CN113659417A - High-stability excimer laser device - Google Patents
High-stability excimer laser device Download PDFInfo
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- CN113659417A CN113659417A CN202110749211.5A CN202110749211A CN113659417A CN 113659417 A CN113659417 A CN 113659417A CN 202110749211 A CN202110749211 A CN 202110749211A CN 113659417 A CN113659417 A CN 113659417A
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
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- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
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Abstract
A high stability excimer laser apparatus comprising: the device comprises a discharge resonant cavity, a line width narrowing module, a detection module and a control module; the line width narrowing module comprises a beam expanding device and a echelle grating which are sequentially arranged along the laser emitting direction of the first side of the discharge resonant cavity; the detection module comprises a central wavelength accurate measurement device and a central wavelength rough measurement device; the device for roughly measuring the central wavelength comprises a reflecting device, a light beam converging device and a first photoelectric detection device, and is used for roughly measuring the central wavelength; the central wavelength precision measurement device is arranged on a second side opposite to the first side of the discharge resonant cavity and used for receiving the laser beam emitted from the second side and carrying out central wavelength precision measurement; the control module is respectively connected with the discharge resonant cavity, the central wavelength accurate measurement device and the central wavelength rough measurement device and is used for adjusting parameters in the discharge resonant cavity according to the measurement results of the central wavelength accurate measurement device and the central wavelength rough measurement device.
Description
Technical Field
The application relates to the field of lasers, in particular to a high-stability excimer laser device.
Background
Laser output by the excimer laser has the characteristics of short wavelength, narrow line width and high energy, and is widely applied to the field of semiconductor chip processing, such as: the laser light output by the excimer laser is the most common light source in the field of lithography machines.
With the continuous development of chip processing technology, the size requirement of the chip reaches 28nm, 14nm or even smaller. Therefore, the demand for excimer lasers for processing chips is also increasing. Not only is the laser required to be capable of releasing higher energy and have a narrower spectrum, but also the laser is required to have a central wavelength with higher stability in the working process. The on-line measurement of the energy and the central wavelength of the alignment molecule laser, the closed-loop device of the central wavelength and the energy and the closed-loop feedback control provide higher requirements.
In patents US6539046 and US6317448, a center wavelength measurement method using a combination of an FP etalon and a grating is proposed, the FP etalon has extremely high wavelength sensitivity, but the measurement range is relatively small, and the requirement of full-range measurement of an excimer laser cannot be met.
In patent CN109073463, two FP etalons are used to measure the center wavelength of the laser simultaneously, wherein one FP etalon has a larger free spectral range for rough measurement of the center wavelength, and the other FP etalon has a smaller free spectral range for precise measurement of the center wavelength, and the two are combined to realize large-range and high-precision measurement of the center wavelength.
The generation of narrow linewidth and the tuning of the center wavelength of the excimer laser are completed by a linewidth narrowing module, in patents US6192064, US6560254, US10416471, CN1232010, CN102576974 and CN107534266, the beam expanding unit and the echelle grating are used for narrowing the spectral width of the laser, and the control of the center wavelength is realized by adjusting the angle of the reflector, the prism or the echelle grating, which is used for tuning the center wavelength of the laser. Patents US6985508, CN 1003977732, CN107851958 and CN107925214 describe a closed-loop feedback method of excimer laser energy and center wavelength, which ensures the long-term stable output of excimer laser by measuring the excimer energy and center wavelength in real time and performing closed-loop feedback.
Therefore, how to design an excimer laser so that the excimer laser can have a stable central wavelength in the working process becomes a technical problem to be solved in the field.
Disclosure of Invention
The application provides a high stability excimer laser device to solve the problem that exists among the prior art.
The application provides a high stability excimer laser device, it includes: the device comprises a discharge resonant cavity, a line width narrowing module, a detection module and a control module;
the line width narrowing module comprises a beam expanding device and a echelle grating which are sequentially arranged along the laser emitting direction of the first side of the discharge resonant cavity;
the detection module comprises a central wavelength accurate measurement device and a central wavelength rough measurement device; the device for roughly measuring the central wavelength comprises a reflecting device, a light beam converging device and a first photoelectric detection device, wherein the reflecting device is used for transmitting part of light beams emitted from the first side of the discharge resonant cavity to the echelle grating;
the central wavelength precision measurement device is arranged on a second side opposite to the first side of the discharge resonant cavity and used for receiving the laser beam emitted from the second side and carrying out central wavelength precision measurement;
the control module is respectively connected with the discharge resonant cavity, the central wavelength accurate measurement device and the central wavelength rough measurement device and is used for adjusting parameters in the discharge resonant cavity according to the measurement results of the central wavelength accurate measurement device and the central wavelength rough measurement device.
Optionally, the beam expanding device is a beam expanding prism group, and the echelle grating is a dispersion grating;
the reflecting device is arranged on one incident side of the light beams of the beam expanding prism group and is positioned in a light path of the incident light reflected by the incident surface of the beam expanding device; the setting angle of the reflecting device meets the requirement that the reflected light is reflected to the echelle grating for the second time after being received.
Optionally, the converging device is a convex lens or a concave mirror; the first photoelectric detection device is a charge coupled device;
the light beam converging device is used for converging the dispersed emergent light so that the converged light irradiates on the detection surface of the first photoelectric detection device to form interference fringes;
the first photoelectric detection device is used for receiving the interference fringes, converting the interference fringes into corresponding interference fringe information and sending the interference fringe information to the control module.
Optionally, the reflection device and the light beam converging device are disposed inside the line width narrowing module.
Optionally, the central wavelength precision measurement device includes a first beam splitter, a light homogenizer, a second beam splitter, a collimating mirror, an FP etalon, a second converging mirror and a second photoelectric detection device, which are sequentially arranged along the light beam emergent direction;
the first beam splitter is used for receiving the laser emitted by the second side of the discharge resonant cavity, splitting the laser, and irradiating one split laser beam on the light equalizer;
the light homogenizing device is arranged between the first beam splitter and the second beam splitter and is used for homogenizing laser so that the homogenized laser enters the second beam splitter;
the second beam splitter is used for splitting the laser emitted by the light equalizer and irradiating one laser beam on the collimating mirror;
the collimating mirror is arranged between the second beam splitter and the FP etalon and is used for collimating laser irradiating the FP etalon;
the FP etalon is used for reflecting laser passing through the FP etalon for multiple times to form multi-level light interference, and the multi-level light interference is converged to the second photoelectric detection device through the second converging mirror to form second interference fringes.
Optionally, the detection module further includes an energy detection device, the energy detection device includes a third photoelectric detection device, and the third photoelectric detection device is disposed in the emitting direction of another beam of light split by the second beam splitter, and is configured to detect laser energy information of the laser, and send the laser energy information to the control device.
Optionally, the control device includes: a central wavelength rough measurement board card and a central wavelength precise measurement board card;
the central wavelength rough measurement board card is respectively connected with the first photoelectric detection device and the central wavelength fine measurement board card;
the central wavelength rough measurement board card is used for obtaining interference fringe information sent by the first photoelectric detection device and obtaining a rough measurement value of the laser wavelength according to the interference fringe information sent by the first photoelectric detection device; sending the rough measurement value of the laser wavelength to the central wavelength precision measurement board card;
the central wavelength accurate measurement board card is also connected with a second photoelectric detection device;
the central wavelength fine measurement board card is used for obtaining second interference fringe information sent by the second photoelectric detection device and obtaining a central wavelength rough measurement value sent by the central wavelength rough measurement board card according to the second interference fringe information; and obtaining a precise measurement value of the central wavelength according to the second interference fringe information and the rough measurement value of the central wavelength.
Optionally, the control device further includes a laser tuning controller, and the laser tuning controller is connected to at least one device of the beam expander and is configured to adjust an angle of a beam irradiated to the echelle grating by the beam expander.
Optionally, the laser tuning controller is specifically configured to adjust rotation of at least one device of the beam expanding device according to a difference between an obtained measured value of the center wavelength and a target value of the center wavelength, so as to adjust an angle of a light beam irradiated to the echelle grating.
Optionally, the control device includes: the energy measuring board card and the high-voltage power supply controller;
the energy measuring board card is respectively connected with the high-voltage power controller and the third photoelectric detection device;
the energy measurement board card is used for receiving laser energy information sent by the third photoelectric detection device; obtaining laser energy information output by the excimer laser device according to the laser energy information, and sending the laser energy information to the high-voltage power controller; and the high-voltage power controller is connected with the discharge resonant cavity and used for receiving the laser energy information and controlling the laser energy released by the discharge resonant cavity according to the laser energy information.
Compared with the prior art, the method has the following advantages:
the application provides a high stability excimer laser device includes: the device comprises a discharge resonant cavity, a line width narrowing module, a detection module and a control module; the line width narrowing module comprises a beam expanding device and a echelle grating which are sequentially arranged along the laser emitting direction of the first side of the discharge resonant cavity; the detection module comprises a central wavelength accurate measurement device and a central wavelength rough measurement device; the device for roughly measuring the central wavelength comprises a reflecting device, a light beam converging device and a first photoelectric detection device, wherein the reflecting device is used for transmitting part of light beams emitted from the first side of the discharge resonant cavity to the echelle grating; the central wavelength precision measurement device is arranged on a second side opposite to the first side of the discharge resonant cavity and used for receiving the laser beam emitted from the second side and carrying out central wavelength precision measurement; the control module is respectively connected with the discharge resonant cavity, the central wavelength accurate measurement device and the central wavelength rough measurement device and is used for adjusting parameters in the discharge resonant cavity according to the measurement results of the central wavelength accurate measurement device and the central wavelength rough measurement device.
The application provides a high stability excimer laser device presses narrow module, center wavelength to survey the device roughly through the line width to and detection module, center wavelength survey the device accurately and realize the real-time accurate measurement of the center wavelength of aiming at the molecule laser the central wavelength of excimer laser does not satisfy under the condition of predetermined center wavelength, makes drive adjustment module control the line width is pressed narrow module and is adjusted, so that the center wavelength of excimer laser satisfies predetermined center wavelength. The device realizes closed-loop feedback of the center wavelength of the alignment molecule laser, and improves the stability of the laser in the working process.
Drawings
Fig. 1 is a schematic structural diagram of a high stability excimer laser device provided in an embodiment of the present application;
fig. 2 is a schematic structural diagram of a discharge resonant cavity provided in an embodiment of the present application;
fig. 3 is a schematic structural diagram of a line width narrowing module and a central wavelength rough measurement device provided in an embodiment of the present application;
fig. 4 is a schematic structural diagram of a center wavelength precision measurement module according to an embodiment of the present disclosure;
FIG. 5 is a schematic diagram of a second interference fringe produced by an FP etalon provided by an embodiment of the present application;
fig. 6 is a flow chart of a closed-loop control of the energy released and the center wavelength of an excimer laser apparatus according to an embodiment of the present application.
Detailed Description
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. This application is capable of embodiments in many different forms than those described herein and is therefore not limited to the specific embodiments disclosed below.
The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The description used in this application and in the appended claims is for example: the terms "a," "an," "first," and "second," etc., are not intended to be limiting in number or order, but rather are used to distinguish one type of information from another.
The application provides a high stability excimer laser device, it realizes aligning the real-time accurate measurement of central wavelength of molecule laser through narrow module, the rough survey device of central wavelength, detection module and the accurate survey device of central wavelength are pressed to the line width it is in the condition of predetermined central wavelength that the central wavelength of excimer laser deviates, accessible line width is pressed narrow module and is adjusted to the central wavelength that makes excimer laser satisfies predetermined central wavelength. The device realizes closed-loop feedback of the center wavelength of the alignment molecule laser, and improves the stability of the laser in the working process.
In order to facilitate understanding of the high stability excimer laser apparatus provided in the present application, the high stability excimer laser apparatus provided in the present application is described below with reference to fig. 1, fig. 2, fig. 3, and fig. 4.
Fig. 1 is a schematic structural diagram of a high-stability excimer laser device according to an embodiment of the present disclosure. Fig. 2 is a schematic structural diagram of a discharge resonant cavity according to an embodiment of the present application. Fig. 3 is a schematic structural diagram of a line width narrowing module and a central wavelength rough measurement device provided in an embodiment of the present application. Fig. 4 is a schematic structural diagram of a center wavelength precision measurement module according to an embodiment of the present application.
In this embodiment, the high-stability excimer laser includes: the device comprises a discharge resonant cavity 1, a line width narrowing module 2, a detection module 3 and a control module 4.
A pumping device 27 is disposed in the discharge cavity 1, the discharge cavity 1 is filled with a mixed gas of an inert gas and a halogen gas, and an Electrode (EL) connected to the pumping device 27, for example: for a laser with a wavelength of 193nm, the interior of the discharge cavity 1 is fluorine (F)2) And argon (Ar); another example is: for a laser with a wavelength of 248nm, the interior of the discharge cavity 1 is fluorine (F)2) And krypton (Kr).
In the working process of the excimer laser, the mixed gas in the discharge resonant cavity 1 generates laser under the action of electric pulses generated by the pumping device 27, and the laser realizes resonance amplification under the reflection of the reflectors at the two sides of the discharge resonant cavity. The laser light is emitted from a first side of the discharge cavity 1 (in this embodiment, the right side of fig. 1, i.e., the side facing the line width narrowing module 2, is the first side) into the line width narrowing module 2. However, since the natural width of the laser light generated by the mixed gas of the inert gas and the halogen gas under the action of the electric pulse is about several hundreds of picometers, the line width narrowing module 2 is further required to narrow the spectrum of the laser light generated by the mixed gas so as to make the spectrum of the laser light emitted from the other side of the discharge cavity 1 meet the requirement.
CaF is arranged at light outlets at two sides of the discharge resonant cavity 12Or the window sheet 10 made of fused quartz, and an included angle between the window sheet 10 and the central axis of the discharge resonant cavity 1 forms a brewster angle, so that the reflection between the window sheet and the emergent laser is reduced, and the energy and the polarization degree of the laser emitted by the laser are improved.
The line width narrowing module 2 comprises a beam expanding device 5 and an echelle grating 6 which are sequentially arranged along the laser emitting direction of the first side of the discharge resonant cavity 1.
The beam expanding device 5 is composed of a plurality of right-angle triangular prisms and is used for expanding the laser entering the line width narrowing module 2 so as to reduce the divergence angle of the laser irradiating the echelle grating 6.
The beam expander 5 is a key component of the line width narrowing module 2, and is also an important element for obtaining narrow-line width laser. Each prism of the beam expanding device 5 expands the laser beam incident between the echelle grating 6, the beam expanding multiple is usually 30 to 60 times, and meanwhile, the dispersion characteristic of the prism also has a certain divergence function on the incident spectrum, so that precondition preparation is provided for the subsequent light splitting of the echelle grating 6. After being expanded by the beam expanding device 5, the divergence angle of the laser beam is compressed to reduce the divergence angle of the beam striking the surface of the echelle grating 6.
In addition, in order to increase the transmittance of each prism in the beam expander 5, the surface of each prism of the beam expander 5 may be further coated with an antireflection film to increase the transmittance of the prism.
The echelle grating 6 is also called a reflection type echelle grating, and has the characteristics of small volume, strong dispersion capability and high diffraction efficiency. The echelle grating 6 is specifically configured to disperse the laser light that is irradiated onto the echelle grating 6 through the beam expander 5, so that the laser light is spread in the direction of the exit angle with light of different wavelengths. When the light beam irradiates on the surface of the echelle grating 6, the incident light and the diffracted light of the light beam satisfy the following grating equation (1):
nd(sinθ+sinβ)＝mλ(1)；
wherein λ is the central wavelength of the laser, θ is the incident angle of the light beam on the echelle grating 6, β is the exit angle of the light beam, d is the grating constant, n is the refractive index of the gas in the linewidth control device, and m is the interference order.
As can be seen from the formula (1), the light with different wavelengths incident on the echelle grating 6 via the beam expander 5 will be spread along different angles, so that only a part of the light with a narrow wavelength range can return to the discharge cavity 1. The other end of the discharge resonant cavity 1, which is opposite to the line width narrowing module 2, is also provided with an output coupling mirror 11, the output coupling mirror 11 and the line width narrowing module 2 form a larger resonant cavity, and light returned according to the original path is oscillated and amplified, so that laser output with narrower line width is generated. At this time, since the incident angle and the exit angle of the incident beam are equal to each other, the blaze angle θ of the echelle grating is equal to the blaze angle θBSubstantially equal to each other when the prism group of the beam expanding device 5 is placedWhen the large power is M and the angle distribution of the light beam incident to the line width narrowing module 2 is f (theta), the distribution of the spectrum emitted from the echelle grating along the angle is the following formula (2)
In order to realize narrower spectrum, the blaze angle of the echelle grating is generally larger than 75 degrees, meanwhile, slits are added at two ends of the discharge cavity DC to further compress the divergence angle of the laser, the laser spectrum passing through the line width narrowing module is greatly narrowed to reach about 0.15 to 0.5pm, and the laser wavelength can meet the requirements of a photoetching light source in semiconductor manufacturing.
The high-stability excimer laser device of the embodiment further comprises a detection module 3, wherein the detection module 3 comprises: a center wavelength rough measurement device 3b and a center wavelength fine measurement device 3 a. In this embodiment, the device for roughly measuring the center wavelength includes: reflecting means 7, beam converging means 8, first photo-detection means 9. The reflecting device 7 is used for transmitting a part of light beams emitted from the first side of the discharge resonant cavity 1 to the echelle grating 6, and the light beam converging device 8 is arranged in the emitting direction of the echelle grating 6 and is used for converging the part of light beams through the emergent light of the echelle grating 6 and then transmitting the part of light beams to the first photoelectric detection device 9;
as shown in fig. 1 and 3, after the laser light emitted from the first side of the discharge cavity 1 irradiates the first prism in the beam expander 5, most of the light will pass through the first prism and propagate to the second prism, but a small part of the light will still be reflected at the incident surface of the first prism. It should be noted that even though the surfaces of the prisms of the prism group are coated with antireflection films, a part of light is still reflected, and the application of the present application is to use this part of reflected light to complete the rough measurement process for the center wavelength of the alignment molecule laser.
With continued reference to fig. 1 and fig. 3, the reflection device 7 is disposed in a reflection optical path of the incident surface of the first prism for reflecting the incident light, the reflected light will be irradiated onto the reflection device 7, and the reflection device 7 may be a plane mirror or a reflection prism. Is provided withThe reflecting device is arranged at an angle so that the reflecting device 7 receives the reflected light and then reflects the reflected light to the echelle grating 6 for the second time. As described above, in the present embodiment, the echelle grating 6 is an echelle grating. The incident angle of the part of the light beam transmitted to the echelle grating by the reflection device 7 is different from the incident angle of the light irradiated on the echelle grating 6 by the beam expansion device 5, and is larger than the blaze angle theta of the echelle gratingBSmall, let the angle of incidence be θ1This part of the light will still be dispersed by the echelle grating 6, wherein the light beam of one order (m1) exits at an angle β1And (3) emitting light, wherein the incident light and the emitted light still satisfy the grating equation of the formula (1), namely: nd (sin theta)1+sinβ1)＝m1λ
The emergent light passing through the echelle grating 6 is irradiated on the light beam converging device 8 and is focused on the surface of the photosensitive element of the first photoelectric detection device 9 by the light beam converging device 8 to generate a first interference fringe. In this embodiment, the light beam converging lens 8 may be a convex lens (group) or a concave mirror, the surface of the convex lens may be coated with an antireflection film, and the surface of the working surface of the concave mirror may be coated with an antireflection film. The first photo-detection device 9 is specifically a charge-coupled device (CCD). In the embodiment of the present application, the first photoelectric detection device 9 is configured to convert the first interference fringes into corresponding first interference fringe information, and send the first interference fringe information to the control module 4 as follows. In an alternative embodiment of the present application, the first photo-detection means 9 employs a linear array CCD,
when the laser wavelength of the discharge resonant cavity 1 changes, the light (called as a first light beam) reflected by the reflecting device 7 and irradiated on the surface of the echelle grating 6 is at an emergent angle beta1And the wavelength λ satisfies the following formula (3):
wherein, DeltaLambda is the variation value of the central wavelength, n is the refractive index of gas in the line width narrowing device, and Deltabeta1As a change value of the laser exit angle, m1D is the grating constant for the interference order.
Further, if the focal length of the beam condensing means 8 is set to f1And the peak position of the first interference fringe is x, the peak variation of the interference fringe and the variation of the central wavelength of the laser satisfy the following formula (4):
wherein, Delta lambda is the variation value of the central wavelength, Delta x is the variation value of the peak value of the first interference fringe, and beta1Is the laser exit angle.
As can be seen from the above formula (4), the change of the center wavelength of the excimer laser is in direct proportion to the change of the peak position of the first interference fringe, the first photoelectric detection device 9 collects the first interference fringe information and sends the first interference fringe information to the control module 4, and the control module 4 can calculate and obtain the peak position of the first interference fringe according to the first interference fringe information, so as to obtain the rough measurement value of the change of the center wavelength Δ λ of the excimer laser. Central wavelength λ ═ λ0+△λ，λ0Is a theoretical value of the center wavelength, thus obtaining a rough measurement of the center wavelength.
In the above embodiment, the line width narrowing and the rough measurement of the center wavelength of the laser are realized by sharing the prism and the echelle grating in the line width narrowing module. This coarse center wavelength measurement may be combined with a precise center measurement to achieve tuning of the center wavelength of the resonant cavity, as follows. The scheme ensures that the whole structure of the laser is compact, and the stability and the accuracy are greatly improved. Therefore, the reflection device 7 (or the reflection device 7 and the light beam converging device 8) can be arranged inside the line width narrowing module 2, so that the structure is more compact. Of course, the above components may also be disposed outside the line width narrowing module 2, and those skilled in the art may make adjustments according to actual needs.
As described above, in this embodiment, the reflected light of the first prism of the beam expander is used, in other embodiments, the light beam for rough measurement may be obtained by splitting the light beam directly output from the first side, or the reflected light of the reflecting surface of any prism in the prism group of the beam expander is used, which is not described herein again, and any scheme that the rough measurement of the center wavelength is realized by using part of the light beam output from the first side and combining the echelle grating 6 of the line width narrowing device is included in the protection scope of this application.
Further, it is preferable that the first photodetecting device 9 is installed outside the line width pressure narrowing module 2 to prevent the circuit board and the electronic components of the first photodetecting device 9 from contaminating the line width pressure control module 2.
In addition, the line width narrowing module 2 provided in the embodiment of the present application can also realize tuning of the center wavelength, a part of the light source path with a narrow wavelength range, which is incident to the echelle grating 6 through the beam expander 5, returns to the discharge resonant cavity 1, at this time, the exit angle of the part of the light beam is the same as the incident angle, and it is assumed that the incident angle of the laser light entering the echelle grating 6 through the beam expander 5 is θ2As can be seen from the grating equation of equation (1), the wavelength λ of the laser light at this time satisfies the following equation (5):
where n is the refractive index of the gas in the line width narrowing module 2 and m2D is the grating constant for the interference order.
It follows that the central wavelength of the laser can be varied by varying the angle at which the light is incident on the echelle grating. As shown in fig. 1 and 3, the center wavelength of the laser can be changed by changing the angle of the last prism of the prism set, the angle of the light refracted by the prism, and the angle of the light incident on the echelle grating, and of course, the center wavelength can be tuned by rotating any one of the other prisms of the prism set, except for the last prism. The rotation of the prism can be controlled by a control mechanism, as will be described in more detail below.
As can be seen from the above equations (4) and (5), both rough measurement and tuning of the center wavelength of the laser are related to the gas refractive index n of the gas inside the line narrowing module 2, and a change in the refractive index causes a change in the center wavelength of the laser and a change in the rough measurement wavelength. And the light beam split in the line width narrowing module 2 after being emitted from the laser is aligned with the central wavelength of the molecular laser for rough measurement, which means that the refractive index n of the gas is consistent in the rough measurement and tuning processes of the central wavelength. Therefore, the rough measurement device 3b for the wavelength of the excimer laser can eliminate the rough measurement error caused by the change of the refractive index of the gas, and improve the rough measurement precision during the rough measurement of the central wavelength.
In addition, in the embodiment of the present application, the detection module 3 further includes a central wavelength precision measurement device 3 a. In this embodiment, the central wavelength precision measurement device 3a is disposed on a second side opposite to the first side of the discharge resonant cavity 1. As shown in fig. 1. The output coupling mirror 11 is arranged on the second side of the discharge resonant cavity 1. The central wavelength precision measuring device 3a is specifically configured to obtain second interference fringe information of the laser light with a narrow line width emitted from the output coupling mirror 11 of the excimer laser.
As shown in fig. 1 and 4, the central wavelength precision measuring device 3a includes a first beam splitter 12, a light homogenizer 13, a second beam splitter 14, a collimator 15, an FP etalon 16, a second condenser 17, and a second photodetector 18.
The first beam splitter 12 is configured to receive the laser light emitted from the second side of the discharge resonant cavity 1, split the laser light emitted from the second side of the discharge resonant cavity 1, and irradiate one of the split laser lights on the light homogenizer 13. Wherein the light homogenizer 13 can be an integrating rod, a micro lens array or a diffractive optical element, or a combination of these elements. The purpose is to homogenize the incident beam.
The homogenized light is split by the second beam splitter 14, and a part enters the collimator 15, is collimated by the collimator 15, and enters the FP etalon 16.
The FP etalon 16 comprises two highly parallel high mirrors, and after entering the FP etalon 16, the light beam is reflected multiple times by the two high mirrors of the FP etalon 16 to form multi-level light interference, and finally is converged on the surface of the second photoelectric detection device 18 by the second converging mirror 17 to form a second interference fringe. The second focusing lens 17 may be a plano-convex lens or a biconvex lens, or may be a group of lenses. In addition, in order to reduce the volume of the central wavelength precision measuring device 3a, a reflecting mirror 26 is further installed between the second converging mirror 17 and the second photodetecting device 18 for reflecting light.
Please refer to fig. 5, which is a schematic diagram illustrating the FP etalon according to an embodiment of the present invention generating a second interference fringe. As shown in FIG. 5, dFPIs the spacing between the two high-reflection mirrors of the FP etalon, f2Is the focal length of the second focusing mirror 17, and r is the radius of the second interference fringe. The laser beam forms a second interference fringe on the second photodetector 18 after passing through the FP etalon 16 and the second condenser mirror 17.
Let λ be the central wavelength of the laser output, n2Is refractive index of gas in FP etalon, m3The order of the FP etalon fringe. The second interference fringes satisfy the following formula (6):
as can be seen, after the second photoelectric detection device 18 converts the second interference fringes into corresponding second interference fringe information, the second interference fringe information is sent to a control module described below, and then the radius r of the second interference fringes can be calculated, and the center wavelength of the excimer laser can be calculated according to the above formula. Further, because of order m of the FP etalon 16 interference fringe3For integers, different m can be selected3To obtain a set of fine measurements of the center wavelength of the excimer laser. Meanwhile, each accurate measurement value in the accurate measurement value group of the center wavelength of the excimer laser is compared with the rough measurement value of the center wavelength of the excimer laser, and the accurate measurement value closest to the rough measurement value of the center wavelength is obtained and used as the final result of the center wavelength of the excimer laser.
In order to avoid the situation where the center wavelength calculated by the FP etalon 16 of different interference orders is relatively close to the rough measured value of the center wavelength, and it is not easy to determine the interference order, it is necessary to make the precision of the rough measured value of the center wavelength higher than 1/2 of the free spectral path of the FP etalon 16.
After the final result of the center wavelength of the excimer laser is determined, the control device 4 compares the final result of the center wavelength of the excimer laser with the target center wavelength, and if the calculated final result of the center wavelength of the excimer laser is different from the target center wavelength, the control device 4 can drive the prism in the beam expander 5 in the line width narrowing module 2 to rotate so as to change the incident angle incident on the echelle grating in the aforementioned fig. 1, so as to compensate the deviation value of the center wavelength. Specifically, in order to implement the above control process, a rotating mechanism may be installed on at least one prism included in the beam expanding device 5, and the control module 4 is connected to the rotating mechanism 19 to rotate the prism through the rotating mechanism under the control of the control module 4.
In addition, the detection module further includes an energy detection device to detect energy of the laser output, in this embodiment, the energy detection device is a third photodetection device 20 as shown in fig. 1. The third photo detection means 20 may be a CCD. Specifically, the third photoelectric detection device 20 receives another beam split by the second beam splitter 14 to detect the energy of the laser beam, and the third photoelectric detection device 20 is further connected to a related control unit in the control module 4, which will be described below, to convert the light intensity signal of the portion of light into an electrical signal and send the electrical signal to the control module 4, and the control module 4 can control the high voltage electrode in the discharge resonant cavity.
Referring to fig. 1, the control module 4 of the present embodiment includes a center wavelength rough measurement board card 21, a center wavelength fine measurement board card 22, a laser tuning controller 23, an energy measurement board card 24, and a high voltage power controller 25. Of course, the control module 4 may also include some of the aforementioned components. For example, only a center wavelength rough measurement board 21, a center wavelength fine measurement board 22, and a laser tuning controller 23.
The central wavelength rough measurement board card 21 is connected with the first photoelectric detection device 9 and the central wavelength fine measurement board card 22 respectively, the central wavelength fine measurement board card 22 is further connected with the output end of the second photoelectric detection device 18 and the input end of the laser tuning controller 23, and the laser tuning controller 23 is connected to a control mechanism of a prism group in the line width narrowing module 2, and the control mechanism can control the rotation of one or more prisms in the prism group, so that the angle of incident light irradiating the echelle grating is changed.
The central wavelength rough measurement board card 21 receives the first interference fringe information output by the first photoelectric detection device 9, obtains a rough measurement value of the central wavelength according to the first interference fringe information, and sends the rough measurement value of the central wavelength to the central wavelength fine measurement board card 22.
The central wavelength fine measurement board 22 receives the second interference fringe information outputted by the second photoelectric detection device 18, and obtains a fine measurement value group of the central wavelength according to the second interference fringe information, and simultaneously compares the fine measurement value group of the central wavelength with the rough measurement value of the central wavelength to obtain a fine measurement value closest to the rough measurement value of the central wavelength as a final result of the central wavelength of the excimer laser. And obtaining a final result of the central wavelength, and sending the final result to the laser tuning controller 23, comparing the final result of the central wavelength with a preset target central wavelength by the laser tuning controller 23 to obtain a corresponding adjusting parameter, and controlling the line width narrowing module 2 to adjust the central wavelength according to the corresponding adjusting parameter. Specifically, the adjustment parameter may be a prism rotation angle, and then the laser tuning controller 23 drives the prism rotation mechanism to compensate for the deviation value of the center wavelength, so as to realize the closed-loop feedback of the center wavelength.
In addition, the input end of the energy detection board 24 is connected with the output end of the third photoelectric detection device 20, and the output end of the energy detection board 24 is connected with the input end of the high-voltage power controller 25; the output of the high voltage power controller 25 is connected to the pumping device 27 of the discharge resonant cavity 1. The energy detection board 24 determines the energy information released by the excimer laser according to the electrical signal output by the third photoelectric detection device 20, calculates the difference between the energy information and the preset energy information, and adjusts the voltage released by the pumping device 27 through the high voltage power controller 25 to adjust the energy released by the excimer laser.
The high-stability excimer laser device provided by the embodiment of the application realizes laser spectrum narrowing, rough measurement and tuning of central wavelength by sharing the prism and the echelle grating 6 in the online width narrowing module 2, and the rough measurement and tuning of the central wavelength are in the same environment, so that measurement errors and feedback errors caused by gas refractive index changes can be eliminated, and the central wavelength measurement precision and the laser stability are improved. Meanwhile, the central wavelength precision measurement device is only provided with one path of FP etalon 16 and an energy measurement component, has compact structure and small volume, is beneficial to improving the stability of gas in a detection module, improves the measurement precision and stability of the energy and the central wavelength of the laser, and ensures the performance and long-term stability of the laser.
The control module 4 obtains the center wavelength of the laser through calculation, compares the center wavelength with a target value of the center wavelength, calculates the rotation angle of the prism, drives the rotating mechanism 19 of the prism to compensate the deviation value of the center wavelength, realizes the closed-loop feedback of the center wavelength, and can effectively improve the stability of the center wavelength of the excimer laser. Through the energy feedback control link, the laser energy is obtained through calculation, the voltage value needing to be adjusted by the high-voltage power supply is calculated, the pumping device 27 of the discharge resonant cavity 1 is controlled, the energy closed-loop feedback of the laser is realized, and the stability of the laser energy or the dose is realized.
Further embodiments of the present application also provide a high stability excimer laser apparatus, which includes: the device comprises a discharge resonant cavity 1, a line width narrowing module 2, a detection module and a control module 4; the line width narrowing module 2 comprises a beam expanding device 5 and a echelle grating 6 which are sequentially arranged along the laser emitting direction of the first side of the discharge resonant cavity 1; the detection module comprises a central wavelength accurate measurement device 3a and a central wavelength rough measurement device 3b, which are respectively used for performing accurate measurement and rough measurement on the central wavelength of emergent light of the discharge resonant cavity 1; the control module 4 is respectively connected with the discharge resonant cavity 1, the central wavelength accurate measurement device 3a and the central wavelength rough measurement device 3b, and is used for adjusting parameters in the discharge resonant cavity 1 according to measurement results of the central wavelength accurate measurement device 3a and the central wavelength rough measurement device 3 b; the control module 4 further includes a laser tuning controller 23, and the laser tuning controller 23 is connected to at least one device of the beam expander 5, and is configured to adjust an angle of a beam irradiated to the echelle grating by the beam expander 5.
To facilitate understanding of the control of the energy released and the center wavelength of the excimer laser apparatus, the control process is described below with reference to fig. 6. Please refer to fig. 6, which is a flowchart illustrating a closed-loop control of the energy and the center wavelength released by the excimer laser apparatus according to an embodiment of the present application.
The process is that under the premise of normal working of the laser, the following steps are executed:
step S601, the center wavelength and energy of the excimer laser apparatus are measured.
Step S602, respectively calculating a difference between the center wavelength and the target center wavelength and a difference between the energy and the target energy, and obtaining a prism adjustment parameter for the line width narrowing module 5 and a voltage adjustment parameter for the pumping device 27 according to the difference between the center wavelength and the target center wavelength and the difference between the energy and the target energy.
Step S603, respectively judging whether the prism adjusting parameter and the voltage adjusting parameter are larger than a preset parameter threshold value;
in step S604, if the prism adjustment parameter and the voltage adjustment parameter are less than or equal to the preset parameter threshold, it is continuously determined whether the excimer laser device is in the light emitting state.
In step S605, if the excimer laser device is in the light emitting state, the process returns to step S602. And if the excimer laser device is not in the light emitting state, ending the control flow.
In step S606, if the prism adjustment parameter and the voltage adjustment parameter are greater than the preset parameter threshold, the prism angle of the line width narrowing module 5 and the voltage released by the pumping device 27 are adjusted according to the prism adjustment parameter and the voltage adjustment parameter, and step S605 is executed.
To sum up, the high-stability excimer laser device provided by the embodiment of the present application realizes the real-time accurate measurement of the center wavelength of the alignment molecule laser by the line width narrowing module 5, the coarse measurement device 3b of the center wavelength, the control module 4 and the fine measurement device 3a of the center wavelength, and under the condition that the center wavelength of the excimer laser does not satisfy the preset center wavelength, the control module 4 controls the line width narrowing module 2 to adjust, so that the center wavelength of the excimer laser satisfies the preset center wavelength. The device realizes closed-loop feedback of the center wavelength of the alignment molecule laser, and improves the stability of the laser in the working process.
Although the present application has been described with reference to the preferred embodiments, it is not intended to limit the present application, and those skilled in the art can make variations and modifications without departing from the spirit and scope of the present application, therefore, the scope of the present application should be determined by the claims that follow.
Claims (10)
1. A high stability excimer laser apparatus, comprising: the device comprises a discharge resonant cavity (1), a line width narrowing module (2), a detection module and a control module (4);
the line width narrowing module (2) comprises a beam expanding device (5) and a echelle grating (6) which are sequentially arranged along the laser emitting direction of the first side of the discharge resonant cavity (1);
the detection module comprises a central wavelength accurate measurement device (3a) and a central wavelength rough measurement device (3 b); the central wavelength rough measurement device (3b) comprises a reflection device (7), a light beam convergence device (8) and a first photoelectric detection device (9), wherein the reflection device (7) is used for transmitting part of light beams emitted from the first side of the discharge resonant cavity (1) to the echelle grating (6), and the light beam convergence device (8) is arranged in the emitting direction of the echelle grating (6) and is used for transmitting the part of light beams to the first photoelectric detection device (9) after being converged by the emitted light of the echelle grating (6);
the central wavelength precision measurement device (3a) is arranged on a second side opposite to the first side of the discharge resonant cavity (1) and used for receiving laser beams emitted from the second side and carrying out central wavelength precision measurement;
the control module (4) is respectively connected with the discharge resonant cavity (1), the central wavelength accurate measurement device (3a) and the central wavelength rough measurement device (3b) and is used for adjusting parameters in the discharge resonant cavity (1) according to measurement results of the central wavelength accurate measurement device (3a) and the central wavelength rough measurement device (3 b).
2. The device according to claim 1, wherein the beam expanding means (5) is a beam expanding prism set;
the reflecting device (7) is arranged on one incident side of the light beams of the beam expanding prism group and is positioned in a light path of the incident light after the incident light is reflected by the incident surface of the beam expanding device (5); the setting angle of the reflecting device (7) meets the requirement that the reflected light is reflected to the echelle grating (6) for the second time after being received.
3. The device according to claim 2, characterized in that the beam converging means (8) are a convex lens or a concave mirror; the first photoelectric detection device (9) is a charge coupled device;
the light beam converging device (8) is used for converging the dispersed emergent light so that the converged light irradiates on the detection surface of the first photoelectric detection device (9) to form interference fringes;
the first photoelectric detection device (9) is used for receiving the interference fringes, converting the interference fringes into corresponding interference fringe information, and sending the interference fringe information to the control module (4).
4. A device according to any one of claims 1 to 3, characterized in that said reflecting means (7) and said beam converging means (8) are arranged inside said line width narrowing module (2).
5. The device according to claim 1, wherein the central wavelength precision measurement device (3a) comprises a first beam splitter (12), a light homogenizer (13), a second beam splitter (14), a collimating mirror (15), an FP etalon (16), a second converging mirror (17) and a second photoelectric detection device (18) which are arranged in sequence along the light beam emergent direction;
the first beam splitter (12) is used for receiving the laser emitted by the second side of the discharge resonant cavity (1), splitting the laser into beams and irradiating one of the split beams on the light homogenizer (13);
the light uniformizer (13) is arranged between the first beam splitter (14) and the second beam splitter (17) and is used for homogenizing the laser light, so that the homogenized laser light enters the second beam splitter (17);
the second beam splitter (14) is used for splitting the laser emitted by the light homogenizer (13) and irradiating one beam of the laser on the collimating mirror (15);
the collimating mirror (15) is arranged between the second beam splitter (17) and the FP etalon (16) and is used for collimating laser irradiating the FP etalon;
the FP etalon (16) is used for reflecting the laser passing through the FP etalon (16) for multiple times to form multi-level light interference, and the multi-level light interference is converged to the second photoelectric detection device (18) through the second converging mirror (17) to form second interference fringes.
6. The device according to claim 5, wherein the detection module (4) further comprises an energy detection device (20), the energy detection device comprises a third photoelectric detection device (20), and the third photoelectric detection device (20) is arranged in the emitting direction of the other beam of light split by the second beam splitter (14) and is used for detecting laser energy information of the laser and sending the laser energy information to the control device.
7. The apparatus of claim 1, 2, 3, 5 or 6, wherein the control means comprises: a central wavelength rough measurement board card (21) and a central wavelength precise measurement board card (22);
the central wavelength rough measurement board card (21) is respectively connected with the first photoelectric detection device (9) and the central wavelength precise measurement board card (22);
the central wavelength rough measurement board card (21) is used for obtaining interference fringe information sent by the first photoelectric detection device (9), and obtaining a rough measurement value of the laser wavelength according to the interference fringe information sent by the first photoelectric detection device (9); sending the rough measurement value of the laser wavelength to the central wavelength precision measurement board card (22);
the central wavelength precision measurement board card (22) is also connected with a second photoelectric detection device (18);
the central wavelength precision measurement board card (22) is configured to obtain second interference fringe information sent by the second photoelectric detection device (18), and obtain a central wavelength rough measurement value sent by the central wavelength rough measurement board card (21) according to the second interference fringe information; and obtaining a precise measurement value of the central wavelength according to the second interference fringe information and the rough measurement value of the central wavelength.
8. The device according to claim 7, wherein the control device (4) further comprises a laser tuning controller (23), the laser tuning controller (23) being connected to at least one component of the beam expanding device (5) for adjusting the angle of the beam expanding device (5) impinging on the echelle grating (6).
9. The apparatus according to claim 8, wherein the laser tuning controller (23) is configured to adjust the angle of the light beam impinging on the echelle grating (6) by adjusting the rotation of at least one element of the beam expanding device (5) based on the difference between the obtained refined center wavelength and the target center wavelength.
10. The device according to claim 7, characterized in that said control means (4) comprise: the energy measuring board card (24) and the high-voltage power controller (25);
the energy measurement board card (24) is respectively connected with the high-voltage power controller (25) and the third photoelectric detection device (20);
the energy measurement board card (24) is used for receiving laser energy information sent by the third photoelectric detection device (20); laser energy information output by the excimer laser device is obtained according to the laser energy information, and the laser energy information is sent to the high-voltage power controller (25);
and the high-voltage power controller (25) is connected with the discharge resonant cavity (1) and is used for receiving the laser energy information and controlling the laser energy released by the discharge resonant cavity (1) according to the laser energy information.
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| CN202110749211.5A CN113659417A (en) | 2021-07-01 | 2021-07-01 | High-stability excimer laser device |
| PCT/CN2022/079621 WO2023273392A1 (en) | 2021-07-01 | 2022-03-07 | High-stability excimer laser apparatus |
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| WO2023273392A1 (en) * | 2021-07-01 | 2023-01-05 | 北京科益虹源光电技术有限公司 | High-stability excimer laser apparatus |
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| US20020048294A1 (en) * | 1998-10-02 | 2002-04-25 | Peter C. Newman | Wavemeter for gas discharge laser |
| US6526086B1 (en) * | 1997-05-09 | 2003-02-25 | Komatsu Ltd. | Band narrowing laser |
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| EP0992093B1 (en) * | 1998-03-11 | 2003-05-07 | Cymer, Inc. | Wavelength system for an excimer laser |
| US6317448B1 (en) * | 1999-09-23 | 2001-11-13 | Cymer, Inc. | Bandwidth estimating technique for narrow band laser |
| CN102155997B (en) * | 2011-03-16 | 2012-11-28 | 中国科学院上海光学精密机械研究所 | Optical-fiber type laser wavemeter |
| CN105973480B (en) * | 2016-07-14 | 2019-03-08 | 中国科学院上海光学精密机械研究所 | Grating re-diffraction type laser wavelength meter |
| CN113659417A (en) * | 2021-07-01 | 2021-11-16 | 北京科益虹源光电技术有限公司 | High-stability excimer laser device |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US6526086B1 (en) * | 1997-05-09 | 2003-02-25 | Komatsu Ltd. | Band narrowing laser |
| US20020048294A1 (en) * | 1998-10-02 | 2002-04-25 | Peter C. Newman | Wavemeter for gas discharge laser |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2023273392A1 (en) * | 2021-07-01 | 2023-01-05 | 北京科益虹源光电技术有限公司 | High-stability excimer laser apparatus |
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