Classifications

• • 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 or 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.

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• Electromagnetism (AREA)
• Analysing Materials By The Use Of Radiation (AREA)
• Electron Beam Exposure (AREA)

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• 2000
  • 2000-12-12 JP JP2000377027A patent/JP2002184336A/ja active Pending
• 2001
  • 2001-11-29 WO PCT/JP2001/010415 patent/WO2002049066A1/ja active Application Filing

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