WO2002049066A1 - Charged particle beam microscope, charged particle beam application device, charged particle beam microscopic method, charged particle beam inspecting method, and electron microscope - Google Patents

Charged particle beam microscope, charged particle beam application device, charged particle beam microscopic method, charged particle beam inspecting method, and electron microscope Download PDF

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Publication number
WO2002049066A1
WO2002049066A1 PCT/JP2001/010415 JP0110415W WO0249066A1 WO 2002049066 A1 WO2002049066 A1 WO 2002049066A1 JP 0110415 W JP0110415 W JP 0110415W WO 0249066 A1 WO0249066 A1 WO 0249066A1
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WIPO (PCT)
Prior art keywords
charged particle
particle beam
sample
lens
image
Prior art date
Application number
PCT/JP2001/010415
Other languages
French (fr)
Japanese (ja)
Inventor
Kuniyasu Nakamura
Kimio Kanda
Mitsugu Sato
Mikio Ichihashi
Hiroyuki Shinada
Ruriko Tsuneta
Original Assignee
Hitachi, Ltd.
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Application filed by Hitachi, Ltd. filed Critical Hitachi, Ltd.
Publication of WO2002049066A1 publication Critical patent/WO2002049066A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement, ion-optical arrangement
    • H01J37/10—Lenses
    • H01J37/14—Lenses magnetic
    • H01J37/141—Electromagnetic lenses
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/26—Electron or ion microscopes; Electron or ion diffraction tubes
    • H01J37/28—Electron or ion microscopes; Electron or ion diffraction tubes with scanning beams

Definitions

  • Charged particle beam microscope device Charged particle beam application device, charged particle beam microscopy method, charged particle beam inspection method, and electron microscope device
  • the present invention relates to a charged particle beam apparatus that scans a sample with a charged particle beam such as an electron beam to obtain an image signal of the sample, and in particular, a charged particle beam microscope apparatus, a charged particle beam application apparatus, and a charged particle beam apparatus.
  • the present invention relates to a particle beam microscopy method, an electron beam inspection method, and an electron microscope device.
  • Japanese Patent Application Laid-Open No. 2000-48575 discloses that it can be achieved by changing the current conditions of a deflector to correct the distortion of the objective lens.
  • a method for acquiring a scanning electron microscope image using a conventional electron microscope apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. H11-250850.
  • the optical system used for such low-magnification image observation methods does not use an objective lens, but uses a single-stage deflection coil.At high magnifications, a deflection coil and an objective lens are used. .
  • Japanese Unexamined Patent Application Publication No. Hei 6-2831128 discloses a combination of a converging lens, a deflection coil, and an objective lens for acquiring a scanning electron microscope image, which has a configuration other than the above method. Have been. In this configuration, a convergent lens and an objective lens are sequentially arranged below the deflection coil.
  • This method employs an electron optical system that irradiates an electron beam deflected by a deflecting coil with respect to a sample placed in an objective lens by a converging lens and an objective lens and irradiates the sample. In short, it can be expressed as an electromagnetic lens under the deflection coil and an objective lens under the deflection coil. However, it is disclosed that the role of the electromagnetic lens here is to change the focal position when the sample is placed below or above the objective lens. '
  • an electron optical system including an electron optical system, that is, a converging lens for converging an electron beam from an electron source, a deflector for scanning the electron beam, and an objective lens having one object point and one image point
  • an electron optical system that is, a converging lens for converging an electron beam from an electron source, a deflector for scanning the electron beam, and an objective lens having one object point and one image point
  • a scanning electron microscope image is acquired with a low accelerating voltage (about 5 kV or less)
  • the electron beam spot spreads due to chromatic aberration.
  • the spread of this spot is constant regardless of the magnification.
  • the resolution is determined by the ratio between the diameter of the electron beam spot and the scanning range of the electron beam. Therefore, the smaller the scanning range of the electron beam, that is, the higher the magnification, the lower the resolution.
  • the resolution increases as the scanning range of the electron beam increases, that is, as the magnification decreases. Therefore, the magnification range in which a high-
  • the magnification here indicates the ratio of the display range of the display device to the scan range on the sample.
  • a human lens is operated at a short focal length in order to achieve resolution.
  • the deflection Observation at a high magnification of 10,000 times or more with a small axial amount can provide a high-resolution scanning electron microscope image, but depending on the objective lens at intermediate magnifications of 1000 to 10,000 times, where the amount of deflected deflection is large. Since distortion occurs, the magnification range over which good images without distortion can be obtained is about 10,000 times or more. It was not a problem to find a field of view on the sample at low magnifications without requiring much resolution-but at intermediate magnifications of 1000 to 10,000 times resolution was required. However, no attempt was made to increase the resolution at this intermediate magnification. In other words, the conventional electron optical system has low magnification and high magnification.
  • the combination of the lenses and coils used in the high and low magnification optical systems and the excitation conditions are all different, so the magnetic hysteresis and optical axis during switching are misaligned.
  • the image position at the same location on the sample was displayed with a shift, causing a problem in the visual field search operation.
  • an object of the present invention is to provide an objective lens having an intermediate magnification (magnification of 100 to 10,000 times and an image plane conversion of 100 to 100 m) at a magnification of 100 m to 100 m, and a distortion aberration in a range of ⁇ on the sample. And a wide magnification range from intermediate magnification to high magnification. It is an object of the present invention to provide a charged particle beam apparatus capable of acquiring a high-resolution and distortion-free good scanning electron microscope image or image signal in a surrounding area.
  • the present invention corrects a distortion caused by an objective lens using a correction lens for charged particle beam deflection, which is installed in front of an objective lens having one object point and one image point. Excitation is performed under the conditions, and the charged particle beam is two-dimensionally scanned on the sample surface by the deflector to acquire a scanning charged particle beam microscope image or image signal with little aberration from low magnification to high magnification.
  • a correction lens for charged particle beam deflection is provided between the converging lens and the objective lens, and the distortion generated in the objective lens is opposite to the aberration. It is in.
  • the configuration of the present invention lies in that the charged particle beam having passed through the correction lens forms an image at the position of the main surface of the objective lens.
  • the configuration of the present invention resides in that the deflector is installed at a stage before the correction lens. Further, in the configuration of the present invention, the deflector comprises a two-stage upper stage deflector and a lower stage deflector, and the correction lens is located below the upper stage deflector and the lower stage deflector or between the upper stage deflector and the lower stage deflector. The configuration is located in
  • the configuration of the present invention is characterized in that a sample chamber for mounting a sample is provided below the magnetic path of the objective lens.
  • the present invention provides one or more stages of an electrostatic lens for accelerating a secondary electron beam generated from an electron source to a predetermined voltage, and a primary electron beam focused on a sample;
  • An electron microscope equipped with a converging lens having at least one stage and an objective lens and a deflector having at least one stage for deflecting the primary electron beam. correction
  • the magnetic lens is excited under the conditions to correct the distortion generated by the objective lens, and the primary electron beam is scanned two-dimensionally on the sample surface by the electron beam deflection by the deflector, the correction magnetic lens, and the objective lens.
  • the intensity of the secondary electron beam generated secondarily or the intensity of the electron beam transmitted through the sample is detected in synchronization with the scanning of the primary electron beam, and the signal is used as a luminance modulation signal of the image display device by the image display device. This is in that it is configured to be displayed as a scanning electron microscope image.
  • the point is that the visual field is searched by continuously zooming up or down from the first magnification to the second magnification.
  • Still another object of the present invention is to detect a physical shape defect and an electrical defect of the sample by comparing the image with a predetermined magnification or a design image which has been taken in advance.
  • the first area and the second area of the repetitive circuit pattern are detected as image signals at the first magnification, and the image signals are compared, and when they do not match, the second area is different from the first magnification.
  • An inspection method is provided in which image signals in areas different in magnification are captured and compared again to determine a defect if they do not match.
  • Still another object of the present invention is to provide an electron optical system with low magnification and low peripheral blur.
  • FIG. 1 is a diagram showing a conventional high-magnification scanning electron microscope image observation optical system
  • FIG. 2 is a diagram showing the result of distortion caused by an objective lens
  • FIG. 3 is a conventional low-magnification scanning electron microscope.
  • FIG. 4 is a diagram illustrating an optical system for observing a microscope image
  • FIG. 4 is a diagram illustrating a basic configuration of a first embodiment of the present invention
  • FIG. 5 is a diagram illustrating a result of correcting distortion generated in an objective lens according to the present invention.
  • Show FIG. 6 is a diagram illustrating a second embodiment of the present invention.
  • FIG. 7 is a diagram illustrating a third embodiment of the present invention.
  • FIG. 8 is a diagram illustrating a fourth embodiment of the present invention.
  • FIG. 9 is a diagram for explaining a fifth embodiment of the present invention.
  • FIG. 1 shows a configuration diagram of an optical system for observing a high-magnification image with a conventional electron microscope apparatus.
  • the primary electron beam generated from the electron source 1 is reduced by the converging lens 2 and forms an image on the image plane position 3 of the converging lens 2.
  • a deflection fulcrum 6 defined as a point at which the primary electron beam deflected by the lower deflection coil 5 intersects the optical axis 1 ′ is positioned in front of the objective lens 7. Make it coincide with the magnetic field focal plane position. At this time, an image is formed at a position distant from the optical axis 1 by the lens action of the objective lens 7 to the primary electron beam. As shown in FIG. 4, this off-axis position is called a deflection position, and the off-axis distance is called a deflection swing width r.
  • the objective lens 7 has one object point and an image point 29.
  • the ratio of the deflecting angles of the upper deflecting coil 4 and the lower deflecting coil 5 so that the position of the deflecting fulcrum 6 is always constant (deflection vertical ratio) is geometric. Size can be determined. If such a deflection vertical ratio is set, the deflection swing width is determined by the deflection angle of the upper deflection coil 4.
  • the purpose of matching the deflection fulcrum 6 with the front magnetic field focal plane position (object point) of the objective lens 7 is that when the primary electron beam is off-axis from the optical axis on the sample 8, This is so that the irradiation angle with respect to the sample 8 is constant at all deflection positions.
  • the deflection amplitude of the scanning electron microscope image is determined by setting the maximum value of the deflection angle of the upper deflection coil 4.
  • the relationship between the coil deflection angle and the magnification of a scanning electron microscope image will be described using parameters such as a typical coil, a lens excitation condition, and a distance between lenses.
  • the distance between the upper deflection coil 4 and the lower deflection coil 5 is 34 mm
  • the distance between the lower deflection coil 5 and the objective lens 9 is 93.5 mm
  • the position of the front magnetic field focal plane of the objective lens 7 is the objective lens 7.
  • the deflection angles of the upper and lower deflection coils be ⁇ 1 and ⁇ 2, respectively.
  • the maximum value of the deflection angle 0 1 of the upper deflection coil is 5 Om r Since it is on the order of ad, the minimum magnification in this optical system is about 100 ⁇ . However, in this case, the distortion becomes larger as the deflection amplitude becomes larger, so that there is a lower limit to the practicable magnification.
  • Fig. 2 shows an example of how a real raster is imaged on a sample surface by an objective lens when a square raster is formed by a deflection coil.
  • an optical system usually used for observing a scanning electron microscope image at a low magnification of 1000 or less will be described with reference to FIG.
  • the method of deflecting the electron beam by aligning the deflection fulcrum with the position of the front magnetic field focal plane of the objective lens is used.
  • the scanning deflection area cannot be increased by the lens action of the objective lens. Therefore, the excitation of the objective lens has been stopped before use. That is, an optical system is used in which the electron beam is inclined by one-stage deflection by the upper stage deflection coil 4 to increase the deflection swing width. Since the deflection by the objective lens is not used, the excitation of the objective lens is set to zero, and the electron beam from the electron source 1 is focused on the sample 8 by the converging lens 2. It is set as follows.
  • the electron optical magnification of the electron source is almost a fraction, so the converging lens 2 has low excitation. Used in.
  • the chromatic aberration coefficient of the converging lens 2 is about 100 Omm.
  • the magnification of the image is 1,000 times, the electron beam deflection amount is 100 m on one side, and if one side is imaged with 500 pixels, the size of one pixel is 0.2111. Therefore, with this optical system, the spot spread (0.25 in) is larger than one pixel (0.2 m), and a high-resolution image cannot be obtained.
  • the magnification at which the spot spread is the same as one pixel is 800 times, which is the upper limit of the magnification of this optical system.
  • the electron beam deflected on the sample 8 is incident on the sample with a larger inclination as the deflection swing width is larger.
  • the optical axis at the time of observing the high-magnification image and the optical axis at the time of observing the low-magnification image do not match, and the image is misaligned between the low-magnification image and the high-magnification image.
  • the conventional low-magnification image observation optical system can obtain a low-magnification image sufficient for searching for a visual field, but the optical system is greatly changed compared to the high-magnification optical system.
  • the electron optical system for high magnification has a limit on the low magnification side
  • the electron optical system for low magnification has a limit on the high magnification side.
  • no good image can be obtained.
  • no correspondence has been made for this intermediate magnification range (the scanning area is in the range of 100 ⁇ to 10 ⁇ m in image plane conversion).
  • An optical system that deflects the primary electron beam on a sample 8 using a conventional converging lens 2, objective lens 7, upper deflection coil 4 and lower deflection coil 5 for observing a high-magnification image to obtain an image.
  • a correction correction magnetic field lens 9 for electron beam deflection is newly added.
  • the primary electron beam deflected by the upper deflecting coil 4 and the lower deflecting coil 5 forms a one-to-one image on the main surface of the objective lens 7 by a correction magnetic lens 9 for deflecting the electron beam.
  • Objective line An image is formed on the sample 8 by the lens 7.
  • the distorted deflection pattern is the main object lens 7.
  • An image is formed at the surface position.
  • the objective lens 7 generates a distortion according to the amount of off-axis deflection of the distorted deflection pattern, and the deflection pattern on the sample 8 is again distorted.
  • the lens polarity and the optical magnification are set so that the distortion generated by the correction magnetic lens 9 for electron beam deflection and the distortion generated by the objective lens 7 become aberrations in opposite directions.
  • the deflection figure finally formed on the sample 8 can be returned to the shape of the deflection figure formed by the upper deflection coil 4 and the lower deflection coil 5.
  • Fig. 5 shows the result of correcting distortion by this method.
  • the conditions are the same as those in FIG. 1 described above, except that the magnification of image acquisition is 100 ⁇ (the deflection amplitude is 50 ni on one side) and the real part of the distortion aberration coefficient (complex value) is set. , the imaginary part was respectively 5 X 1 0- 5, 1 X 1 0- 5.
  • the square raster created by the upper deflection coil 4 and the lower deflection coil 5 has a direction opposite to the distortion of the objective lens due to the correction magnetic lens 9 for electron beam deflection.
  • the distortion for cancellation is imaged as a distorted figure at the position of the main surface of the objective lens 7.
  • Fig. 5 (b) shows this situation.
  • the correction magnetic lens 9 side is the reverse distortion with respect to the objective lens.
  • the coil polarity and the excitation conditions which cause the occurrence of the distortion are set, the distortion can also be corrected by changing the polarity of the objective lens and the excitation conditions with respect to the correction magnetic lens.
  • This correction method is applied not only to a visual field search for searching for a target in a wide area, but also to the case where an electron beam or an ion beam is used to expose a wafer coated with a resist disposed under an objective lens.
  • the present invention can be applied to batch exposure or variable shaping using a mask, and also to a type of spot drawing using an electron beam.
  • the present invention can be applied to inspection processing by arranging a sample under an objective lens using an electron beam.
  • the sample placed on the sample stage is irradiated with the primary charged particle beam (ion beam) from the charged particle source.
  • the size of the illuminated scanning width on the display device indicates the magnification, and the scanning is performed while varying from a low magnification of less than 1000 times to a high magnification area of 500,000 times. This is achieved by adding a lens that corrects deflection distortion (distortion aberration) generated when the primary charged particle beam scanned by the deflector passes through the objective lens.
  • An electrostatic deflector may be used as the correction lens here.
  • the magnification may be increased slightly and the image may be focused at the center of the image, and then reset to the minimum magnification.
  • a current is passed through the correction magnetic lens 9 for electron beam deflection to excite it.
  • the correction magnetic lens 9 for electron beam deflection is formed so that a magnetic field in the opposite direction to the objective lens 7 is formed, for example, the winding direction of the coil is opposite and the same current direction, or the winding direction of the coil is the same.
  • the current is set to reverse.
  • the excitation is changed by the current supplied to the correction magnetic field lens 9 for electron beam deflection so that the distortion of the image is reduced.
  • An image is acquired in the vicinity of the current value at which the distortion of the image becomes small, the ratio of the length and width of the grid mesh sample is measured, and the ratio becomes appropriate, and the magnification error between the center and the periphery of the image is within 5%.
  • the excitation of the correction magnetic field lens 9 for electron beam deflection is adjusted, and the focus is accurately adjusted by the converging lens 2.
  • the excitation current values of the correction magnetic lens 9 and the converging lens 2 for electron beam deflection determined in this way are recorded with respect to the acceleration voltage, and the magnification and the correction value are displayed on the display device as necessary.
  • the acceleration voltage at the time of incidence on the sample is changed by changing the retarding voltage applied between the electrode applied to the sample and the electrode provided below the magnetic path of the objective lens, and the sample table and the lower part of the objective lens.
  • a deceleration electric field is formed during the operation.
  • the speed of the primary electron beam changes and the deflection distortion amount also changes.
  • the electric field caused by this retarding voltage moves like a kind of electrostatic lens.
  • the deflection distortion generated in this way and the distortion difference of the objective lens are combined so that the correction magnetic lens absorbs the distortion and the same method as described above.
  • the excitation current value of the correction magnetic field lens 9 for electron beam deflection and the convergent lens 2 is determined by the method.
  • the excitation current values of the correction magnetic lens 9 for electron beam deflection and the converging lens 2 determined by the combination of all acceleration voltages and retarding voltages are incorporated into the device control program as a table, and the acceleration voltage and the retarding voltage are determined. When this is done, the distortion is corrected, and the conditions for focusing on the sample are automatically set.
  • the invention of the present application is established even if an ion source is used as a charged particle source and an ion beam is applied as a charged particle beam.
  • a positive polarity voltage is applied to the electrode as the retarding voltage. That is, the difference is that a voltage is applied to the electrode so as to form an electric field so as to decelerate the ion beam.
  • the lens adjustment conditions at intermediate magnifications' Even if it is, there is no hindrance to image formation by the secondary charged particle beam obtained from the sample May not be. In this case, it is not necessary to change the table of the excitation current values of the correction magnetic field lens 9 for electron beam deflection and the converging lens 2 depending on the magnification.
  • the acceleration voltage and the retarding voltage By controlling the electron optics conditions more, from the intermediate magnification (the scanning area is in the range of 100 m to 10 m in the image plane conversion) to the high magnification (the scanning area is less than 10 ⁇ m in the image plane conversion to 1 ⁇ m)
  • high resolution scanning electron microscope images without distortion can be obtained from low magnification (the scanning area is larger than 100- ⁇ and several hundreds larger than the image plane; several hundreds in the range of im) to high magnification.
  • the acquired image is displayed on the display device, and the magnification at the time of acquisition is also displayed.
  • the magnification of an image is divided into an intermediate magnification area of 1,000 to 10,000 times and a high magnification area of 10,000 to 500,000 times.
  • I was getting an image with a magnification of
  • the diameter of the electron beam is set large in the intermediate magnification range.
  • the resolution of the image deteriorated due to the large diameter of the electron beam, and only a blurred image could be obtained, which was very difficult to see.
  • the method of the present invention it has become possible to achieve display without shifting the center position of the image over an area where the magnification of the image is 1000 to 500,000.
  • the magnification error between the center and the periphery of the image is larger than 5%, the amount of displacement of the center position of the image can be judged by the human eye only on the display screen by lmm (image plane at 10,000 times magnification). The equivalent is about 0.1 im). Therefore, in this method, a value smaller than this value is obtained.
  • the excitation conditions of the correction magnetic field lens 9 for electron beam deflection and the objective lens 7 are set to the conditions for correcting the distortion as described above, and the upper deflection coil 4 and the lower
  • magnification can be changed by changing the deflection current value of the deflection coil 5.
  • image observation in a wide range from low magnification to high magnification can be performed without blurring the image, and operability is improved.
  • the deflector is described using a deflection coil as an example.
  • the present invention is not limited to this, and is applicable to an electrostatic deflection plate.
  • the mounting operation can be performed so that the off-axis deflection distortion of the objective lens is canceled by the electrostatic lens.
  • the acceleration voltage and the retarding voltage have the opposite polarity to that of the electron beam.
  • FIG. 6 shows a second embodiment of the present invention, and is an example for installing a correction magnetic field lens for electron beam deflection below a deflection coil.
  • a correction magnetic field lens magnetic path 12 for electron beam deflection is installed between the convergent lens magnetic path 10 and the objective lens magnetic path 14, and the upper deflection coil 4 and the lower deflection coil 4 are installed.
  • 5 is wound around a deflecting coil pobin 16 and installed in a collection magnetic field lens 13 for electron beam deflection.
  • the sample 8 is mounted on the sample stage 19 and placed in the gap of the objective lens magnetic path. Inside each lens, a converging lens coil 11 for lens excitation, a correction magnetic field lens coil 13 for electron beam deflection, and an objective lens coil 15 are arranged. Since the gap of the lens magnetic path 12 of the correction magnetic field lens for electron beam deflection, that is, the lens main surface is below the lower deflection coil 5, it can be used as an optical system for correcting distortion as described above.
  • FIG. 7 shows an example of a configuration for realizing the above-described optical system, similarly to FIG. 6, and shows a third embodiment of the present invention.
  • the correction magnetic field lens magnetic path 12 for electron beam deflection is disposed on the objective lens magnetic path 14, and the spacer 17 is disposed between the objective lens magnetic path 14 and the convergent lens magnetic path 10. This spacer position is biased By arranging the directional coil pobins 16, an optical system configuration similar to that of FIG. 6 can be obtained.
  • FIG. 8 is an example of a configuration for realizing the above-described optical system as in FIG. 6, and shows a fourth embodiment of the present invention.
  • the deflection coil pobins 16 are arranged above and below the correction magnetic field lens magnetic path 12 for electron beam deflection, and the distortion for canceling the distortion of the objective lens in the middle stage of the deflection by the deflection coil. Is generated in the gap of the magnetic path of the correction magnetic field lens for electron beam deflection, thereby forming an optical system similar to that shown in FIG.
  • the sample 8 is held on a sample stage 19 in a sample chamber 18 placed below the objective lens magnetic path 14.
  • This is an objective lens type lens generally used in a general-purpose scanning electron microscope, and is capable of observing a large-sized sample unlike the in-lens type.
  • a charged particle source a converging lens for converging a charged particle beam generated from the charged particle source, a sample stage on which a sample is placed, and an objective lens for forming an image of the charged particle beam on the sample.
  • a correction lens for correcting distortion caused by the objective lens is disposed on the charged particle source side of the objective lens, and the first deflector and the second deflector are sandwiched by the correction lens. It has a point.
  • FIG. 9 shows a fifth embodiment of the present invention, and is an example of a configuration for realizing the optical system by using an art lens type objective lens commonly used in a general-purpose scanning electron microscope.
  • secondary electron detectors 20 for detecting the intensity of the secondary electron beam generated from the sample by the irradiation of the primary electron beam are installed.
  • An electric field orthogonal deflector (EXB deflector) _2 1 is installed in the magnetic path of the objective lens, and a secondary electron detector 2 on which the secondary electrons are placed on the objective lens without bending the primary electron beam. Driven under conditions for efficient detection to 0 I have.
  • the backscattered electron detector 22 is provided between the sample 8 and the objective lens magnetic path 14 and detects the intensity of the electron beam reflected by the sample 8.
  • the sample 8 is held on a sample stage 19 via an insulating plate 27.
  • the sample stage may be insulated in a two-stage structure.
  • a retarding voltage 28 is applied to the sample 8, and the setting is made so as to reduce the energy of the primary electron beam incident on the sample 8. This is to reduce the influence of aberration by passing the primary electron beam with high acceleration energy when passing through the deflector and the objective lens. This is because the energy of the primary electron beam is reduced just before the sample 8 is incident, and the electron beam irradiation damage of the sample is reduced.
  • the electrode 23 is grounded, and forms an electric field for retarding with the sample 8.
  • An electron gun accelerating voltage 26 is applied to the electron gun electrode 24, which functions to extract a primary electron beam from the electron source chip 25 and accelerate the electron beam to a predetermined accelerating voltage.
  • Correction correction for electron beam deflection that eliminates the distortion of the magnetic field generated by the gap of the objective lens magnetic path 14 and the aberration generated by the retarding electric field
  • the magnetic lens is connected to the objective lens magnetic path 14 and the deflectors 4 and 5. This is the point provided between
  • a charged particle source a deflector for deflecting a charged particle beam
  • a sample stage on which a sample is mounted an objective lens for forming an image on the sample
  • the sample stage and the objective lens A second lens for generating a deceleration electric field provided between them, and a load of the objective lens!
  • the first lens is provided on the particle source side for correcting the objective lens and the deflection distortion generated by the second lens.
  • the second lens here has an electrode on the lower surface of the magnetic path of the objective lens and an electrode that can apply a deceleration voltage to the sample on the sample table.
  • the function of the electrostatic lens is to apply a voltage between them. do.
  • distortion can be corrected at an intermediate magnification of the objective lens, so that the image is not distorted even if the deflection amplitude is increased. That is, since one image acquisition area can be made larger than that of the conventional method, the throughput can be improved by repeatedly using the same for the inspection of the circuit pattern.
  • inspection of one line is performed a predetermined number of times in synchronization with movement of the stage, and then inspection of the next line is sequentially performed by moving the stage.
  • the throughput in one-line inspection is determined by the time to compare and inspect one acquired image, and the total execution time is calculated by how many lines are repeated.
  • the inspection is performed in a 1 mm square.
  • the number of inspections for one image in the total inspection is reduced from 200 ⁇ 200 to 200 ⁇ 200, but under the condition that inspection is performed at the same resolution, If the inspection area is enlarged, the inspection pixels become large, so there is no effect on improving the throughput in consideration of the calculation time.
  • the number of stage movements to the next line is reduced from 200 to 200. Assuming that the time required for each movement of the stage is 1 second, this is 30 minutes This will improve the output.
  • the total inspection time is as long as about 7 hours, so the degree of throughput improvement is low, but if the total inspection time is shortened by improving the calculation time in the future, this method will be effective for improving throughput. It is one of the means.
  • a sample having a repetitive circuit pattern is placed on a sample stage, and the primary charged particle beam from the charged particle source is accelerated to form an image of the primary charged particle beam on the sample. Irradiation is performed by passing through the objective lens, the primary charged particle beam that has passed through the objective lens is decelerated by the decelerating electric field on the sample stage, and deflection distortion generated when passing through the objective lens and deflection generated when passing through the decelerating electric field A deflection distortion correction amount is supplied to a correction lens for correcting distortion.
  • the first area of the repetitive pattern of the sample is detected by scanning the scanning area on the sample at the first intermediate magnification in the range of 100 to 100 m, stored as the first image, and stored as the second image.
  • the area is scanned and detected at a first magnification or a second intermediate magnification and stored as a second image.
  • the circuit pattern is inspected for defects by comparing and inspecting the first and second images.
  • a previously determined correction value is set in the correction lens according to the magnification.
  • the corrected image is stored as information on the magnification or running range at the time of measurement, and the image and the information on the magnification or running range are displayed on the screen upon request.
  • the correction value stored in advance by obtaining the deflection distortion due to the retarding voltage that differs depending on the sample in the range of 100 ⁇ m to 10 ⁇ m in terms of the image plane in the scanning area, and scanning is performed.
  • the detection of the area in the range of 100 / zm to 10 / im in terms of the image plane has the effect of improving the efficiency of the inspection.
  • the wafer has a wafer on which chips having a repeating pattern are formed. So The wafer is placed on the sample stage, and the chip is divided into a plurality of areas. This area is 100 m. After aiming at this area, scan while zooming up with a scanning width of 100 ⁇ m to 100 ⁇ m. When the circuit pattern in the previous area is different, the scanning is stopped and the area having the defect is registered. When this is performed on the entire chip, if the defect is large, it is detected at a low magnification, and the result can be obtained without scanning the entire surface from 100 m to 100 ⁇ m. This has the effect of shortening the inspection time. Using this method, defects can be found on a region basis, and portions without defects can be removed on a region basis.
  • the area and zooming range here are not limited to actual examples, but may be any of low magnification, intermediate magnification, and high magnification.
  • a defect inspection method comprising:
  • the sample stage is tilted, and the charged particle beam is scanned using a deflector to scan the area including the target on the sample to search for the target.
  • the focus position will shift.
  • the image plane position of the objective lens that is, the focus is readjusted by changing the current of the objective lens.
  • the eucentric sample stage is used without going through such a process, Because the height of the irradiation position can always be the same in this state, there is no need to re-adjust the focal position, and an in-focus image can be obtained because the correction operates so as to cancel the distortion when passing through the objective lens If the lens is arranged between the deflector and the objective lens, it is possible to search for the visual field even when the sample stage is inclined. In this state, the scanning range of the charged particle beam is 100 m or less, and the ratio when displaying on the display screen is from 100,000 times the intermediate magnification to 10,000 magnifications based on the image signal. Look for and implement. The microscope enables the field of view to be searched while the sample stage is tilted.
  • the eucentric structure of the sample stage here refers to a sample stage that can be adjusted so that the center of the field of view always coincides with the center of rotation of the sample stage when irradiated with a charged particle beam. .
  • correction magnetic lens 9 operates as an auxiliary lens to assist the deflector without canceling the distortion.
  • the magnification of the scanning electron microscope image can be changed by changing the deflection swing width.
  • the distance between coils, and the excitation conditions used in the calculation of the deflection amplitude in the optical system for high-magnification image observation if the auxiliary magnetic field lens 9 is installed 66 mm above the objective lens, Assume. It is also assumed that the convergent lens image plane 3 is formed 78 mm above the auxiliary magnetic field lens 9.
  • the deflection angle of the upper deflection coil is set to 5 Om rad
  • the deflection angle of the lower deflection coil will be 18 m rad from the condition that the electron beam is returned to the center of the lens action of the auxiliary magnetic field lens 9.
  • Swing width is 0.1 mm.
  • An advantage of this optical system is that by aligning the optical axis of the auxiliary magnetic field lens 9 with the optical axis of the objective lens 7 mechanically or by a deflector, image displacement does not occur when switching between intermediate magnification and low magnification. Astigmatism is also common. Although not shown here, the astigmatism corrector is disposed between the objective lens and the charged particle source. This eliminates the need for adjustment when switching. Also, the objective lens 7 may be used with the same excitation at the intermediate magnification and the high magnification in some cases. At that time, the image will not be blurred due to hysteresis at the time of switching.
  • the present invention is applied to a short focus (2 mm below) objective lens generally used in an in-lens type electron microscope, but is applied to a long focus (5 mm) used in an out lens type electron microscope. Therefore, when the above-mentioned optical system is applied to the above-mentioned objective lens, the effect is even greater.
  • the focal length of the objective lens is 10 mm in the above lens configuration
  • the deflection angle of the upper deflection coil is set to 50 mrad
  • the deflection amplitude will be 0.4 mm
  • a high-resolution and distortion-free good image can be acquired in a wide magnification range from low magnification to high magnification. It has become possible to acquire images continuously with little image shift between the low magnification image and the high magnification image.

Abstract

An electron microscope comprising a short-focus objective is used for capturing a favorable image with high resolution and free of distortion in a wide magnification range from low to high magnification during observation under low acceleration voltage condition. The distortion caused by the objective is canceled by the opposite distortion caused by a correction magnetic field lens for electron beam deflection, thereby forming a scanning electron microscope image with high resolution and no distortion in a wide magnification range from low magnification to high magnification.

Description

明 細 書 荷電粒子線顕微鏡装置、 荷電粒子線応用装置、 荷電粒子線顕微方法、 荷電粒子線検査方法、 及ぴ電子顕微鏡装置  Description Charged particle beam microscope device, charged particle beam application device, charged particle beam microscopy method, charged particle beam inspection method, and electron microscope device
- 技術分野 - 本発明は、電子線等の荷電粒子線により試料を走査して試料の像信 号を得る荷電粒子線装置に係り、 特に、 荷電粒子線顕微鏡装置、 荷電 粒子線応用装置、 荷電粒子線顕微方法、 荷電 子線検査方法、 および 電子顕微鏡装置に関する。 背景技術 ' ， 例えば、 特開 2 0 0 0— 4 8 7 5 5号が有り、 対物レンズの歪曲収 差を補正するために偏向器の電流条件を変えることにより達成でき ることが開示されていた。  -TECHNICAL FIELD-The present invention relates to a charged particle beam apparatus that scans a sample with a charged particle beam such as an electron beam to obtain an image signal of the sample, and in particular, a charged particle beam microscope apparatus, a charged particle beam application apparatus, and a charged particle beam apparatus. The present invention relates to a particle beam microscopy method, an electron beam inspection method, and an electron microscope device. BACKGROUND ART For example, Japanese Patent Application Laid-Open No. 2000-48575 discloses that it can be achieved by changing the current conditions of a deflector to correct the distortion of the objective lens. Was.
ま 7こ、 H. C. Pfeiffer and W. Sticke丄 Large Fiel d Jilectron Optics - Limitions and Enhancements" 、 Proc. SPIE、 vol. 2522、 第 2 3 頁〜第 2 9頁 （1 9 9 5 . 7 . 1 0 ) に対物レンズ内に上偏向と下偏 向器の間に収差を動的に補正するビーム絞り付き補正器が開示され ているが詳細に付いては記載されていない。  Ma Koko, HC Pfeiffer and W. Sticke 丄 Large Field Jilectron Optics-Limitions and Enhancements ", Proc. SPIE, vol. 2522, pp. 23-29 (1999.5.10) Although a correction device with a beam stop for dynamically correcting aberrations between an upper deflection and a lower deflection device in an objective lens is disclosed, the details are not described.
また、従来の電子顕微鏡装置を用いた走査電子顕微鏡画像の取得方 法は、例えば特開平 1 1一 2 5 0 8 5 0号公報に開示されている。従 来、このような低倍率像の観察方法に用いる光学系としては対物レン ズを使用せず、偏向コイルを 1段だけで使用し、 高倍率時には偏向コ ィルと対物レンズを用いていた。  A method for acquiring a scanning electron microscope image using a conventional electron microscope apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. H11-250850. Conventionally, the optical system used for such low-magnification image observation methods does not use an objective lens, but uses a single-stage deflection coil.At high magnifications, a deflection coil and an objective lens are used. .
このようにこれら 2つの光学条件を切り替えながら、低倍率像で観 - 察視野探し、 高倍率像で形状観察、 高分解能観察を行っている。 In this way, switching between these two optical conditions while viewing with a low magnification image -Searching for the field of view, performing shape observation and high-resolution observation with high magnification images.
また、走査電子顕微鏡像を取得するための収束レンズ、偏向コイル、 対物レンズの構成の組み合わせとして上記方法以外の構成を持つも のとしては、 特開平 6— 2 8 3 1 2 8号公報に開示されている。 これ は偏向コイル下部に順に収束レンズ、対物レンズを配置した構成であ る。この方法では対物レンズ中に設置した試料に対して偏向コイルに よって偏向された電子線を、収束レンズ及ぴ対物レンズで縮小して照 射する電子光学系が採用されている。.簡略..し,て表現すると、偏向コィ ルの下に電磁レンズ更にそめ下に対物'レンズが配置された構成を取 つている。 しかしここでの電磁レンズの役目は試料が対物レンズの下 又は上に配置された際の焦点位置を変更するためのものであること が開示されている。'  Japanese Unexamined Patent Application Publication No. Hei 6-2831128 discloses a combination of a converging lens, a deflection coil, and an objective lens for acquiring a scanning electron microscope image, which has a configuration other than the above method. Have been. In this configuration, a convergent lens and an objective lens are sequentially arranged below the deflection coil. This method employs an electron optical system that irradiates an electron beam deflected by a deflecting coil with respect to a sample placed in an objective lens by a converging lens and an objective lens and irradiates the sample. In short, it can be expressed as an electromagnetic lens under the deflection coil and an objective lens under the deflection coil. However, it is disclosed that the role of the electromagnetic lens here is to change the focal position when the sample is placed below or above the objective lens. '
従来、電子光学系即ち電子源からの電子線を収束するための収束レ ' ンズと、 電子線を走査する偏向器と、 一つ物点と一つの像点を有する 対物レンズとを含む電子光学系を有し、 低加速電圧 （約 5 k V以下） で走査電子顕微鏡像を取得する場合、色収差による電子線スポットの 広がりが発生する。このスポットの広がりは倍率に関係なく一定とす る。解像度は電子線スポットの径と電子線走查範囲との割合で決まる 従って、電子線の走查範囲が狭く即ち高倍率に成ればなるほど解像度 が低下する。これに対し逆に電子線の走査範囲が広く成れば即ち倍率 が低く成ればなるほど解像度は上昇する。従って、 高解像度の画像が 得られる倍率範囲は、 約 1 0 0 0倍以下程度である。  2. Description of the Related Art Conventionally, an electron optical system including an electron optical system, that is, a converging lens for converging an electron beam from an electron source, a deflector for scanning the electron beam, and an objective lens having one object point and one image point When a scanning electron microscope image is acquired with a low accelerating voltage (about 5 kV or less), the electron beam spot spreads due to chromatic aberration. The spread of this spot is constant regardless of the magnification. The resolution is determined by the ratio between the diameter of the electron beam spot and the scanning range of the electron beam. Therefore, the smaller the scanning range of the electron beam, that is, the higher the magnification, the lower the resolution. Conversely, the resolution increases as the scanning range of the electron beam increases, that is, as the magnification decreases. Therefore, the magnification range in which a high-resolution image can be obtained is about 100 × or less.
ここでの倍率とは、試料上の走査範囲に対する表示装置の表示範囲 - の比率を示す。  The magnification here indicates the ratio of the display range of the display device to the scan range on the sample.
一方、一万倍以上の高倍率用光学系では、 分解能を達成することを 目的として对物レンズを短焦点で動作させている。 この場合、 偏向離 軸量の小さい一万倍以上の高倍率 ¾の観察では高解像度の走査電子 顕微鏡像が得られるが、偏向離軸量が大きくなる 1 0 0 0倍から 1万 倍の中間倍率では対物レンズによる歪曲収差が発生するため、歪みの ない良好な画像が得られる倍率範囲は約 1万倍以上である。試料上の 視野探しとしては低倍率ではそれほど解像度を必要とせずとも問題 -でなかったが 1 0 0 0倍から 1万倍の中間倍率では解像度が要求さ れていた。 しかし、 この中間倍率での解像度を上げることの工夫がな されていなかった。 すなわち、従来の電子光学系では低倍率及ぴ高倍On the other hand, in a high-magnification optical system with a magnification of 10,000 or more, a human lens is operated at a short focal length in order to achieve resolution. In this case, the deflection Observation at a high magnification of 10,000 times or more with a small axial amount can provide a high-resolution scanning electron microscope image, but depending on the objective lens at intermediate magnifications of 1000 to 10,000 times, where the amount of deflected deflection is large. Since distortion occurs, the magnification range over which good images without distortion can be obtained is about 10,000 times or more. It was not a problem to find a field of view on the sample at low magnifications without requiring much resolution-but at intermediate magnifications of 1000 to 10,000 times resolution was required. However, no attempt was made to increase the resolution at this intermediate magnification. In other words, the conventional electron optical system has low magnification and high magnification.
' 率用光学系のいずれに,おいても 1 0 0 0倍から 1万倍程度め中間倍 率範囲（像面換算 Ι Ο μ π！〜 1 0 0 m )において高解像度で歪みの ない良好な画像が得られていない。 '' In any of the optical systems for magnification, good resolution without distortion in the intermediate magnification range of about 100 to 10,000 times (image plane conversion Ι Ο μπ! To 100 m) Images have not been obtained.
また、 従来の電子光学系では、 高、 低倍率それぞれの光学系におい て使用するレンズ、 コイルの組み合わせや励磁条件がすべて異なるた めに切り替え時の磁気ヒステリシスや光学的軸がズレているため、低- 倍率像と高倍率像を切り替えた場合に、試料の同一個所の画像位置に ずれが生じて表示され、 視野探し操作での不具合が発生していた。  Also, in the conventional electron optical system, the combination of the lenses and coils used in the high and low magnification optical systems and the excitation conditions are all different, so the magnetic hysteresis and optical axis during switching are misaligned. When switching between the low-magnification image and the high-magnification image, the image position at the same location on the sample was displayed with a shift, causing a problem in the visual field search operation.
以上のように、例えば低加速電圧で短焦点の対物レンズを使用して 走査電子顕微鏡像を取得する場合には、 1 0 0 0倍から 1万倍程度の 中間倍率範囲での画像の高画質化が課題であり、偏向コイルやレンズ の励磁条件を変化させないで.中間倍率像から高倍率像までの広い倍 • 率範囲での観察を可能とする電子光学系が必要であった。 発明の開示  As described above, for example, when acquiring a scanning electron microscope image using a short-focus objective lens at a low acceleration voltage, high image quality in an intermediate magnification range of about 1000 to 10,000 times Therefore, there is a need for an electron optical system that enables observation in a wide magnification range from an intermediate magnification image to a high magnification image without changing the excitation conditions of the deflection coil and lens. Disclosure of the invention
そこで、 本発明の目的は、 対物レンズで発生する中間倍率（倍率 1 0 0 0倍から 1万倍で像面換算 1 0 mから 1 0 0 ^ m)で試料上走 查の範囲で歪曲収差を補正し、中間倍率から高倍率までの広い倍率範 囲において高解像度で歪みのない良好な走査電子顕微鏡画像または 画像信号を取得することを可能とする荷電粒子線装置を提供するこ とにある。 Accordingly, an object of the present invention is to provide an objective lens having an intermediate magnification (magnification of 100 to 10,000 times and an image plane conversion of 100 to 100 m) at a magnification of 100 m to 100 m, and a distortion aberration in a range of 上 on the sample. And a wide magnification range from intermediate magnification to high magnification. It is an object of the present invention to provide a charged particle beam apparatus capable of acquiring a high-resolution and distortion-free good scanning electron microscope image or image signal in a surrounding area.
上記目的を達成するために、本発明は、一つの物点と一つの像点を 有する対物レンズの前段に設置した荷電粒子線偏向'用の補正レンズ を対物レンズで発生する歪曲収差を補正する条件で励磁し、偏向器に よつて荷電粒子線を試料面上で 2次元的に走査し、低倍率から高倍率 まで収差の少ない走査荷電粒子線顕微鏡画像または画像信号を取得 する。  In order to achieve the above object, the present invention corrects a distortion caused by an objective lens using a correction lens for charged particle beam deflection, which is installed in front of an objective lens having one object point and one image point. Excitation is performed under the conditions, and the charged particle beam is two-dimensionally scanned on the sample surface by the deflector to acquire a scanning charged particle beam microscope image or image signal with little aberration from low magnification to high magnification.
また、本発明の構成は、収束レンズと対物レンズとの間に荷電粒子 線偏向用の補正レンズを設け、対物レンズで発生する歪曲収差とが互 いに逆方向の収差となるように構成したことにある。  Further, in the configuration of the present invention, a correction lens for charged particle beam deflection is provided between the converging lens and the objective lens, and the distortion generated in the objective lens is opposite to the aberration. It is in.
また、 本発明の構成は、 補正レンズを経た荷電粒子線が、 対物レン ズの主面位置に結像するよう構成した点にある。  Further, the configuration of the present invention lies in that the charged particle beam having passed through the correction lens forms an image at the position of the main surface of the objective lens.
また、本発明の構成は、偏向器が補正レンズの前段に設置されてい ることにある。 また、 本発明の構成は、 偏向器は 2段の上段偏向器と 下段偏向器よりなり、補正レンズが上段偏向器及び下段偏向器より下 に位置するか上段偏向器と下段偏向器との間に位置する構成となつ ている。  Further, the configuration of the present invention resides in that the deflector is installed at a stage before the correction lens. Further, in the configuration of the present invention, the deflector comprises a two-stage upper stage deflector and a lower stage deflector, and the correction lens is located below the upper stage deflector and the lower stage deflector or between the upper stage deflector and the lower stage deflector. The configuration is located in
' また、本発明の構成は、試料を載置する試料室を対物レンズの磁路 下部に設けてなることを特徴とする。 Further, the configuration of the present invention is characterized in that a sample chamber for mounting a sample is provided below the magnetic path of the objective lens.
さらに、 本発明は、 電子源より発生した 次電子線を所定の電圧ま で加速するための 1段以上の静電レンズと、一次電子線を試料に収束 さ; ¾:て照射するための 1段以上の収束レンズおょぴ対物レンズと、一 次電子線を偏向させるための 1段以上の偏向器とを具備した電子顕 微鏡装置において、対物レンズの前段に設置した電子線偏向用の補正 磁界レンズを対物レンズで ^生する歪曲収差を補正する条件で励磁 して偏向器、補正磁界レンズおよび対物レンズによる電子線偏向によ つて一次電子線を試料面上で 2次元的に走査し試料から 2次的に発 生する二次電子線や試料を透過した電子線の強 を一次電子線の走 査と同期して検出し、その信号を画像表示装置の輝度変調信号として 画像表示装置により走査電子顕微鏡画像として表示するように構成 した点に有る。 Further, the present invention provides one or more stages of an electrostatic lens for accelerating a secondary electron beam generated from an electron source to a predetermined voltage, and a primary electron beam focused on a sample; An electron microscope equipped with a converging lens having at least one stage and an objective lens and a deflector having at least one stage for deflecting the primary electron beam. correction The magnetic lens is excited under the conditions to correct the distortion generated by the objective lens, and the primary electron beam is scanned two-dimensionally on the sample surface by the electron beam deflection by the deflector, the correction magnetic lens, and the objective lens. The intensity of the secondary electron beam generated secondarily or the intensity of the electron beam transmitted through the sample is detected in synchronization with the scanning of the primary electron beam, and the signal is used as a luminance modulation signal of the image display device by the image display device. This is in that it is configured to be displayed as a scanning electron microscope image.
試料中の目的物視野探しの際、第 1の倍率から第 2の倍率に連続 ½ にズーミングアップ又はズーミングダウンして視野探しする点にあ る。  When searching for the visual field of the object in the sample, the point is that the visual field is searched by continuously zooming up or down from the first magnification to the second magnification.
さらにまた、本発明は、 あらかじめ取.り込んだ所定倍率の画像ある いは設計画像とを比較して、前記試料の物理的な形状不良及ぴ電気的 な不良を検查する点にある。 また、繰り返し回路パターンの第 1の領 域と第 2の領域を第 1の倍率で画像信号として検出し、その画像信号 を比較し一致しない時に再.度第 1の倍率とは異なる第 2の倍率で相 違する領域の画像信号を各々取り込み再度比較して一致しない場合 に欠陥と判定する検査方法にある。  Still another object of the present invention is to detect a physical shape defect and an electrical defect of the sample by comparing the image with a predetermined magnification or a design image which has been taken in advance. In addition, the first area and the second area of the repetitive circuit pattern are detected as image signals at the first magnification, and the image signals are compared, and when they do not match, the second area is different from the first magnification. An inspection method is provided in which image signals in areas different in magnification are captured and compared again to determine a defect if they do not match.
更にまた、本発明は、低倍率で周辺ボケが少ない電子光学系を提供 することにある。 図面の簡単な説明  Still another object of the present invention is to provide an electron optical system with low magnification and low peripheral blur. BRIEF DESCRIPTION OF THE FIGURES
. 図 1は、従来の高倍率の走査電子顕微鏡画像観察用光学系を表わす 図、 図 2は、 対物レンズで発生する歪曲収差の結果を表わす図、 図 3 は、従来の低倍率の走査電子顕微鏡画像観察用光学系を表わす図、 図 4は、 本発明の第 1の実施例の基本的構成を説明する図、 図 5は、 本 発明により対物レンズで発生する歪曲収差を補正した結果を表わす 図、 図 6は、 本発明の第 2の実施例を説明する図、 図' 7は、 本発明の 第 3の実施例を説明する図、 図 8は、本発明の第 4の実施例を説明す る図、 図 9は、 本発明の第 5の実施例を説明する図である。 発明を実施するための最良め形態 FIG. 1 is a diagram showing a conventional high-magnification scanning electron microscope image observation optical system, FIG. 2 is a diagram showing the result of distortion caused by an objective lens, and FIG. 3 is a conventional low-magnification scanning electron microscope. FIG. 4 is a diagram illustrating an optical system for observing a microscope image, FIG. 4 is a diagram illustrating a basic configuration of a first embodiment of the present invention, and FIG. 5 is a diagram illustrating a result of correcting distortion generated in an objective lens according to the present invention. Show FIG. 6 is a diagram illustrating a second embodiment of the present invention. FIG. 7 is a diagram illustrating a third embodiment of the present invention. FIG. 8 is a diagram illustrating a fourth embodiment of the present invention. FIG. 9 is a diagram for explaining a fifth embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION
以下、荷電粒子源として電子源、荷電粒子線として電子線を例に挙 げ具体的に説明する。本発明を電子顕微鏡装置を用いて、対物レンズ で発生する歪曲収差を補正し、低倍率から中間倍率を経由して高倍率 まで走査電子顕微鏡画像または画像信号を取得する方法を説明する。 図 1は、従来の電子顕微鏡装置にて高倍率の像を観察するための光 学系の構成図を示すものである。電子源 1から発生した一次電子線を 収束レンズ 2により縮小し、 収束レンズ 2の像面位置 3に結像する。 次に、上段偏向コイル 4と下段偏向コイル 5を動作させ、 下段偏向コ ィル 5により偏向された一次電子線が光軸 1 'と交わる点として定義 される偏向支点 6を対物レンズ 7の前磁場焦点面位置と一致させる。 この時、 一次電子線ま対物レンズ 7のレンズ作用によって光軸 1，か ら離れた位置に結像される。 図 4に示すように、 この離軸位置を偏向 位置、離軸距離を偏向振り幅 r という。 ここでの対物レンズ 7は一つ の物点と像点 2 9とを有するものとする。  Hereinafter, an electron source will be described as an example of a charged particle source, and an electron beam will be described as an example of a charged particle beam. The present invention describes a method for correcting a distortion generated in an objective lens using an electron microscope apparatus and acquiring a scanning electron microscope image or image signal from a low magnification to a high magnification through an intermediate magnification. FIG. 1 shows a configuration diagram of an optical system for observing a high-magnification image with a conventional electron microscope apparatus. The primary electron beam generated from the electron source 1 is reduced by the converging lens 2 and forms an image on the image plane position 3 of the converging lens 2. Next, the upper deflection coil 4 and the lower deflection coil 5 are operated, and a deflection fulcrum 6 defined as a point at which the primary electron beam deflected by the lower deflection coil 5 intersects the optical axis 1 ′ is positioned in front of the objective lens 7. Make it coincide with the magnetic field focal plane position. At this time, an image is formed at a position distant from the optical axis 1 by the lens action of the objective lens 7 to the primary electron beam. As shown in FIG. 4, this off-axis position is called a deflection position, and the off-axis distance is called a deflection swing width r. Here, the objective lens 7 has one object point and an image point 29.
上段偏向コイル 4の偏向角度を変化させた場合に、偏向支点 6の位 置が常に一定となるような上段偏向コイル 4と下段偏向コイル 5の 偏向角度の比 （偏向上下比） は幾何学的な寸法で決定できる。 このよ うな偏向上下比を設定すれば、偏向振り幅は上段偏向コイル 4の偏向 角度によって決定される。  When the deflection angle of the upper deflecting coil 4 is changed, the ratio of the deflecting angles of the upper deflecting coil 4 and the lower deflecting coil 5 so that the position of the deflecting fulcrum 6 is always constant (deflection vertical ratio) is geometric. Size can be determined. If such a deflection vertical ratio is set, the deflection swing width is determined by the deflection angle of the upper deflection coil 4.
ここで、偏向'支点 6を対物レンズ 7の前磁場焦点面位置（物点）と一 致させる目的は、一次電子線が試料 8上で光軸より離軸された場合に、 試料 8に対する照射角度がすべての偏向位置において一定となるよ うにするためである。 Here, the purpose of matching the deflection fulcrum 6 with the front magnetic field focal plane position (object point) of the objective lens 7 is that when the primary electron beam is off-axis from the optical axis on the sample 8, This is so that the irradiation angle with respect to the sample 8 is constant at all deflection positions.
上段偏向コイル 4の偏向角度を一定ステップで直交する 2方向に 変化させ、 それと同期して透過電子線、 2次電子線、 反射電子線等め 強度を検出し、輝度変調して表示させることによって走査電子顕微鏡 画像を得ることができる。走査電子顕微鏡画像の偏向振り幅は上段偏 向コイル 4の偏向角度の最大値を設定することによって決定される。 ここで、 典型的なコイル、 レ ズ励磁条件、 レンズ間距離等のパラ メータを用いてコイル偏向角度と走査電子顕微鏡画像の倍率との関 係を説明する。上段偏向コイル 4と下段偏向コイル 5との間隔が 3 4 mm、 下段偏向コイル 5と対物レンズ 7との距離が 9 3. 5 mm、 対 物レンズ 7の前磁場焦点面位置を対物レンズ 7  By changing the deflection angle of the upper deflection coil 4 in two directions perpendicular to each other in a certain step, synchronously detecting the transmitted electron beam, secondary electron beam, reflected electron beam, etc. Scanning electron microscope Images can be obtained. The deflection amplitude of the scanning electron microscope image is determined by setting the maximum value of the deflection angle of the upper deflection coil 4. Here, the relationship between the coil deflection angle and the magnification of a scanning electron microscope image will be described using parameters such as a typical coil, a lens excitation condition, and a distance between lenses. The distance between the upper deflection coil 4 and the lower deflection coil 5 is 34 mm, the distance between the lower deflection coil 5 and the objective lens 9 is 93.5 mm, and the position of the front magnetic field focal plane of the objective lens 7 is the objective lens 7.
の上 2. 5 mmと仮定する。 Assume 2.5 mm above
まず、 上段、 下段偏向コイルの偏向角度をそれぞれ Θ 1、 Θ 2とす る。 偏向支点位置を固定して、試料面上で電子線を偏向させるための 偏向角度の上下比は、 Θ 2 = ( 1 + 3 4/ ( 9 3. 5 - 2. 5) ) θ 1 = 1. 3 8 Θ 1である。  First, let the deflection angles of the upper and lower deflection coils be Θ1 and Θ2, respectively. The vertical ratio of the deflection angle for deflecting the electron beam on the sample surface while fixing the deflection fulcrum position is 、 2 = (1 + 34 / (93.5-2.5)) θ1 = 1 3 8 Θ 1
この上下偏向比率の設定は、上下段偏向コイルを逆位相にして卷数 、 上： 下 = 1 ： 1. 3 8にして巻き込み、 上下段偏向コイルを直列 に通電する。 偏向振 幅 r ½'、 r = 2. 5 X 3 4/ 9 1 X 0 1 = 0. 9 4 X 0 1 となる。  The upper and lower deflection ratios are set by winding the upper and lower deflection coils in opposite phases and setting the number of turns to: upper: lower = 1: 1.38, and energizing the upper and lower deflection coils in series. The deflection amplitude r ½ ', r = 2.5 X34 / 91X01 = 0.994X01.
よって、例えば、 上段偏向コイルの偏向角度を 5 0 m r a dに設定 すると、偏向振り幅は r = 4 7 / mとなる。 画像の表示を 1 0 0 mm 角に設定すれば、 走査電子顕微鏡画像の倍率は、 1 0 0 X 1 0 0 0ノ ( 4 7 X 2 )= 1 0 64倍となる。  Thus, for example, if the deflection angle of the upper deflection coil is set to 50 mrad, the deflection swing width is r = 47 / m. If the image display is set to 100 mm square, the magnification of the scanning electron microscope image is 100 × 100 × (47 × 2) = 1064 ×.
ここで、 通常、上段偏向コイルの偏向角度 0 1の最大値は 5 Om r a d程度なので、この光学系での最低倍率は約 1 0 0 0倍ということ になる。 ただし、 この場合、 偏向振り幅が大きくなるほど、 歪曲収差 が大きくなるために実用可能な倍率には下限がある。 Here, normally, the maximum value of the deflection angle 0 1 of the upper deflection coil is 5 Om r Since it is on the order of ad, the minimum magnification in this optical system is about 100 ×. However, in this case, the distortion becomes larger as the deflection amplitude becomes larger, so that there is a lower limit to the practicable magnification.
図 2は、 偏向コイルによって正方形のラスター,を形成した場合に、 実際のラスターが対物レンズによってどのような形状で試料面上に 結像されるのかを示した例である。.条件としては、 歪曲収差の影響の みを考慮し、 歪曲収差の係数 （«素数値） は、 実数部、 虚数部ともに 5 X 1 0 _5とした。 Fig. 2 shows an example of how a real raster is imaged on a sample surface by an objective lens when a square raster is formed by a deflection coil. The. Conditions, taking into account only the effects of the distortion aberration, the coefficient of distortion aberration ( «prime number) is, the real part, was 5 X 1 0 _ 5 in both the imaginary part.
図 2の （ a ) に示すように、 倍率 1 0 0 0倍の場合には、 正方形の ラスターが糸卷き状に歪んでいる。 この条件で画像を取得すれば、 そ の画像は中心より右上がり及ぴ左下がり方向に画像の倍率が順次低 くなるような歪んだ像となる。 一方、 図 2の （b ) に示すように、 1 万倍の場合には、 ラスターは正方形の形で結像され、歪みのない良好 な画像が得られる。 以上のように、 高倍率の像を取得するための電子 光学系には歪曲収差の影響により最低倍率に制 がある。  As shown in (a) of FIG. 2, when the magnification is 100 ×, the square raster is distorted like a pincushion. If an image is acquired under these conditions, the image will be distorted such that the magnification of the image will gradually decrease in the rightward and leftward directions from the center. On the other hand, as shown in Fig. 2 (b), when the magnification is 10,000, the raster is imaged in a square shape, and a good image without distortion is obtained. As described above, the electron optical system for acquiring a high-magnification image has a minimum magnification due to the influence of distortion.
次に、 1 0 0 0倍以下の低倍率の走查電子顕微鏡画像を観察するた めに通常用いられている光学系について、 図 3を用いて説明する。 低 倍率像を観察するためには試料 8上での偏向振り幅を大きくする必 要があるので、対物レンズの前磁場焦点面位置に偏向支点を一致させ て電子線を偏向させるという方法では試料上での走查偏向領域を対 物レンズのレンズ作用によって大きくすることができない。 従って、 対物レンズの励磁を停止して使用することがなされていた。 即ち、 上 段偏向コイル 4による 1段偏向で電子線を傾斜させて偏向振り幅を 大きくする光学系が用いられる。（いわゆる一段偏向）対物レンズによ る偏向を利用しないので対物レンズの励磁をゼロとなるようにし、電 子源 1からの電子線は収束レンズ 2によって試料 8上に焦点を結ぶ ように設定される。 Next, an optical system usually used for observing a scanning electron microscope image at a low magnification of 1000 or less will be described with reference to FIG. In order to observe a low-magnification image, it is necessary to increase the deflection swing width on the sample 8.Therefore, the method of deflecting the electron beam by aligning the deflection fulcrum with the position of the front magnetic field focal plane of the objective lens is used. The scanning deflection area cannot be increased by the lens action of the objective lens. Therefore, the excitation of the objective lens has been stopped before use. That is, an optical system is used in which the electron beam is inclined by one-stage deflection by the upper stage deflection coil 4 to increase the deflection swing width. Since the deflection by the objective lens is not used, the excitation of the objective lens is set to zero, and the electron beam from the electron source 1 is focused on the sample 8 by the converging lens 2. It is set as follows.
上記の高倍率像観察条件と同一のコイル、 レンズを用いた場合、 1 段偏向コイルの偏向角度 ø 3と偏向振り幅 r との関係は、 r = 1 2 7 X Θ 3 となる。  When the same coil and lens are used under the above-described high-magnification image observation conditions, the relationship between the deflection angle ø3 of the single-stage deflection coil and the deflection swing width r is r = 127 X3.
すなわち、 上段偏向コイルの偏向角度を 5 m r a dに設定すると、 偏向振り幅 r = 0. 64 mmとなり、 走査電子顕微鏡画像の倍率は 1 00ノ （0. 6 4 X 2)= 78倍となる。 _  That is, when the deflection angle of the upper deflection coil is set to 5 mrad, the deflection swing width becomes r = 0.64 mm, and the magnification of the scanning electron microscope image becomes 100 × (0.64 × 2) = 78 times. _
このように、この電子光学系では十分に低倍率の像を偏向コイルに 小さな偏向角度を与えることによって得ることができるが、次のよう な問題点がある。収束レンズ 2を 1段のみで使用して電子源を試料面 上に結像する電子光学系であり、電子源に対する電子光学倍率はほぼ 数分の 1程度となるので、 収束レンズ 2は低い励磁で使用する。  Thus, in this electron optical system, a sufficiently low magnification image can be obtained by giving a small deflection angle to the deflection coil, but there are the following problems. This is an electron optical system that focuses the electron source on the sample surface using only one stage of the converging lens 2.The electron optical magnification of the electron source is almost a fraction, so the converging lens 2 has low excitation. Used in.
この場合、 収束レンズ 2の色収差係数が 1 00 Omm程度となる。 この色収差によるスポッ トの広がりを計算する。 加速電圧を 1 k V、 電子源のエネルギー広がりを 0.5 V、スポッ トの照射角度を 0. 5 m r a dと仮定すると、 スポットの広がり量は 1 00 0 (色収差係数） X (0. 5 (電子源のエネルギー広がり）/ 1 000 (加速電圧）） X 0. 000 5 (照射角度） =0. 2 5 μ mとなる。  In this case, the chromatic aberration coefficient of the converging lens 2 is about 100 Omm. The spread of the spot due to this chromatic aberration is calculated. Assuming that the accelerating voltage is 1 kV, the energy spread of the electron source is 0.5 V, and the irradiation angle of the spot is 0.5 mrad, the spread amount of the spot is 100 000 (chromatic aberration coefficient) X (0.5 (electron source Energy spread) / 1 000 (acceleration voltage)) X 0.005 (irradiation angle) = 0.25 μm.
一方、画像の倍率が 1 000倍の場合に、 電子線偏向量は一辺が 1 00 mであり、 一辺を 500画素で画像化するとしたら、 1画素の 大きさは 0. 2 111となる。 よって、 この光学系では 1画素（0. 2 m)よりもスポッ ト広がり（0.2 5 in)のほうが大きくなり、高解像 度の画像が得られない。 1画素とスポット広がりが同じ量となる倍率 は 800倍であり、 これがこの光学系の倍率の上限となる。  On the other hand, when the magnification of the image is 1,000 times, the electron beam deflection amount is 100 m on one side, and if one side is imaged with 500 pixels, the size of one pixel is 0.2111. Therefore, with this optical system, the spot spread (0.25 in) is larger than one pixel (0.2 m), and a high-resolution image cannot be obtained. The magnification at which the spot spread is the same as one pixel is 800 times, which is the upper limit of the magnification of this optical system.
また、上段偏向コイル 4による 1段偏向であるために、試料 8上で 偏向された電子線は偏向振り幅が大きいほど傾斜レて試料に入射す ることになり、 走査電子顕微鏡画像の周辺ほど画像が歪む、 いわゆる 画像の周辺ぼけが発生する。 さらに、 高倍率像観察時の光軸と低倍率 像観察時の光軸は一致しておらず、低倍率像と高倍率像で画像の位置 ずれが生ずる。 Also, since the single-stage deflection is performed by the upper deflection coil 4, the electron beam deflected on the sample 8 is incident on the sample with a larger inclination as the deflection swing width is larger. In other words, the more the periphery of the scanning electron microscope image is, the more distorted the image is. Furthermore, the optical axis at the time of observing the high-magnification image and the optical axis at the time of observing the low-magnification image do not match, and the image is misaligned between the low-magnification image and the high-magnification image.
以上より、従来の低倍率像観察用光学系は、視野探しに十分な低倍 率像を得ることができるが、高倍率用の光学系と比較して大きく光学 系を変化させているために様々な問題点を持っている。 さらに、高倍 率用の電子光学系では低倍率側に制限を有し、低倍率用の電子光学系 では高倍率側に制限があり中間倍率に対してはいずれの光学系でも 高解像度で歪みのない良好な画像が得られないという問題がある。従 来この中間倍率範囲（走査領域を像面換算 1 0 0 μ πι〜 1 0 μ mの範 囲）については対応がなされていなかった。  As described above, the conventional low-magnification image observation optical system can obtain a low-magnification image sufficient for searching for a visual field, but the optical system is greatly changed compared to the high-magnification optical system. Has various problems. In addition, the electron optical system for high magnification has a limit on the low magnification side, and the electron optical system for low magnification has a limit on the high magnification side. There is a problem that no good image can be obtained. Conventionally, no correspondence has been made for this intermediate magnification range (the scanning area is in the range of 100 μπι to 10 μm in image plane conversion).
以上のような従来の電子光学系の問題点を解決するためには、中間 倍率範囲での画像の高画質化が課題であり、偏向コイルやレンズの励 磁条件を変化させないで、低倍率像から高倍率像までの広い倍率範囲 での観察を可能とする電子光学系が望まれていた。  In order to solve the above-mentioned problems of the conventional electron optical system, it is necessary to improve the image quality in an intermediate magnification range. There has been a demand for an electron optical system that enables observation in a wide magnification range from images to high magnification images.
そこで、本発明の第 1の実施例として、対物レンズで発生する歪曲 収差を別レンズで補正し、低倍率から高倍率の走査電子顕微鏡画像を 取得する方法を示す。その実施例の基本的構成を図 4を用いて説明す る。  Therefore, as a first embodiment of the present invention, a method will be described in which distortion caused by an objective lens is corrected by another lens, and a scanning electron microscope image from low magnification to high magnification is obtained. The basic configuration of the embodiment will be described with reference to FIG.
従来の高倍率像観察用の収束レンズ 2、対物レンズ 7、 上段偏向コ ィル 4と下段偏向コイル 5を用いて試 >斗 8上で一次電子線を偏向し て像を得るという光学系に、新たに電子線偏向用の補正補正磁界レン' ズ 9を追加している。上段偏向コイル 4及び下段偏向コイル 5によつ て偏向された一次電子線を、電子線偏向用の補正磁界レンズ 9により 対物レンズ 7の主面位置に 1対 1に結像し、さらにその電子線を対物 レンズ 7によって試料 8上に結像する。 An optical system that deflects the primary electron beam on a sample 8 using a conventional converging lens 2, objective lens 7, upper deflection coil 4 and lower deflection coil 5 for observing a high-magnification image to obtain an image. In addition, a correction correction magnetic field lens 9 for electron beam deflection is newly added. The primary electron beam deflected by the upper deflecting coil 4 and the lower deflecting coil 5 forms a one-to-one image on the main surface of the objective lens 7 by a correction magnetic lens 9 for deflecting the electron beam. Objective line An image is formed on the sample 8 by the lens 7.
この時、上段偏向コイル 4及ぴ下段偏向コイル 5によって形成した 偏向離軸量に応じて電子線偏向用の補正磁界'レンズ 9で歪曲収差が 発生し、 歪んだ偏向図形が対物レンズ 7の主面位置に結像される。 さ らに、対物レンズ 7によって、 その歪んだ偏向図形の偏向離軸量に応 じた歪曲収差が発生し、 試料 8上で偏向図形は、 再度歪曲する。 ここで、電子線偏向用の補正磁界レンズ 9で発生する歪曲収差と対 物レンズ 7で発生する歪曲収差が逆方向の収差となるようにレンズ 極性、光学倍率を設.定してやることによ.つて、最終的に試料 8上に結 像される偏向図形は、上段偏向コイル 4及ぴ下段偏向コイル 5によつ て形成した偏向図形の形状に戻すことができる。  At this time, distortion occurs in the correction magnetic field lens 9 for electron beam deflection according to the amount of deflection off-axis formed by the upper deflection coil 4 and the lower deflection coil 5, and the distorted deflection pattern is the main object lens 7. An image is formed at the surface position. Further, the objective lens 7 generates a distortion according to the amount of off-axis deflection of the distorted deflection pattern, and the deflection pattern on the sample 8 is again distorted. Here, the lens polarity and the optical magnification are set so that the distortion generated by the correction magnetic lens 9 for electron beam deflection and the distortion generated by the objective lens 7 become aberrations in opposite directions. The deflection figure finally formed on the sample 8 can be returned to the shape of the deflection figure formed by the upper deflection coil 4 and the lower deflection coil 5.
本方法により歪曲収差の補正を行なった結果を図 5に示す。条件と しては、先述した図 1の条件と同様であるが、画像取得の倍率は 1 0 0 0倍 （偏向振り幅が片側 5 0 ni ) 、 歪曲収差の係数 （複素数値） の実数部、 虚数部はそれぞれ 5 X 1 0—5、 1 X 1 0— 5とした。 Fig. 5 shows the result of correcting distortion by this method. The conditions are the same as those in FIG. 1 described above, except that the magnification of image acquisition is 100 × (the deflection amplitude is 50 ni on one side) and the real part of the distortion aberration coefficient (complex value) is set. , the imaginary part was respectively 5 X 1 0- 5, 1 X 1 0- 5.
すなわち、 図 5の （ a ) に示すように、 上段偏向コイル 4及び下段 偏向コイル 5によって作成した正方形のラスターは、電子線偏向用の 補正磁界レンズ 9により対物レンズの歪曲収差とは逆向きのキャン セル用の歪曲収差を発生させる。このキャンセル用歪曲収差は対物レ ンズ 7の主面位置に歪んだ図形として結像される。 図 5の （b ) にそ の様子を示す。 これを用い、 その図形に対して逆方向の歪曲収差を発 生させる条件で対物レンズ 7を励磁してやることによって、試料 8上 ではラスターは、 図 5の （ c ) に示すように、 ほぼ正方形となって結 像されており、この倍率条件にて歪みのない良好な画像が得られるこ とがわかる。 '  That is, as shown in (a) of FIG. 5, the square raster created by the upper deflection coil 4 and the lower deflection coil 5 has a direction opposite to the distortion of the objective lens due to the correction magnetic lens 9 for electron beam deflection. Generates distortion for cancellation. The distortion for cancellation is imaged as a distorted figure at the position of the main surface of the objective lens 7. Fig. 5 (b) shows this situation. By using this and exciting the objective lens 7 under the condition of generating distortion in the opposite direction to the figure, the raster on the sample 8 becomes almost square as shown in (c) of FIG. It can be seen that good images without distortion can be obtained under these magnification conditions. '
ここでは補正磁界レンズ 9側を対物レンズに対し逆方向歪曲収差 を発生するようになるコイル極性と励磁条件を設定したがその逆、即 ち、補正磁界レンズに対して対物レンズの極性と励磁条件を変えるこ とによっても歪曲収差を補正することができる。 Here, the correction magnetic lens 9 side is the reverse distortion with respect to the objective lens. Although the coil polarity and the excitation conditions which cause the occurrence of the distortion are set, the distortion can also be corrected by changing the polarity of the objective lens and the excitation conditions with respect to the correction magnetic lens.
この補正方法は、 広い領域に目的物を探す視野探しだけではなく、 電子線又はイオン線を用い対物レンズの下に配置されたレジス トが 塗布されたウェハに露光する場合にも適用される。当然マスクを用い た一括露光又は可変整形更には電子線で点描画するタイプにも適用 が可能である。 更にまた、 電子線を用い対物レンズの下に試料を配置 して検查ゃ加工にも適用できるものである。  This correction method is applied not only to a visual field search for searching for a target in a wide area, but also to the case where an electron beam or an ion beam is used to expose a wafer coated with a resist disposed under an objective lens. Naturally, the present invention can be applied to batch exposure or variable shaping using a mask, and also to a type of spot drawing using an electron beam. Furthermore, the present invention can be applied to inspection processing by arranging a sample under an objective lens using an electron beam.
以上の内容を荷電粒子線であるイオン線まで拡張しても以下の如 く成立する。荷電粒子源からの一次荷電粒子線（イオンビーム）を試料 台に載置された試料に照射する。照射され.る走査幅に対する表示装置 上での大きさが倍率を表し、その倍率が低倍率の 1 0 0 0倍未満から 高倍率領域の 5 0 0万倍まで可変して走査する。その偏向器で走査さ れた一次荷電粒子線が対物レンズを通過する際に発生する偏向歪み (歪曲収差）を補正するレンズを付加することにより達成される。ここ での補正レンズとして静電偏向器を用いても良い。  Even if the above contents are extended to the ion beam which is a charged particle beam, the following holds. The sample placed on the sample stage is irradiated with the primary charged particle beam (ion beam) from the charged particle source. The size of the illuminated scanning width on the display device indicates the magnification, and the scanning is performed while varying from a low magnification of less than 1000 times to a high magnification area of 500,000 times. This is achieved by adding a lens that corrects deflection distortion (distortion aberration) generated when the primary charged particle beam scanned by the deflector passes through the objective lens. An electrostatic deflector may be used as the correction lens here.
次に、電子線偏向用の補正磁界レンズを歪曲収差が補正される条件 で使用するための励磁条件の決定方法について説明する。最初に加速 電圧をある所定の値に設定する。次に所定の試料位置に歪曲収差量の 評価を行うための試料を試料台に载置する。この試料には縦横の歪み 量が明確に評価できる 1ィンチあたり 1 0 0 0から 2 0 0 0本の直 交ラインを持つダリッドメッシュやライン幅 5力 ら 0 . 5 μ ηι程度の グレーティングを用いる。次に電子顕微鏡の倍率を最' :低倍率に設定し 、 対物レンズによって試料面に焦点を合わせる。 この時歪曲収差によ つて画像に大きな歪みが生じているので画像の中央部で焦点を合わ せる、あるいは中央部でも焦点が一致したかどうかの判定が困難な場 合には少し倍率を上昇させて画像の中央部で焦点を合わせた後に最 低倍率に再設定してもよい。次に電子線偏向用の補正磁界レンズ 9に 電流を流して励磁する。 ここで、 電子線偏向用の補正磁界レンズ 9は 対物レンズ 7と逆方向の磁界が形成されるように、例えばコイルの卷 き方向が逆で同一電流方向、あるいはコイルの卷き方向が同一で電流 が逆方向になるように設定してある。電子線偏向用の補正磁界レンズ 9を励磁すると走査電子顕微鏡像の焦点がずれると共に画像の歪み 量が変化する。焦点のずれを収束レンズ 2の電流励磁を変化させるこ とによって補正しながら電子線偏向用の補正磁界レンズ 9に通電す る電流によって励磁を変化させて画像の歪みが小くなるように調整 する。 画像の歪みが小さくなる電流値の近傍において画像を取得し、 グリ ッドメッシュ試料の縦横の比率を計測し、 その比が適切となり、 かつ画像の中心と周辺とで倍率誤差が 5 %以内となるように電子線 偏向用の補正磁界レンズ 9の励磁を調整し、収束レンズ 2によって正 確に焦点を合わせる。このようにして決定された電子線偏向用の補正 磁界レンズ 9 と収束レンズ 2の励磁電流値を加速電圧に対して記録 し必要に応じて倍率と補正値が表示装置に表示される。 Next, a method of determining excitation conditions for using the correction magnetic lens for electron beam deflection under the condition that distortion is corrected will be described. First, set the acceleration voltage to a certain value. Next, a sample for evaluating the amount of distortion is placed on a sample stage at a predetermined sample position. For this sample, a dalid mesh with 100 to 2000 orthogonal lines per inch and a grating with a line width of 5 to 0.5 μηι, which can clearly evaluate the amount of vertical and horizontal distortion, was used. Used. Next, set the magnification of the electron microscope to the lowest : low magnification, and focus on the sample surface by the objective lens. At this time, since the image is greatly distorted due to distortion, the image is focused at the center of the image. If it is difficult to determine whether or not the focus is coincident even at the center, the magnification may be increased slightly and the image may be focused at the center of the image, and then reset to the minimum magnification. Next, a current is passed through the correction magnetic lens 9 for electron beam deflection to excite it. Here, the correction magnetic lens 9 for electron beam deflection is formed so that a magnetic field in the opposite direction to the objective lens 7 is formed, for example, the winding direction of the coil is opposite and the same current direction, or the winding direction of the coil is the same. The current is set to reverse. When the correction magnetic lens 9 for electron beam deflection is excited, the scanning electron microscope image is defocused and the amount of image distortion changes. While correcting the defocus by changing the current excitation of the converging lens 2, the excitation is changed by the current supplied to the correction magnetic field lens 9 for electron beam deflection so that the distortion of the image is reduced. . An image is acquired in the vicinity of the current value at which the distortion of the image becomes small, the ratio of the length and width of the grid mesh sample is measured, and the ratio becomes appropriate, and the magnification error between the center and the periphery of the image is within 5%. Then, the excitation of the correction magnetic field lens 9 for electron beam deflection is adjusted, and the focus is accurately adjusted by the converging lens 2. The excitation current values of the correction magnetic lens 9 and the converging lens 2 for electron beam deflection determined in this way are recorded with respect to the acceleration voltage, and the magnification and the correction value are displayed on the display device as necessary.
次に、加速電圧を変化させた場合'について述べる。 試料に入射する 時の加速電圧は、試料に印加する電極と.、対物レンズの磁路の下部に 設けられた電極との間に印加するリターディング電圧を変化させて 試料台と対物レンズの下部の間に減速電界を形成する。この減速電界 の度合いにより一次電子線の速度が変化すると共に偏向歪み量も変 - 化する。このリターディング電圧による電界は一種の静電レンズのご とき動きをする。このように発生した偏向歪みと対物レンズの歪曲収 差を合わせて、補正磁界レンズで歪みを吸収する如く上記と同様な方 法にて電子線偏向用の補正磁界レンズ 9 と収束レンズ 2の励磁電流 値を決定する。全ての加速電圧とリターディング電圧との組み合わせ により決定される電子線偏向用の補正磁界レンズ 9と収束レンズ 2 の励磁電流値をテーブルとして装置制御プログラムに組込み、加速電 圧とリターディング電圧が決定された時に歪曲収差が補正され、かつ 試料に焦点があう条件が自動で設定されるようにする。 Next, the case where the acceleration voltage is changed will be described. The acceleration voltage at the time of incidence on the sample is changed by changing the retarding voltage applied between the electrode applied to the sample and the electrode provided below the magnetic path of the objective lens, and the sample table and the lower part of the objective lens. A deceleration electric field is formed during the operation. Depending on the degree of the deceleration electric field, the speed of the primary electron beam changes and the deflection distortion amount also changes. The electric field caused by this retarding voltage moves like a kind of electrostatic lens. The deflection distortion generated in this way and the distortion difference of the objective lens are combined so that the correction magnetic lens absorbs the distortion and the same method as described above. The excitation current value of the correction magnetic field lens 9 for electron beam deflection and the convergent lens 2 is determined by the method. The excitation current values of the correction magnetic lens 9 for electron beam deflection and the converging lens 2 determined by the combination of all acceleration voltages and retarding voltages are incorporated into the device control program as a table, and the acceleration voltage and the retarding voltage are determined. When this is done, the distortion is corrected, and the conditions for focusing on the sample are automatically set.
一方、荷電粒子源としてイオン源を用い、荷電粒子線としてイオン 線を適用しても本願の発明は成立する。 但し、 リターディング電圧は 正の極性の電圧を電極に印加する。 即ち、 イオン線に対しては、 減速 する如く電界を形成するように電圧を電極に印加する点が異なる。 歪曲収差は偏向器の走査範囲を広く して、即ち中間倍率を設定した 場合、 電子線の偏向離軸が大きくなり歪曲収差が大きく生じる。 従つ て、 最低倍率の場合歪曲収差が最大となる。 高い倍率では走査幅が狭 く成り偏向離軸は小さくなる。 この時、補正磁界レンズ 9及び対物レ ンズ 7の中心部分を通過するため、補正磁界レンズ 9及び対物レンズ 7の中心から離れたところを通過する際に発生する歪みは非常に小 さく成る。 従って、対物レンズ 7に対する電子線偏向用の捕正磁界レ ンズ 9による補正は不必要となる場合がある。倍率を中間倍率から高 倍率又は高倍率から中間倍率に可変するに当たっては、中間倍率の偏 向歪みを小さくする条件に補正磁界レンズ 9 と収束レンズ 2の条件 を規定しておくだけで十分である。 なぜならば、 高倍率では電子線は レンズの中心近くを通過するため、中間倍率の時のレンズ調整条件'で ; あつたとしても試料から得られる二次荷電粒子線による像形成には 障害とはならない場合がある。 この場合は、電子線偏向用の補正磁界 レンズ 9 と収束レンズ 2の励磁電流値のテーブルは倍率に依存して 変化させる必要はない。このように加速電圧とリターディング電圧に より電子光学条件を制御することにより中間倍率（走査領域を像面換 算 1 0 0 m〜 1 0 mの範囲で）から高倍率（走査領域を像面換算 1 0 μ m未満〜 1 μ mの範囲で）更には低倍率（走査領域を像面換算 1 0 0- μ πιより大きく数百； i mの範囲で）から高倍率ま,で歪みのない 高解像度の走査電子顕微鏡像が取得できる。 この際、表示装置に取得 された画像を表示すると共に取得した際の倍率も併せて表示する。 従来、画像の倍率は 1 0 0 0倍から 1万倍の中間倍率領域と 1万倍 から 5 0 0万倍の高倍率領域とに分けられそれぞれの領域でレンズ の条件を調整して所望とする倍率の画像を得ていた。 このため、 中間 倍率領域では電子線の径が大きく設定されている。この状態で高倍率 領域に.切り替えると電子線の径が大きいため画像の分解能が悪くな りボケた画像しか得られないこととなり非常に見ずらかった。 これに 対し、本願の方法により画像の倍率が 1 0 0 0倍から 5 0 0万倍の領 域に跨って画像の中心位置がずれること無く表示することが達成で きるようになった。 因みに、 画像の中心部と周辺部との倍率誤差が 5 %より大きければ、画像中心位置の位置ズレ量が人間の目で判断で きるのは表示画面上では l m m (倍率 1万倍で像面換算 0 . 1 i m相 当）程度である。 従って、 本方法ではこの値より小さい値が得られて いるものである。 On the other hand, the invention of the present application is established even if an ion source is used as a charged particle source and an ion beam is applied as a charged particle beam. However, a positive polarity voltage is applied to the electrode as the retarding voltage. That is, the difference is that a voltage is applied to the electrode so as to form an electric field so as to decelerate the ion beam. When the scanning range of the deflector is widened, that is, when the intermediate magnification is set, the deflection off-axis of the electron beam becomes large, and the distortion becomes large. Therefore, the distortion becomes maximum at the lowest magnification. At a higher magnification, the scanning width becomes narrower and the deflection off-axis becomes smaller. At this time, since the light passes through the central part of the correction magnetic lens 9 and the objective lens 7, the distortion generated when the light passes through a position distant from the center of the correction magnetic lens 9 and the objective lens 7 is extremely small. Therefore, there is a case where the correction of the objective lens 7 by the collection magnetic field lens 9 for electron beam deflection is unnecessary. In changing the magnification from intermediate magnification to high magnification or from high magnification to intermediate magnification, it is sufficient to specify the conditions of the correction magnetic lens 9 and the convergent lens 2 in the condition for reducing the deflection distortion of the intermediate magnification. . Because, at high magnifications, the electron beam passes near the center of the lens, the lens adjustment conditions at intermediate magnifications'; Even if it is, there is no hindrance to image formation by the secondary charged particle beam obtained from the sample May not be. In this case, it is not necessary to change the table of the excitation current values of the correction magnetic field lens 9 for electron beam deflection and the converging lens 2 depending on the magnification. Thus, the acceleration voltage and the retarding voltage By controlling the electron optics conditions more, from the intermediate magnification (the scanning area is in the range of 100 m to 10 m in the image plane conversion) to the high magnification (the scanning area is less than 10 μm in the image plane conversion to 1 μm) In addition, high resolution scanning electron microscope images without distortion can be obtained from low magnification (the scanning area is larger than 100-μπι and several hundreds larger than the image plane; several hundreds in the range of im) to high magnification. . At this time, the acquired image is displayed on the display device, and the magnification at the time of acquisition is also displayed. Conventionally, the magnification of an image is divided into an intermediate magnification area of 1,000 to 10,000 times and a high magnification area of 10,000 to 500,000 times. I was getting an image with a magnification of For this reason, the diameter of the electron beam is set large in the intermediate magnification range. When switching to a high magnification area in this state, the resolution of the image deteriorated due to the large diameter of the electron beam, and only a blurred image could be obtained, which was very difficult to see. On the other hand, according to the method of the present invention, it has become possible to achieve display without shifting the center position of the image over an area where the magnification of the image is 1000 to 500,000. By the way, if the magnification error between the center and the periphery of the image is larger than 5%, the amount of displacement of the center position of the image can be judged by the human eye only on the display screen by lmm (image plane at 10,000 times magnification). The equivalent is about 0.1 im). Therefore, in this method, a value smaller than this value is obtained.
このように、 この光学系は、 電子線偏向用の補正補正磁界レンズ 9 及ぴ対物レンズ 7の励磁条件を上記のような歪曲収差を補正する条 件に設定し、上段偏向コイル 4及ぴ下段偏向コイル 5の偏向用電流値 を変えることによって倍率変化が可能であるという利点を持つ。すな わち、低倍率から高倍率までの広い範囲での像観察が画像がボケるこ と無く行ことが可能であり、 操作性の向上が図られる。  As described above, in this optical system, the excitation conditions of the correction magnetic field lens 9 for electron beam deflection and the objective lens 7 are set to the conditions for correcting the distortion as described above, and the upper deflection coil 4 and the lower There is an advantage that the magnification can be changed by changing the deflection current value of the deflection coil 5. In other words, image observation in a wide range from low magnification to high magnification can be performed without blurring the image, and operability is improved.
なお、 偏向器は偏向コイルを例にして説明しているが、 本発明は、 これに限らず、 静電偏向板に対しても適用可能である。 The deflector is described using a deflection coil as an example. The present invention is not limited to this, and is applicable to an electrostatic deflection plate.
更に、電子源をイオン源とし、補正磁界レンズを静電レンズに変え ても対物レンズの離軸偏向歪みを静電レンズにより打ち消す如く取 り付け動作させることは可能である。 但し、 イオン源からのイオンビ ームに対しては、加速電圧やリターディング電圧は電子ビームの時と は逆極性となる。  Further, even if the electron source is an ion source and the correction magnetic field lens is changed to an electrostatic lens, the mounting operation can be performed so that the off-axis deflection distortion of the objective lens is canceled by the electrostatic lens. However, for the ion beam from the ion source, the acceleration voltage and the retarding voltage have the opposite polarity to that of the electron beam.
次に、上記の対物レンズで発生する歪曲収差を補正し、 中間倍率及 び高倍率でボケること無く走査電子顕微鏡画像を取得するためのレ ンズ、 コイルの実装構成を、 以下、 図 6〜図 9を用いて説明する。  Next, the lens and coil mounting configuration for correcting the distortion generated by the objective lens described above and obtaining a scanning electron microscope image without blurring at intermediate magnifications and high magnifications will be described below. This will be described with reference to FIG.
.図 6は、本発明の第 2の実施例を示し、 電子線偏向用の補正磁界レ ンズを偏向コイル下部に設置するための 1つの例である。図 6に示す ように、収束レンズ磁路 1 0と対物レンズ磁路 1 4 との間に電子線偏 向用の補正磁界レンズ磁路 1 2を設置し、上段偏向コイル 4と下段偏 向コイル 5 とを偏向コイルポビン 1 6に卷いて電子線偏向用の捕正 磁界レンズ 1 3中に設置した構成である。  FIG. 6 shows a second embodiment of the present invention, and is an example for installing a correction magnetic field lens for electron beam deflection below a deflection coil. As shown in Fig. 6, a correction magnetic field lens magnetic path 12 for electron beam deflection is installed between the convergent lens magnetic path 10 and the objective lens magnetic path 14, and the upper deflection coil 4 and the lower deflection coil 4 are installed. 5 is wound around a deflecting coil pobin 16 and installed in a collection magnetic field lens 13 for electron beam deflection.
試料 8は、試料ステージ 1 9に取りつけ、 対物レンズ磁路のギヤッ プ中に配置している。各レンズ内部にはそれぞれのレンズ励磁用の収 束レンズコイル 1 1、 電子線偏向用の補正磁界レンズコイル 1 3、 対 物レンズコイル 1 5が配置される。電子線偏向用の補正磁界レンズの レンズ磁路 1 2のギヤップ、すなわちレンズ主面が下段偏向コイル 5 , よりも下にあるので上記のような歪曲収差補正用の光学系として使 用できる。  The sample 8 is mounted on the sample stage 19 and placed in the gap of the objective lens magnetic path. Inside each lens, a converging lens coil 11 for lens excitation, a correction magnetic field lens coil 13 for electron beam deflection, and an objective lens coil 15 are arranged. Since the gap of the lens magnetic path 12 of the correction magnetic field lens for electron beam deflection, that is, the lens main surface is below the lower deflection coil 5, it can be used as an optical system for correcting distortion as described above.
図 7は、図 6と同様に上記光学系を実現するための構成の一例であ り、 本発明の第 3の実施例を示す。 この場合は、 対物レンズ磁路 1 4 上に電子線偏向用の補正磁界レンズ磁路 1 2を配置し、収束レンズ磁 路 1 0との間にスぺーサ 1 7を配置してある。このスぺーサ位置に偏 向コイルポビン 1 6を配置することにより、図 6と同様な光学系の構 成とすることができる。 FIG. 7 shows an example of a configuration for realizing the above-described optical system, similarly to FIG. 6, and shows a third embodiment of the present invention. In this case, the correction magnetic field lens magnetic path 12 for electron beam deflection is disposed on the objective lens magnetic path 14, and the spacer 17 is disposed between the objective lens magnetic path 14 and the convergent lens magnetic path 10. This spacer position is biased By arranging the directional coil pobins 16, an optical system configuration similar to that of FIG. 6 can be obtained.
図 8は、図 6と同様に上記光学系を実現するための構成の一例であ り、 本発明の第 4の実施例を示す。 この場合は、 偏向コイルポビン 1 6を電子線偏向用の補正磁界レンズ磁路 1 2の上下に配置し、偏向コ ィルによる偏向の中間段階で対物レンズの歪曲収差のキャンセルを 行うための歪曲収差を電子線偏向用の補正磁界レンズ磁路のギヤッ プに発生させる'ことにより、図 6と同様な光学系の構成としたもので ある。試料 8は対物レンズ磁路 1 4の下に設置した試料室 1 8内の試 料ステージ 1 9上に保持されている。これは汎用の走査電子顕微鏡で 通常用いられているァゥ トレンズタイプの対物レンズであり、インレ ンズタイプと異なって大型サイズの試料の観察が可能である。  FIG. 8 is an example of a configuration for realizing the above-described optical system as in FIG. 6, and shows a fourth embodiment of the present invention. In this case, the deflection coil pobins 16 are arranged above and below the correction magnetic field lens magnetic path 12 for electron beam deflection, and the distortion for canceling the distortion of the objective lens in the middle stage of the deflection by the deflection coil. Is generated in the gap of the magnetic path of the correction magnetic field lens for electron beam deflection, thereby forming an optical system similar to that shown in FIG. The sample 8 is held on a sample stage 19 in a sample chamber 18 placed below the objective lens magnetic path 14. This is an objective lens type lens generally used in a general-purpose scanning electron microscope, and is capable of observing a large-sized sample unlike the in-lens type.
すなわち、荷電粒子源と、荷電粒子源より発生した荷電粒子線を収 束させるための収束レンズと、試料を載置した試料台と、荷電粒子線 を試料上に結像させるための対物レンズとを有し、対物レンズの荷電 粒子源側に、対物レンズで発生する歪曲収差を補正するための補正レ ンズを配置し、補正レンズを挟んで第 1の偏向器と第 2の偏向器とを 有する点にある。  That is, a charged particle source, a converging lens for converging a charged particle beam generated from the charged particle source, a sample stage on which a sample is placed, and an objective lens for forming an image of the charged particle beam on the sample. A correction lens for correcting distortion caused by the objective lens is disposed on the charged particle source side of the objective lens, and the first deflector and the second deflector are sandwiched by the correction lens. It has a point.
図 9は、本発明の第 5の実施例を示し、汎用の走査電子顕微鏡で通 常用いられているァゥトレンズタイプの対物レンズを用いて上記光 学系を実現するための構成の一例である。対物レンズ磁路 1 4の上下 には一次電子線の照射により試料から発生した 2次電子線の強度を 棱出するための 2次電子検出器 2 0が設置されている。電界磁界直交 型偏向器（E X B型偏向器) _2 1は対物レンズ磁路内に設置されてお り、一次電子線を曲げること無く 2次電子が対物レンズ上に配置した 2次電子検出器 2 0に効率良く検出されるための条件で駆動されて いる。反射電子検出器 2 2は試料 8と対物レンズ磁路 1 4との間に設 置され、試料 8で反射した電子線強度を検出する。試料 8は絶縁板 2 7を介して試料ステージ 1 9上に保持されている。 尚、試料ステージ が 2段構造で絶縁されていても良い。試料 8にはリターディング電圧 2 8が印加され、試料 8に入射する 1次電子線のエネルギーを減少さ せるように設定されている。 これは一次電子線を偏向器、対物レンズ を通過時に高加速エネルギーで通.過する事により収差の影響を低減 することにある。試料 8に入射する直前で 1次電子線のエネルギーを 減少させ、試料の電子線照射ダメージを軽減させるためである.。 電極 2 3は接地されており、試料 8との間でリタ一デイングのための電界 を形成している。電子銃電極 2 4には電子銃加速電圧 2 6が印加され、 電子源チップ 2 5から 1次電子線を引き出し、 所定の加速電圧まで加 速させる働きをしている。 FIG. 9 shows a fifth embodiment of the present invention, and is an example of a configuration for realizing the optical system by using an art lens type objective lens commonly used in a general-purpose scanning electron microscope. . Above and below the objective lens magnetic path 14, secondary electron detectors 20 for detecting the intensity of the secondary electron beam generated from the sample by the irradiation of the primary electron beam are installed. An electric field orthogonal deflector (EXB deflector) _2 1 is installed in the magnetic path of the objective lens, and a secondary electron detector 2 on which the secondary electrons are placed on the objective lens without bending the primary electron beam. Driven under conditions for efficient detection to 0 I have. The backscattered electron detector 22 is provided between the sample 8 and the objective lens magnetic path 14 and detects the intensity of the electron beam reflected by the sample 8. The sample 8 is held on a sample stage 19 via an insulating plate 27. The sample stage may be insulated in a two-stage structure. A retarding voltage 28 is applied to the sample 8, and the setting is made so as to reduce the energy of the primary electron beam incident on the sample 8. This is to reduce the influence of aberration by passing the primary electron beam with high acceleration energy when passing through the deflector and the objective lens. This is because the energy of the primary electron beam is reduced just before the sample 8 is incident, and the electron beam irradiation damage of the sample is reduced. The electrode 23 is grounded, and forms an electric field for retarding with the sample 8. An electron gun accelerating voltage 26 is applied to the electron gun electrode 24, which functions to extract a primary electron beam from the electron source chip 25 and accelerate the electron beam to a predetermined accelerating voltage.
対物レンズ磁路 1 4のギャップで発生する磁界の歪曲収差と、リタ 一ディング電界で発生する収差とを除去する電子線偏向用補正補正 磁界レンズを対物レンズ磁路 1 4と偏向器 4、 5との間に設けた点に ある。  Correction correction for electron beam deflection that eliminates the distortion of the magnetic field generated by the gap of the objective lens magnetic path 14 and the aberration generated by the retarding electric field The magnetic lens is connected to the objective lens magnetic path 14 and the deflectors 4 and 5. This is the point provided between
また、言い方を変えると、 荷電粒子源と荷電粒子線を偏向するため の偏向器と試料を載置した試料台と試料上に結像させるための対物 レンズと前記試料台と前記対物レンズとの間に設けられた減速電界 を発生する第 2レンズとを有し、対物レンズの荷！;粒子源側に対物レ. ンズと第 2レンズで発生する偏向歪みとを補正するための第 1のレ ンズを設けた点にある。  In other words, in other words, a charged particle source, a deflector for deflecting a charged particle beam, a sample stage on which a sample is mounted, an objective lens for forming an image on the sample, and the sample stage and the objective lens. A second lens for generating a deceleration electric field provided between them, and a load of the objective lens! The first lens is provided on the particle source side for correcting the objective lens and the deflection distortion generated by the second lens.
ここでの第 2のレンズは対物レンズの磁路下面に有する電極と、試 料台上の試料に減速電圧が印加できる電極とを有しその間に電圧を • 印加して成る静電レンズの働きをする。 このような方法よつて、画像の倍率が 1 0 0 0倍から 5 0 0万倍の 領域において連続的に画像中心部と周辺部との倍率誤差が 5 %以内 で表示することを可能とした。 The second lens here has an electrode on the lower surface of the magnetic path of the objective lens and an electrode that can apply a deceleration voltage to the sample on the sample table. The function of the electrostatic lens is to apply a voltage between them. do. By using such a method, it is possible to continuously display the magnification error between the center and the periphery of the image within 5% in the area where the magnification of the image is 1000 to 500,000 times. .
次に、本発明の第 6の実施例として、 電子顕微鏡装置を半導体素子 等の回路パターンの検査に適用した場合の例について説明する。半導 体素子の不良検査では、高スループッ トでの検査が必要とされている c これに対して、 1回の検査領域を大きくすることによってトータルの 検査時間を短くするのが 1つの方法となる。 Next, as a sixth embodiment of the present invention, an example in which the electron microscope apparatus is applied to inspection of a circuit pattern of a semiconductor element or the like will be described. The defect inspection of semiconductor element, and one way to shorten the inspection time of the total by relative c which the inspection at high throughput is required, a larger one of the inspection area Become.
本発明の電子顕微鏡では、対物レンズの中間倍率での歪曲収差を補 正するこができるので偏向振り幅を大きく しても画像には歪みがな い。 すなわち、 1回の画像取得領域を従来方法に比較して大きくでき るので、これを繰り返し回路パターンの検査に用いればスループッ ト の向上がなされる。 従来の検查方法では、 1ラインの検查をステージ の移動と同期して所定回数の検査を実行後、次のラインの検査をステ ージの移動によって順次実行する。 1ラインの検査におけるスループ ットは、 1枚の取得画像を比較検査する時間によって決定され、 トー タルの実行時間はこれを何ライン繰り返すかにより算出される。  In the electron microscope of the present invention, distortion can be corrected at an intermediate magnification of the objective lens, so that the image is not distorted even if the deflection amplitude is increased. That is, since one image acquisition area can be made larger than that of the conventional method, the throughput can be improved by repeatedly using the same for the inspection of the circuit pattern. In the conventional inspection method, inspection of one line is performed a predetermined number of times in synchronization with movement of the stage, and then inspection of the next line is sequentially performed by moving the stage. The throughput in one-line inspection is determined by the time to compare and inspect one acquired image, and the total execution time is calculated by how many lines are repeated.
ここで、 2 0 0 m m角の領域を検査する場合について説明する。 従 来 0 . 1 m m角で 1回の検査を実行していると仮定し、 本発明では 1 m m角で実行するものとする。 まず、 トータルの検查における 1画像 の検査回数は、 2 0 0 0 X 2 0 0 0回から 2 0 0 X 2 0 0回に削減さ れるが、 同一解像度で検査を実行するという条件では、 検査領域を大 きく した場合には検査画素も大きくなるので、計算時間を考えるとス ループット向上への効果はない。 1ラインの検査後、 次のラインへの ステージの移動回数は 2 0 0 0回から 2 0 0回に削減される。ステー ジの移動 1回あたりの所要時間を 1秒とすると、これは 3 0分のスル ープッ ト向上となる。 現在は、 トータルの検査時間が 7時間程度と長 いのでスループット向上の度合いは低いが、今後計算時間の向上によ り トータルの検査時間が短縮されれば、本方法は、 スループッ ト向上 に対する有効手段の 1つとなる。 Here, a case of inspecting a 200 mm square area will be described. Conventionally, it is assumed that one inspection is performed in a 0.1 mm square, and in the present invention, the inspection is performed in a 1 mm square. First, the number of inspections for one image in the total inspection is reduced from 200 × 200 to 200 × 200, but under the condition that inspection is performed at the same resolution, If the inspection area is enlarged, the inspection pixels become large, so there is no effect on improving the throughput in consideration of the calculation time. After the inspection of one line, the number of stage movements to the next line is reduced from 200 to 200. Assuming that the time required for each movement of the stage is 1 second, this is 30 minutes This will improve the output. Currently, the total inspection time is as long as about 7 hours, so the degree of throughput improvement is low, but if the total inspection time is shortened by improving the calculation time in the future, this method will be effective for improving throughput. It is one of the means.
言い換えると、繰り返し回路パターンを有する試料を試料台に載置 し荷電粒子源からの一次荷電粒子線を加速して一次荷電粒子線を試 料に結像させる。 対物レンズを通過して照射させ、対物レンズを通過 した一次荷電粒子線を試料台上で減速電界 より減速させ対物レン ズを通過して発生する偏向歪みと減速電界を通過した際に発生する 偏向歪みを補正する補正レンズに偏向歪み補正量を供給する。試料の 繰り返しパターンの第 1 の領域を第 1 の中間倍率で試料上の走査領 域が 1 0〜 1 0 0 mの範囲を走査して検出し第 1 の画像として記 憶し、第 2の領域を第 1倍率又は第 2の中間倍率で走査して検出して 第 2の画像として記憶する。第 1 と第 2の画像を比較検査することに より回路パターンの欠陥を検査する。 この際、 倍率に併せて、 補正レ ンズに予め求めた補正値を設定する。補正して得られた画像を計測時 の倍率または走查範囲を情報として記憶し、要求により画面に画像と 倍率または走查範囲の情報を付けて表示する。  In other words, a sample having a repetitive circuit pattern is placed on a sample stage, and the primary charged particle beam from the charged particle source is accelerated to form an image of the primary charged particle beam on the sample. Irradiation is performed by passing through the objective lens, the primary charged particle beam that has passed through the objective lens is decelerated by the decelerating electric field on the sample stage, and deflection distortion generated when passing through the objective lens and deflection generated when passing through the decelerating electric field A deflection distortion correction amount is supplied to a correction lens for correcting distortion. The first area of the repetitive pattern of the sample is detected by scanning the scanning area on the sample at the first intermediate magnification in the range of 100 to 100 m, stored as the first image, and stored as the second image. The area is scanned and detected at a first magnification or a second intermediate magnification and stored as a second image. The circuit pattern is inspected for defects by comparing and inspecting the first and second images. At this time, a previously determined correction value is set in the correction lens according to the magnification. The corrected image is stored as information on the magnification or running range at the time of measurement, and the image and the information on the magnification or running range are displayed on the screen upon request.
これにより、 検查装置においては、 走査領域を像面換算 1 0 0 μ m 〜 1 0 μ mの範囲で試料により異なるリターディング電圧による偏 向歪みを予め求めて記憶した補正値を呼び出し、走査領域を像面換算 1 0 0 /z m〜 1 0 /i mの範囲で検出することにより検査の効率化を 達成することが出来る効果を有するようになった。  Thus, in the inspection apparatus, the correction value stored in advance by obtaining the deflection distortion due to the retarding voltage that differs depending on the sample in the range of 100 μm to 10 μm in terms of the image plane in the scanning area, and scanning is performed. The detection of the area in the range of 100 / zm to 10 / im in terms of the image plane has the effect of improving the efficiency of the inspection.
次に、第 7実施例として、 ズーミンク'、 機能を利用した検査及ぴレ ビュー装置について説明する。  Next, as a seventh embodiment, a description will be given of an inspection and review apparatus using a zooming function.
繰り返しパターンを有するチップが形成されたウェハを有する。そ のウェハを試料ステージ上に載置し、 チップ中を複数の領域分ける。 この領域を 1 0 0 mとする。 この領域に照準を合わせた後、 走査幅 を 1 0 0 μ mから 1 0 mの幅でズーミングアップしながら走査す る。 一つ前の領域での回路パターンが異なる時に走査を中止し、 その 欠陥を有する領域を登録する。これをチップ全体に実行すると欠陥が 大きい場合には倍率の低い状態で検出し、 1 0 0 mから 1 0 μ m全 部走査しなく とも結果を得ることが可能になるため、回路パターンの 欠陥検査時間を短縮する効果を有する。この方法を用いれば領域単位 で欠陥を見出すことが可能となり欠陥のない部分は領域単位で除去 することが可能となる。ここでの領域及びズーミング範囲は実 ¾例限 定されるものではなく低倍率、 中間倍率、 高倍率のいずれについても 可能である。 It has a wafer on which chips having a repeating pattern are formed. So The wafer is placed on the sample stage, and the chip is divided into a plurality of areas. This area is 100 m. After aiming at this area, scan while zooming up with a scanning width of 100 μm to 100 μm. When the circuit pattern in the previous area is different, the scanning is stopped and the area having the defect is registered. When this is performed on the entire chip, if the defect is large, it is detected at a low magnification, and the result can be obtained without scanning the entire surface from 100 m to 100 μm. This has the effect of shortening the inspection time. Using this method, defects can be found on a region basis, and portions without defects can be removed on a region basis. The area and zooming range here are not limited to actual examples, but may be any of low magnification, intermediate magnification, and high magnification.
チップ内の繰り返し回路パターンを複数の領域に分ける工程と、そ の領域毎に第 1の走査範囲から第 2の走查範囲間をズーミングアツ プする工程と、ズーミングァップしている間に欠陥パターンを検出す る工程と、 を有する欠陥検査方法にある。  A step of dividing the repetitive circuit pattern in the chip into a plurality of areas, a step of zooming up from the first scanning range to the second scanning range for each area, and a defect pattern during the zooming up. And a defect inspection method comprising:
第 8実施例として本荷電粒子線光学系とユーセント リ ック試料ス テージの組み合わせについて説明する。  As an eighth embodiment, a combination of the present charged particle beam optical system and a eucentric sample stage will be described.
試料を試料ステージに載置し、所定の位置特に試料の構造を色々な 角度から顕微することが要求されることがある。 その時は、試料ステ ージを傾斜させた状態にし、荷電粒子線を偏向器を用いて試料上の目 的物を含む領域を走査して目的物を探す。 その際、試料ステージが傾 斜しているため照射位置が高さ方向に変化してしまう と焦点位置が ずれる。これを捕正し焦点を合わす為には対物レンズの像面位置即ち 焦点を対物レンズの電流を変化させて再調整する。このような工程を 経ることなくユーセントリック型試料ステージを用いれば、傾いた状 態で常に照射位置の高さが同じにできるため焦点位置を合わせ直す 必要が無く ピントの合った画像を得ることができるのは、対物レンズ を通過した際の歪曲歪みを打ち消す如く動作させた補正レンズを偏 向器と対物レンズの間に配置して有れば、試料ステージが傾斜した状 態であっても視野探しをすることが可能となる。この状態で荷電粒子 線の走査範囲を 1 0 0 m以下で走查しその画像信号によ ^表示画 面に表示する際の割合が中間倍率の 1 0 0 0倍から 1万倍率にして 視野探し実施する。このよ うに顕微する事により試料ステージを傾斜 した状態で視野探しを可能とするものである。ここでの試料ステージ のユーセントリック型構造とは、荷電粒子線が照射した際に試料ステ ージの回転中心に常に視野中心が合う如く調整を可能とする試料ス テージを言う。 . It is sometimes required to place a sample on a sample stage and to observe a predetermined position, particularly the structure of the sample, from various angles. At that time, the sample stage is tilted, and the charged particle beam is scanned using a deflector to scan the area including the target on the sample to search for the target. At that time, if the irradiation position changes in the height direction because the sample stage is tilted, the focus position will shift. In order to correct this and focus, the image plane position of the objective lens, that is, the focus is readjusted by changing the current of the objective lens. If the eucentric sample stage is used without going through such a process, Because the height of the irradiation position can always be the same in this state, there is no need to re-adjust the focal position, and an in-focus image can be obtained because the correction operates so as to cancel the distortion when passing through the objective lens If the lens is arranged between the deflector and the objective lens, it is possible to search for the visual field even when the sample stage is inclined. In this state, the scanning range of the charged particle beam is 100 m or less, and the ratio when displaying on the display screen is from 100,000 times the intermediate magnification to 10,000 magnifications based on the image signal. Look for and implement. The microscope enables the field of view to be searched while the sample stage is tilted. The eucentric structure of the sample stage here refers to a sample stage that can be adjusted so that the center of the field of view always coincides with the center of rotation of the sample stage when irradiated with a charged particle beam. .
次に、 第 9の実施例を以下に示す。  Next, a ninth embodiment will be described below.
補正磁界レンズ 9を歪曲収差キャンセル用にせずに偏向器を補助 する補助レンズとして動作した例について説明する。  An example in which the correction magnetic lens 9 operates as an auxiliary lens to assist the deflector without canceling the distortion will be described.
偏向振り幅を変化させ、走査電子顕微鏡画像の倍率を変化させるこ とができる。 ここで、上記高倍率像観察用光学系での偏向振り幅の計 算に用いたレンズ、 コイル間距離、 励磁条件に加えて、 補助磁界レン ズ 9を対物レンズの上 6 6 mmに設置すると仮定する。 また、収束レ ンズ像面 3が補助磁場レンズ 9の上 7 8 mmにできていると仮定す る。 偏向支点を対物レンズ前磁場焦点面に一致させるための条件は、 補助磁界レンズ 9の焦点距離を、 1 / (177 8 + 1ノ 66) = 3 5 . 8 mmにすることである。  The magnification of the scanning electron microscope image can be changed by changing the deflection swing width. Here, in addition to the lens, the distance between coils, and the excitation conditions used in the calculation of the deflection amplitude in the optical system for high-magnification image observation, if the auxiliary magnetic field lens 9 is installed 66 mm above the objective lens, Assume. It is also assumed that the convergent lens image plane 3 is formed 78 mm above the auxiliary magnetic field lens 9. The condition for making the deflection fulcrum coincide with the magnetic field focal plane before the objective lens is that the focal length of the auxiliary magnetic field lens 9 is set to 1 / (1778 + 1 866) = 35.8 mm.
この時、 上段偏向コイル偏向角度を 5 Om r a dに設定すると、 下 段偏向コイ^^の偏向角度は、補助磁界レンズ 9のレンズ作用の中心に 電子線を振り戻す条件から 1 8m r a dとなり、 偏向振り幅は 0. 1 m mとなる。上記と同様な走査電子顕微鏡画像の表示条件での像倍率 は、 1 0 0 / 0 . 2 = 5 0 0倍となる。 これは、 図 1の場合の偏向振 り幅 r = 4 7 ^ mに比べて、 約 2倍となる。 よって、'収束レンズ 2、 ■ 対物レンズ 7、上段偏向コイル 4と下段偏向コイル 5の条件を全て変 更せずに、補助磁界レンズ 9のレンズ作用のみで中間倍率（1 0 0 0 倍） の 2分の 1の低倍率の像を観察できること【こなる。 At this time, if the deflection angle of the upper deflection coil is set to 5 Om rad, the deflection angle of the lower deflection coil will be 18 m rad from the condition that the electron beam is returned to the center of the lens action of the auxiliary magnetic field lens 9. Swing width is 0.1 mm. The image magnification under the same scanning electron microscope image display condition as above is 100 / 0.2 = 500. This is about twice as large as the deflection amplitude r = 47 ^ m in the case of Fig. 1. Therefore, without changing all the conditions of the converging lens 2, the objective lens 7, the upper deflecting coil 4 and the lower deflecting coil 5, only the lens action of the auxiliary magnetic field lens 9 allows the intermediate magnification (100.times.). To be able to observe a low-magnification image of one half.
この光学系の利点として、補助磁場レンズ 9の光軸を対物レンズ 7 の光軸に機械的又は偏向器によって一致させることによって、中間倍 率と低倍率との切り替え時に像の位置ずれが無くなり、非点収差も共 通となる。ここでは図示しなかったが非点収差補正器は対物レンズと、 荷電粒子源との間に配置されている。 これにより、切り替え時の調整 が不要になる。 また、 対物レンズ 7は、 中間倍率と高倍率とで同じ励 磁で使用できる場合がある。 その時は、 切り替え時のヒステリシスに よる像のにげが無くなる。  An advantage of this optical system is that by aligning the optical axis of the auxiliary magnetic field lens 9 with the optical axis of the objective lens 7 mechanically or by a deflector, image displacement does not occur when switching between intermediate magnification and low magnification. Astigmatism is also common. Although not shown here, the astigmatism corrector is disposed between the objective lens and the charged particle source. This eliminates the need for adjustment when switching. Also, the objective lens 7 may be used with the same excitation at the intermediate magnification and the high magnification in some cases. At that time, the image will not be blurred due to hysteresis at the time of switching.
さらに、上段偏向コイル 4と下段偏向コイル 5を用いた振り戻し偏 向系なので 1段偏向の場合に生ずる画像の周辺ぼけも無くなるとい う点がある。 上記の実施例は、 インレンズタイプの電子顕微鏡で通常 用いられる短焦点（2 m m下）の対物レンズに適用した場合であるが、 アウトレンズタイプの電子顕微鏡で用いられている長焦点（5 m m以 、上）の対物レンズに上記光学系を適用した場合には、 さらに効果が大 きい。 例えば、 上記のレンズ構成で対物レンズの.焦点距離を 1 0 m m に仮定した場合、上段偏向コイル偏向角度を 5 0 m r a dに設定する と、 偏向振り幅は 0 . 4 m mとなり、 像倍率は、 1 0 0 / 0 . 8 = 1 2 5倍という低倍率が得られる。  In addition, since there is a back deflection system using the upper stage deflection coil 4 and the lower stage deflection coil 5, there is also a point that there is no peripheral blurring of the image caused in the case of single stage deflection. The above embodiment is a case where the present invention is applied to a short focus (2 mm below) objective lens generally used in an in-lens type electron microscope, but is applied to a long focus (5 mm) used in an out lens type electron microscope. Therefore, when the above-mentioned optical system is applied to the above-mentioned objective lens, the effect is even greater. For example, assuming that the focal length of the objective lens is 10 mm in the above lens configuration, if the deflection angle of the upper deflection coil is set to 50 mrad, the deflection amplitude will be 0.4 mm, and the image magnification will be A low magnification of 100 / 0.8 = 12.5 times is obtained.
即ち、低倍率であっても周辺ボケの少ない画像得るという効果を奏 する。 産業上の利用可能性 That is, there is an effect that an image with less peripheral blur is obtained even at a low magnification. Industrial applicability
本発明によれば、荷電粒子線装置において、低倍率から高倍率まで の広い倍率範囲において高解像度で歪みのない良好な画像を取得で きる。低倍率像と高倍率像で画像ずれがほとんどなく連続して画像を 取得することが可能となった。  ADVANTAGE OF THE INVENTION According to this invention, in a charged particle beam apparatus, a high-resolution and distortion-free good image can be acquired in a wide magnification range from low magnification to high magnification. It has become possible to acquire images continuously with little image shift between the low magnification image and the high magnification image.

Claims

請 求 の 範 囲 The scope of the claims
1 . 荷電粒子線を収束させるための収束レンズと、試料を载置した試 料台と、 荷電粒子線を前記試料上に結像させるための対物レンズと、 前記対物レンズで発生する歪曲収差を打ち消す如く補正する如く励 磁された補正レンズと、前記補正レンズを挟んで前記試料台に载置さ れた試料上を荷電粒子線が走査するための偏向器と、を有することを 特徴とする荷電粒子線顕微鏡装置。 1. A converging lens for converging the charged particle beam, a sample table on which the sample is placed, an objective lens for forming an image of the charged particle beam on the sample, and a distortion generated by the objective lens. A correction lens that is excited so as to perform correction so as to cancel each other, and a deflector for allowing a charged particle beam to scan a sample placed on the sample stage with the correction lens interposed therebetween. Charged particle beam microscope equipment.
2 . 荷電粒子源と、 前記荷電粒子源より発生した荷電粒子線を収束さ せるための収束レンズと、前記収束レンズを経た荷電粒子線を偏向す るための偏向器と、試料を载置した試料台と、 前記偏向器により偏向 された荷電粒子線を前記試料台の試料上に結像させるための対物レ ンズと、前記対物レンズと前記偏向器との間に前記対物レンズで発生 する歪曲収差を補正するための補正レンズと、を具備することを特徴 とする荷電粒子線応用装置。  2. A charged particle source, a converging lens for converging the charged particle beam generated from the charged particle source, a deflector for deflecting the charged particle beam passing through the converging lens, and a sample were arranged. A sample stage, an objective lens for imaging the charged particle beam deflected by the deflector on the sample on the sample stage, and distortion generated by the objective lens between the objective lens and the deflector A charged particle beam application apparatus, comprising: a correction lens for correcting aberration.
3 .前記偏向器は上段偏向器と下段振り戻し偏向器から成ることを特 徴とする請求の範囲第 2項記載の荷電粒子線応用装置。  3. The charged particle beam application device according to claim 2, wherein the deflector comprises an upper deflector and a lower swing back deflector.
4 .前記補正レンズは前記対物レンズの歪曲収差を打ち消す方向の歪 曲収差を有することを特徴とする請求の範囲第 2項記載の荷電粒子 線応用装置。  3. The charged particle beam application apparatus according to claim 2, wherein the correction lens has a distortion in a direction to cancel the distortion of the objective lens.
5 .荷電粒子線を偏向するための偏向器と、試料を載置した試料台と、 前記偏向器により偏向された荷電粒子線を前記試料台の試料上に結 像させるための対物レンズと、前記試料台と前記対物レンズとの間に 設けられた第 2 レンズと、前記対物レンズと前記偏向器との間に'前記 対物レンズと前記第 2のレンズで発生する偏向歪みを補正するため の第 1 のレンズを設けてなることを特徴とする荷電粒子線応用装置。 5.A deflector for deflecting the charged particle beam, a sample stage on which a sample is placed, an objective lens for imaging the charged particle beam deflected by the deflector on the sample on the sample stage, A second lens provided between the sample stage and the objective lens, and a second lens between the objective lens and the deflector for correcting deflection distortion generated by the objective lens and the second lens. A charged particle beam application device comprising a first lens.
6 . 前記第 2のレンズは前記対物レンズの磁路下面に有する電極と、 前記試料台上の試料に減速電圧が印加できる電極と、の間に電圧を印 加して成る静電レンズであることを特徴とする請求の範囲第 5項記 載の荷電粒子線応用装置。 6. The second lens is an electrostatic lens formed by applying a voltage between an electrode provided on the lower surface of the magnetic path of the objective lens and an electrode capable of applying a deceleration voltage to the sample on the sample stage. A charged particle beam application apparatus according to claim 5, characterized in that:
7 .—次荷電粒子線を試料台上の試料に収束させて照射するための対 物レンズと、 一次荷電粒子線を偏向させるための偏向器と、 前記対物 レンズの磁路の下部に設けた第 1電極と、試料台に設けられた第 2電 極と、前記第 1 と第 2電極間で発生する減速電界中を一次荷電粒子線 が通過する際に受ける収差を補正するための捕正レンズを前記偏向 器と前記対物レンズとの間に具備することを特徴とする荷電粒子線 応用装置。  7.—An objective lens for converging and irradiating the secondary charged particle beam to the sample on the sample stage, a deflector for deflecting the primary charged particle beam, and provided below the magnetic path of the objective lens A first electrode, a second electrode provided on the sample stage, and a correction for correcting aberrations caused when the primary charged particle beam passes through the deceleration electric field generated between the first and second electrodes. A charged particle beam application device comprising a lens provided between the deflector and the objective lens.
' '
8 . 試料を試料台に載置する工程と、荷電粒子線を集束するための荷 電粒子線光学系を通過し、荷電粒子線を試料上の走査幅を 1 0 8. The process of placing the sample on the sample stage and passing the charged particle beam through the charged particle beam optical system for focusing the charged particle beam so that the scanning width on the sample is 10
1 0 0 πιまでの範囲で照射する照射工程と、前記照射工程で荷電粒 子線が前記荷電粒子線光学系を通過した際に発生する偏向歪みを補 正する工程と、 前記走査範囲内に目的物を検出'する視野探し工程と、 を有することを特徴とする荷電粒子線顕微方法。  An irradiation step of irradiating in the range of up to 100 πι; a step of correcting deflection distortion generated when the charged particle beam passes through the charged particle beam optical system in the irradiation step; A charged particle beam microscopy method, comprising: a visual field searching step of detecting an object.
9 . 前記視野探し工程として、前記検出器からの信号を画像化して記 憶する画像記憶工程と、記憶された画像を画像中心部と周辺部とで倍 率誤差が 5 %以内に表示することを特徴とする請求の範囲第 8項記 載の荷電粒子線顕微方法。  9. As the visual field searching step, an image storing step of imaging and storing a signal from the detector, and displaying the stored image within 5% of a magnification error between a central portion and a peripheral portion of the image. 9. The charged particle beam microscopy method according to claim 8, wherein:
1 0 . 試料を試料台に載置する工程と、荷電粒子線を集束するための 荷電粒子線光学系を通過し荷電粒子線を試料上で走査幅が 1 0 0 μ mより大きい第 1の走査幅で走査した際の表示装置上の表示割合が 1 0 0 0倍未満の低倍率で表示する如く試料上を走查する第 1の走 査工程と、前記低倍率で荷電粒子線が前記荷電粒子線光学系を通過し た際に発生する第 1の歪みを補正する工程と、試料からの第 1の走查 幅に基づく二次荷電粒子を検出器で検出する第 1の検出工程と、前記 検出器からの第ュの信号を画像化して記憶する第 1画像記憶工程と、 記憶された第 1画像を表示する第 1画像表示工程と、荷電粒子線を試 料上で走查幅が 1 0 0 m以下 1 0 m以内の第 2の走査幅の大き さで走査した際の表示装置上の表示割合が 1 0 0 0倍から 1万倍の 中間倍率で表示する如く試料上を走査する第 2の走査工程と、前記中 間倍率で荷電粒子線が前記荷電粒子線光学系を通過した際に発生す る第 2の歪みを補正する工程と、試料からの第 2の走査幅に基づく二 次荷電粒子を前記検出器から検出する第 2の検出工程と、前記検出器 からの第 2の信号を画像化して記憶する翁 2画像記憶工程と、記憶さ れた第 2画像を表示する第 2画像表示工程と、を有することを特徴と する荷電粒子線顕微方法。 100. The step of placing the sample on the sample stage and the first step in which the charged particle beam passes through the charged particle beam optical system for focusing the charged particle beam and the scanning width of the charged particle beam is larger than 100 μm on the sample A first scanning step of running on the sample so that the display ratio on the display device when scanning at a scanning width is less than 1000 times is performed at a low magnification, and the charged particle beam at the low magnification is Through the charged particle beam optics Correcting a first distortion that occurs when the first detection is performed, a first detection step of detecting a secondary charged particle based on a first scanning width from the sample with a detector, and a first detection step from the detector. A first image storing step of imaging and storing the first signal, a first image displaying step of displaying the stored first image, and a scanning width of the charged particle beam on the sample of 100 m or less. a second scanning step of scanning over the sample so that the display ratio on the display device when the scanning is performed with a second scanning width of less than m is displayed at an intermediate magnification of 1000 to 10,000 times. Correcting the second distortion generated when the charged particle beam passes through the charged particle beam optical system at the intermediate magnification, and converting the secondary charged particles based on a second scanning width from the sample to the above. A second detection step of detecting from the detector, an image storage step of imaging and storing a second signal from the detector, A second image displaying step for displaying a second image.
1 1 .チップ内の繰り返し回路パターンを複数の領域に分ける工程と、 前記複数の領域の第 1の領域に荷電粒子線を照射し第 1の走査^範囲 から第 2の走査範囲間を第 1のズーミングァップする如く走查する 第 1の走査工程と、前記第 1のズーミングアップ間にウェハからの二 次荷電粒子を検出器で検出し第 1の像信号を得る第 1像形成工程と、 前記第 1の像信号を記憶する第 1の記憶工程と、前記複数の領域の第 2の領域に荷電粒子線を照射し第 1の走査範囲から第 2の走査範囲 間を第 2のズーミングアップする如く走查する第 2の走査工程と、前 記第 2の走查工程中に第 2ズーミングアップで走査しウェハからの 二次荷電粒子を前記検出器で検出し前記第 2の像形成する工程と、第 1と第 2像信号から欠陥パターンを検出する工程と、を有することを 特徴とする荷電粒子線検査方法。  1 1.Dividing the repetitive circuit pattern in the chip into a plurality of regions; irradiating a charged particle beam to a first region of the plurality of regions to form a first region between the first scanning region and the second scanning region. A first scanning step that runs so as to perform zooming up, and a first image forming step in which a secondary charged particle from the wafer is detected by a detector during the first zooming up to obtain a first image signal; A first storage step of storing the first image signal, and irradiating a second area of the plurality of areas with a charged particle beam to perform a second zooming up between a first scanning range and a second scanning range. A second scanning step that scans the wafer during scanning and a second zooming-up scan during the second scanning step to detect secondary charged particles from the wafer with the detector and form the second image. And detecting a defective pattern from the first and second image signals. Characterized charged particle beam inspection method.
1 2 .繰り返し回路パターンを有する試料を試料台に載置する工程と- 荷電粒子源からの一次荷電粒子線を加速する工程と、一次荷電粒子線 を試料に結像させるための対物レンズを通過して照射する工程と、前 記対物レンズを通過した一次荷電粒子線を前記試料台上で減速電界 により減速する工程と、前記対物レンズを通過して発生する偏向歪み と減速電界を通過した際に発生する'偏向歪みを補正する補正レンズ に偏向歪み補正量を供給する工程と、試料の繰り返しパターンの第 1 の領域を第 1の倍率で走査して検出し第 1の画像として記憶する第 1の記憶工程と、第 2の領域を第 1倍率で走査して検出し第 2の画像 として記憶する第 2の記憶工程と、前記第 1 と第 2の画像を比較検査 することを有することを特徴とする荷電粒子線検査方法。 1 2.The process of placing a sample with a repetitive circuit pattern on the sample stage. A step of accelerating the primary charged particle beam from the charged particle source, a step of irradiating the primary charged particle beam through an objective lens for imaging the sample, and a step of irradiating the primary charged particle beam passing through the objective lens. A step of decelerating by a deceleration electric field on the sample stage, and supplying a deflection distortion correction amount to a correction lens for correcting a deflection distortion generated by passing through the objective lens and a deflection distortion generated by passing through the deceleration electric field. A first storage step of scanning and detecting the first area of the repetitive pattern of the sample at a first magnification and storing it as a first image, and a scanning and detection of the second area at a first magnification. A charged particle beam inspection method, comprising: a second storage step of storing the first and second images as a second image; and a comparative inspection of the first and second images.
1 3 .電子源より発生した電子線を所定の電圧まで加速するための 1 段以上の静電レンズと、該電子線を試料に収束させて照射するための 1段以上の収束レンズおよび対物レンズと、該電子線を偏向させるた ' めの 1段以上の偏向器と、前記対物レンズで発生する歪曲収差を補正 する補正磁界レンズと、 を有し前記偏向器、 前記補正磁界レンズおよ ぴ前記対物レンズによる電子線偏向によって電子線を前記試料面上 で 2次元的に走査し、前記試料から 2次的に発生する電子線の強度を 電子線の走査と同期して検出し輝度変調して走查電子顕微鏡画像を 表示する画像表示装置と、を具備したことを特徴とする電子顕微鏡装 置。  1 3. One or more stages of electrostatic lens for accelerating the electron beam generated from the electron source to a predetermined voltage, and one or more stages of converging lens and objective lens for focusing and irradiating the sample with the electron beam A deflector for deflecting the electron beam, one or more stages, and a correction magnetic lens for correcting distortion generated by the objective lens. The electron beam is two-dimensionally scanned on the sample surface by the electron beam deflection by the objective lens, and the intensity of the electron beam secondary generated from the sample is detected in synchronization with the electron beam scanning, and the brightness is modulated. And an image display device for displaying a scanning electron microscope image.
1 4 . 電子線源と、 該電子線源より発生した電子線を収束させるため . の収束レンズと、該収束レンズを経た電子線を偏向するための偏向器 と、該偏向器により偏向された電子線を試料上に結像させるための対 物レンズとを用いて、該試料上に電子線を走査し、該試料から 2次的 に発生する電子線を検出して 2次元走查電子顕微鏡画像を取得する ようにした電子顕微鏡装置において、前記対物レンズの電子線源側に、 前記対物レンズの励磁方向とは逆の方向の励磁磁界レンズを設けて なることを特徴とする電子顕微鏡装置。 14. An electron beam source, a converging lens for converging an electron beam generated from the electron beam source, a deflector for deflecting the electron beam passing through the converging lens, and a beam deflected by the deflector A two-dimensional scanning electron microscope scans an electron beam on the sample using an objective lens for imaging the electron beam on the sample, and detects an electron beam generated secondary from the sample. In an electron microscope apparatus configured to acquire an image, on the electron beam source side of the objective lens, An electron microscope apparatus comprising an exciting magnetic field lens in a direction opposite to an exciting direction of the objective lens.
PCT/JP2001/010415 2000-12-12 2001-11-29 Charged particle beam microscope, charged particle beam application device, charged particle beam microscopic method, charged particle beam inspecting method, and electron microscope WO2002049066A1 (en)

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