown in FIG. 2, the spatial light modulator 5 includes a drive circuit layer 52, a pixel electrode layer 53, a reflective film 54, an alignment film 55, a liquid crystal layer 56, an alignment film 57, and a transparent conductive film on a semiconductor substrate 51. 58 and a transparent substrate 59 are laminated in this order.
- LCOS liquid crystal
- SLM spatial light modulator
- the semiconductor substrate 51 is, for example, a silicon substrate.
- the drive circuit layer 52 constitutes an active matrix circuit on the semiconductor substrate 51.
- the pixel electrode layer 53 includes a plurality of pixel electrodes 53a arranged in a matrix along the surface of the semiconductor substrate 51.
- Each pixel electrode 53a is made of, for example, a metal material such as aluminum. A voltage is applied to each pixel electrode 53a by the drive circuit layer 52.
- the reflective film 54 is, for example, a dielectric multilayer film.
- the alignment film 55 is provided on the surface of the liquid crystal layer 56 on the reflective film 54 side, and the alignment film 57 is provided on the surface of the liquid crystal layer 56 on the opposite side to the reflective film 54 .
- Each of the alignment films 55 and 57 is made of a polymeric material such as polyimide, and the contact surface of each of the alignment films 55 and 57 with the liquid crystal layer 56 is subjected to, for example, a rubbing treatment.
- the alignment films 55 and 57 align liquid crystal molecules 56a included in the liquid crystal layer 56 in a certain direction.
- the transparent conductive film 58 is provided on the surface of the transparent substrate 59 on the alignment film 57 side, and faces the pixel electrode layer 53 with the liquid crystal layer 56 and the like interposed therebetween.
- the transparent substrate 59 is, for example, a glass substrate.
- the transparent conductive film 58 is made of a light-transmitting and conductive material such as ITO, for example.
- the transparent substrate 59 and the transparent conductive film 58 transmit the laser beam L.
- the spatial light modulator 5 when a signal indicating a modulation pattern is input from the control unit 10 to the drive circuit layer 52, a voltage according to the signal is applied to each pixel electrode 53a, and each An electric field is formed between the pixel electrode 53a and the transparent conductive film 58.
- the electric field is formed, in the liquid crystal layer 56, the arrangement direction of the liquid crystal molecules 216a changes for each region corresponding to each pixel electrode 53a, and the refractive index changes for each region corresponding to each pixel electrode 53a.
- This state is a state in which a modulation pattern is displayed on the liquid crystal layer 56.
- laser light L enters the liquid crystal layer 56 from the outside via the transparent substrate 59 and the transparent conductive film 58, is reflected by the reflective film 54, and is emitted from the liquid crystal layer 56.
- the laser light L is modulated according to the modulation pattern displayed on the liquid crystal layer 56.
- the modulation of the laser beam L for example, modulation of the intensity, amplitude, phase, polarization, etc. of the laser beam L
- the modulation of the laser beam L can be performed.
- the light condensing section 6 is attached to the bottom wall of the housing H.
- the condensing section 6 condenses the laser beam L modulated by the spatial light modulator 5 onto the wafer 11 supported by the support section 2 .
- the laser beam L reflected horizontally along the Y direction by the spatial light modulator 5 is reflected downward along the Z direction by the dichroic mirror M2, and the laser beam L reflected by the dichroic mirror M2 enters the light condensing section 6.
- the condensing unit 6 condenses the laser beam L thus incident on the wafer 11 from the surface 11a (first surface) side along the Z direction.
- the condensing section 6 is configured by a condensing lens unit 61 attached to the bottom wall of the housing H via a drive mechanism 62.
- the condensing lens unit 61 has a function of condensing parallel light onto one point on the optical axis.
- the drive mechanism 62 moves the condenser lens unit 61 along the Z direction by, for example, a drive force of a piezoelectric element.
- an imaging optical system (not shown) is arranged between the spatial light modulator 5 and the light condensing section 6.
- the imaging optical system constitutes a double-sided telecentric optical system in which the reflective surface of the spatial light modulator 5 and the entrance pupil plane of the condenser 6 are in an imaging relationship.
- the image of the laser light L on the reflective surface of the spatial light modulator 5 (the image of the laser light L modulated by the spatial light modulator 5) is similarly transformed (formed) onto the entrance pupil plane of the condenser 6. image) to be done.
- a pair of distance measuring sensors S1 and S2 are attached to the bottom wall of the housing H so as to be located on both sides of the condenser lens unit 61 in the X direction.
- Each distance measurement sensor S1, S2 emits distance measurement light (for example, a laser beam) to the surface 11a of the wafer 11, and detects the distance measurement light reflected by the surface 11a. Obtain displacement data of 11a.
- the moving unit 7 moves the light condensing unit 6 relative to the surface 11a of the wafer 11 in the optical axis direction (that is, the Z direction), which is a direction perpendicular to the surface 11a.
- the moving unit 7 includes a moving mechanism (a driving source such as an actuator or a motor) that moves the light condensing unit 6 relative to the surface 11a of the wafer 11 by moving at least one of the housing H and the supporting unit 2. ).
- the moving unit 7 moves the support unit 2 along each of the X direction and the Y direction, rotates the support unit 2 about an axis parallel to the Z direction, and rotates the support unit 2 along the Z direction. to move the housing H.
- the visible imaging unit 8 is placed inside the housing H.
- the visible imaging unit 8 emits visible light V and obtains an image of the wafer 11 using the visible light V.
- the visible light V emitted from the visible imaging section 8 is irradiated onto the wafer 11 via the dichroic mirror M2 and the light condensing section 6, and the visible light V reflected by the wafer 11 is transmitted to the light condensing section 6 and the dichroic mirror M2. It is detected by the visible imaging unit 8 via the mirror M2. That is, the visible imaging section 8 acquires a captured image by detecting the light propagated through the wafer 11 via the light condensing section 6.
- the control unit 10 controls the operation of each part of the laser processing device 1.
- the control unit 10 includes a processing unit 101, a storage unit 102, and an interface unit 103.
- the processing unit 101 is configured as a computer device including a processor, memory, storage, communication device, and the like.
- a processor executes software (program) read into a memory or the like, and controls reading and writing of data in the memory and storage, and communication by a communication device.
- the storage unit 102 is, for example, a hard disk or the like, and stores various data.
- the interface unit 103 displays various data to the operator and receives input of various data from the operator. In this embodiment, the interface unit 103 constitutes a GUI (Graphical User Interface).
- the modified region 12 is a region that differs in density, refractive index, mechanical strength, and other physical properties from the surrounding unmodified region.
- Examples of the modified region 12 include a melt-treated region, a crack region, a dielectric breakdown region, and a refractive index change region.
- the modified region 12 has a characteristic that cracks tend to extend from the modified region 12 to the incident side of the laser beam L and the opposite side thereof. Such characteristics of the modified region 12 are utilized for cutting the wafer 11, for example.
- the operation of the laser processing apparatus 1 when forming the modified region 12 inside the wafer 11 along the line 15 for cutting the wafer 11 will be described.
- the laser processing apparatus 1 rotates the support part 2 about an axis parallel to the Z direction as a center line so that the line 15 set on the wafer 11 is parallel to the X direction.
- the laser processing device 1 moves the support part 2 along the X direction and the Y direction so that the condensing point C of the laser beam L is located on the line 15 when viewed from the Z direction. move it.
- the laser processing apparatus 1 adjusts the focus point C of the laser beam L to be located on the surface 11a based on the image acquired by the visible imaging unit 8 (for example, the image of the surface 11a of the wafer 11). , move the housing H (that is, the light condensing section 6) along the Z direction. Next, the laser processing apparatus 1 moves the housing H (i.e., the light condensing part) along the Z direction so that the condensing point C of the laser beam L is located at a predetermined depth from the surface 11a, with this position as a reference. 6) Move.
- the laser processing device 1 emits the laser beam L from the light source 3, and moves the support section 2 along the X direction so that the condensing point C of the laser beam L moves relatively along the line 15. move.
- the laser processing apparatus 1 uses displacement data of the surface 11a acquired by the distance measurement sensor located on the front side (the front side in the relative movement direction of the laser beam L with respect to the wafer 11) among the pair of distance measurement sensors S1 and S2. Based on this, the drive mechanism 62 of the light focusing section 6 is operated so that the focusing point C of the laser beam L is located at a predetermined depth from the surface 11a.
- a row of modified regions 12 are formed along line 15 and at a constant depth from surface 11a of wafer 11.
- a plurality of modification spots 12s are formed in a line along the X direction.
- One modification spot 12s is formed by irradiation with one pulse of laser light L.
- a row of modified regions 12 is a collection of a plurality of modified spots 12s arranged in a row.
- Adjacent modification spots 12s may be connected to each other or separated from each other depending on the pulse pitch of the laser beam L (the value obtained by dividing the relative moving speed of the focal point C with respect to the wafer 11 by the repetition frequency of the laser beam L). There is also. [Obtain optical axis profile]
- the optical axis profile is the light reflected by the visible imaging section 8 on the back surface 11b of the wafer 11 in a state where the light condensing section 6 moves relative to the front surface 11a in the Z direction and the laser beam is emitted.
- This data is obtained by combining a plurality of captured images that are detected and sequentially obtained.
- the optical axis profile is a profile image of the laser beam along the Z direction, which is obtained by combining the plurality of captured images.
- the irradiation status of the laser light along the optical axis direction (for example, the position and intensity of the focal point on the wafer 11) is specified. Thereby, it is possible to determine, for example, whether any abnormality has occurred in the laser processing apparatus 1, whether or not the modulation pattern set in the spatial light modulator 5 needs to be adjusted (details will be described later).
- FIG. 3(a) is a diagram illustrating continuous imaging along the Z direction.
- FIG. 3A from the left, imaging of cross section A, imaging of cross section B, imaging of cross section C, and imaging of cross section D are shown.
- the light condensing section 6 is relatively moved in the Z direction so as to gradually approach the wafer 11 from left to right in the figure.
- FIG. 3(a) when the position of the light condensing unit 6 moves by ⁇ Z, the path of the laser light reflected on the back surface 11b of the wafer 11 and imaged by the visible imaging unit 8 changes by combining the outgoing and returning paths. This results in a change of ⁇ Z ⁇ 2.
- the light collecting section 6 is moved together with the visible imaging section 8, for example, by the moving section 7. That is, the focal point of the laser beam and the observation plane (camera imaging plane) of the visible imaging section 8 move together.
- the condensing lens unit 61 and the like of the condensing section 6 may be moved by the drive mechanism 62.
- the control unit 10 controls the moving unit 7 so that the condensing unit 6 moves relative to the surface 11a of the wafer 11 in the Z direction, and the first process is executed.
- a second process of controlling the light source 3 so that the laser beam is continuously emitted in the state is executed.
- the control unit 10 controls the light source 3 so that a laser beam with a lower output than the output when processing the wafer 11 is emitted.
- the control unit 10 controls the visible imaging unit 8 so that the light reflected on the back surface 11b of the wafer 11 is detected and a plurality of captured images are continuously acquired while the second process is being executed.
- a third process to control is executed.
- the control unit 10 executes a fourth process of acquiring an optical axis profile, which is a profile image of the laser beam along the Z direction, by combining the plurality of captured images sequentially acquired in the third process. do.
- FIG. 3(b) is a diagram showing an optical axis profile obtained by combining captured images.
- captured images of each of cross sections A, B, C, and D are shown.
- an optical axis is created that allows identification of the laser light irradiation status (for example, the position and intensity of the condensing point C).
- a profile is obtained.
- FIG. 4(a) is a cross-sectional view showing an optical axis profile represented by two-dimensional data
- FIG. 4(b) is a diagram showing an optical axis profile represented by three-dimensional data.
- the optical axis profile may be, for example, three-dimensional data obtained by combining a plurality of two-dimensional captured images (see FIG. 4(b)).
- the three-dimensional data may be color-coded according to the intensity of the laser beam.
- the optical axis profile may be two-dimensional data (see FIG. 4(a)) generated from the acquired three-dimensional data.
- a graph showing the intensity of laser light in each region may be displayed alongside the two-dimensional data.
- FIG. 5 is a flowchart showing the optical axis profile acquisition process performed by the laser processing apparatus 1.
- a film to be attached to the wafer 11 is attracted by the support section 2 (step S1).
- the moving unit 7 moves the condensing unit 6 under the control of the control unit 10, so that the wafer 11 is moved directly below the objective lens of the condensing unit 6 (step S2).
- the moving unit 7 moves under the control of the control unit 10 so that the height in the Z direction is set at the reticle focus position (step S3).
- the moving unit 7 moves under the control of the control unit 10 so that the height in the Z direction is lowered by the thickness of the wafer 11 (step S4).
- a signal indicating a modulation pattern is input from the control unit 10 to the spatial light modulator 5.
- a distortion correction pattern and a modulation pattern having a spherical aberration twice the wafer thickness are displayed (step S5).
- step S6 all light sources other than the light source 3 in the laser processing apparatus 1 are turned off, and the light source 3 is controlled by the control unit 10 so that the laser beam is emitted (step S6).
- Various settings such as the output of the laser beam are performed by the control unit 10 so that the laser beam can be reliably confirmed.
- step S8 it is determined whether or not ablation has occurred on the surface of the wafer 11 (step S8). If ablation has occurred, the state is set such that ablation does not occur by adjusting the laser output or attenuator output (step S9). Then, the light sources other than the light source 3 in the laser processing apparatus 1 are turned on (step S10), and it is confirmed that the objective lens of the condenser 6 is located above the wafer 11 and at a position where no ablation is occurring (step S11). , the process is executed again from step S3.
- step S8 fine adjustment in the Z direction is performed to the position where the laser beam is most focused (step S12), and the visible imaging unit that confirms the laser beam is A set value such as 8 is set to the optimum state (step S13).
- control unit 10 controls the drive mechanism 62, which is an actuator for the objective lens of the condensing unit 6, or the moving unit 7, which is related to movement in the Z-axis direction, moves, the visible imaging unit 8 continuously An image is taken (step S14). Finally, the control unit 10 combines the plurality of captured images to obtain an optical axis profile near the focal point (step S15).
- FIG. 6(a) is a diagram showing an optical axis profile of a wafer 11 that includes a birefringent material.
- a laser beam enters a birefringent material, unlike silicon or glass, two focal points are generated: a focal point C1 for ordinary rays and a focal point C2 for extraordinary rays due to the difference in refractive index due to polarization. I will do it.
- dicing is performed by irradiation with laser light, there is no major problem even if the focal point branches upward and downward in the dicing direction (Z direction).
- processing accuracy may deteriorate due to the influence of the light condensing point being branched.
- the lower light focusing point (here, the focusing point C2 of the extraordinary ray) is sufficiently spaced from the device (for example, the electrode 200) on the back surface 11b. In this case, damage to the electrode 200 due to light leakage is not a problem.
- the lower light focusing point (here, the focusing point C2 of the extraordinary ray) is close to the device (for example, the electrode 200) on the back surface 11b. The problem is that the electrode 200 is damaged by the light passing through.
- some kind of countermeasure is required to prevent deterioration of processing accuracy and damage to the device.
- the focal point C1 of ordinary rays is higher than the focal point C2 of extraordinary rays. Whether it is branched (see FIG. 7(a)) or, conversely, branched below the focal point C2 of the extraordinary ray (see FIG. 7(b)) depends on the type of birefringent material. Specifically, for a positive birefringent material such as GaN or quartz, as shown in FIG. 7(a), the focal point C1 of the ordinary ray is branched above the focal point C2 of the extraordinary ray. Ru. On the other hand, for a negative birefringent material such as calcite or sapphire, as shown in FIG. 7(b), the focal point C1 of the ordinary ray is branched below the focal point C2 of the extraordinary ray.
- the control unit 10 is configured to further execute a fifth process of adjusting the modulation pattern of the spatial light modulator 5 based on the optical axis profile acquired in the fourth process described above.
- the control unit 10 specifies a focal point C1 for ordinary rays and a focal point C2 for extraordinary rays based on the optical axis profile, and selects one of the two identified focal points.
- the modulation pattern is adjusted so that the intensity of light at one light point is increased and the intensity of light at the other focal point is decreased.
- FIG. 8(a) is a diagram showing an optical axis profile of the wafer 11 including a birefringent material
- FIG. 8(b) is a diagram showing a modulation pattern in consideration of the optical axis profile shown in FIG. 8(a). It is a figure which shows the optical axis profile when adjusted.
- the control unit 10 specifies a focal point C1 of the vertically branched ordinary ray and a focal point C2 of the extraordinary ray from the optical axis profile. Then, the control unit 10 checks the optical axis profile, and as shown in FIG.
- the intensity of the light at the focal point C2 due to the extraordinary ray increases, and the intensity of the light at the focal point C1 due to the ordinary ray increases. Adjust the modulation pattern so that the intensity of the light is reduced. This makes it possible to minimize the influence of the condensing point C1 where the intensity of light is reduced, and to suppress the adverse effects caused by the converging point branching upward and downward.
- the wafer 11 is made of a positive birefringent material (Fig. 7(a)) or a negative birefringent material (see FIG. 7(b)).
- FIG. 7(a) a case will be described in which a positive birefringent material (see FIG. 7(a)) is used.
- Figure 9(a) is an image of the focal point when no measures are taken (the intensity ratio of the two focal points is not changed)
- Figure 9(b) is an image of the focal point when the intensity of the front-side focal point is increased
- FIG. 9C is an image of the focal point when the intensity of the back surface side focal point is increased.
- the surface-side light convergence point is the light convergence point C1 of ordinary rays.
- the back surface side focal point is the focal point C2 of the extraordinary ray.
- the intensity ratio of the two condensing points C1 and C2 when the intensity ratio of the two condensing points C1 and C2 is not changed, the light passing through the condensing point C2 due to the extraordinary ray closer to the back surface 11b causes the back surface 11b to It is conceivable that the provided device (for example, the electrode 200) may be damaged.
- the intensity of the focal point C1 due to the ordinary ray when the intensity of the focal point C1 due to the ordinary ray is increased and the intensity of the focal point C2 due to the extraordinary ray is decreased, the intensity is closer to the back surface 11b. Since the intensity of the condensing point C2 due to the extraordinary ray becomes smaller, the device (for example, the electrode 200) is less likely to be damaged than the example shown in FIG. For example, damage to the electrode 200) cannot be sufficiently reduced.
- the convergence point C1 of the ordinary ray is set at the processing target height (see FIGS. 9(a) and 9(b)).
- the focal point C2 of the extraordinary ray is set to the processing target height, the intensity of the focal point C2 of the extraordinary ray is increased, and the focal point C2 of the ordinary ray is set to the processing target height.
- the intensity of C1 is reduced, the distance from the back surface 11b to the condensing point C2 becomes longer than in the example shown in FIG. 9(b).
- the focal point C2 of the extraordinary ray is set at the processing target height, laser processing can be appropriately performed using the laser beam related to the focal point C2 of the extraordinary ray.
- the control unit 10 performs the fifth process to control the light focusing point on the side closer to the back surface 11b (the focusing point caused by the extraordinary ray) of the two light focusing points.
- the modulation pattern may be adjusted so that the intensity of the light C2) increases, and the intensity of the light at the focal point on the far side from the back surface 11b (the focal point C1 of ordinary rays) decreases.
- the control unit 10 may adjust the modulation pattern using a slit pattern that blocks some polarized components of the laser beam.
- a slit pattern is set as part of the modulation pattern displayed on the liquid crystal layer 56 of the spatial light modulator 5.
- the laser beam L can be modulated (for example, the intensity, amplitude, phase, polarization, etc. of the laser beam L can be modulated) by appropriately setting the modulation pattern displayed on the liquid crystal layer 56.
- the modulation pattern is a hologram pattern that imparts modulation, and includes a slit pattern.
- FIG. 10(a) is a diagram showing the intensity ratio without a slit pattern
- FIG. 10(b) is a diagram showing the intensity ratio with slit A
- FIG. 11(a) is a diagram showing the intensity ratio with slit B
- 11(b) is a diagram showing the intensity ratio when a slit C is provided.
- FIG. 10(a) to 11(b) the upper row shows the modulation pattern (including the slit pattern) displayed on the liquid crystal layer 56 of the spatial light modulator 5, and the lower row shows the optical axis. Two-dimensional data of the profile is shown.
- the slit patterns shown in FIGS. 10(b), 11(a), and 11(b) are each provided with fan-shaped slits. Below, the concept of bringing the focal point closer to one point regarding birefringent materials and the reason for using fan-shaped slits will be explained.
- the P-polarized light component and the S-polarized light component of the laser light have different refractive indices.
- the laser beam is divided into ordinary rays and extraordinary rays, but the extraordinary rays do not follow Snell's law and propagate at a different angle of refraction from the ordinary rays. Therefore, the P-polarized light component and the S-polarized light component are focused at different positions in the depth direction of the wafer (there are two focused points).
- the radial polarized light enters the wafer as P-polarized light.
- the azimuthal polarized light enters the wafer as S-polarized light. Therefore, by converting linearly polarized light into either radial or azimuth polarized light, the polarization components of the laser beam can be unified into either P-polarized light or S-polarized light, and the focal point can be appropriately focused on one point. You can get close.
- the azimuthal polarization component When using a linear slit, the azimuthal polarization component will remain unless the slit is narrowed, but if the slit is narrowed, the effective pattern area will become narrower.
- processing can be performed using areas with strong radial components while maintaining an effective pattern area.
- the area of the slit pattern SP3 is larger than the area of the slit pattern SP2.
- the area of slit pattern SP4 is larger than the area of .
- the difference in intensity between the focal point C2 due to the extraordinary ray and the focal point C1 due to the ordinary ray is the smallest for the case without a slit pattern (FIG. 10(a)), and the difference in intensity between the focal point C2 due to the extraordinary ray and the focal point C1 due to the ordinary ray is the smallest for the modulation pattern MP2 including the slit pattern SP2 (FIG. 10(a)).
- b)) becomes the next smallest
- the modulation pattern MP3 (FIG. 11(a)) including the slit pattern SP3 becomes the next smallest
- the modulation pattern MP4 (FIG. 11(b)) including the slit pattern SP4 becomes the largest.
- the slit pattern area increases, the difference in intensity between the two focal points increases, but since the effective pattern area narrows, it is necessary to increase the output of the laser beam. In addition, it is more likely to be affected when combined with other patterns such as branches. For example, in the modulation pattern MP4 shown in FIG. 11(b), the laser beam is cut too much by the slit pattern SP4, resulting in astigmatism and other adverse effects on light focusing performance.
- FIG. 12 is a flowchart of modulation pattern adjustment processing.
- the modulation pattern adjustment process first, an optical axis profile near the focal point is acquired (step S101).
- step S102 the distance from the focal point C1 of the ordinary ray to the focal point C2 of the extraordinary ray is measured. This distance is necessary when setting the focal point C2 of the extraordinary ray to the processing target height when using the extraordinary ray in laser processing, assuming that the processing conditions are created using the refractive index of the ordinary ray. This is information that will become
- step S103 it is determined whether or not to use an extraordinary ray in laser processing. If it is determined in step S103 that an extraordinary ray is to be used, the modulation pattern is adjusted so that the intensity of the focal point C2 due to the extraordinary ray is increased (step S104).
- step S105 After adjusting the modulation pattern, the optical axis profile near the focal point is acquired again (step S105). Then, the intensities of the focal point C2 due to the extraordinary ray and the focal point C1 due to the ordinary ray are compared (step S106), and it is determined whether they are within the normal range (step S107). If it is not within the normal range, the process of step S104 is performed again. If it is within the normal range, the distance acquired in step S102 is reflected in the machining recipe, and the focal point C2 of the abnormal ray is set to the target machining height (step S108).
- step S103 determines whether the extraordinary ray is not used (ordinary ray is used). If it is determined in step S103 that the extraordinary ray is not used (ordinary ray is used), the modulation pattern is adjusted so that the intensity of the focal point C1 by the ordinary ray is increased (step S109). .
- the optical axis profile near the focal point is acquired again (step S110). Then, the intensities of the focal point C1 of the ordinary ray and the focal point C2 of the extraordinary ray are compared (step S111), and it is determined whether they are within the normal range (step S112). If it is not within the normal range, the process of step S109 is executed again, and if it is within the normal range, the process ends. [Identification of error status of laser processing equipment]
- the control unit 10 compares the optical axis profile acquired in the fourth process with comparison data that is a profile image for comparison, and determines that the optical axis profile is normal if the difference between the compared data is within a predetermined range. If the difference is outside a predetermined range, the optical axis profile is determined to be abnormal, and a sixth process may be further executed in which the determination result is output.
- the fact that the optical axis profile is abnormal means that the laser processing apparatus 1 is in some kind of error state.
- the control unit 10 may use, for example, an optical axis profile acquired in the past as a profile image for comparison. Alternatively, the control unit 10 may use, for example, data created based on simulation as the profile image for comparison.
- the control unit 10 determines that there is a severe error and outputs the determination result.
- Severe errors include, for example, abnormalities in laser processing equipment and measurement errors (wafer errors).
- the control unit 10 determines that there is an abnormality in the spatial light modulator 5 (for example, spherical aberration, error in distortion correction, etc.). If the adjustment of the laser beam is incorrect, the laser beam is readjusted.
- FIG. 13 is a flowchart of the error state identification process of the laser processing apparatus 1.
- an optical axis profile near the focal point is acquired (step S201).
- the acquired optical axis profile is compared with comparison data that is a profile image for comparison (for example, an optical axis profile acquired in the past) (step S202), and the difference between the compared data is determined to be normal. It is determined whether it is within the range (step S203). The difference between the data is, for example, the difference in the position of the focal point, the intensity, etc. If it is determined in step S203 that it is normal, the control unit 10 displays that it is normal (step S204).
- step S203 If it is determined in step S203 that it is not normal, the control unit 10 displays an error message (step S205). Then, the control unit 10 confirms the error details and determines whether or not there is no focal point (step S206). If it is determined in step S206 that the focal point does not exist, it is determined that a serious error has occurred (step S207).
- a severe error is, for example, an abnormality in a laser processing device or a measurement error (wafer error, etc.).
- step S208 determines whether the adjustment of the laser beam is correct. If the adjustment of the laser beam is correct, it is determined that there is an abnormality in the spatial light modulator 5 (for example, spherical aberration, error in distortion correction, etc.) (step S209); if the adjustment of the laser beam is incorrect, the laser beam is Readjustment is performed (step S210).
- an abnormality in the spatial light modulator 5 for example, spherical aberration, error in distortion correction, etc.
- the control unit 10 performs the above-described first processing, second processing, third processing, and fourth processing under each condition while changing the spherical aberration conditions determined by the modulation pattern, and in the fifth processing,
- the maximum brightness values of the laser beams indicated by the optical axis profiles obtained under each condition are compared, and the modulation pattern is adjusted to meet the spherical aberration conditions associated with the optical axis profile with the maximum brightness value. It's okay.
- a wafer 11 whose refractive index is unknown may be processed with an inappropriate modulation pattern.
- FIG. 14(a) by acquiring the optical axis profile, it is determined that the position of the focal point is shifted, and it is not appropriate for the wafer 11 whose refractive index is unknown. You can notice that a modulation pattern has been set. Then, while checking the optical axis profile as shown in FIG. 14(a), the control unit 10 performs spherical aberration correction so that the optical axis profile as shown in FIG. 14(b) is acquired. This makes it possible to set an appropriate modulation pattern for laser processing of the wafer 11 whose refractive index is unknown.
- control unit 10 corrects the reference spherical aberration while changing the correction value, selects the correction value that maximizes the brightness value at the focal point, and adjusts the spherical aberration after correction using the correction value. Adjust the modulation pattern to meet the conditions.
- the reference spherical aberration may be, for example, twice the thickness of the wafer 11.
- FIG. 16 is a flowchart showing the spherical aberration adjustment process.
- a spherical aberration of twice the wafer thickness which is considered to be optimal, is determined as a reference (step S301).
- the control unit 10 sets a modulation pattern to satisfy the reference spherical aberration condition (step S302), and obtains an optical axis profile near the focal point (step S303).
- control unit 10 sets a modulation pattern such that the spherical aberration is smaller by an arbitrary value than the reference spherical aberration (step S304), and obtains an optical axis profile near the focal point (step S304). S305).
- control unit 10 sets a modulation pattern such that the spherical aberration is larger than the reference spherical aberration by an arbitrary value (step S306), and obtains an optical axis profile near the focal point (step S306). S307).
- control unit 10 determines whether the maximum brightness value is larger if the spherical aberration is set to an arbitrary value smaller than the reference spherical aberration, based on the acquired optical axis profile (step S308). If it is determined in step S308 that setting the spherical aberration smaller by an arbitrary value will result in a larger maximum luminance value, the control unit 10 sets the spherical aberration smaller by an arbitrary value as a new standard (step S309), and again Processing after step S302 is performed.
- step S308 if it is determined in step S308 that the maximum brightness value is not larger when the spherical aberration is set to a smaller arbitrary value (that is, the maximum brightness value is larger when set to the standard), the control unit 10 It is determined whether or not the maximum brightness value of the spherical aberration is the maximum (step S310). In step S310, if it is determined that the reference spherical aberration has the maximum maximum brightness value, the control unit 10 reflects a value of 1/2 of the reference spherical aberration in the processing recipe (step S311 ).
- step S310 determines whether the maximum brightness value of the reference spherical aberration is not the maximum (that is, the spherical aberration that is arbitrarily large has the maximum maximum brightness value)
- the control unit 10 A spherical aberration with an arbitrarily large value is set as a new reference (step S312), and the processes from step S302 onwards are performed again.
- the laser processing apparatus 1 includes a support section 2 that supports a wafer 11 having a front surface 11a and a back surface 11b, a light source 3 that emits laser light, and a spatial light modulator 5 that modulates the laser light emitted from the light source 3.
- a focusing section 6 focuses the laser beam modulated by the spatial light modulator 5 onto the wafer 11 from the surface 11a side of the wafer 11, and the focusing section 6 is aligned in the optical axis direction, which is a direction perpendicular to the surface 11a.
- a laser beam is irradiated while moving the light condensing unit 6 in the optical axis direction, and the light reflected on the back surface 11b of the wafer 11 is detected and a plurality of captured images are continuously generated. is obtained.
- a plurality of captured images are combined to obtain an optical axis profile that is a profile image of the laser beam along the optical axis direction. In this way, while moving the focal point of the laser beam in the optical axis direction (in the depth direction of the wafer 11), the reflected light from the back surface 11b of the wafer 11 is detected, and the optical axis profile is acquired.
- the control unit 10 may further execute a fifth process of adjusting the modulation pattern of the spatial light modulator 5 based on the optical axis profile acquired in the fourth process.
- the modulation pattern can be optimized in consideration of the optical axis profile, and desired laser processing can be performed more appropriately.
- the wafer 11 is configured to include a birefringent material, and in the fifth process, the control unit 10 identifies a focal point for ordinary rays and a focal point for extraordinary rays based on the optical axis profile.
- the modulation pattern may be adjusted so that the intensity of light at one of the two identified focal points is increased and the intensity of light at the other focal point is decreased.
- the refractive indexes of the P-polarized light component and the S-polarized light component of the incident light are different from each other.
- these incident lights are divided into ordinary rays and extraordinary rays, but the extraordinary rays do not follow Snell's law and propagate at a different angle of refraction than the ordinary rays.
- the P-polarized light component and the S-polarized light component are focused at different positions in the depth direction of the wafer 11.
- a plurality of focal points are unintentionally formed on the wafer 11, resulting in formation of inappropriate cracks. This may reduce the quality of processing such as slicing.
- the modulation pattern based on the optical axis profile so that the intensity of one focal point becomes large and the intensity of the other focal point becomes small, the plurality of focal points described above can be adjusted. It is possible to suppress deterioration in processing quality due to the formation of .
- the control unit 10 increases the intensity of the light at the focal point closer to the back surface 11b among the two focal points, and decreases the intensity of the light at the focal point farther from the back surface 11b.
- the modulation pattern may be adjusted so that Although the intensity ratio of the two focal points can be changed by adjusting the modulation pattern, one of the focal points cannot be completely eliminated. For example, if you mainly use the focal point on the side far from the back surface 11b and make the focal point on the side close to the back surface 11b as small as possible, the focal point on the side far from the back surface 11b is set to the processing target height. Therefore, there is a focal point near the back surface 11b, although it is weak.
- the focal point on the side closer to the back surface 11b is mainly used, the focal point on the side closer to the back surface 11b is set at the processing target height, and the focal point on the side closer to the back surface 11b is set to the processing target height. Since it does not exist, damage to the device on the back surface 11b can be reduced.
- control unit may adjust the modulation pattern using a slit pattern that blocks some polarized components of the laser beam. According to such a configuration, the intensity of any one of the focal points can be easily weakened.
- the control unit 10 performs the first processing, the second processing, the third processing, and the fourth processing under each condition while changing the spherical aberration conditions determined by the modulation pattern, and in the fifth processing, each condition is changed.
- the maximum brightness values of the laser beams indicated by the optical axis profiles obtained below are compared with each other, and the modulation pattern is adjusted to meet the spherical aberration conditions related to the optical axis profile with the maximum brightness value. good. According to such a configuration, appropriate spherical aberration correction can be performed, for example, even for the wafer 11 whose refractive index is unknown.
- the control unit 10 compares the optical axis profile acquired in the fourth process with comparison data that is a profile image for comparison, and determines that the optical axis profile is normal if the difference between the compared data is within a predetermined range. If the difference is outside a predetermined range, the optical axis profile is determined to be abnormal, and a sixth process may be further executed in which the determination result is output.
- a sixth process may be further executed in which the determination result is output.
- control unit 10 may control the light source 3 so that a laser beam with a lower output than the output when processing the wafer 11 is emitted. Thereby, an optical axis profile can be obtained without performing actual laser processing.
- the optical axis profile may be three-dimensional data obtained by combining a plurality of two-dimensional captured images.
- SYMBOLS 1 Laser processing device, 2... Support part, 3... Light source, 5... Spatial light modulator, 6... Condensing part, 7... Moving part, 8... Visible imaging part (imaging part), 10... Control part, 11... Wafer, 11a...front surface (first surface), 11b...back surface (second surface).
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Abstract
This laser processing device comprises: a support unit that supports a wafer; a light source; a spatial optical modulator; a light collecting unit; a moving unit that moves the light collecting unit in an optical axis direction perpendicular to the surface thereof, relative to the surface; a visible image capturing unit that acquires a captured image by detecting light that has propagated in the wafer through the light collecting unit; and a control unit. The control unit is configured to perform: a first process for controlling the moving unit; a second process for controlling a light source 3 so as to emit laser light continuously; a third process for controlling the visible image capturing unit so that the light reflected on the back surface of the wafer can be detected to acquire a plurality of captured images continuously; and a fourth process for composing the plurality of captured images to thereby acquire an optical axis profile which is a profile image of the laser light along the optical axis direction.
Description
本発明の一態様は、レーザ加工装置及びレーザ加工方法に関する。
One aspect of the present invention relates to a laser processing device and a laser processing method.
対象物にレーザ光を照射することで対象物に改質領域を形成するレーザ加工装置が知られている(例えば、特許文献1参照)。このようなレーザ加工装置は、例えば、対象物を支持する支持部と、レーザ光を出射する光源と、光源から出射されたレーザ光を変調する空間光変調器と、空間光変調器によって変調されたレーザ光を集光する集光部と、を備えている。
A laser processing device is known that forms a modified region on an object by irradiating the object with laser light (for example, see Patent Document 1). Such a laser processing device includes, for example, a support part that supports an object, a light source that emits laser light, a spatial light modulator that modulates the laser light emitted from the light source, and a spatial light modulator that modulates the laser light emitted from the light source. and a condensing section that condenses the laser beam.
空間光変調器に設定される変調パターンは、例えば、シミュレーション等に基づき設定され、実際に加工が行われることにより最適化が図られる。ここで、上記方法により変調パターンを最適化した場合であっても、様々な要因によって、該変調パターンを用いて所望のレーザ加工ができないことがある。
The modulation pattern set in the spatial light modulator is set based on, for example, simulation, and is optimized through actual processing. Here, even if the modulation pattern is optimized by the above method, it may not be possible to perform desired laser processing using the modulation pattern due to various factors.
本発明の一態様は上記実情に鑑みてなされたものであり、所望のレーザ加工を実施することができるレーザ加工装置及びレーザ加工方法を提供することを目的とする。
One aspect of the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a laser processing device and a laser processing method that can perform desired laser processing.
[E1]
本発明の一態様に係るレーザ加工装置は、第1表面及び第2表面を有するウエハを支持する支持部と、レーザ光を出射する光源と、光源から出射されたレーザ光を変調する空間光変調器と、空間光変調器によって変調されたレーザ光をウエハの第1表面側からウエハに集光する集光部と、集光部を、第1表面に対して垂直な方向である光軸方向に、第1表面に対して相対的に移動させる移動部と、集光部を介してウエハを伝搬した光を検出することにより撮像画像を取得する撮像部と、集光部が光軸方向において第1表面に対して相対的に移動するように移動部を制御する第1処理と、第1処理が実行されている状態において連続的にレーザ光が出射されるように光源を制御する第2処理と、第2処理が実行されている状態においてウエハの第2表面において反射された光が検出されて連続的に複数の撮像画像が取得されるように撮像部を制御する第3処理と、第3処理において連続的に取得された複数の撮像画像を合成することにより、光軸方向に沿ったレーザ光のプロファイル画像である光軸プロファイルを取得する第4処理と、を実行するように構成された制御部と、を備える。 [E1]
A laser processing apparatus according to one aspect of the present invention includes a support part that supports a wafer having a first surface and a second surface, a light source that emits laser light, and a spatial light modulator that modulates the laser light that is emitted from the light source. a light-concentrating section that focuses the laser beam modulated by the spatial light modulator onto the wafer from the first surface side of the wafer; a moving part that moves relative to the first surface; an imaging part that acquires a captured image by detecting light propagated through the wafer via a light condensing part; A first process that controls the moving unit to move relative to the first surface; and a second process that controls the light source so that the laser beam is continuously emitted while the first process is being performed. and a third process of controlling the imaging unit so that light reflected on the second surface of the wafer is detected and a plurality of captured images are continuously acquired while the second process is being executed; A fourth process of acquiring an optical axis profile, which is a profile image of the laser beam along the optical axis direction, by combining a plurality of captured images sequentially acquired in the third process. and a control unit.
本発明の一態様に係るレーザ加工装置は、第1表面及び第2表面を有するウエハを支持する支持部と、レーザ光を出射する光源と、光源から出射されたレーザ光を変調する空間光変調器と、空間光変調器によって変調されたレーザ光をウエハの第1表面側からウエハに集光する集光部と、集光部を、第1表面に対して垂直な方向である光軸方向に、第1表面に対して相対的に移動させる移動部と、集光部を介してウエハを伝搬した光を検出することにより撮像画像を取得する撮像部と、集光部が光軸方向において第1表面に対して相対的に移動するように移動部を制御する第1処理と、第1処理が実行されている状態において連続的にレーザ光が出射されるように光源を制御する第2処理と、第2処理が実行されている状態においてウエハの第2表面において反射された光が検出されて連続的に複数の撮像画像が取得されるように撮像部を制御する第3処理と、第3処理において連続的に取得された複数の撮像画像を合成することにより、光軸方向に沿ったレーザ光のプロファイル画像である光軸プロファイルを取得する第4処理と、を実行するように構成された制御部と、を備える。 [E1]
A laser processing apparatus according to one aspect of the present invention includes a support part that supports a wafer having a first surface and a second surface, a light source that emits laser light, and a spatial light modulator that modulates the laser light that is emitted from the light source. a light-concentrating section that focuses the laser beam modulated by the spatial light modulator onto the wafer from the first surface side of the wafer; a moving part that moves relative to the first surface; an imaging part that acquires a captured image by detecting light propagated through the wafer via a light condensing part; A first process that controls the moving unit to move relative to the first surface; and a second process that controls the light source so that the laser beam is continuously emitted while the first process is being performed. and a third process of controlling the imaging unit so that light reflected on the second surface of the wafer is detected and a plurality of captured images are continuously acquired while the second process is being executed; A fourth process of acquiring an optical axis profile, which is a profile image of the laser beam along the optical axis direction, by combining a plurality of captured images sequentially acquired in the third process. and a control unit.
本発明の一態様に係るレーザ加工装置では、集光部を光軸方向に移動させながらレーザ光が照射され、ウエハの第2表面において反射された光が検出されて連続的に複数の撮像画像が取得される。そして、本レーザ加工装置では、複数の撮像画像が合成されることにより、光軸方向に沿ったレーザ光のプロファイル画像である光軸プロファイルが取得される。このように、レーザ光の集光点を光軸方向(ウエハの深さ方向)に移動させながら、ウエハの裏面である第2表面からの反射光が検出されて、上記光軸プロファイルが取得されることにより、光軸方向に沿ったレーザ光の照射状況(例えば集光点の位置や強度)の把握、すなわちレーザ内部加工の集光状態の把握が可能になる。これにより、例えば、レーザ加工装置における何らかの異常の発生有無や、空間光変調器に設定される変調パターンの調整の要否等を判断することができ、より適切に所望のレーザ加工を実施することができる。なお、本発明の一態様に係るレーザ加工装置では、ウエハに対する実際のレーザ加工を行うことなく(レーザ加工前に)レーザ内部加工の集光状態を把握し、変調パターンの最適化等を実現することができる。
In the laser processing apparatus according to one aspect of the present invention, laser light is irradiated while moving the light condensing part in the optical axis direction, and the light reflected on the second surface of the wafer is detected to continuously produce a plurality of captured images. is obtained. In this laser processing apparatus, a plurality of captured images are combined to obtain an optical axis profile that is a profile image of laser light along the optical axis direction. In this way, while moving the focal point of the laser beam in the optical axis direction (in the depth direction of the wafer), the reflected light from the second surface, which is the back surface of the wafer, is detected, and the above optical axis profile is obtained. By doing so, it becomes possible to grasp the irradiation state of the laser light along the optical axis direction (for example, the position and intensity of the condensing point), that is, the condensed state of the laser for internal processing. As a result, it is possible to determine, for example, whether any abnormality has occurred in the laser processing equipment, whether or not the modulation pattern set in the spatial light modulator needs to be adjusted, and more appropriately perform the desired laser processing. Can be done. Note that in the laser processing apparatus according to one embodiment of the present invention, the convergence state of the laser internal processing can be grasped without actually performing laser processing on the wafer (before laser processing), and optimization of the modulation pattern can be realized. be able to.
[E2]
上記[E1]記載のレーザ加工装置において、制御部は、第4処理において取得された光軸プロファイルに基づき、空間光変調器の変調パターンを調整する第5処理を更に実行してもよい。このような構成によれば、光軸プロファイルを考慮して変調パターンを最適化することができ、より適切に所望のレーザ加工を実施することができる。すなわち、取得済みのレーザ内部加工の集光状態の情報を変調パターン生成にフィードバックすることができ、所望のレーザ加工を実施することができる。 [E2]
In the laser processing apparatus described in [E1] above, the control unit may further execute a fifth process of adjusting the modulation pattern of the spatial light modulator based on the optical axis profile acquired in the fourth process. According to such a configuration, the modulation pattern can be optimized in consideration of the optical axis profile, and desired laser processing can be performed more appropriately. That is, the information on the focused state of the laser internal processing that has already been obtained can be fed back to the modulation pattern generation, and the desired laser processing can be performed.
上記[E1]記載のレーザ加工装置において、制御部は、第4処理において取得された光軸プロファイルに基づき、空間光変調器の変調パターンを調整する第5処理を更に実行してもよい。このような構成によれば、光軸プロファイルを考慮して変調パターンを最適化することができ、より適切に所望のレーザ加工を実施することができる。すなわち、取得済みのレーザ内部加工の集光状態の情報を変調パターン生成にフィードバックすることができ、所望のレーザ加工を実施することができる。 [E2]
In the laser processing apparatus described in [E1] above, the control unit may further execute a fifth process of adjusting the modulation pattern of the spatial light modulator based on the optical axis profile acquired in the fourth process. According to such a configuration, the modulation pattern can be optimized in consideration of the optical axis profile, and desired laser processing can be performed more appropriately. That is, the information on the focused state of the laser internal processing that has already been obtained can be fed back to the modulation pattern generation, and the desired laser processing can be performed.
[E3]
上記[E2]記載のレーザ加工装置において、ウエハは、複屈折材料を含んで構成されており、制御部は、第5処理において、光軸プロファイルに基づき、常光線に係る集光点と異常光線に係る集光点とを特定し、特定した2つの集光点のうち一方の集光点における光の強度が大きくなり、他方の集光点における光の強度が小さくなるように、変調パターンを調整してもよい。複屈折材料を含んで構成されたウエハにレーザ光を集光させる場合、入射光におけるP偏光成分とS偏光成分とで屈折率が互いに異なる。また、それらの入射光は常光線と異常光線とに分けられるが、その中の異常光線はスネルの法則に従わず常光線とは異なる屈折角で光が伝搬する。これらのことから、ウエハの深さ方向において、互いに異なる位置にP偏光成分及びS偏光成分が集光する。このように集光点が深さ方向に分岐することによってウエハにおいて意図せず複数の集光点が形成されることとなり、適切でない亀裂を生じさせてしまう。このことで、例えばスライシング等の加工の品質が低下するおそれがある。この点、光軸プロファイルに基づき、一方の集光点の強度が大きくなり、且つ、他方の集光点の強度が小さくなるように変調パターンが調整されることにより、上述した複数の集光点が形成されることによる加工品質の低下を抑制することができる。 [E3]
In the laser processing apparatus described in [E2] above, the wafer is configured to include a birefringent material, and in the fifth process, the control unit determines the focal point related to the ordinary ray and the extraordinary ray based on the optical axis profile. A modulation pattern is created so that the intensity of light at one of the two identified focal points increases and the intensity of light at the other focal point decreases. May be adjusted. When laser light is focused on a wafer including a birefringent material, the refractive indexes of the P-polarized light component and the S-polarized light component of the incident light are different from each other. Furthermore, these incident lights are divided into ordinary rays and extraordinary rays, but the extraordinary rays do not follow Snell's law and propagate at a different angle of refraction than the ordinary rays. For these reasons, the P-polarized light component and the S-polarized light component are focused at different positions in the depth direction of the wafer. This branching of the focal point in the depth direction causes a plurality of unintentional focal points to be formed on the wafer, resulting in the formation of inappropriate cracks. This may reduce the quality of processing such as slicing. In this regard, by adjusting the modulation pattern based on the optical axis profile so that the intensity of one focal point becomes large and the intensity of the other focal point becomes small, the plurality of focal points described above can be adjusted. It is possible to suppress deterioration in processing quality due to the formation of .
上記[E2]記載のレーザ加工装置において、ウエハは、複屈折材料を含んで構成されており、制御部は、第5処理において、光軸プロファイルに基づき、常光線に係る集光点と異常光線に係る集光点とを特定し、特定した2つの集光点のうち一方の集光点における光の強度が大きくなり、他方の集光点における光の強度が小さくなるように、変調パターンを調整してもよい。複屈折材料を含んで構成されたウエハにレーザ光を集光させる場合、入射光におけるP偏光成分とS偏光成分とで屈折率が互いに異なる。また、それらの入射光は常光線と異常光線とに分けられるが、その中の異常光線はスネルの法則に従わず常光線とは異なる屈折角で光が伝搬する。これらのことから、ウエハの深さ方向において、互いに異なる位置にP偏光成分及びS偏光成分が集光する。このように集光点が深さ方向に分岐することによってウエハにおいて意図せず複数の集光点が形成されることとなり、適切でない亀裂を生じさせてしまう。このことで、例えばスライシング等の加工の品質が低下するおそれがある。この点、光軸プロファイルに基づき、一方の集光点の強度が大きくなり、且つ、他方の集光点の強度が小さくなるように変調パターンが調整されることにより、上述した複数の集光点が形成されることによる加工品質の低下を抑制することができる。 [E3]
In the laser processing apparatus described in [E2] above, the wafer is configured to include a birefringent material, and in the fifth process, the control unit determines the focal point related to the ordinary ray and the extraordinary ray based on the optical axis profile. A modulation pattern is created so that the intensity of light at one of the two identified focal points increases and the intensity of light at the other focal point decreases. May be adjusted. When laser light is focused on a wafer including a birefringent material, the refractive indexes of the P-polarized light component and the S-polarized light component of the incident light are different from each other. Furthermore, these incident lights are divided into ordinary rays and extraordinary rays, but the extraordinary rays do not follow Snell's law and propagate at a different angle of refraction than the ordinary rays. For these reasons, the P-polarized light component and the S-polarized light component are focused at different positions in the depth direction of the wafer. This branching of the focal point in the depth direction causes a plurality of unintentional focal points to be formed on the wafer, resulting in the formation of inappropriate cracks. This may reduce the quality of processing such as slicing. In this regard, by adjusting the modulation pattern based on the optical axis profile so that the intensity of one focal point becomes large and the intensity of the other focal point becomes small, the plurality of focal points described above can be adjusted. It is possible to suppress deterioration in processing quality due to the formation of .
[E4]
上記[E3]記載のレーザ加工装置において、制御部は、第5処理において、2つの集光点のうち、第2表面に近い側の集光点における光の強度が大きくなり、第2表面に遠い側の集光点における光の強度が小さくなるように、変調パターンを調整してもよい。変調パターンの調整によって、2つの集光点の強度比を変えることはできるが、いずれかの集光点を完全になくすことはできない。例えば、第2表面に遠い側の集光点を主に利用し、第2表面に近い側の集光点における光の強度を極力小さくする場合には、第2表面に遠い側の集光点が加工狙い高さに設定され、微弱ではあるものの第2表面に近い側の集光点が存在することとなる。第2表面には、デバイスが設けられているため、第2表面に近い側の集光点の影響によってデバイスにダメージが生じてしまうことが考えられる。この点、第2表面に近い側の集光点を主に利用する場合には、第2表面に近い側の集光点が加工狙い高さに設定され、それよりも第2表面側に集光点が存在しないこととなるので、第2表面のデバイスのダメージを軽減することができる。なお、第2表面にデバイスが設けられていないウエハについても、レーザ加工装置が上記構成を備えることにより、第2表面におけるダメージを軽減することができる。 [E4]
In the laser processing apparatus described in [E3] above, the control unit may cause the control unit to control, in the fifth process, the intensity of the light at the focal point on the side closer to the second surface of the two focal points increases, and The modulation pattern may be adjusted so that the intensity of light at the focal point on the far side becomes smaller. Although the intensity ratio of the two focal points can be changed by adjusting the modulation pattern, one of the focal points cannot be completely eliminated. For example, if you mainly use the light convergence point on the side far from the second surface and minimize the intensity of light at the light convergence point on the side close to the second surface, then is set at the processing target height, and there is a focal point near the second surface, although it is weak. Since a device is provided on the second surface, it is conceivable that the device may be damaged due to the influence of the focal point on the side closer to the second surface. In this regard, when mainly using the light convergence point on the side closer to the second surface, the light convergence point on the side closer to the second surface is set at the processing target height, and the light is focused on the second surface side. Since no light spot exists, damage to the device on the second surface can be reduced. Note that even for a wafer in which no device is provided on the second surface, damage on the second surface can be reduced by providing the laser processing apparatus with the above configuration.
上記[E3]記載のレーザ加工装置において、制御部は、第5処理において、2つの集光点のうち、第2表面に近い側の集光点における光の強度が大きくなり、第2表面に遠い側の集光点における光の強度が小さくなるように、変調パターンを調整してもよい。変調パターンの調整によって、2つの集光点の強度比を変えることはできるが、いずれかの集光点を完全になくすことはできない。例えば、第2表面に遠い側の集光点を主に利用し、第2表面に近い側の集光点における光の強度を極力小さくする場合には、第2表面に遠い側の集光点が加工狙い高さに設定され、微弱ではあるものの第2表面に近い側の集光点が存在することとなる。第2表面には、デバイスが設けられているため、第2表面に近い側の集光点の影響によってデバイスにダメージが生じてしまうことが考えられる。この点、第2表面に近い側の集光点を主に利用する場合には、第2表面に近い側の集光点が加工狙い高さに設定され、それよりも第2表面側に集光点が存在しないこととなるので、第2表面のデバイスのダメージを軽減することができる。なお、第2表面にデバイスが設けられていないウエハについても、レーザ加工装置が上記構成を備えることにより、第2表面におけるダメージを軽減することができる。 [E4]
In the laser processing apparatus described in [E3] above, the control unit may cause the control unit to control, in the fifth process, the intensity of the light at the focal point on the side closer to the second surface of the two focal points increases, and The modulation pattern may be adjusted so that the intensity of light at the focal point on the far side becomes smaller. Although the intensity ratio of the two focal points can be changed by adjusting the modulation pattern, one of the focal points cannot be completely eliminated. For example, if you mainly use the light convergence point on the side far from the second surface and minimize the intensity of light at the light convergence point on the side close to the second surface, then is set at the processing target height, and there is a focal point near the second surface, although it is weak. Since a device is provided on the second surface, it is conceivable that the device may be damaged due to the influence of the focal point on the side closer to the second surface. In this regard, when mainly using the light convergence point on the side closer to the second surface, the light convergence point on the side closer to the second surface is set at the processing target height, and the light is focused on the second surface side. Since no light spot exists, damage to the device on the second surface can be reduced. Note that even for a wafer in which no device is provided on the second surface, damage on the second surface can be reduced by providing the laser processing apparatus with the above configuration.
[E5]
上記[E2]~[E4]のいずれか一項記載のレーザ加工装置において、制御部は、第5処理において、レーザ光における一部の偏光成分を遮断するスリットパターンにより変調パターンを調整してもよい。このような構成によれば、容易に、いずれかの集光点における光の強度を小さくすることができる。 [E5]
In the laser processing apparatus according to any one of [E2] to [E4] above, in the fifth process, the control unit adjusts the modulation pattern using a slit pattern that blocks some polarized components of the laser beam. good. According to such a configuration, the intensity of light at any focal point can be easily reduced.
上記[E2]~[E4]のいずれか一項記載のレーザ加工装置において、制御部は、第5処理において、レーザ光における一部の偏光成分を遮断するスリットパターンにより変調パターンを調整してもよい。このような構成によれば、容易に、いずれかの集光点における光の強度を小さくすることができる。 [E5]
In the laser processing apparatus according to any one of [E2] to [E4] above, in the fifth process, the control unit adjusts the modulation pattern using a slit pattern that blocks some polarized components of the laser beam. good. According to such a configuration, the intensity of light at any focal point can be easily reduced.
[E6]
上記[E2]~[E5]のいずれか一項記載のレーザ加工装置において、制御部は、変調パターンにより定まる球面収差の条件を変えながら、それぞれの条件下で、第1処理、第2処理、第3処理、及び第4処理を実施し、第5処理において、各条件下で取得された光軸プロファイルが示すレーザ光の輝度値の最大値を互いに比較し、輝度値が最大である光軸プロファイルに係る球面収差の条件となるように、変調パターンを調整してもよい。このような構成によれば、例えば屈折率が未知のウエハに対しても、適切な球面収差補正を実施することができる。 [E6]
In the laser processing apparatus according to any one of [E2] to [E5] above, the control unit changes the spherical aberration conditions determined by the modulation pattern and performs the first processing, second processing, The third process and the fourth process are carried out, and in the fifth process, the maximum values of the brightness values of the laser beams indicated by the optical axis profiles acquired under each condition are compared with each other, and the optical axis having the maximum brightness value is The modulation pattern may be adjusted to meet the spherical aberration conditions related to the profile. According to such a configuration, appropriate spherical aberration correction can be performed, for example, even for a wafer whose refractive index is unknown.
上記[E2]~[E5]のいずれか一項記載のレーザ加工装置において、制御部は、変調パターンにより定まる球面収差の条件を変えながら、それぞれの条件下で、第1処理、第2処理、第3処理、及び第4処理を実施し、第5処理において、各条件下で取得された光軸プロファイルが示すレーザ光の輝度値の最大値を互いに比較し、輝度値が最大である光軸プロファイルに係る球面収差の条件となるように、変調パターンを調整してもよい。このような構成によれば、例えば屈折率が未知のウエハに対しても、適切な球面収差補正を実施することができる。 [E6]
In the laser processing apparatus according to any one of [E2] to [E5] above, the control unit changes the spherical aberration conditions determined by the modulation pattern and performs the first processing, second processing, The third process and the fourth process are carried out, and in the fifth process, the maximum values of the brightness values of the laser beams indicated by the optical axis profiles acquired under each condition are compared with each other, and the optical axis having the maximum brightness value is The modulation pattern may be adjusted to meet the spherical aberration conditions related to the profile. According to such a configuration, appropriate spherical aberration correction can be performed, for example, even for a wafer whose refractive index is unknown.
[E7]
上記[E1]~[E6]のいずれか一項記載のレーザ加工装置において、制御部は、第4処理において取得された光軸プロファイルと、比較用のプロファイル画像である比較データとを比較し、比較したデータ間の差分が所定範囲内である場合に光軸プロファイルが正常であると判定し、差分が所定範囲外である場合に光軸プロファイルが異常であると判定し、判定結果を出力する第6処理を更に実行してもよい。このような構成によれば、レーザ加工装置が正常である場合のプロファイル画像を比較データとして設定しておくことにより、光軸プロファイルと比較データとの比較に基づき、レーザ加工装置において何らかの異常が発生しているか否かを容易に判定することができる。そして、判定結果が出力されることによって、該判定結果を考慮してレーザ加工装置の調整を実施することが可能になる。以上のように、上述した構成によれば、より適切に所望のレーザ加工を実施することができる。 [E7]
In the laser processing apparatus according to any one of [E1] to [E6] above, the control unit compares the optical axis profile acquired in the fourth process with comparison data that is a profile image for comparison, If the difference between the compared data is within a predetermined range, the optical axis profile is determined to be normal; if the difference is outside the predetermined range, the optical axis profile is determined to be abnormal, and the determination result is output. A sixth process may be further executed. According to such a configuration, by setting a profile image when the laser processing device is normal as comparison data, it is possible to detect whether any abnormality occurs in the laser processing device based on the comparison between the optical axis profile and the comparison data. It can be easily determined whether the Then, by outputting the determination result, it becomes possible to adjust the laser processing apparatus in consideration of the determination result. As described above, according to the configuration described above, desired laser processing can be performed more appropriately.
上記[E1]~[E6]のいずれか一項記載のレーザ加工装置において、制御部は、第4処理において取得された光軸プロファイルと、比較用のプロファイル画像である比較データとを比較し、比較したデータ間の差分が所定範囲内である場合に光軸プロファイルが正常であると判定し、差分が所定範囲外である場合に光軸プロファイルが異常であると判定し、判定結果を出力する第6処理を更に実行してもよい。このような構成によれば、レーザ加工装置が正常である場合のプロファイル画像を比較データとして設定しておくことにより、光軸プロファイルと比較データとの比較に基づき、レーザ加工装置において何らかの異常が発生しているか否かを容易に判定することができる。そして、判定結果が出力されることによって、該判定結果を考慮してレーザ加工装置の調整を実施することが可能になる。以上のように、上述した構成によれば、より適切に所望のレーザ加工を実施することができる。 [E7]
In the laser processing apparatus according to any one of [E1] to [E6] above, the control unit compares the optical axis profile acquired in the fourth process with comparison data that is a profile image for comparison, If the difference between the compared data is within a predetermined range, the optical axis profile is determined to be normal; if the difference is outside the predetermined range, the optical axis profile is determined to be abnormal, and the determination result is output. A sixth process may be further executed. According to such a configuration, by setting a profile image when the laser processing device is normal as comparison data, it is possible to detect whether any abnormality occurs in the laser processing device based on the comparison between the optical axis profile and the comparison data. It can be easily determined whether the Then, by outputting the determination result, it becomes possible to adjust the laser processing apparatus in consideration of the determination result. As described above, according to the configuration described above, desired laser processing can be performed more appropriately.
[E8]
上記[E1]~[E7]のいずれか一項記載のレーザ加工装置において、制御部は、第2処理において、ウエハ加工時における出力よりも低い出力のレーザ光が出射されるように、光源を制御してもよい。これにより、実際のレーザ加工を行うことなく、光軸プロファイルを取得することができる。 [E8]
In the laser processing apparatus according to any one of [E1] to [E7] above, the control unit controls the light source in the second process so that a laser beam with a lower output than the output during wafer processing is emitted. May be controlled. Thereby, an optical axis profile can be obtained without performing actual laser processing.
上記[E1]~[E7]のいずれか一項記載のレーザ加工装置において、制御部は、第2処理において、ウエハ加工時における出力よりも低い出力のレーザ光が出射されるように、光源を制御してもよい。これにより、実際のレーザ加工を行うことなく、光軸プロファイルを取得することができる。 [E8]
In the laser processing apparatus according to any one of [E1] to [E7] above, the control unit controls the light source in the second process so that a laser beam with a lower output than the output during wafer processing is emitted. May be controlled. Thereby, an optical axis profile can be obtained without performing actual laser processing.
[E9]
上記[E1]~[E8]のいずれか一項記載のレーザ加工装置において、光軸プロファイルは、複数の2次元の撮像画像が合成されることにより取得される3次元データであってもよい。3次元データとして光軸プロファイルが取得されることによって、光軸方向に沿ったレーザ光の照射状況(例えば集光点の位置や強度)をより詳細に把握することができる。 [E9]
In the laser processing apparatus described in any one of [E1] to [E8] above, the optical axis profile may be three-dimensional data obtained by combining a plurality of two-dimensional captured images. By acquiring the optical axis profile as three-dimensional data, it is possible to understand the laser beam irradiation situation (for example, the position and intensity of the condensing point) along the optical axis direction in more detail.
上記[E1]~[E8]のいずれか一項記載のレーザ加工装置において、光軸プロファイルは、複数の2次元の撮像画像が合成されることにより取得される3次元データであってもよい。3次元データとして光軸プロファイルが取得されることによって、光軸方向に沿ったレーザ光の照射状況(例えば集光点の位置や強度)をより詳細に把握することができる。 [E9]
In the laser processing apparatus described in any one of [E1] to [E8] above, the optical axis profile may be three-dimensional data obtained by combining a plurality of two-dimensional captured images. By acquiring the optical axis profile as three-dimensional data, it is possible to understand the laser beam irradiation situation (for example, the position and intensity of the condensing point) along the optical axis direction in more detail.
[E10]
本発明の一態様に係るレーザ加工方法は、空間光変調器によって変調されたレーザ光を第1表面及び第2表面を有するウエハの第1表面側からウエハに集光する集光部を、第1表面に対して垂直な方向である光軸方向に移動させる第1ステップと、第1ステップが実行されている状態において、連続的にレーザ光を出射する第2ステップと、第2ステップが実行されている状態において、第2表面において反射された光を検出することにより連続的に複数の撮像画像を取得する第3ステップと、第3ステップにおいて連続的に取得された複数の撮像画像を合成することにより、光軸方向に沿ったレーザ光のプロファイル画像である光軸プロファイルを取得する第4ステップと、を含む。 [E10]
A laser processing method according to one aspect of the present invention includes a condensing section that condenses laser light modulated by a spatial light modulator onto a wafer from a first surface side of a wafer having a first surface and a second surface. a first step of moving in the optical axis direction that is perpendicular to one surface; a second step of continuously emitting a laser beam while the first step is being executed; and the second step is executed. a third step of continuously acquiring a plurality of captured images by detecting the light reflected on the second surface in a state where the A fourth step of acquiring an optical axis profile which is a profile image of the laser beam along the optical axis direction.
本発明の一態様に係るレーザ加工方法は、空間光変調器によって変調されたレーザ光を第1表面及び第2表面を有するウエハの第1表面側からウエハに集光する集光部を、第1表面に対して垂直な方向である光軸方向に移動させる第1ステップと、第1ステップが実行されている状態において、連続的にレーザ光を出射する第2ステップと、第2ステップが実行されている状態において、第2表面において反射された光を検出することにより連続的に複数の撮像画像を取得する第3ステップと、第3ステップにおいて連続的に取得された複数の撮像画像を合成することにより、光軸方向に沿ったレーザ光のプロファイル画像である光軸プロファイルを取得する第4ステップと、を含む。 [E10]
A laser processing method according to one aspect of the present invention includes a condensing section that condenses laser light modulated by a spatial light modulator onto a wafer from a first surface side of a wafer having a first surface and a second surface. a first step of moving in the optical axis direction that is perpendicular to one surface; a second step of continuously emitting a laser beam while the first step is being executed; and the second step is executed. a third step of continuously acquiring a plurality of captured images by detecting the light reflected on the second surface in a state where the A fourth step of acquiring an optical axis profile which is a profile image of the laser beam along the optical axis direction.
[E11]
上記[E10]記載のレーザ加工方法において、上記レーザ加工方法は、第4ステップにおいて取得された光軸プロファイルに基づき、空間光変調器の変調パターンを調整する第5ステップ、を更に含んでいてもよい。 [E11]
In the laser processing method described in [E10] above, the laser processing method may further include a fifth step of adjusting the modulation pattern of the spatial light modulator based on the optical axis profile acquired in the fourth step. good.
上記[E10]記載のレーザ加工方法において、上記レーザ加工方法は、第4ステップにおいて取得された光軸プロファイルに基づき、空間光変調器の変調パターンを調整する第5ステップ、を更に含んでいてもよい。 [E11]
In the laser processing method described in [E10] above, the laser processing method may further include a fifth step of adjusting the modulation pattern of the spatial light modulator based on the optical axis profile acquired in the fourth step. good.
[E12]
上記[E11]記載のレーザ加工方法において、ウエハは、複屈折材料を含んで構成されており、第5ステップでは、光軸プロファイルに基づき、常光線に係る集光点と異常光線に係る集光点とを特定し、特定した2つの集光点のうち一方の集光点における光の強度が大きくなり、他方の集光点における光の強度が小さくなるように、変調パターンを調整してもよい。 [E12]
In the laser processing method described in [E11] above, the wafer includes a birefringent material, and in the fifth step, based on the optical axis profile, a focal point for ordinary rays and a focal point for extraordinary rays are determined. Even if the modulation pattern is adjusted so that the intensity of light at one of the two identified focal points increases and the intensity of light at the other focal point decreases. good.
上記[E11]記載のレーザ加工方法において、ウエハは、複屈折材料を含んで構成されており、第5ステップでは、光軸プロファイルに基づき、常光線に係る集光点と異常光線に係る集光点とを特定し、特定した2つの集光点のうち一方の集光点における光の強度が大きくなり、他方の集光点における光の強度が小さくなるように、変調パターンを調整してもよい。 [E12]
In the laser processing method described in [E11] above, the wafer includes a birefringent material, and in the fifth step, based on the optical axis profile, a focal point for ordinary rays and a focal point for extraordinary rays are determined. Even if the modulation pattern is adjusted so that the intensity of light at one of the two identified focal points increases and the intensity of light at the other focal point decreases. good.
[E13]
上記[E12]記載のレーザ加工方法において、第5ステップでは、2つの集光点のうち、第2表面に近い側の集光点における光の強度が大きくなり、第2表面に遠い側の集光点における光の強度が小さくなるように、変調パターンを調整してもよい。 [E13]
In the laser processing method described in [E12] above, in the fifth step, the intensity of the light at the focal point on the side closer to the second surface increases among the two focal points, and the intensity of the light on the side farther from the second surface increases. The modulation pattern may be adjusted so that the intensity of light at the light spot is reduced.
上記[E12]記載のレーザ加工方法において、第5ステップでは、2つの集光点のうち、第2表面に近い側の集光点における光の強度が大きくなり、第2表面に遠い側の集光点における光の強度が小さくなるように、変調パターンを調整してもよい。 [E13]
In the laser processing method described in [E12] above, in the fifth step, the intensity of the light at the focal point on the side closer to the second surface increases among the two focal points, and the intensity of the light on the side farther from the second surface increases. The modulation pattern may be adjusted so that the intensity of light at the light spot is reduced.
[E14]
上記[E11]~[E13]のいずれか一項記載のレーザ加工方法において、第5ステップでは、レーザ光における一部の偏光成分を遮断するスリットパターンにより変調パターンを調整してもよい。 [E14]
In the laser processing method described in any one of [E11] to [E13] above, in the fifth step, the modulation pattern may be adjusted by a slit pattern that blocks part of the polarized component of the laser beam.
上記[E11]~[E13]のいずれか一項記載のレーザ加工方法において、第5ステップでは、レーザ光における一部の偏光成分を遮断するスリットパターンにより変調パターンを調整してもよい。 [E14]
In the laser processing method described in any one of [E11] to [E13] above, in the fifth step, the modulation pattern may be adjusted by a slit pattern that blocks part of the polarized component of the laser beam.
[E15]
上記[E11]~[E14]のいずれか一項記載のレーザ加工方法において、変調パターンにより定まる球面収差の条件を変えながら、それぞれの条件下で、第1ステップ、第2ステップ、第3ステップ、及び第4ステップを実施し、第5ステップでは、各条件下で取得された光軸プロファイルが示すレーザ光の輝度値の最大値を互いに比較し、輝度値が最大である光軸プロファイルに係る球面収差の条件となるように、変調パターンを調整してもよい。 [E15]
In the laser processing method described in any one of [E11] to [E14] above, while changing the spherical aberration conditions determined by the modulation pattern, the first step, second step, third step, and the fourth step, and in the fifth step, the maximum values of the brightness values of the laser beams indicated by the optical axis profiles acquired under each condition are compared with each other, and the spherical surface according to the optical axis profile with the maximum brightness value is The modulation pattern may be adjusted to meet the aberration conditions.
上記[E11]~[E14]のいずれか一項記載のレーザ加工方法において、変調パターンにより定まる球面収差の条件を変えながら、それぞれの条件下で、第1ステップ、第2ステップ、第3ステップ、及び第4ステップを実施し、第5ステップでは、各条件下で取得された光軸プロファイルが示すレーザ光の輝度値の最大値を互いに比較し、輝度値が最大である光軸プロファイルに係る球面収差の条件となるように、変調パターンを調整してもよい。 [E15]
In the laser processing method described in any one of [E11] to [E14] above, while changing the spherical aberration conditions determined by the modulation pattern, the first step, second step, third step, and the fourth step, and in the fifth step, the maximum values of the brightness values of the laser beams indicated by the optical axis profiles acquired under each condition are compared with each other, and the spherical surface according to the optical axis profile with the maximum brightness value is The modulation pattern may be adjusted to meet the aberration conditions.
[E16]
上記[E10]~[E15]のいずれか一項記載のレーザ加工方法は、第4ステップにおいて取得された光軸プロファイルと、比較用のプロファイル画像である比較データとを比較し、比較したデータ間の差分が所定範囲内である場合に光軸プロファイルが正常であると判定し、差分が所定範囲外である場合に光軸プロファイルが異常であると判定し、判定結果を出力する第6ステップ、を更に含んでいてもよい。 [E16]
The laser processing method described in any one of [E10] to [E15] above compares the optical axis profile acquired in the fourth step with comparison data that is a profile image for comparison, and a sixth step of determining that the optical axis profile is normal when the difference is within a predetermined range, determining that the optical axis profile is abnormal when the difference is outside the predetermined range, and outputting the determination result; may further include.
上記[E10]~[E15]のいずれか一項記載のレーザ加工方法は、第4ステップにおいて取得された光軸プロファイルと、比較用のプロファイル画像である比較データとを比較し、比較したデータ間の差分が所定範囲内である場合に光軸プロファイルが正常であると判定し、差分が所定範囲外である場合に光軸プロファイルが異常であると判定し、判定結果を出力する第6ステップ、を更に含んでいてもよい。 [E16]
The laser processing method described in any one of [E10] to [E15] above compares the optical axis profile acquired in the fourth step with comparison data that is a profile image for comparison, and a sixth step of determining that the optical axis profile is normal when the difference is within a predetermined range, determining that the optical axis profile is abnormal when the difference is outside the predetermined range, and outputting the determination result; may further include.
[E17]
上記[E10]~[E16]のいずれか一項記載のレーザ加工方法において、第2ステップでは、ウエハ加工時における出力よりも低い出力のレーザ光を出射してもよい。 [E17]
In the laser processing method described in any one of [E10] to [E16] above, in the second step, a laser beam having an output lower than that during wafer processing may be emitted.
上記[E10]~[E16]のいずれか一項記載のレーザ加工方法において、第2ステップでは、ウエハ加工時における出力よりも低い出力のレーザ光を出射してもよい。 [E17]
In the laser processing method described in any one of [E10] to [E16] above, in the second step, a laser beam having an output lower than that during wafer processing may be emitted.
[E18]
上記[E10]~[E17]のいずれか一項記載のレーザ加工方法において、光軸プロファイルは、複数の2次元の撮像画像が合成されることにより取得される3次元データであってもよい。 [E18]
In the laser processing method described in any one of [E10] to [E17] above, the optical axis profile may be three-dimensional data obtained by combining a plurality of two-dimensional captured images.
上記[E10]~[E17]のいずれか一項記載のレーザ加工方法において、光軸プロファイルは、複数の2次元の撮像画像が合成されることにより取得される3次元データであってもよい。 [E18]
In the laser processing method described in any one of [E10] to [E17] above, the optical axis profile may be three-dimensional data obtained by combining a plurality of two-dimensional captured images.
本発明の一態様に係るレーザ加工装置及びレーザ加工方法によれば、所望のレーザ加工を実施することができる。
According to the laser processing apparatus and laser processing method according to one aspect of the present invention, desired laser processing can be performed.
以下、本発明の実施形態について、図面を参照して詳細に説明する。なお、各図において同一又は相当部分には同一符号を付し、重複する説明を省略する。
[レーザ加工装置の構成] Embodiments of the present invention will be described in detail below with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations will be omitted.
[Laser processing equipment configuration]
[レーザ加工装置の構成] Embodiments of the present invention will be described in detail below with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations will be omitted.
[Laser processing equipment configuration]
図1に示されるように、レーザ加工装置1は、支持部2と、光源3と、光軸調整部4と、空間光変調器5と、集光部6と、移動部7と、可視撮像部8(撮像部)と、制御部10と、を備えている。なお、撮像部は赤外カメラであってもよい。レーザ加工装置1は、ウエハ11にレーザ光Lを照射することでウエハ11に改質領域12を形成する装置である。以下の説明では、互いに直交する3方向を、それぞれ、X方向、Y方向及びZ方向という。本実施形態では、X方向は第1水平方向であり、Y方向は第1水平方向に垂直な第2水平方向であり、Z方向は鉛直方向である。
As shown in FIG. 1, the laser processing apparatus 1 includes a support section 2, a light source 3, an optical axis adjustment section 4, a spatial light modulator 5, a condensing section 6, a moving section 7, and a visible imaging section. It includes a section 8 (imaging section) and a control section 10. Note that the imaging unit may be an infrared camera. The laser processing apparatus 1 is an apparatus that forms a modified region 12 on the wafer 11 by irradiating the wafer 11 with a laser beam L. In the following description, three mutually orthogonal directions will be referred to as an X direction, a Y direction, and a Z direction, respectively. In this embodiment, the X direction is a first horizontal direction, the Y direction is a second horizontal direction perpendicular to the first horizontal direction, and the Z direction is a vertical direction.
支持部2は、表面11a(第1表面)及び裏面11b(第2表面)を有するウエハ11を支持する。一例として、支持部2は、ウエハ11に貼り付けられたフィルム(図示省略)を吸着することで、ウエハ11の表面11aがZ方向と直交するようにウエハ11を支持する。支持部2は、X方向及びY方向のそれぞれの方向に沿って移動可能であり、Z方向に平行な軸線を中心線として回転可能である。
The support section 2 supports the wafer 11 having a front surface 11a (first surface) and a back surface 11b (second surface). As an example, the support section 2 supports the wafer 11 by adsorbing a film (not shown) attached to the wafer 11 so that the surface 11a of the wafer 11 is perpendicular to the Z direction. The support portion 2 is movable along each of the X direction and the Y direction, and is rotatable about an axis parallel to the Z direction.
光源3は、レーザ光Lを出射する。一例として、光源3は、パルス発振方式によってレーザ光Lを出射する。レーザ光Lは、ウエハ11に対して透過性を有している。
The light source 3 emits laser light L. As an example, the light source 3 emits the laser beam L using a pulse oscillation method. The laser beam L is transparent to the wafer 11.
光軸調整部4は、光源3から出射されたレーザ光Lの光軸を調整する。本実施形態では、光軸調整部4は、光源3から出射されたレーザ光Lの進行方向をZ方向に沿うように変更しつつ、レーザ光Lの光軸を調整する。光軸調整部4は、例えば、位置及び角度の調整が可能な複数の反射ミラーによって構成されている。
The optical axis adjustment unit 4 adjusts the optical axis of the laser beam L emitted from the light source 3. In this embodiment, the optical axis adjustment unit 4 adjusts the optical axis of the laser beam L while changing the traveling direction of the laser beam L emitted from the light source 3 so as to follow the Z direction. The optical axis adjustment section 4 is composed of, for example, a plurality of reflecting mirrors whose positions and angles can be adjusted.
空間光変調器5は、筐体H内に配置されている。空間光変調器5は、光源3から出射されたレーザ光Lを変調する。本実施形態では、光軸調整部4からZ方向に沿って下側に進行したレーザ光Lが筐体H内に入射し、筐体H内に入射したレーザ光LがミラーM1によってY方向に対して角度を成すように水平に反射され、ミラーM1によって反射されたレーザ光Lが空間光変調器5に入射する。空間光変調器5は、そのように入射したレーザ光LをY方向に沿って水平に反射しつつ変調する。
The spatial light modulator 5 is placed inside the housing H. The spatial light modulator 5 modulates the laser beam L emitted from the light source 3. In this embodiment, the laser beam L that has traveled downward along the Z direction from the optical axis adjustment unit 4 enters the housing H, and the laser beam L that has entered the housing H is directed in the Y direction by the mirror M1. The laser beam L is reflected horizontally at an angle to the mirror M1 and enters the spatial light modulator 5. The spatial light modulator 5 modulates the thus incident laser light L while horizontally reflecting it along the Y direction.
本実施形態の空間光変調器5は、反射型液晶(LCOS:Liquid Crystal on Silicon)の空間光変調器(SLM:Spatial Light Modulator)である。図2に示されるように、空間光変調器5は、半導体基板51上に、駆動回路層52、画素電極層53、反射膜54、配向膜55、液晶層56、配向膜57、透明導電膜58及び透明基板59がこの順序で積層されることで、構成されている。
The spatial light modulator 5 of this embodiment is a reflective liquid crystal (LCOS) spatial light modulator (SLM). As shown in FIG. 2, the spatial light modulator 5 includes a drive circuit layer 52, a pixel electrode layer 53, a reflective film 54, an alignment film 55, a liquid crystal layer 56, an alignment film 57, and a transparent conductive film on a semiconductor substrate 51. 58 and a transparent substrate 59 are laminated in this order.
半導体基板51は、例えば、シリコン基板である。駆動回路層52は、半導体基板51上において、アクティブ・マトリクス回路を構成している。画素電極層53は、半導体基板51の表面に沿ってマトリックス状に配列された複数の画素電極53aを含んでいる。各画素電極53aは、例えば、アルミニウム等の金属材料によって形成されている。各画素電極53aには、駆動回路層52によって電圧が印加される。
The semiconductor substrate 51 is, for example, a silicon substrate. The drive circuit layer 52 constitutes an active matrix circuit on the semiconductor substrate 51. The pixel electrode layer 53 includes a plurality of pixel electrodes 53a arranged in a matrix along the surface of the semiconductor substrate 51. Each pixel electrode 53a is made of, for example, a metal material such as aluminum. A voltage is applied to each pixel electrode 53a by the drive circuit layer 52.
反射膜54は、例えば、誘電体多層膜である。配向膜55は、液晶層56における反射膜54側の表面に設けられており、配向膜57は、液晶層56における反射膜54とは反対側の表面に設けられている。各配向膜55,57は、例えば、ポリイミド等の高分子材料によって形成されており、各配向膜55,57における液晶層56との接触面には、例えば、ラビング処理が施されている。配向膜55,57は、液晶層56に含まれる液晶分子56aを一定方向に配列させる。
The reflective film 54 is, for example, a dielectric multilayer film. The alignment film 55 is provided on the surface of the liquid crystal layer 56 on the reflective film 54 side, and the alignment film 57 is provided on the surface of the liquid crystal layer 56 on the opposite side to the reflective film 54 . Each of the alignment films 55 and 57 is made of a polymeric material such as polyimide, and the contact surface of each of the alignment films 55 and 57 with the liquid crystal layer 56 is subjected to, for example, a rubbing treatment. The alignment films 55 and 57 align liquid crystal molecules 56a included in the liquid crystal layer 56 in a certain direction.
透明導電膜58は、透明基板59における配向膜57側の表面に設けられており、液晶層56等を挟んで画素電極層53と向かい合っている。透明基板59は、例えば、ガラス基板である。透明導電膜58は、例えば、ITO等の光透過性且つ導電性材料によって形成されている。透明基板59及び透明導電膜58は、レーザ光Lを透過させる。
The transparent conductive film 58 is provided on the surface of the transparent substrate 59 on the alignment film 57 side, and faces the pixel electrode layer 53 with the liquid crystal layer 56 and the like interposed therebetween. The transparent substrate 59 is, for example, a glass substrate. The transparent conductive film 58 is made of a light-transmitting and conductive material such as ITO, for example. The transparent substrate 59 and the transparent conductive film 58 transmit the laser beam L.
以上のように構成された空間光変調器5では、変調パターンを示す信号が制御部10から駆動回路層52に入力されると、当該信号に応じた電圧が各画素電極53aに印加され、各画素電極53aと透明導電膜58との間に電界が形成される。当該電界が形成されると、液晶層56において、各画素電極53aに対応する領域ごとに液晶分子216aの配列方向が変化し、各画素電極53aに対応する領域ごとに屈折率が変化する。この状態が、液晶層56に変調パターンが表示された状態である。
In the spatial light modulator 5 configured as described above, when a signal indicating a modulation pattern is input from the control unit 10 to the drive circuit layer 52, a voltage according to the signal is applied to each pixel electrode 53a, and each An electric field is formed between the pixel electrode 53a and the transparent conductive film 58. When the electric field is formed, in the liquid crystal layer 56, the arrangement direction of the liquid crystal molecules 216a changes for each region corresponding to each pixel electrode 53a, and the refractive index changes for each region corresponding to each pixel electrode 53a. This state is a state in which a modulation pattern is displayed on the liquid crystal layer 56.
液晶層56に変調パターンが表示された状態で、レーザ光Lが、外部から透明基板59及び透明導電膜58を介して液晶層56に入射し、反射膜54で反射されて、液晶層56から透明導電膜58及び透明基板59を介して外部に出射させられると、液晶層56に表示された変調パターンに応じて、レーザ光Lが変調される。このように、空間光変調器5によれば、液晶層56に表示する変調パターンを適宜設定することで、レーザ光Lの変調(例えば、レーザ光Lの強度、振幅、位相、偏光等の変調)が可能である。
With the modulation pattern displayed on the liquid crystal layer 56, laser light L enters the liquid crystal layer 56 from the outside via the transparent substrate 59 and the transparent conductive film 58, is reflected by the reflective film 54, and is emitted from the liquid crystal layer 56. When emitted to the outside via the transparent conductive film 58 and the transparent substrate 59, the laser light L is modulated according to the modulation pattern displayed on the liquid crystal layer 56. As described above, according to the spatial light modulator 5, by appropriately setting the modulation pattern displayed on the liquid crystal layer 56, the modulation of the laser beam L (for example, modulation of the intensity, amplitude, phase, polarization, etc. of the laser beam L) can be performed. ) is possible.
図1に戻り、集光部6は、筐体Hの底壁に取り付けられている。集光部6は、空間光変調器5によって変調されたレーザ光Lを、支持部2によって支持されたウエハ11に集光する。本実施形態では、空間光変調器5によってY方向に沿って水平に反射されたレーザ光LがダイクロイックミラーM2によってZ方向に沿って下側に反射され、ダイクロイックミラーM2によって反射されたレーザ光Lが集光部6に入射する。集光部6は、そのように入射したレーザ光LをZ方向に沿って表面11a(第1表面)側からウエハ11に集光する。本実施形態では、集光部6は、集光レンズユニット61が駆動機構62を介して筐体Hの底壁に取り付けられることで構成されている。集光レンズユニット61は、平行光を光軸上の一点に集光する機能を有している。駆動機構62は、例えば圧電素子の駆動力によって、集光レンズユニット61をZ方向に沿って移動させる。
Returning to FIG. 1, the light condensing section 6 is attached to the bottom wall of the housing H. The condensing section 6 condenses the laser beam L modulated by the spatial light modulator 5 onto the wafer 11 supported by the support section 2 . In this embodiment, the laser beam L reflected horizontally along the Y direction by the spatial light modulator 5 is reflected downward along the Z direction by the dichroic mirror M2, and the laser beam L reflected by the dichroic mirror M2 enters the light condensing section 6. The condensing unit 6 condenses the laser beam L thus incident on the wafer 11 from the surface 11a (first surface) side along the Z direction. In this embodiment, the condensing section 6 is configured by a condensing lens unit 61 attached to the bottom wall of the housing H via a drive mechanism 62. The condensing lens unit 61 has a function of condensing parallel light onto one point on the optical axis. The drive mechanism 62 moves the condenser lens unit 61 along the Z direction by, for example, a drive force of a piezoelectric element.
なお、筐体H内において、空間光変調器5と集光部6との間には、結像光学系(図示省略)が配置されている。結像光学系は、空間光変調器5の反射面と集光部6の入射瞳面とが結像関係にある両側テレセントリック光学系を構成している。これにより、空間光変調器5の反射面でのレーザ光Lの像(空間光変調器5によって変調されたレーザ光Lの像)が集光部6の入射瞳面に相似に転像(結像)される。
Note that within the housing H, an imaging optical system (not shown) is arranged between the spatial light modulator 5 and the light condensing section 6. The imaging optical system constitutes a double-sided telecentric optical system in which the reflective surface of the spatial light modulator 5 and the entrance pupil plane of the condenser 6 are in an imaging relationship. As a result, the image of the laser light L on the reflective surface of the spatial light modulator 5 (the image of the laser light L modulated by the spatial light modulator 5) is similarly transformed (formed) onto the entrance pupil plane of the condenser 6. image) to be done.
筐体Hの底壁には、X方向において集光レンズユニット61の両側に位置するように一対の測距センサS1,S2が取り付けられている。各測距センサS1,S2は、ウエハ11の表面11aに対して測距用の光(例えば、レーザ光)を出射し、表面11aで反射された測距用の光を検出することで、表面11aの変位データを取得する。
A pair of distance measuring sensors S1 and S2 are attached to the bottom wall of the housing H so as to be located on both sides of the condenser lens unit 61 in the X direction. Each distance measurement sensor S1, S2 emits distance measurement light (for example, a laser beam) to the surface 11a of the wafer 11, and detects the distance measurement light reflected by the surface 11a. Obtain displacement data of 11a.
移動部7は、集光部6を、ウエハ11の表面11aに対して垂直な方向である光軸方向(すなわちZ方向)に、表面11aに対して相対的に移動させる。移動部7は、筐体H及び支持部2の少なくとも一方を移動させることで、集光部6をウエハ11の表面11aに対して相対的に移動させる移動機構(アクチュエータ、モータ等の駆動源を含む)である。本実施形態では、移動部7は、X方向及びY方向のそれぞれの方向に沿って支持部2を移動させ、Z方向に平行な軸線を中心線として支持部2を回転させ、Z方向に沿って筐体Hを移動させる。
The moving unit 7 moves the light condensing unit 6 relative to the surface 11a of the wafer 11 in the optical axis direction (that is, the Z direction), which is a direction perpendicular to the surface 11a. The moving unit 7 includes a moving mechanism (a driving source such as an actuator or a motor) that moves the light condensing unit 6 relative to the surface 11a of the wafer 11 by moving at least one of the housing H and the supporting unit 2. ). In this embodiment, the moving unit 7 moves the support unit 2 along each of the X direction and the Y direction, rotates the support unit 2 about an axis parallel to the Z direction, and rotates the support unit 2 along the Z direction. to move the housing H.
可視撮像部8は、筐体H内に配置されている。可視撮像部8は、可視光Vを出射し、可視光Vによるウエハ11の像を画像として取得する。本実施形態では、可視撮像部8から出射された可視光VがダイクロイックミラーM2及び集光部6を介してウエハ11に照射され、ウエハ11で反射された可視光Vが集光部6及びダイクロイックミラーM2を介して可視撮像部8で検出される。すなわち、可視撮像部8は、集光部6を介してウエハ11を伝搬した光を検出することにより撮像画像を取得する。
The visible imaging unit 8 is placed inside the housing H. The visible imaging unit 8 emits visible light V and obtains an image of the wafer 11 using the visible light V. In this embodiment, the visible light V emitted from the visible imaging section 8 is irradiated onto the wafer 11 via the dichroic mirror M2 and the light condensing section 6, and the visible light V reflected by the wafer 11 is transmitted to the light condensing section 6 and the dichroic mirror M2. It is detected by the visible imaging unit 8 via the mirror M2. That is, the visible imaging section 8 acquires a captured image by detecting the light propagated through the wafer 11 via the light condensing section 6.
制御部10は、レーザ加工装置1の各部の動作を制御する。制御部10は、処理部101と、記憶部102と、インターフェース部103と、を有している。処理部101は、プロセッサ、メモリ、ストレージ及び通信デバイス等を含むコンピュータ装置として構成されている。処理部101では、プロセッサが、メモリ等に読み込まれたソフトウェア(プログラム)を実行し、メモリ及びストレージにおけるデータの読み出し及び書き込み、並びに、通信デバイスによる通信を制御する。記憶部102は、例えばハードディスク等であり、各種データを記憶する。インターフェース部103は、オペレータに各種データを表示したり、オペレータから各種データの入力を受け付けたりする。本実施形態では、インターフェース部103は、GUI(Graphical User Interface)を構成している。
The control unit 10 controls the operation of each part of the laser processing device 1. The control unit 10 includes a processing unit 101, a storage unit 102, and an interface unit 103. The processing unit 101 is configured as a computer device including a processor, memory, storage, communication device, and the like. In the processing unit 101, a processor executes software (program) read into a memory or the like, and controls reading and writing of data in the memory and storage, and communication by a communication device. The storage unit 102 is, for example, a hard disk or the like, and stores various data. The interface unit 103 displays various data to the operator and receives input of various data from the operator. In this embodiment, the interface unit 103 constitutes a GUI (Graphical User Interface).
以上のように構成されたレーザ加工装置1では、ウエハ11の内部にレーザ光Lが集光されると、レーザ光Lの集光点Cに対応する部分においてレーザ光Lが吸収され、ウエハ11の内部に改質領域12が形成される。改質領域12は、密度、屈折率、機械的強度、その他の物理的特性が周囲の非改質領域とは異なる領域である。改質領域12としては、例えば、溶融処理領域、クラック領域、絶縁破壊領域、屈折率変化領域等がある。改質領域12は、改質領域12からレーザ光Lの入射側及びその反対側に亀裂が延び易いという特性を有している。このような改質領域12の特性は、例えば、ウエハ11の切断に利用される。
In the laser processing apparatus 1 configured as described above, when the laser beam L is focused inside the wafer 11, the laser beam L is absorbed in the portion corresponding to the converging point C of the laser beam L, and the wafer 11 A modified region 12 is formed inside. The modified region 12 is a region that differs in density, refractive index, mechanical strength, and other physical properties from the surrounding unmodified region. Examples of the modified region 12 include a melt-treated region, a crack region, a dielectric breakdown region, and a refractive index change region. The modified region 12 has a characteristic that cracks tend to extend from the modified region 12 to the incident side of the laser beam L and the opposite side thereof. Such characteristics of the modified region 12 are utilized for cutting the wafer 11, for example.
一例として、ウエハ11を切断するためのライン15に沿って、ウエハ11の内部に改質領域12を形成する場合におけるレーザ加工装置1の動作について説明する。
As an example, the operation of the laser processing apparatus 1 when forming the modified region 12 inside the wafer 11 along the line 15 for cutting the wafer 11 will be described.
まず、レーザ加工装置1は、ウエハ11に設定されたライン15がX方向に平行となるように、Z方向に平行な軸線を中心線として支持部2を回転させる。続いて、レーザ加工装置1は、Z方向から見た場合にレーザ光Lの集光点Cがライン15上に位置するように、X方向及びY方向のそれぞれの方向に沿って支持部2を移動させる。
First, the laser processing apparatus 1 rotates the support part 2 about an axis parallel to the Z direction as a center line so that the line 15 set on the wafer 11 is parallel to the X direction. Next, the laser processing device 1 moves the support part 2 along the X direction and the Y direction so that the condensing point C of the laser beam L is located on the line 15 when viewed from the Z direction. move it.
続いて、レーザ加工装置1は、可視撮像部8によって取得された画像(例えば、ウエハ11の表面11aの像)に基づいて、レーザ光Lの集光点Cが表面11a上に位置するように、Z方向に沿って筐体H(すなわち、集光部6)を移動させる。続いて、レーザ加工装置1は、その位置を基準として、レーザ光Lの集光点Cが表面11aから所定深さに位置するように、Z方向に沿って筐体H(すなわち、集光部6)を移動させる。
Next, the laser processing apparatus 1 adjusts the focus point C of the laser beam L to be located on the surface 11a based on the image acquired by the visible imaging unit 8 (for example, the image of the surface 11a of the wafer 11). , move the housing H (that is, the light condensing section 6) along the Z direction. Next, the laser processing apparatus 1 moves the housing H (i.e., the light condensing part) along the Z direction so that the condensing point C of the laser beam L is located at a predetermined depth from the surface 11a, with this position as a reference. 6) Move.
続いて、レーザ加工装置1は、光源3からレーザ光Lを出射させると共に、レーザ光Lの集光点Cがライン15に沿って相対的に移動するように、X方向に沿って支持部2を移動させる。このとき、レーザ加工装置1は、一対の測距センサS1,S2のうち前側(ウエハ11に対するレーザ光Lの相対的移動方向における前側)に位置する測距センサによって取得された表面11aの変位データに基づいて、レーザ光Lの集光点Cが表面11aから所定深さに位置するように、集光部6の駆動機構62を動作させる。
Subsequently, the laser processing device 1 emits the laser beam L from the light source 3, and moves the support section 2 along the X direction so that the condensing point C of the laser beam L moves relatively along the line 15. move. At this time, the laser processing apparatus 1 uses displacement data of the surface 11a acquired by the distance measurement sensor located on the front side (the front side in the relative movement direction of the laser beam L with respect to the wafer 11) among the pair of distance measurement sensors S1 and S2. Based on this, the drive mechanism 62 of the light focusing section 6 is operated so that the focusing point C of the laser beam L is located at a predetermined depth from the surface 11a.
以上により、ライン15に沿って且つウエハ11の表面11aから一定深さに、一列の改質領域12が形成される。パルス発振方式によって光源3からレーザ光Lが出射されると、複数の改質スポット12sがX方向に沿って一列に並ぶように形成される。一つの改質スポット12sは、1パルスのレーザ光Lの照射によって形成される。一列の改質領域12は、一列に並んだ複数の改質スポット12sの集合である。隣り合う改質スポット12sは、レーザ光Lのパルスピッチ(ウエハ11に対する集光点Cの相対的な移動速度をレーザ光Lの繰り返し周波数で除した値)によって、互いに繋がる場合も、互いに離れる場合もある。
[光軸プロファイルの取得] As a result, a row of modifiedregions 12 are formed along line 15 and at a constant depth from surface 11a of wafer 11. When the laser beam L is emitted from the light source 3 using the pulse oscillation method, a plurality of modification spots 12s are formed in a line along the X direction. One modification spot 12s is formed by irradiation with one pulse of laser light L. A row of modified regions 12 is a collection of a plurality of modified spots 12s arranged in a row. Adjacent modification spots 12s may be connected to each other or separated from each other depending on the pulse pitch of the laser beam L (the value obtained by dividing the relative moving speed of the focal point C with respect to the wafer 11 by the repetition frequency of the laser beam L). There is also.
[Obtain optical axis profile]
[光軸プロファイルの取得] As a result, a row of modified
[Obtain optical axis profile]
以下では、レーザ加工装置1において実行される光軸プロファイルの取得処理について説明する。光軸プロファイルとは、集光部6が表面11aに対してZ方向に相対的に移動すると共にレーザ光が出射されている状態において、可視撮像部8によってウエハ11の裏面11bにおいて反射された光が検出されて連続的に取得された複数の撮像画像を合成することにより取得されるデータである。具体的には、光軸プロファイルは、上記複数の撮像画像を合成することにより取得される、Z方向に沿ったレーザ光のプロファイル画像である。光軸プロファイルによれば、光軸方向に沿ったレーザ光の照射状況(例えばウエハ11における集光点の位置や強度)が特定される。これにより、例えば、レーザ加工装置1における何らかの異常の発生有無や、空間光変調器5に設定される変調パターンの調整の要否等を判断することができる(詳細は後述)。
Hereinafter, the optical axis profile acquisition process executed in the laser processing apparatus 1 will be described. The optical axis profile is the light reflected by the visible imaging section 8 on the back surface 11b of the wafer 11 in a state where the light condensing section 6 moves relative to the front surface 11a in the Z direction and the laser beam is emitted. This data is obtained by combining a plurality of captured images that are detected and sequentially obtained. Specifically, the optical axis profile is a profile image of the laser beam along the Z direction, which is obtained by combining the plurality of captured images. According to the optical axis profile, the irradiation status of the laser light along the optical axis direction (for example, the position and intensity of the focal point on the wafer 11) is specified. Thereby, it is possible to determine, for example, whether any abnormality has occurred in the laser processing apparatus 1, whether or not the modulation pattern set in the spatial light modulator 5 needs to be adjusted (details will be described later).
図3(a)はZ方向に沿った連続的な撮像を説明する図である。図3(a)においては、左から、断面Aの撮像、断面Bの撮像、断面Cの撮像、及び断面Dの撮像が示されている。図3(a)に示される例では、図中の左から右に向かって、集光部6が、ウエハ11に徐々に近づくようにZ方向に相対的に移動している。図3(a)に示されるように、集光部6の位置がΔZだけ動くと、ウエハ11の裏面11bにおいて反射し可視撮像部8に撮像されるレーザ光の経路は、往路・復路を合わせてΔZ×2だけ変化することとなる。集光部6は、例えば移動部7によって、可視撮像部8と共に移動させられる。すなわち、レーザ光の集光点と可視撮像部8の観察面(カメラ結像面)とが共に移動する。なお、集光部6の集光レンズユニット61等は、駆動機構62によって移動させられてもよい。
FIG. 3(a) is a diagram illustrating continuous imaging along the Z direction. In FIG. 3A, from the left, imaging of cross section A, imaging of cross section B, imaging of cross section C, and imaging of cross section D are shown. In the example shown in FIG. 3A, the light condensing section 6 is relatively moved in the Z direction so as to gradually approach the wafer 11 from left to right in the figure. As shown in FIG. 3(a), when the position of the light condensing unit 6 moves by ΔZ, the path of the laser light reflected on the back surface 11b of the wafer 11 and imaged by the visible imaging unit 8 changes by combining the outgoing and returning paths. This results in a change of ΔZ×2. The light collecting section 6 is moved together with the visible imaging section 8, for example, by the moving section 7. That is, the focal point of the laser beam and the observation plane (camera imaging plane) of the visible imaging section 8 move together. Note that the condensing lens unit 61 and the like of the condensing section 6 may be moved by the drive mechanism 62.
この場合、制御部10は、集光部6がZ方向においてウエハ11の表面11aに対して相対的に移動するように移動部7を制御する第1処理と、第1処理が実行されている状態において連続的にレーザ光が出射されるように光源3を制御する第2処理と、を実行する。制御部10は、第2処理において、ウエハ11の加工時における出力よりも低い出力のレーザ光が出射されるように、光源3を制御する。更に、制御部10は、第2処理が実行されている状態においてウエハ11の裏面11bにおいて反射された光が検出されて連続的に複数の撮像画像が取得されるように、可視撮像部8を制御する第3処理を実行する。更に、制御部10は、第3処理において連続的に取得された複数の撮像画像を合成することにより、Z方向に沿ったレーザ光のプロファイル画像である光軸プロファイルを取得する第4処理を実行する。
In this case, the control unit 10 controls the moving unit 7 so that the condensing unit 6 moves relative to the surface 11a of the wafer 11 in the Z direction, and the first process is executed. A second process of controlling the light source 3 so that the laser beam is continuously emitted in the state is executed. In the second process, the control unit 10 controls the light source 3 so that a laser beam with a lower output than the output when processing the wafer 11 is emitted. Further, the control unit 10 controls the visible imaging unit 8 so that the light reflected on the back surface 11b of the wafer 11 is detected and a plurality of captured images are continuously acquired while the second process is being executed. A third process to control is executed. Furthermore, the control unit 10 executes a fourth process of acquiring an optical axis profile, which is a profile image of the laser beam along the Z direction, by combining the plurality of captured images sequentially acquired in the third process. do.
図3(b)は撮像画像を合成することにより取得される光軸プロファイルを示す図である。図3(a)の下段には、断面A、断面B、断面C、断面Dのそれぞれの撮像画像が示されている。連続的に取得される各撮像画像が合成されることにより、図3(b)に示されるように、レーザ光の照射状況(例えば集光点Cの位置や強度)の特定が可能な光軸プロファイルが取得される。
FIG. 3(b) is a diagram showing an optical axis profile obtained by combining captured images. In the lower part of FIG. 3A, captured images of each of cross sections A, B, C, and D are shown. As shown in FIG. 3(b), by combining the continuously acquired images, an optical axis is created that allows identification of the laser light irradiation status (for example, the position and intensity of the condensing point C). A profile is obtained.
図4(a)は2次元データで示された光軸プロファイルを示す断面図であり、図4(b)は3次元データで示された光軸プロファイルを示す図である。光軸プロファイルは、例えば、複数の2次元の撮像画像が合成されることにより取得される3次元データ(図4(b)参照)であってもよい。図4(b)に示されるように、3次元データにおいては、レーザ光の強度に応じて色分けされていてもよい。或いは、光軸プロファイルは、取得された3次元データから生成される2次元データ(図4(a)参照)であってもよい。図4(a)の右図に示されるように、2次元データに並べて、各領域におけるレーザ光の強度を示すグラフが表示されてもよい。
FIG. 4(a) is a cross-sectional view showing an optical axis profile represented by two-dimensional data, and FIG. 4(b) is a diagram showing an optical axis profile represented by three-dimensional data. The optical axis profile may be, for example, three-dimensional data obtained by combining a plurality of two-dimensional captured images (see FIG. 4(b)). As shown in FIG. 4(b), the three-dimensional data may be color-coded according to the intensity of the laser beam. Alternatively, the optical axis profile may be two-dimensional data (see FIG. 4(a)) generated from the acquired three-dimensional data. As shown in the right diagram of FIG. 4(a), a graph showing the intensity of laser light in each region may be displayed alongside the two-dimensional data.
図5は、レーザ加工装置1によって実施される光軸プロファイル取得処理を示すフローチャートである。光軸プロファイル取得処理では、最初に、支持部2によってウエハ11に貼り付けられるフィルムが吸着される(ステップS1)。
FIG. 5 is a flowchart showing the optical axis profile acquisition process performed by the laser processing apparatus 1. In the optical axis profile acquisition process, first, a film to be attached to the wafer 11 is attracted by the support section 2 (step S1).
つづいて、制御部10の制御に応じて移動部7が集光部6を移動させることにより、集光部6の対物レンズの直下にウエハ11が移動する(ステップS2)。この状態で、レチクルピント位置にZ方向の高さが設定されるように、制御部10の制御に応じて移動部7が移動する(ステップS3)。さらに、ウエハ11の厚さ分だけZ方向の高さが下がるように、制御部10の制御に応じて移動部7が移動する(ステップS4)。
Subsequently, the moving unit 7 moves the condensing unit 6 under the control of the control unit 10, so that the wafer 11 is moved directly below the objective lens of the condensing unit 6 (step S2). In this state, the moving unit 7 moves under the control of the control unit 10 so that the height in the Z direction is set at the reticle focus position (step S3). Further, the moving unit 7 moves under the control of the control unit 10 so that the height in the Z direction is lowered by the thickness of the wafer 11 (step S4).
つづいて、制御部10から空間光変調器5に対して、変調パターンを示す信号が入力される。具体的には、空間光変調器5において、例えば、歪補正パターンとウエハ厚さの2倍の球面収差となる変調パターンが表示される(ステップS5)。
Subsequently, a signal indicating a modulation pattern is input from the control unit 10 to the spatial light modulator 5. Specifically, in the spatial light modulator 5, for example, a distortion correction pattern and a modulation pattern having a spherical aberration twice the wafer thickness are displayed (step S5).
つづいて、レーザ加工装置1における光源3以外の光源を全てOFFし、制御部10によって、レーザ光が出射されるように光源3が制御される(ステップS6)。レーザ光が確実に確認されるように、制御部10によってレーザ光の出力等の各種設定が行われる。
Subsequently, all light sources other than the light source 3 in the laser processing apparatus 1 are turned off, and the light source 3 is controlled by the control unit 10 so that the laser beam is emitted (step S6). Various settings such as the output of the laser beam are performed by the control unit 10 so that the laser beam can be reliably confirmed.
つづいて、ウエハ11の表面においてアブレーションが発生しているか否かが判定される(ステップS8)。アブレーションが発生している場合には、レーザ出力調整又はアッテネータ出力調整等でアブレーションが発生しない状態とされる(ステップS9)。そして、レーザ加工装置1における光源3以外の光源がONされて(ステップS10)、アブレーションを起こしていない位置且つウエハ11の上方に集光部6の対物レンズがあることが確認され(ステップS11)、再度ステップS3の処理から実施される。
Subsequently, it is determined whether or not ablation has occurred on the surface of the wafer 11 (step S8). If ablation has occurred, the state is set such that ablation does not occur by adjusting the laser output or attenuator output (step S9). Then, the light sources other than the light source 3 in the laser processing apparatus 1 are turned on (step S10), and it is confirmed that the objective lens of the condenser 6 is located above the wafer 11 and at a position where no ablation is occurring (step S11). , the process is executed again from step S3.
一方で、ステップS8においてアブレーションが発生していないと判定された場合には、レーザ光が最集光する位置にZ方向の微調整が行われ(ステップS12)、レーザ光を確認する可視撮像部8等の設定値が最適状態にされる(ステップS13)。
On the other hand, if it is determined in step S8 that ablation has not occurred, fine adjustment in the Z direction is performed to the position where the laser beam is most focused (step S12), and the visible imaging unit that confirms the laser beam is A set value such as 8 is set to the optimum state (step S13).
そして、制御部10の制御に応じて、集光部6の対物レンズ用のアクチュエータである駆動機構62又はZ軸方向の移動に係る移動部7が移動しながら、可視撮像部8によって連続的に撮像される(ステップS14)。最後に、制御部10によって複数の撮像画像が合成されることにより、集光点付近の光軸プロファイルが取得される(ステップS15)。
Then, under the control of the control unit 10, while the drive mechanism 62, which is an actuator for the objective lens of the condensing unit 6, or the moving unit 7, which is related to movement in the Z-axis direction, moves, the visible imaging unit 8 continuously An image is taken (step S14). Finally, the control unit 10 combines the plurality of captured images to obtain an optical axis profile near the focal point (step S15).
以上が、光軸プロファイル取得処理の一例である。以下では、上述した第4処理において取得された光軸プロファイルを用いて行う処理として、複屈折材料の集光点調整、レーザ加工装置1のエラー状態特定、及び、球面収差調整の各処理を順に説明する。
[複屈折材料の集光点調整] The above is an example of the optical axis profile acquisition process. In the following, the processes of adjusting the focal point of the birefringent material, identifying the error state of thelaser processing device 1, and adjusting the spherical aberration will be sequentially performed using the optical axis profile obtained in the fourth process described above. explain.
[Focusing point adjustment of birefringent material]
[複屈折材料の集光点調整] The above is an example of the optical axis profile acquisition process. In the following, the processes of adjusting the focal point of the birefringent material, identifying the error state of the
[Focusing point adjustment of birefringent material]
図6(a)は、複屈折材料を含んで構成されたウエハ11についての光軸プロファイルを示す図である。複屈折材料にレーザ光が入射すると、シリコンやガラスとは異なり、偏光による屈折率の違いにより、常光線による集光点C1、及び、異常光線による集光点C2の2つの集光点が発生することとなる。例えば、レーザ光の照射によってダイシングを行う場合には、ダイシング方向(Z方向)において上下に集光点が分岐しても大きな問題とはならない。一方で、スライス方向においてスライシングをする場合には、集光点が分岐している影響を受けて、加工精度が悪化するおそれがある。また、図6(b)に示されるように、ウエハ11が薄くなるにつれて、抜け光によるデバイスのダメージ対策が必要になってきている。例えば、図6(b)の左図に示されるように、下側の集光点(ここでは、異常光線による集光点C2)が裏面11bのデバイス(例えば電極200)から十分に離間している場合には、抜け光による電極200へのダメージが問題とならない。一方で、図6(b)の右図に示されるように、下側の集光点(ここでは、異常光線による集光点C2)が裏面11bのデバイス(例えば電極200)に近い場合には、抜け光によって電極200がダメージを受けることが問題となる。以上のように、複屈折材料にレーザ光を入射させる場合には、加工精度悪化及びデバイスのダメージを抑制するために、何らかの対策が必要になっている。
FIG. 6(a) is a diagram showing an optical axis profile of a wafer 11 that includes a birefringent material. When a laser beam enters a birefringent material, unlike silicon or glass, two focal points are generated: a focal point C1 for ordinary rays and a focal point C2 for extraordinary rays due to the difference in refractive index due to polarization. I will do it. For example, when dicing is performed by irradiation with laser light, there is no major problem even if the focal point branches upward and downward in the dicing direction (Z direction). On the other hand, when slicing is performed in the slicing direction, processing accuracy may deteriorate due to the influence of the light condensing point being branched. Further, as shown in FIG. 6B, as the wafer 11 becomes thinner, it becomes necessary to take measures against damage to devices due to light leakage. For example, as shown in the left diagram of FIG. 6(b), the lower light focusing point (here, the focusing point C2 of the extraordinary ray) is sufficiently spaced from the device (for example, the electrode 200) on the back surface 11b. In this case, damage to the electrode 200 due to light leakage is not a problem. On the other hand, as shown in the right diagram of FIG. 6(b), when the lower light focusing point (here, the focusing point C2 of the extraordinary ray) is close to the device (for example, the electrode 200) on the back surface 11b, The problem is that the electrode 200 is damaged by the light passing through. As described above, when laser light is incident on a birefringent material, some kind of countermeasure is required to prevent deterioration of processing accuracy and damage to the device.
なお、図7(a)及び図7(b)に示されるように、複屈折材料にレーザ光が入射した際に常光線による集光点C1が、異常光線による集光点C2よりも上方に分岐されるか(図7(a)参照)、反対に、異常光線による集光点C2よりも下方に分岐されるか(図7(b)参照)は、複屈折材料の種類による。具体的には、GaN又は水晶等の正の複屈折材料については、図7(a)に示されるように、常光線による集光点C1が異常光線による集光点C2よりも上方に分岐される。一方で、方解石又はサファイヤ等の負の複屈折材料については、図7(b)に示されるように、常光線による集光点C1が異常光線による集光点C2よりも下方に分岐される。
As shown in FIGS. 7(a) and 7(b), when laser light is incident on a birefringent material, the focal point C1 of ordinary rays is higher than the focal point C2 of extraordinary rays. Whether it is branched (see FIG. 7(a)) or, conversely, branched below the focal point C2 of the extraordinary ray (see FIG. 7(b)) depends on the type of birefringent material. Specifically, for a positive birefringent material such as GaN or quartz, as shown in FIG. 7(a), the focal point C1 of the ordinary ray is branched above the focal point C2 of the extraordinary ray. Ru. On the other hand, for a negative birefringent material such as calcite or sapphire, as shown in FIG. 7(b), the focal point C1 of the ordinary ray is branched below the focal point C2 of the extraordinary ray.
制御部10は、上述した第4処理において取得された光軸プロファイルに基づき、空間光変調器5の変調パターンを調整する第5処理を更に実行するように構成されている。制御部10は、第5処理において、光軸プロファイルに基づき、常光線に係る集光点C1と異常光線に係る集光点C2とを特定し、特定した2つの集光点のうち一方の集光点における光の強度が大きくなり、他方の集光点における光の強度が小さくなるように、変調パターンを調整する。
The control unit 10 is configured to further execute a fifth process of adjusting the modulation pattern of the spatial light modulator 5 based on the optical axis profile acquired in the fourth process described above. In the fifth process, the control unit 10 specifies a focal point C1 for ordinary rays and a focal point C2 for extraordinary rays based on the optical axis profile, and selects one of the two identified focal points. The modulation pattern is adjusted so that the intensity of light at one light point is increased and the intensity of light at the other focal point is decreased.
図8(a)は複屈折材料を含んで構成されたウエハ11の光軸プロファイルを示す図であり、図8(b)は図8(a)に示される光軸プロファイルを考慮して変調パターンが調整された場合の光軸プロファイルを示す図である。図8(a)に示される例では、制御部10は、光軸プロファイルから、上下に分岐された常光線による集光点C1及び異常光線による集光点C2を特定する。そして、制御部10は、当該光軸プロファイルを確認して、図8(b)に示されるように、異常光線による集光点C2における光の強度が大きくなり、常光線による集光点C1における光の強度が小さくなるように、変調パターンを調整する。これにより、光の強度を小さくした集光点C1の影響を極力小さくし、上下に集光点が分岐することによる弊害を抑制することができる。
FIG. 8(a) is a diagram showing an optical axis profile of the wafer 11 including a birefringent material, and FIG. 8(b) is a diagram showing a modulation pattern in consideration of the optical axis profile shown in FIG. 8(a). It is a figure which shows the optical axis profile when adjusted. In the example shown in FIG. 8A, the control unit 10 specifies a focal point C1 of the vertically branched ordinary ray and a focal point C2 of the extraordinary ray from the optical axis profile. Then, the control unit 10 checks the optical axis profile, and as shown in FIG. 8(b), the intensity of the light at the focal point C2 due to the extraordinary ray increases, and the intensity of the light at the focal point C1 due to the ordinary ray increases. Adjust the modulation pattern so that the intensity of the light is reduced. This makes it possible to minimize the influence of the condensing point C1 where the intensity of light is reduced, and to suppress the adverse effects caused by the converging point branching upward and downward.
ここで、常光線による集光点C1及び異常光線による集光点C2のいずれの強度を大きくするか(いずれの集光点を利用するか)については、ウエハ11が正の複屈折材料(図7(a)参照)により構成されているか、又は、負の複屈折材料(図7(b)参照)により構成されているか、によって異なっていてもよい。
Here, the wafer 11 is made of a positive birefringent material (Fig. 7(a)) or a negative birefringent material (see FIG. 7(b)).
例えば、正の複屈折材料(図7(a)参照)を用いる場合について説明する。図9(a)は対策をしていない(2つの集光点の強度比を変えていない)場合の集光点のイメージであり、図9(b)は表面側集光点の強度を大きくした場合の集光点のイメージであり、図9(c)は裏面側集光点の強度を大きくした場合の集光点のイメージである。いま、正の複屈折材料を用いているため、表面側集光点とは常光線による集光点C1である。また、裏面側集光点とは異常光線による集光点C2である。
For example, a case will be described in which a positive birefringent material (see FIG. 7(a)) is used. Figure 9(a) is an image of the focal point when no measures are taken (the intensity ratio of the two focal points is not changed), and Figure 9(b) is an image of the focal point when the intensity of the front-side focal point is increased. FIG. 9C is an image of the focal point when the intensity of the back surface side focal point is increased. Now, since a positive birefringent material is used, the surface-side light convergence point is the light convergence point C1 of ordinary rays. Further, the back surface side focal point is the focal point C2 of the extraordinary ray.
図9(a)に示されるように、2つの集光点C1,C2の強度比を変えていない場合には、より裏面11bに近い異常光線による集光点C2に係る抜け光によって裏面11bに設けられたデバイス(例えば電極200)がダメージを受けることが考えられる。これに対して、図9(b)に示されるように、常光線による集光点C1の強度を大きくし、異常光線による集光点C2の強度を小さくした場合には、より裏面11bに近い異常光線による集光点C2の強度が小さくなるため、図9(a)に示される例よりはデバイス(例えば電極200)がダメージを受けにくくなるものの、集光点C2の影響が残るためデバイス(例えば電極200)のダメージを十分に軽減することができない。ここまでは、常光線による集光点C1を加工狙い高さに設定している例である(図9(a)及び図9(b)参照)。
As shown in FIG. 9(a), when the intensity ratio of the two condensing points C1 and C2 is not changed, the light passing through the condensing point C2 due to the extraordinary ray closer to the back surface 11b causes the back surface 11b to It is conceivable that the provided device (for example, the electrode 200) may be damaged. On the other hand, as shown in FIG. 9(b), when the intensity of the focal point C1 due to the ordinary ray is increased and the intensity of the focal point C2 due to the extraordinary ray is decreased, the intensity is closer to the back surface 11b. Since the intensity of the condensing point C2 due to the extraordinary ray becomes smaller, the device (for example, the electrode 200) is less likely to be damaged than the example shown in FIG. For example, damage to the electrode 200) cannot be sufficiently reduced. Up to this point, the convergence point C1 of the ordinary ray is set at the processing target height (see FIGS. 9(a) and 9(b)).
一方で、図9(c)に示されるように、異常光線による集光点C2を加工狙い高さに設定すると共に、異常光線による集光点C2の強度を大きくし、常光線による集光点C1の強度を小さくした場合には、図9(b)に示される例と比較して、裏面11bから集光点C2までの距離が離れることとなる。この場合、広がった抜け光がデバイス(例えば電極200)にあたることとなるので、デバイス(例えば電極200)のダメージを十分に軽減することができる。なお、異常光線による集光点C2を加工狙い高さに設定するため、異常光線による集光点C2に係るレーザ光によって、適切にレーザ加工を実施することができる。以上のように、正の複屈折材料を用いる場合においては、制御部10は、上記第5処理において、2つの集光点のうち裏面11bに近い側の集光点(異常光線による集光点C2)の光の強度が大きくなり、裏面11bに遠い側の集光点(常光線による集光点C1)における光の強度が小さくなるように、変調パターンを調整してもよい。
On the other hand, as shown in FIG. 9(c), the focal point C2 of the extraordinary ray is set to the processing target height, the intensity of the focal point C2 of the extraordinary ray is increased, and the focal point C2 of the ordinary ray is set to the processing target height. When the intensity of C1 is reduced, the distance from the back surface 11b to the condensing point C2 becomes longer than in the example shown in FIG. 9(b). In this case, since the expanded leaked light hits the device (for example, the electrode 200), damage to the device (for example, the electrode 200) can be sufficiently reduced. In addition, since the focal point C2 of the extraordinary ray is set at the processing target height, laser processing can be appropriately performed using the laser beam related to the focal point C2 of the extraordinary ray. As described above, in the case of using a positive birefringence material, the control unit 10 performs the fifth process to control the light focusing point on the side closer to the back surface 11b (the focusing point caused by the extraordinary ray) of the two light focusing points. The modulation pattern may be adjusted so that the intensity of the light C2) increases, and the intensity of the light at the focal point on the far side from the back surface 11b (the focal point C1 of ordinary rays) decreases.
制御部10は、上記第5処理において、レーザ光における一部の偏光成分を遮断するスリットパターンにより変調パターンを調整してもよい。このようなスリットパターンは、空間光変調器5の液晶層56に表示される変調パターンの一部として設定される。空間光変調器5では、液晶層56に表示される変調パターンが適宜設定されることにより、レーザ光Lが変調(例えば、レーザ光Lの強度、振幅、位相、偏光等が変調)可能となる。変調パターンとは、変調を付与するホログラムパターンであり、スリットパターンを含んでいる。
In the fifth process, the control unit 10 may adjust the modulation pattern using a slit pattern that blocks some polarized components of the laser beam. Such a slit pattern is set as part of the modulation pattern displayed on the liquid crystal layer 56 of the spatial light modulator 5. In the spatial light modulator 5, the laser beam L can be modulated (for example, the intensity, amplitude, phase, polarization, etc. of the laser beam L can be modulated) by appropriately setting the modulation pattern displayed on the liquid crystal layer 56. . The modulation pattern is a hologram pattern that imparts modulation, and includes a slit pattern.
図10(a)はスリットパターン無しの場合の強度比を示す図であり、図10(b)はスリットAを設けた場合の強度比を示す図であり、図11(a)はスリットBを設けた場合の強度比を示す図であり、図11(b)はスリットCを設けた場合の強度比を示す図である。図10(a)~図11(b)のそれぞれにおいて、上段には空間光変調器5の液晶層56に表示される変調パターン(スリットパターンを含む)が示されており、下段には光軸プロファイルの2次元データが示されている。
FIG. 10(a) is a diagram showing the intensity ratio without a slit pattern, FIG. 10(b) is a diagram showing the intensity ratio with slit A, and FIG. 11(a) is a diagram showing the intensity ratio with slit B. 11(b) is a diagram showing the intensity ratio when a slit C is provided. FIG. In each of FIGS. 10(a) to 11(b), the upper row shows the modulation pattern (including the slit pattern) displayed on the liquid crystal layer 56 of the spatial light modulator 5, and the lower row shows the optical axis. Two-dimensional data of the profile is shown.
図10(b)、図11(a)、及び図11(b)に示されるスリットパターンは、それぞれ扇形のスリットが設けられている。以下では、複屈折材料に関して集光点を一点に近づけるための考え方と、扇形のスリットを用いる理由について、説明する。
The slit patterns shown in FIGS. 10(b), 11(a), and 11(b) are each provided with fan-shaped slits. Below, the concept of bringing the focal point closer to one point regarding birefringent materials and the reason for using fan-shaped slits will be explained.
通常、複屈折材料を含むウエハにレーザ光を集光させた場合、レーザ光におけるP偏光成分とS偏光成分とで互いに屈折率が異なる。該レーザ光は常光線と異常光線とに分けられるが、異常光線はスネルの法則に従わずに常光線とは異なる屈折角で光が伝搬する。このため、ウエハの深さ方向において、互いに異なる位置にP偏光成分及びS偏光成分が集光する(集光点が二点となる)。
Normally, when laser light is focused on a wafer containing a birefringent material, the P-polarized light component and the S-polarized light component of the laser light have different refractive indices. The laser beam is divided into ordinary rays and extraordinary rays, but the extraordinary rays do not follow Snell's law and propagate at a different angle of refraction from the ordinary rays. Therefore, the P-polarized light component and the S-polarized light component are focused at different positions in the depth direction of the wafer (there are two focused points).
ラジアル偏光(放射状偏光)はP偏光でウエハに入射する。また、アジマス偏光(方位状偏光)はS偏光でウエハに入射する。このため、直線偏光がラジアル偏光又はアジマス偏光の一方に変換されることにより、レーザ光の偏光成分をP偏光又はS偏光のいずれか一方に統一することができ、集光点を適切に一点に近づけることができる。
The radial polarized light enters the wafer as P-polarized light. Further, the azimuthal polarized light (azimuthally polarized light) enters the wafer as S-polarized light. Therefore, by converting linearly polarized light into either radial or azimuth polarized light, the polarization components of the laser beam can be unified into either P-polarized light or S-polarized light, and the focal point can be appropriately focused on one point. You can get close.
なお、直線偏光から完全にラジアル偏光又はアジマス偏光の一方だけを取り出すことはできない。ただし、上述したようなスリットをかけることにより、どちらか一方の強度比を高めることができる。特に、図10(b)、図11(a)、及び図11(b)に記載したような、光軸の中心を境にした扇形のスリットを用いることにより、効果的に、ラジアル偏光又はアジマス偏光の一方の偏光を利用することができる。例えば、直線偏光からラジアル偏光成分のみを活用して加工したい場合を考える。直線型のスリットを用いる場合、スリットを狭めないとアジマス偏光成分が残ってしまうが、スリットを狭めると有効なパターン面積が狭くなってしまう。この点、扇形のスリットでは、有効なパターン面積を確保したまま、ラジアル成分が強い部分を用いた加工を行うことができる。
Note that it is not possible to completely extract either radial polarization or azimuth polarization from linearly polarized light. However, by providing slits as described above, the strength ratio of either one can be increased. In particular, by using a fan-shaped slit bordering the center of the optical axis as shown in FIGS. 10(b), 11(a), and 11(b), radial polarization or azimuth One of the polarizations can be used. For example, consider a case where you want to process using only the radial polarized component of linearly polarized light. When using a linear slit, the azimuthal polarization component will remain unless the slit is narrowed, but if the slit is narrowed, the effective pattern area will become narrower. In this regard, with fan-shaped slits, processing can be performed using areas with strong radial components while maintaining an effective pattern area.
図10(b)に示される扇形のスリットAが設けられたスリットパターンSP2を含む変調パターンMP2と、図11(a)に示される扇形のスリットBが設けられたスリットパターンSP3を含む変調パターンMP3と、図11(b)に示される扇形のスリットCが設けられたスリットパターンSP4を含む変調パターンMP4とを比較すると、スリットパターンSP2の面積よりもスリットパターンSP3の面積が大きく、該スリットパターンSP3の面積よりもスリットパターンSP4の面積が大きい。この場合、異常光線による集光点C2及び常光線による集光点C1の強度差は、スリットパターン無し(図10(a))が最も小さくなり、スリットパターンSP2を含む変調パターンMP2(図10(b))が次に小さくなり、スリットパターンSP3を含む変調パターンMP3(図11(a))が次に小さくなり、スリットパターンSP4を含む変調パターンMP4(図11(b))が最も大きくなる。
A modulation pattern MP2 including a slit pattern SP2 provided with a sector-shaped slit A shown in FIG. 10(b), and a modulation pattern MP3 including a slit pattern SP3 provided with a sector-shaped slit B shown in FIG. 11(a). When compared with the modulation pattern MP4 including the slit pattern SP4 provided with fan-shaped slits C shown in FIG. 11(b), the area of the slit pattern SP3 is larger than the area of the slit pattern SP2. The area of slit pattern SP4 is larger than the area of . In this case, the difference in intensity between the focal point C2 due to the extraordinary ray and the focal point C1 due to the ordinary ray is the smallest for the case without a slit pattern (FIG. 10(a)), and the difference in intensity between the focal point C2 due to the extraordinary ray and the focal point C1 due to the ordinary ray is the smallest for the modulation pattern MP2 including the slit pattern SP2 (FIG. 10(a)). b)) becomes the next smallest, the modulation pattern MP3 (FIG. 11(a)) including the slit pattern SP3 becomes the next smallest, and the modulation pattern MP4 (FIG. 11(b)) including the slit pattern SP4 becomes the largest.
上述したように、スリットパターン面積を広げるほど2つの集光点の強度差が大きくなるが、有効なパターン面積が狭まるためレーザ光の出力を上げる必要がある。また、分岐等の他のパターンと合成した際の影響が出やすくなる。例えば、図11(b)に示される変調パターンMP4では、スリットパターンSP4によりレーザ光をカットしすぎてしまい、非点収差が発生する等、集光性に悪影響が出てしまっている。
As mentioned above, as the slit pattern area increases, the difference in intensity between the two focal points increases, but since the effective pattern area narrows, it is necessary to increase the output of the laser beam. In addition, it is more likely to be affected when combined with other patterns such as branches. For example, in the modulation pattern MP4 shown in FIG. 11(b), the laser beam is cut too much by the slit pattern SP4, resulting in astigmatism and other adverse effects on light focusing performance.
図12は、変調パターン調整処理のフローチャートである。変調パターン調整処理では、最初に、集光点付近の光軸プロファイルが取得される(ステップS101)。
FIG. 12 is a flowchart of modulation pattern adjustment processing. In the modulation pattern adjustment process, first, an optical axis profile near the focal point is acquired (step S101).
つづいて、常光線による集光点C1から異常光線による集光点C2までの距離が測定される(ステップS102)。当該距離は、常光線の屈折率で加工条件を作成していると仮定した場合、レーザ加工において異常光線を用いる場合に、異常光線による集光点C2を加工狙い高さに設定する際に必要になる情報である。
Next, the distance from the focal point C1 of the ordinary ray to the focal point C2 of the extraordinary ray is measured (step S102). This distance is necessary when setting the focal point C2 of the extraordinary ray to the processing target height when using the extraordinary ray in laser processing, assuming that the processing conditions are created using the refractive index of the ordinary ray. This is information that will become
つづいて、レーザ加工において異常光線を用いるか否かが判定される(ステップS103)。ステップS103において異常光線を用いると判定された場合には、異常光線による集光点C2の強度が大きくなるように変調パターンの調整が行われる(ステップS104)。
Next, it is determined whether or not to use an extraordinary ray in laser processing (step S103). If it is determined in step S103 that an extraordinary ray is to be used, the modulation pattern is adjusted so that the intensity of the focal point C2 due to the extraordinary ray is increased (step S104).
そして、変調パターンの調整後において、再度集光点付近の光軸プロファイルが取得される(ステップS105)。そして、異常光線による集光点C2及び常光線による集光点C1の強度が比較され(ステップS106)、正常範囲内であるか否かが判定される(ステップS107)。正常範囲内でない場合には、再度ステップS104の処理が実施される。正常範囲内である場合には、ステップS102において取得された距離が加工レシピに反映され、異常光線による集光点C2が加工狙い高さに設定される(ステップS108)。
After adjusting the modulation pattern, the optical axis profile near the focal point is acquired again (step S105). Then, the intensities of the focal point C2 due to the extraordinary ray and the focal point C1 due to the ordinary ray are compared (step S106), and it is determined whether they are within the normal range (step S107). If it is not within the normal range, the process of step S104 is performed again. If it is within the normal range, the distance acquired in step S102 is reflected in the machining recipe, and the focal point C2 of the abnormal ray is set to the target machining height (step S108).
一方で、ステップS103において異常光線を用いない(常光線を用いる)と判定された場合には、常光線による集光点C1の強度が大きくなるように変調パターンの調整が行われる(ステップS109)。
On the other hand, if it is determined in step S103 that the extraordinary ray is not used (ordinary ray is used), the modulation pattern is adjusted so that the intensity of the focal point C1 by the ordinary ray is increased (step S109). .
そして、変調パターンの調整後において、再度集光点付近の光軸プロファイルが取得される(ステップS110)。そして、常光線による集光点C1及び異常光線による集光点C2の強度が比較され(ステップS111)、正常範囲内であるか否かが判定される(ステップS112)。正常範囲内でない場合には、再度ステップS109の処理が実施され、正常範囲内である場合には処理が終了する。
[レーザ加工装置のエラー状態特定] After adjusting the modulation pattern, the optical axis profile near the focal point is acquired again (step S110). Then, the intensities of the focal point C1 of the ordinary ray and the focal point C2 of the extraordinary ray are compared (step S111), and it is determined whether they are within the normal range (step S112). If it is not within the normal range, the process of step S109 is executed again, and if it is within the normal range, the process ends.
[Identification of error status of laser processing equipment]
[レーザ加工装置のエラー状態特定] After adjusting the modulation pattern, the optical axis profile near the focal point is acquired again (step S110). Then, the intensities of the focal point C1 of the ordinary ray and the focal point C2 of the extraordinary ray are compared (step S111), and it is determined whether they are within the normal range (step S112). If it is not within the normal range, the process of step S109 is executed again, and if it is within the normal range, the process ends.
[Identification of error status of laser processing equipment]
制御部10は、第4処理において取得された光軸プロファイルと、比較用のプロファイル画像である比較データとを比較し、比較したデータ間の差分が所定範囲内である場合に光軸プロファイルが正常であると判定し、該差分が所定範囲外である場合に光軸プロファイルが異常であると判定し、判定結果を出力する第6処理を更に実行してもよい。ここでの光軸プロファイルが異常であるとは、レーザ加工装置1が何らかのエラー状態にあることを意味している。
The control unit 10 compares the optical axis profile acquired in the fourth process with comparison data that is a profile image for comparison, and determines that the optical axis profile is normal if the difference between the compared data is within a predetermined range. If the difference is outside a predetermined range, the optical axis profile is determined to be abnormal, and a sixth process may be further executed in which the determination result is output. Here, the fact that the optical axis profile is abnormal means that the laser processing apparatus 1 is in some kind of error state.
制御部10は、例えば過去に取得された光軸プロファイルを、比較用のプロファイル画像としてもよい。或いは、制御部10は、例えばシミュレーションを基に作成されたデータを、比較用のプロファイル画像としてもよい。
The control unit 10 may use, for example, an optical axis profile acquired in the past as a profile image for comparison. Alternatively, the control unit 10 may use, for example, data created based on simulation as the profile image for comparison.
制御部10は、光軸プロファイルにおいて集光点が確認されない場合には、重度のエラーと判定し、該判定結果を出力する。重度のエラーとは、例えばレーザ加工装置の異常や測定ミス(ウエハ誤り)等である。また、制御部10は、集光状態が理想的な状態と異なる場合において、レーザ光の調整が正しい場合には空間光変調器5の異常(例えば球面収差、歪補正の誤り等)であると判定し、レーザ光の調整が正しくない場合にはレーザ光の再調整を実施する。
If the focal point is not confirmed in the optical axis profile, the control unit 10 determines that there is a severe error and outputs the determination result. Severe errors include, for example, abnormalities in laser processing equipment and measurement errors (wafer errors). In addition, when the condensing state differs from the ideal state and the adjustment of the laser beam is correct, the control unit 10 determines that there is an abnormality in the spatial light modulator 5 (for example, spherical aberration, error in distortion correction, etc.). If the adjustment of the laser beam is incorrect, the laser beam is readjusted.
図13は、レーザ加工装置1のエラー状態特定処理のフローチャートである。エラー状態特定処理では、最初に、集光点付近の光軸プロファイルが取得される(ステップS201)。
FIG. 13 is a flowchart of the error state identification process of the laser processing apparatus 1. In the error state identification process, first, an optical axis profile near the focal point is acquired (step S201).
つづいて、取得された光軸プロファイルと、比較用のプロファイル画像(例えば過去に取得された光軸プロファイル)である比較データとが比較され(ステップS202)、比較したデータ間の差分が所定の正常範囲内であるか否かが判定される(ステップS203)。データ間の差分とは、例えば集光点の位置、強度等の差分である。ステップS203において正常であると判定された場合には、制御部10によって正常である旨が表示される(ステップS204)。
Subsequently, the acquired optical axis profile is compared with comparison data that is a profile image for comparison (for example, an optical axis profile acquired in the past) (step S202), and the difference between the compared data is determined to be normal. It is determined whether it is within the range (step S203). The difference between the data is, for example, the difference in the position of the focal point, the intensity, etc. If it is determined in step S203 that it is normal, the control unit 10 displays that it is normal (step S204).
ステップS203において正常でないと判定された場合には、制御部10によってエラーである旨が表示される(ステップS205)。そして、制御部10によってエラー内容が確認され、集光点が存在しないか否かが判定される(ステップS206)。ステップS206において集光点が存在しないと判定された場合には、重度のエラーであると判定される(ステップS207)。重度のエラーとは、例えばレーザ加工装置の異常や測定ミス(ウエハ誤り等)である。
If it is determined in step S203 that it is not normal, the control unit 10 displays an error message (step S205). Then, the control unit 10 confirms the error details and determines whether or not there is no focal point (step S206). If it is determined in step S206 that the focal point does not exist, it is determined that a serious error has occurred (step S207). A severe error is, for example, an abnormality in a laser processing device or a measurement error (wafer error, etc.).
ステップS206において集光点が存在すると判定された場合には、制御部10によって、レーザ光の調整が正しいか否かが判定される(ステップS208)。レーザ光の調整が正しい場合には、空間光変調器5の異常(例えば球面収差、歪補正の誤り等)であると判定され(ステップS209)、レーザ光の調整が正しくない場合にはレーザ光の再調整が実施される(ステップS210)。
[球面収差調整] If it is determined in step S206 that a focal point exists, thecontrol unit 10 determines whether the adjustment of the laser beam is correct (step S208). If the adjustment of the laser beam is correct, it is determined that there is an abnormality in the spatial light modulator 5 (for example, spherical aberration, error in distortion correction, etc.) (step S209); if the adjustment of the laser beam is incorrect, the laser beam is Readjustment is performed (step S210).
[Spherical aberration adjustment]
[球面収差調整] If it is determined in step S206 that a focal point exists, the
[Spherical aberration adjustment]
制御部10は、変調パターンにより定まる球面収差の条件を変えながら、それぞれの条件下で、上述した第1処理、第2処理、第3処理、及び第4処理を実施し、第5処理において、各条件下で取得された光軸プロファイルが示すレーザ光の輝度値の最大値を互いに比較し、輝度値が最大である光軸プロファイルに係る球面収差の条件となるように、変調パターンを調整してもよい。
The control unit 10 performs the above-described first processing, second processing, third processing, and fourth processing under each condition while changing the spherical aberration conditions determined by the modulation pattern, and in the fifth processing, The maximum brightness values of the laser beams indicated by the optical axis profiles obtained under each condition are compared, and the modulation pattern is adjusted to meet the spherical aberration conditions associated with the optical axis profile with the maximum brightness value. It's okay.
例えば屈折率が未知のウエハ11については、適切でない変調パターンで加工されてしまう場合がある。この点、図14(a)に示されるように、光軸プロファイルが取得されることによって、集光点の位置がずれていることが特定され、屈折率が未知のウエハ11に対して適切でない変調パターンが設定されていることに気づくことができる。そして、制御部10は、図14(a)に示されるような光軸プロファイルを確認しながら、図14(b)に示されるような光軸プロファイルが取得されるように、球面収差補正を行うことにより、屈折率が未知のウエハ11のレーザ加工に関して、適切な変調パターンを設定することができる。
For example, a wafer 11 whose refractive index is unknown may be processed with an inappropriate modulation pattern. In this regard, as shown in FIG. 14(a), by acquiring the optical axis profile, it is determined that the position of the focal point is shifted, and it is not appropriate for the wafer 11 whose refractive index is unknown. You can notice that a modulation pattern has been set. Then, while checking the optical axis profile as shown in FIG. 14(a), the control unit 10 performs spherical aberration correction so that the optical axis profile as shown in FIG. 14(b) is acquired. This makes it possible to set an appropriate modulation pattern for laser processing of the wafer 11 whose refractive index is unknown.
制御部10は、例えば基準とする球面収差に対して、補正値を変更しながら補正を行い、集光点における輝度値が最大となる補正値を選択し、該補正値による補正後の球面収差の条件となるように変調パターンを調整する。基準とする球面収差は、例えば、ウエハ11の厚さの2倍の球面収差とされてもよい。
For example, the control unit 10 corrects the reference spherical aberration while changing the correction value, selects the correction value that maximizes the brightness value at the focal point, and adjusts the spherical aberration after correction using the correction value. Adjust the modulation pattern to meet the conditions. The reference spherical aberration may be, for example, twice the thickness of the wafer 11.
図15に示される例では、基準となる球面収差に対して、補正値Aにより補正を行った場合、補正値Bにより補正を行った場合、補正値Cにより補正を行った場合、補正値Dにより補正を行った場合、のそれぞれについて、最大輝度値が示されている。そして、これらの結果を考慮して、最適な補正値により補正を行って、最大輝度:248の球面収差の条件となるように変調パターンが調整されている。
In the example shown in FIG. 15, when the reference spherical aberration is corrected using the correction value A, when it is corrected using the correction value B, when it is corrected using the correction value C, when it is corrected using the correction value D, The maximum luminance value is shown for each of the cases in which the correction is performed. Then, in consideration of these results, the modulation pattern is adjusted using the optimum correction value to achieve the spherical aberration condition of maximum brightness: 248.
図16は、球面収差調整処理を示すフローチャートである。球面収差調整処理では、最初に、最適と思われる、ウエハ厚さの2倍の球面収差が基準に決定される(ステップS301)。そして、制御部10によって、基準とした球面収差の条件となるように変調パターンが設定され(ステップS302)、集光点付近の光軸プロファイルが取得される(ステップS303)。
FIG. 16 is a flowchart showing the spherical aberration adjustment process. In the spherical aberration adjustment process, first, a spherical aberration of twice the wafer thickness, which is considered to be optimal, is determined as a reference (step S301). Then, the control unit 10 sets a modulation pattern to satisfy the reference spherical aberration condition (step S302), and obtains an optical axis profile near the focal point (step S303).
また、制御部10によって、基準とした球面収差より任意の値だけ小さい球面収差の条件となるように変調パターンが設定され(ステップS304)、集光点付近の光軸プロファイルが取得される(ステップS305)。また、制御部10によって、基準とした球面収差より任意の値だけ大きい球面収差の条件となるように変調パターンが設定され(ステップS306)、集光点付近の光軸プロファイルが取得される(ステップS307)。
In addition, the control unit 10 sets a modulation pattern such that the spherical aberration is smaller by an arbitrary value than the reference spherical aberration (step S304), and obtains an optical axis profile near the focal point (step S304). S305). In addition, the control unit 10 sets a modulation pattern such that the spherical aberration is larger than the reference spherical aberration by an arbitrary value (step S306), and obtains an optical axis profile near the focal point (step S306). S307).
つづいて、制御部10によって、取得された光軸プロファイルに基づき、基準とした球面収差より任意の値小さい球面収差に設定したほうが、最大輝度値が大きいか否かが判定される(ステップS308)。ステップS308において任意の値小さい球面収差に設定したほうが、最大輝度値が大きいと判定された場合、制御部10によって、任意の値小さい球面収差が新たな基準に設定されて(ステップS309)、再度ステップS302以降の処理が実施される。
Next, the control unit 10 determines whether the maximum brightness value is larger if the spherical aberration is set to an arbitrary value smaller than the reference spherical aberration, based on the acquired optical axis profile (step S308). . If it is determined in step S308 that setting the spherical aberration smaller by an arbitrary value will result in a larger maximum luminance value, the control unit 10 sets the spherical aberration smaller by an arbitrary value as a new standard (step S309), and again Processing after step S302 is performed.
一方で、ステップS308において、任意の値小さい球面収差に設定したほうが、最大輝度値が大きくない(すなわち基準に設定したほうが、最大輝度値が大きい)と判定された場合、制御部10によって、基準とした球面収差が、最大輝度値が最大であるか否かが判定される(ステップS310)。ステップS310において、基準とした球面収差が、最大輝度値が最大であると判定された場合、制御部10によって、基準とした球面収差の1/2の値が加工レシピに反映される(ステップS311)。
On the other hand, if it is determined in step S308 that the maximum brightness value is not larger when the spherical aberration is set to a smaller arbitrary value (that is, the maximum brightness value is larger when set to the standard), the control unit 10 It is determined whether or not the maximum brightness value of the spherical aberration is the maximum (step S310). In step S310, if it is determined that the reference spherical aberration has the maximum maximum brightness value, the control unit 10 reflects a value of 1/2 of the reference spherical aberration in the processing recipe (step S311 ).
一方で、ステップS310において、基準とした球面収差が、最大輝度値が最大でない(すなわち、任意の値大きい球面収差が、最大輝度値が最大である)と判定された場合、制御部10によって、任意の値大きい球面収差が新たな基準に設定されて(ステップS312)、再度ステップS302以降の処理が実施される。
[作用効果] On the other hand, if it is determined in step S310 that the maximum brightness value of the reference spherical aberration is not the maximum (that is, the spherical aberration that is arbitrarily large has the maximum maximum brightness value), the control unit 10 A spherical aberration with an arbitrarily large value is set as a new reference (step S312), and the processes from step S302 onwards are performed again.
[Effect]
[作用効果] On the other hand, if it is determined in step S310 that the maximum brightness value of the reference spherical aberration is not the maximum (that is, the spherical aberration that is arbitrarily large has the maximum maximum brightness value), the control unit 10 A spherical aberration with an arbitrarily large value is set as a new reference (step S312), and the processes from step S302 onwards are performed again.
[Effect]
レーザ加工装置1は、表面11a及び裏面11bを有するウエハ11を支持する支持部2と、レーザ光を出射する光源3と、光源3から出射されたレーザ光を変調する空間光変調器5と、空間光変調器5によって変調されたレーザ光をウエハ11の表面11a側からウエハ11に集光する集光部6と、集光部6を、表面11aに対して垂直な方向である光軸方向に、表面11aに対して相対的に移動させる移動部7と、集光部6を介してウエハ11を伝搬した光を検出することにより撮像画像を取得する可視撮像部8と、集光部6が光軸方向において表面11aに対して相対的に移動するように移動部7を制御する第1処理と、第1処理が実行されている状態において連続的にレーザ光が出射されるように光源3を制御する第2処理と、第2処理が実行されている状態においてウエハ11の裏面11bにおいて反射された光が検出されて連続的に複数の撮像画像が取得されるように可視撮像部8を制御する第3処理と、第3処理において連続的に取得された複数の撮像画像を合成することにより、光軸方向に沿ったレーザ光のプロファイル画像である光軸プロファイルを取得する第4処理と、を実行するように構成された制御部10と、を備える。
The laser processing apparatus 1 includes a support section 2 that supports a wafer 11 having a front surface 11a and a back surface 11b, a light source 3 that emits laser light, and a spatial light modulator 5 that modulates the laser light emitted from the light source 3. A focusing section 6 focuses the laser beam modulated by the spatial light modulator 5 onto the wafer 11 from the surface 11a side of the wafer 11, and the focusing section 6 is aligned in the optical axis direction, which is a direction perpendicular to the surface 11a. , a moving section 7 that moves relative to the surface 11a, a visible imaging section 8 that acquires a captured image by detecting the light propagated through the wafer 11 via the light condensing section 6, and a light condensing section 6. A first process for controlling the moving unit 7 so that the moving part 7 moves relative to the surface 11a in the optical axis direction, and a light source for continuously emitting laser light while the first process is being performed. 3, and a visible imaging unit 8 so that light reflected on the back surface 11b of the wafer 11 is detected and a plurality of captured images are continuously acquired while the second processing is being executed. and a fourth process to obtain an optical axis profile, which is a profile image of the laser beam along the optical axis direction, by combining a plurality of captured images continuously acquired in the third process. and a control unit 10 configured to execute the following.
本実施形態に係るレーザ加工装置1では、集光部6を光軸方向に移動させながらレーザ光が照射され、ウエハ11の裏面11bにおいて反射された光が検出されて連続的に複数の撮像画像が取得される。そして、本レーザ加工装置1では、複数の撮像画像が合成されることにより、光軸方向に沿ったレーザ光のプロファイル画像である光軸プロファイルが取得される。このように、レーザ光の集光点を光軸方向(ウエハ11の深さ方向)に移動させながら、ウエハ11の裏面11bからの反射光が検出されて、上記光軸プロファイルが取得されることにより、光軸方向に沿ったレーザ光の照射状況(例えば集光点の位置や強度)の把握が可能になる。これにより、例えば、レーザ加工装置1における何らかの異常の発生有無や、空間光変調器5に設定される変調パターンの調整の要否等を判断することができ、より適切に所望のレーザ加工を実施することができる。
In the laser processing apparatus 1 according to the present embodiment, a laser beam is irradiated while moving the light condensing unit 6 in the optical axis direction, and the light reflected on the back surface 11b of the wafer 11 is detected and a plurality of captured images are continuously generated. is obtained. In the present laser processing apparatus 1, a plurality of captured images are combined to obtain an optical axis profile that is a profile image of the laser beam along the optical axis direction. In this way, while moving the focal point of the laser beam in the optical axis direction (in the depth direction of the wafer 11), the reflected light from the back surface 11b of the wafer 11 is detected, and the optical axis profile is acquired. This makes it possible to grasp the laser beam irradiation status (for example, the position and intensity of the condensing point) along the optical axis direction. As a result, it is possible to determine, for example, whether any abnormality has occurred in the laser processing device 1, whether or not the modulation pattern set in the spatial light modulator 5 needs to be adjusted, and perform the desired laser processing more appropriately. can do.
制御部10は、第4処理において取得された光軸プロファイルに基づき、空間光変調器5の変調パターンを調整する第5処理を更に実行してもよい。このような構成によれば、光軸プロファイルを考慮して変調パターンを最適化することができ、より適切に所望のレーザ加工を実施することができる。
The control unit 10 may further execute a fifth process of adjusting the modulation pattern of the spatial light modulator 5 based on the optical axis profile acquired in the fourth process. According to such a configuration, the modulation pattern can be optimized in consideration of the optical axis profile, and desired laser processing can be performed more appropriately.
ウエハ11は、複屈折材料を含んで構成されており、制御部10は、第5処理において、光軸プロファイルに基づき、常光線に係る集光点と異常光線に係る集光点とを特定し、特定した2つの集光点のうち一方の集光点における光の強度が大きくなり、他方の集光点における光の強度が小さくなるように、変調パターンを調整してもよい。複屈折材料を含んで構成されたウエハ11にレーザ光を集光させる場合、入射光におけるP偏光成分とS偏光成分とで屈折率が互いに異なる。また、それらの入射光は常光線と異常光線とに分けられるが、その中の異常光線はスネルの法則に従わず常光線とは異なる屈折角で光が伝搬する。これらのことから、ウエハ11の深さ方向において、互いに異なる位置にP偏光成分及びS偏光成分が集光する。このように集光点が深さ方向に分岐することによってウエハ11において意図せず複数の集光点が形成されることとなり、適切でない亀裂を生じさせてしまう。このことで、例えばスライシング等の加工の品質が低下するおそれがある。この点、光軸プロファイルに基づき、一方の集光点の強度が大きくなり、且つ、他方の集光点の強度が小さくなるように変調パターンが調整されることにより、上述した複数の集光点が形成されることによる加工品質の低下を抑制することができる。
The wafer 11 is configured to include a birefringent material, and in the fifth process, the control unit 10 identifies a focal point for ordinary rays and a focal point for extraordinary rays based on the optical axis profile. The modulation pattern may be adjusted so that the intensity of light at one of the two identified focal points is increased and the intensity of light at the other focal point is decreased. When laser light is focused on the wafer 11 that includes a birefringent material, the refractive indexes of the P-polarized light component and the S-polarized light component of the incident light are different from each other. Furthermore, these incident lights are divided into ordinary rays and extraordinary rays, but the extraordinary rays do not follow Snell's law and propagate at a different angle of refraction than the ordinary rays. For these reasons, the P-polarized light component and the S-polarized light component are focused at different positions in the depth direction of the wafer 11. By branching the focal point in the depth direction in this manner, a plurality of focal points are unintentionally formed on the wafer 11, resulting in formation of inappropriate cracks. This may reduce the quality of processing such as slicing. In this regard, by adjusting the modulation pattern based on the optical axis profile so that the intensity of one focal point becomes large and the intensity of the other focal point becomes small, the plurality of focal points described above can be adjusted. It is possible to suppress deterioration in processing quality due to the formation of .
制御部10は、第5処理において、2つの集光点のうち、裏面11bに近い側の集光点における光の強度が大きくなり、裏面11bに遠い側の集光点における光の強度が小さくなるように、変調パターンを調整してもよい。変調パターンの調整によって、2つの集光点の強度比を変えることはできるが、いずれかの集光点を完全になくすことはできない。例えば、裏面11bに遠い側の集光点を主に利用し、裏面11bに近い側の集光点を極力小さくする場合には、裏面11bに遠い側の集光点が加工狙い高さに設定され、微弱ではあるものの裏面11bに近い側の集光点が存在することとなる。裏面11bには、デバイスが設けられているため、裏面11bに近い側の集光点の影響によってデバイスにダメージが生じてしまうことが考えられる。この点、裏面11bに近い側の集光点を主に利用する場合には、裏面11bに近い側の集光点が加工狙い高さに設定され、それよりも裏面11b側に集光点が存在しないこととなるので、裏面11bのデバイスのダメージを軽減することができる。
In the fifth process, the control unit 10 increases the intensity of the light at the focal point closer to the back surface 11b among the two focal points, and decreases the intensity of the light at the focal point farther from the back surface 11b. The modulation pattern may be adjusted so that Although the intensity ratio of the two focal points can be changed by adjusting the modulation pattern, one of the focal points cannot be completely eliminated. For example, if you mainly use the focal point on the side far from the back surface 11b and make the focal point on the side close to the back surface 11b as small as possible, the focal point on the side far from the back surface 11b is set to the processing target height. Therefore, there is a focal point near the back surface 11b, although it is weak. Since a device is provided on the back surface 11b, it is conceivable that the device may be damaged due to the influence of the light condensing point on the side closer to the back surface 11b. In this regard, if the focal point on the side closer to the back surface 11b is mainly used, the focal point on the side closer to the back surface 11b is set at the processing target height, and the focal point on the side closer to the back surface 11b is set to the processing target height. Since it does not exist, damage to the device on the back surface 11b can be reduced.
制御部は、第5処理において、レーザ光における一部の偏光成分を遮断するスリットパターンにより変調パターンを調整してもよい。このような構成によれば、容易に、いずれかの集光点の強度を弱めることができる。
In the fifth process, the control unit may adjust the modulation pattern using a slit pattern that blocks some polarized components of the laser beam. According to such a configuration, the intensity of any one of the focal points can be easily weakened.
制御部10は、変調パターンにより定まる球面収差の条件を変えながら、それぞれの条件下で、第1処理、第2処理、第3処理、及び第4処理を実施し、第5処理において、各条件下で取得された光軸プロファイルが示すレーザ光の輝度値の最大値を互いに比較し、輝度値が最大である光軸プロファイルに係る球面収差の条件となるように、変調パターンを調整してもよい。このような構成によれば、例えば屈折率が未知のウエハ11に対しても、適切な球面収差補正を実施することができる。
The control unit 10 performs the first processing, the second processing, the third processing, and the fourth processing under each condition while changing the spherical aberration conditions determined by the modulation pattern, and in the fifth processing, each condition is changed. The maximum brightness values of the laser beams indicated by the optical axis profiles obtained below are compared with each other, and the modulation pattern is adjusted to meet the spherical aberration conditions related to the optical axis profile with the maximum brightness value. good. According to such a configuration, appropriate spherical aberration correction can be performed, for example, even for the wafer 11 whose refractive index is unknown.
制御部10は、第4処理において取得された光軸プロファイルと、比較用のプロファイル画像である比較データとを比較し、比較したデータ間の差分が所定範囲内である場合に光軸プロファイルが正常であると判定し、差分が所定範囲外である場合に光軸プロファイルが異常であると判定し、判定結果を出力する第6処理を更に実行してもよい。このような構成によれば、レーザ加工装置が正常である場合のプロファイル画像を比較データとして設定しておくことにより、光軸プロファイルと比較データとの比較に基づき、レーザ加工装置1において何らかの異常が発生しているか否かを容易に判定することができる。そして、判定結果が出力されることによって、該判定結果を考慮してレーザ加工装置1の調整を実施することが可能になる。以上のように、上述した構成によれば、より適切に所望のレーザ加工を実施することができる。
The control unit 10 compares the optical axis profile acquired in the fourth process with comparison data that is a profile image for comparison, and determines that the optical axis profile is normal if the difference between the compared data is within a predetermined range. If the difference is outside a predetermined range, the optical axis profile is determined to be abnormal, and a sixth process may be further executed in which the determination result is output. According to such a configuration, by setting the profile image when the laser processing device is normal as comparison data, it is possible to detect any abnormality in the laser processing device 1 based on the comparison between the optical axis profile and the comparison data. It is possible to easily determine whether or not this has occurred. Then, by outputting the determination result, it becomes possible to adjust the laser processing apparatus 1 in consideration of the determination result. As described above, according to the configuration described above, desired laser processing can be performed more appropriately.
制御部10は、第2処理において、ウエハ11加工時における出力よりも低い出力のレーザ光が出射されるように、光源3を制御してもよい。これにより、実際のレーザ加工を行うことなく、光軸プロファイルを取得することができる。
In the second process, the control unit 10 may control the light source 3 so that a laser beam with a lower output than the output when processing the wafer 11 is emitted. Thereby, an optical axis profile can be obtained without performing actual laser processing.
光軸プロファイルは、複数の2次元の撮像画像が合成されることにより取得される3次元データであってもよい。3次元データとして光軸プロファイルが取得されることによって、光軸方向に沿ったレーザ光の照射状況(例えば集光点の位置や強度)をより詳細に把握することができる。
The optical axis profile may be three-dimensional data obtained by combining a plurality of two-dimensional captured images. By acquiring the optical axis profile as three-dimensional data, it is possible to understand the laser beam irradiation situation (for example, the position and intensity of the condensing point) along the optical axis direction in more detail.
1…レーザ加工装置、2…支持部、3…光源、5…空間光変調器、6…集光部、7…移動部、8…可視撮像部(撮像部)、10…制御部、11…ウエハ、11a…表面(第1表面)、11b…裏面(第2表面)。
DESCRIPTION OF SYMBOLS 1... Laser processing device, 2... Support part, 3... Light source, 5... Spatial light modulator, 6... Condensing part, 7... Moving part, 8... Visible imaging part (imaging part), 10... Control part, 11... Wafer, 11a...front surface (first surface), 11b...back surface (second surface).
Claims (18)
- 第1表面及び第2表面を有するウエハを支持する支持部と、
レーザ光を出射する光源と、
前記光源から出射された前記レーザ光を変調する空間光変調器と、
前記空間光変調器によって変調された前記レーザ光を前記ウエハの前記第1表面側から前記ウエハに集光する集光部と、
前記集光部を、前記第1表面に対して垂直な方向である光軸方向に、前記第1表面に対して相対的に移動させる移動部と、
前記集光部を介して前記ウエハを伝搬した光を検出することにより撮像画像を取得する撮像部と、
前記集光部が前記光軸方向において前記第1表面に対して相対的に移動するように前記移動部を制御する第1処理と、前記第1処理が実行されている状態において連続的に前記レーザ光が出射されるように前記光源を制御する第2処理と、前記第2処理が実行されている状態において前記ウエハの第2表面において反射された光が検出されて連続的に複数の前記撮像画像が取得されるように前記撮像部を制御する第3処理と、前記第3処理において連続的に取得された前記複数の撮像画像を合成することにより、前記光軸方向に沿った前記レーザ光のプロファイル画像である光軸プロファイルを取得する第4処理と、を実行するように構成された制御部と、を備えるレーザ加工装置。 a support part that supports a wafer having a first surface and a second surface;
a light source that emits laser light;
a spatial light modulator that modulates the laser light emitted from the light source;
a condensing unit that condenses the laser beam modulated by the spatial light modulator onto the wafer from the first surface side of the wafer;
a moving unit that moves the light condensing unit relative to the first surface in an optical axis direction that is perpendicular to the first surface;
an imaging unit that acquires a captured image by detecting light propagated through the wafer via the light condensing unit;
a first process of controlling the moving unit so that the light condensing unit moves relative to the first surface in the optical axis direction; a second process of controlling the light source so that a laser beam is emitted; and a second process of controlling the light source so that a laser beam is emitted; A third process of controlling the image capturing unit so that a captured image is obtained, and a combination of the plurality of captured images that are continuously captured in the third process, the laser beam along the optical axis direction is A laser processing device comprising: a control unit configured to execute a fourth process of acquiring an optical axis profile that is a profile image of light; - 前記制御部は、前記第4処理において取得された前記光軸プロファイルに基づき、前記空間光変調器の変調パターンを調整する第5処理を更に実行する、請求項1記載のレーザ加工装置。 The laser processing apparatus according to claim 1, wherein the control unit further executes a fifth process of adjusting a modulation pattern of the spatial light modulator based on the optical axis profile acquired in the fourth process.
- 前記ウエハは、複屈折材料を含んで構成されており、
前記制御部は、前記第5処理において、前記光軸プロファイルに基づき、常光線に係る集光点と異常光線に係る集光点とを特定し、特定した2つの集光点のうち一方の集光点における光の強度が大きくなり、他方の集光点における光の強度が小さくなるように、前記変調パターンを調整する、請求項2記載のレーザ加工装置。 The wafer is configured to include a birefringent material,
In the fifth process, the control unit specifies a focal point for ordinary rays and a focal point for extraordinary rays based on the optical axis profile, and selects one of the two identified focal points. 3. The laser processing apparatus according to claim 2, wherein the modulation pattern is adjusted so that the intensity of light at one light point is increased and the intensity of light at the other focal point is decreased. - 前記制御部は、前記第5処理において、前記2つの集光点のうち、前記第2表面に近い側の集光点における光の強度が大きくなり、前記第2表面に遠い側の集光点における光の強度が小さくなるように、前記変調パターンを調整する、請求項3記載のレーザ加工装置。 In the fifth process, the control unit may increase the intensity of light at a focal point closer to the second surface among the two focal points, and increase the intensity of light at a focal point farther from the second surface. 4. The laser processing apparatus according to claim 3, wherein the modulation pattern is adjusted so that the intensity of the light at is reduced.
- 前記制御部は、前記第5処理において、前記レーザ光における一部の偏光成分を遮断するスリットパターンにより前記変調パターンを調整する、請求項2記載のレーザ加工装置。 3. The laser processing apparatus according to claim 2, wherein the control unit adjusts the modulation pattern in the fifth process using a slit pattern that blocks some polarized components in the laser beam.
- 前記制御部は、
前記変調パターンにより定まる球面収差の条件を変えながら、それぞれの条件下で、前記第1処理、前記第2処理、前記第3処理、及び前記第4処理を実施し、
前記第5処理において、各条件下で取得された前記光軸プロファイルが示す前記レーザ光の輝度値の最大値を互いに比較し、輝度値が最大である前記光軸プロファイルに係る球面収差の条件となるように、前記変調パターンを調整する、請求項2記載のレーザ加工装置。 The control unit includes:
Performing the first processing, the second processing, the third processing, and the fourth processing under each condition while changing the spherical aberration conditions determined by the modulation pattern,
In the fifth process, the maximum brightness values of the laser beams indicated by the optical axis profiles acquired under each condition are compared with each other, and the spherical aberration condition related to the optical axis profile with the maximum brightness value is determined. The laser processing apparatus according to claim 2, wherein the modulation pattern is adjusted so that - 前記制御部は、前記第4処理において取得された前記光軸プロファイルと、比較用のプロファイル画像である比較データとを比較し、比較したデータ間の差分が所定範囲内である場合に前記光軸プロファイルが正常であると判定し、前記差分が所定範囲外である場合に前記光軸プロファイルが異常であると判定し、判定結果を出力する第6処理を更に実行する、請求項1~6のいずれか一項記載のレーザ加工装置。 The control unit compares the optical axis profile acquired in the fourth process with comparison data that is a profile image for comparison, and when the difference between the compared data is within a predetermined range, the optical axis profile is 7. A sixth process of determining that the profile is normal, determining that the optical axis profile is abnormal when the difference is outside a predetermined range, and outputting a determination result. The laser processing device according to any one of the items.
- 前記制御部は、前記第2処理において、ウエハ加工時における出力よりも低い出力の前記レーザ光が出射されるように、前記光源を制御する、請求項1~6のいずれか一項記載のレーザ加工装置。 The laser according to any one of claims 1 to 6, wherein the control unit controls the light source so that in the second process, the laser beam is emitted with an output lower than an output during wafer processing. Processing equipment.
- 前記光軸プロファイルは、複数の2次元の前記撮像画像が合成されることにより取得される3次元データである、請求項1~6のいずれか一項記載のレーザ加工装置。 The laser processing apparatus according to any one of claims 1 to 6, wherein the optical axis profile is three-dimensional data obtained by combining a plurality of two-dimensional captured images.
- 空間光変調器によって変調されたレーザ光を第1表面及び第2表面を有するウエハの前記第1表面側から前記ウエハに集光する集光部を、前記第1表面に対して垂直な方向である光軸方向に移動させる第1ステップと、
前記第1ステップが実行されている状態において、連続的にレーザ光を出射する第2ステップと、
前記第2ステップが実行されている状態において、前記第2表面において反射された光を検出することにより連続的に複数の撮像画像を取得する第3ステップと、
前記第3ステップにおいて連続的に取得された前記複数の撮像画像を合成することにより、前記光軸方向に沿った前記レーザ光のプロファイル画像である光軸プロファイルを取得する第4ステップと、を含むレーザ加工方法。 A condensing unit that condenses the laser beam modulated by the spatial light modulator onto the wafer from the first surface side of the wafer having a first surface and a second surface in a direction perpendicular to the first surface. a first step of moving in a certain optical axis direction;
a second step of continuously emitting laser light while the first step is being executed;
a third step of continuously acquiring a plurality of captured images by detecting light reflected on the second surface while the second step is being executed;
a fourth step of acquiring an optical axis profile that is a profile image of the laser beam along the optical axis direction by combining the plurality of captured images sequentially acquired in the third step; Laser processing method. - 前記第4ステップにおいて取得された前記光軸プロファイルに基づき、前記空間光変調器の変調パターンを調整する第5ステップ、を更に含む、請求項10記載のレーザ加工方法。 The laser processing method according to claim 10, further comprising a fifth step of adjusting a modulation pattern of the spatial light modulator based on the optical axis profile acquired in the fourth step.
- 前記ウエハは、複屈折材料を含んで構成されており、
前記第5ステップでは、前記光軸プロファイルに基づき、常光線に係る集光点と異常光線に係る集光点とを特定し、特定した2つの集光点のうち一方の集光点における光の強度が大きくなり、他方の集光点における光の強度が小さくなるように、前記変調パターンを調整する、請求項11記載のレーザ加工方法。 The wafer is configured to include a birefringent material,
In the fifth step, based on the optical axis profile, a focal point for ordinary rays and a focal point for extraordinary rays are identified, and the light at one of the two identified focal points is determined. 12. The laser processing method according to claim 11, wherein the modulation pattern is adjusted so that the intensity of the light increases and the intensity of the light at the other focal point decreases. - 前記第5ステップでは、前記2つの集光点のうち、前記第2表面に近い側の集光点における光の強度が大きくなり、前記第2表面に遠い側の集光点における光の強度が小さくなるように、前記変調パターンを調整する、請求項12記載のレーザ加工方法。 In the fifth step, of the two light focusing points, the intensity of light at the focusing point closer to the second surface increases, and the intensity of light at the focusing point farther from the second surface increases. 13. The laser processing method according to claim 12, wherein the modulation pattern is adjusted so that the modulation pattern becomes smaller.
- 前記第5ステップでは、前記レーザ光における一部の偏光成分を遮断するスリットパターンにより前記変調パターンを調整する、請求項11記載のレーザ加工方法。 12. The laser processing method according to claim 11, wherein in the fifth step, the modulation pattern is adjusted by a slit pattern that blocks some polarized components in the laser beam.
- 前記変調パターンにより定まる球面収差の条件を変えながら、それぞれの条件下で、前記第1ステップ、前記第2ステップ、前記第3ステップ、及び前記第4ステップを実施し、
前記第5ステップでは、各条件下で取得された前記光軸プロファイルが示す前記レーザ光の輝度値の最大値を互いに比較し、輝度値が最大である前記光軸プロファイルに係る球面収差の条件となるように、前記変調パターンを調整する、請求項11記載のレーザ加工方法。 Performing the first step, the second step, the third step, and the fourth step under each condition while changing the spherical aberration conditions determined by the modulation pattern,
In the fifth step, the maximum brightness values of the laser beams indicated by the optical axis profiles obtained under each condition are compared with each other, and the spherical aberration condition related to the optical axis profile with the maximum brightness value is determined. 12. The laser processing method according to claim 11, wherein the modulation pattern is adjusted so that - 前記第4ステップにおいて取得された前記光軸プロファイルと、比較用のプロファイル画像である比較データとを比較し、比較したデータ間の差分が所定範囲内である場合に前記光軸プロファイルが正常であると判定し、前記差分が所定範囲外である場合に前記光軸プロファイルが異常であると判定し、判定結果を出力する第6ステップ、を更に含む、請求項10~15のいずれか一項記載のレーザ加工方法。 The optical axis profile acquired in the fourth step is compared with comparison data that is a profile image for comparison, and if the difference between the compared data is within a predetermined range, the optical axis profile is determined to be normal. 16. A sixth step of determining that the optical axis profile is abnormal when the difference is outside a predetermined range, and outputting a determination result. Laser processing method.
- 前記第2ステップでは、ウエハ加工時における出力よりも低い出力の前記レーザ光を出射する、請求項10~15のいずれか一項記載のレーザ加工方法。 The laser processing method according to any one of claims 10 to 15, wherein in the second step, the laser beam is emitted with a lower output than the output during wafer processing.
- 前記光軸プロファイルは、複数の2次元の前記撮像画像が合成されることにより取得される3次元データである、請求項10~15のいずれか一項記載のレーザ加工方法。 The laser processing method according to any one of claims 10 to 15, wherein the optical axis profile is three-dimensional data obtained by combining a plurality of two-dimensional captured images.
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