JP2000223542A - Inspection method and inspection apparatus using electron beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection method and an inspection apparatus using an electron beam, which enhances resolution and aims to improve the speed, reliability, and downsizing. SOLUTION: When applying voltage to a sample 13 via a sample stage 12 and focusing an electron beam on the sample 13 for scanning and shifting the sample stage 12 continuously during the scanning and detecting the charged particles generated from the sample 13, thereby detecting the defect of the sample 13, the dimension between the sample stage and a shield frame is decided, based on the limit of the discharge generated between the sample stage 12 and the shield frame, and this apparatus is provided with a coil of at least six poles to correct the shape of an electron beam. During the shifting of the sample 13, it is blanked and deflected with the crossover of the electron beam as the fulcrum for blanking, and the magnitude of the voltage applied to the sample 13 is decided by the kind of the sample 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection method and an inspection apparatus using an electron beam, and more particularly to an inspection method using an electron beam suitable for inspecting a pattern of a circuit or the like on a wafer in a semiconductor device manufacturing process. The present invention relates to an inspection method and an inspection device.

[0002]

2. Description of the Related Art An optical inspection apparatus for irradiating light and detecting its reflection with a CCD or the like to detect defects is known as an inspection apparatus for a circuit pattern used in a manufacturing process of a semiconductor device, a mask, a reticle, and the like. Are known. As the width of the pattern becomes finer, the resolution of the optical inspection device is limited. Therefore, an inspection apparatus using an electron beam with high resolution has been attracting attention.

One of devices for observing a sample using an electron beam is a scanning electron microscope (scanning electron microscope).
(hereinafter referred to as SEM). One of the devices for inspecting semiconductor devices is a critical dimension scanning electron microscopy.
pe, hereafter referred to as CDSEM). However, although the above SEM and CDSEM are suitable for observing a limited field of view at high magnification, they are not suitable for searching for a defect on a semiconductor wafer. This is because such a defect search requires inspection of a very large area, that is, the entire surface area of a wafer having a diameter of 200 mm to 300 mm. However, when such a large area is inspected by the above-described SEM or CDSEM, a very long time is required. The reason is that the scanning speed is low because the electron beam current of the SEM or CDSEM is low. Therefore, the above SEM and CD
When an SEM is used for an inspection in the course of a semiconductor device manufacturing process, an extremely impractical inspection time is required. An inspection apparatus used for inspection in the course of a semiconductor device manufacturing process needs to have a faster inspection time called throughput.

[0004] An apparatus for solving such a problem is described in, for example, Japanese Patent Application Laid-Open No. 5-258703. This apparatus is an inspection apparatus that detects a defect on a wafer using image comparison. The features of this apparatus are (a) a large current electron beam is used, (b) the sample stage is continuously moved while irradiating the sample or the substrate with the electron beam, and (c) the electron source is generated. When accelerating the electron beam, a high accelerating voltage is used. (D) A retarding voltage is applied to the sample to decelerate the electron beam to prevent the sample from being charged. (E) The sample is irradiated by the electron beam. (TTL method (Through TheLens typ.)
e)). The use of this inspection apparatus makes it possible to perform a defect inspection of a pattern of a mask or a wafer more efficiently and at a higher speed than a conventional SEM.

In the TTL system, charged particles coming out of a sample are detected through an objective lens. With this structure, the distance between the objective lens and the sample can be reduced. And the objective lens can be a short focus,
The aberration of the electron beam is reduced, and a high-resolution image can be obtained. However, there is a non-negligible problem that when the height of the sample changes, the rotation of the electron beam changes greatly and the obtained image rotates. Therefore, the height accuracy of the sample must be ensured, and the improvement of the inspection speed is limited.

The inspection apparatus described in the above-mentioned Japanese Patent Application Laid-Open No. 5-258703 employs a parallel beam in order to avoid defocusing due to the mutual repulsion of electrons of an electron beam. With a parallel beam, when blanking occurs during the movement of the sample on the sample stage, during blanking, there is an electron beam that cannot be cut off by the aperture in the middle of the trajectory of the electron beam. The area that you do not want is slightly irradiated. As described above, during a period from the start to the completion of blanking, a portion which is originally not preferable to be irradiated with the electron beam is irradiated with the electron beam. As a result, there is a problem that the obtained image is different from an actual image.

FIG. 14 shows an example of the relationship between the retarding voltage and the secondary electron detection efficiency using a wafer as a sample in a semiconductor device manufacturing process. In the case of the TTL method of (2) in FIG. 14, there is a problem that when the retarding voltage is reduced, the detection efficiency of secondary electrons is reduced to a considerable extent. Secondary electrons generated from the sample converge through the magnetic field of the objective lens. The main reason why the detection efficiency of the secondary electrons is reduced is that when the retarding voltage is changed, the irradiation energy of the electron beam to the sample changes, and the convergence position of the secondary electrons in the axial direction changes.

Therefore, it is conceivable to increase the retarding voltage in order not to lower the detection efficiency of secondary electrons. However, when the retarding voltage is increased,
Since a retarding voltage is applied to the sample stage and the shield frame surrounding the end of the sample stage is grounded, discharge occurs between the end of the sample stage and the shield frame. As a result, the effect of the application of the retarding voltage is reduced, or noise is generated to make the electron beam unstable, which is not preferable.

Further, since the sample is easily charged by a difference in material, the magnitude of the retarding voltage must be changed according to the sample being easily charged. The irradiation position of the electron beam is determined based on the position of the sample stage on which the sample is mounted accurately measured. An interferometer using laser light is used for measuring the position of the sample stage. In this method, a laser beam is applied to a mirror attached to a sample stage, and a minute change in the position is measured by observing interference of reflected light. On the other hand, the above-mentioned retarding voltage is applied to a sample via a sample stage on which the sample is mounted. Therefore, the mirror is attached to the two ends of the sample stage, and a retarding voltage is also applied to the mirror. However, since the mirror is glassy, an electric field is concentrated at the end and the mirror is close to the mirror. Since other members such as the shielded frame are grounded, there is a possibility that a discharge may occur between them. The same applies to the case where the end is sharp, because the discharge is easy even if it is not glassy. Therefore, it is necessary to consider not only the discharge between the end of the sample stage to which the retarding voltage is applied and the shield frame surrounding the end, but also the electric field concentration on the position measurement mirror of the sample stage. No.

The discharge phenomenon of the sample stage to which such a high retarding voltage is applied can be prevented by sufficiently widening the dimension between the sample stage and its periphery.
This can be solved by increasing the size of the device. However, in a semiconductor device manufacturing process, it is necessary to install a manufacturing apparatus and an inspection apparatus inside a clean room, and the larger the floor area of the clean room, the higher the capital investment amount. Therefore, it is desired that the inspection apparatus used therein not only has a high speed but also saves space by downsizing.

On the other hand, in the inspection apparatus using an electron beam as described above, when the resolution is improved, the cross-sectional shape of the electron beam irradiated on the sample is not circular but its corner is rounded. It becomes a triangle with.

For example, when a circular sample is scanned with a triangular electron beam, not a circular image but a triangular image is obtained. In addition, assuming that the beam diameter of an original normal electron beam is substantially the same as the size of one pixel, the beam becomes triangular, so that it cannot fit in the original one pixel size, and the surrounding several pixels The hem of the beam spreads.
In other words, the beam diameter increases accordingly. Therefore, the image obtained by scanning the sample with the electron beam becomes larger than the original size, and the image is blurred.

An inspection apparatus to which the present invention is applied compares two patterns and detects a different portion as an abnormality or a defect. When detecting defects in microstructures, blurring of the image is fatal, and as with reduced detection sensitivity, undetectable defects may occur.

It is considered that the cross-sectional shape of the electron beam becomes triangular because the shape of the chip as the electron source or the converging lens of the electron optical system is not completely axially symmetric. Therefore, even if the apparatus can obtain a high resolution, if these troubles occur, a correct inspection result cannot be obtained.

[0015]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, increases the resolution, and increases the speed, reliability and size of the inspection using an electron beam. It is an object to provide a method and an inspection device.

[0016]

In order to achieve the above object, the present invention applies a voltage to a sample via a sample stage, focuses and scans the electron beam on the sample, and continuously scans the sample stage during scanning. When detecting the defect of the sample by detecting the charged particles generated from the sample, the distance between the sample stage and the shield frame based on the limit of the discharge generated between the sample stage and the shield frame Is determined.

Further, the present invention is characterized in that at least a six-pole coil for correcting the shape of the electron beam is provided.

Further, the present invention is characterized in that a blanking deflection is performed using the crossover of the electron beam as a fulcrum of the blanking during the movement of the sample.

Further, the present invention is characterized in that the magnitude of the voltage applied to the sample is determined according to the type of the sample.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram showing a procedure of a semiconductor device manufacturing process. As can be seen from the figure, in manufacturing a semiconductor device, a number of pattern forming steps 51 to 55 on a semiconductor device wafer are repeated. Each of the pattern forming steps roughly includes the steps of film formation 56, resist coating 57, exposure 58, development 59, etching 60, resist removal 61 and cleaning 62. If the manufacturing conditions are not optimized in each step, the circuit pattern on the semiconductor wafer will not be formed properly.

Therefore, the visual inspection step 6 is performed between the steps.
3 or 64 is provided, and the inspection of the circuit pattern is executed. When a defect is found as a result of the inspection performed in the appearance inspection step 63 or 64, the inspection result is reflected in a process step which causes the defect to occur, and the occurrence of the same defect is suppressed. The way of reflection is determined by the defect management system 65 shown in FIG.
It is also possible to transmit data to 7, 58, and 59 manufacturing apparatuses and automatically change manufacturing conditions.

FIG. 3 shows an example of an image 70 obtained by observing a circuit pattern on a semiconductor wafer in a manufacturing process with a scanning electron microscope (SEM). FIG. 3A shows a normally processed pattern, and FIG. 3B shows a pattern in which a processing failure has occurred. For example, if an abnormality occurs in the step of film formation 56 in FIG. 2, particles adhere to the surface of the semiconductor wafer, and
The isolated defect A in FIG. Further, if conditions such as focus and exposure time are not optimal at the time of exposure after resist application, there may be places where the amount or intensity of light irradiating the resist is too large or insufficient, and short circuit C shown in FIG. And disconnection E, pattern thinning and chipping D. If there is a defect on the mask or reticle at the time of exposure, similar pattern shape abnormality is likely to occur.

When the etching amount is not optimized or when there is a thin film or a particle generated during the etching, a short circuit C, a protrusion B, an isolated defect A, and an opening defect G also occur. At the time of washing, abnormal oxidation is likely to occur at the corners of the pattern and other places depending on the condition of running out of water during drying, and a thin film residue F which is difficult to observe with an optical microscope is generated.

Therefore, in the wafer manufacturing process, it is necessary to optimize the processing conditions so that these defects do not occur, and it is necessary to detect the occurrence of an abnormality at an early stage and feed it back to the relevant step.

In order to detect such a defect, for example, appearance inspections 63 and 64 are performed after the step of development 59 and after the step of resist removal 61 in FIG. An inspection apparatus using an electron beam according to the present invention is used for this inspection.

FIG. 1 is an embodiment of the present invention and is a longitudinal sectional view schematically showing a configuration of an inspection apparatus using an electron beam.

In FIG. 1, an electron gun 1 comprises an electron source 2, an extraction electrode 3 and an acceleration electrode 4. An extraction voltage V1 is applied between the electron source 2 and the extraction electrode 3 by an extraction power supply 5, whereby an electron beam 36 is extracted from the electron source 2. The accelerating electrode 4 is maintained at the ground potential, and an accelerating voltage Vacc is applied between the accelerating electrode 4 and the electron source 2 by the accelerating power supply 6, so that the electron beam 36 is accelerated by the accelerating voltage Vacc.

The accelerated electron beam is transmitted by a first converging lens 8 connected to a lens power source 7 between the first converging lens 8 and an objective lens 9 which is a second converging lens connected to the lens power source 7. A sample 13 such as a semiconductor wafer on a sample stage 12 which is converged so as to generate a crossover 10 and is horizontally movable by an objective lens 9 by a stage driving device (not shown) and a length measuring device 11 for position monitoring. Converges. That is, the sample 13 is irradiated with the focused electron beam. The above configuration is housed in a container 43 maintained in a vacuum atmosphere so as to be suitable for electron beam irradiation.

A negative voltage is applied to the sample stage 12 as a retarding voltage for decelerating the electron beam 36.
Is applied by the variable deceleration power supply 14 through the, and further, to the electrode 34 provided between the sample 13 and the objective lens 9,
A positive voltage is applied to the sample 13, and the electron beam 36 is decelerated by the retarding voltage. Usually, the electrode 34 is set to the ground potential, and the retarding voltage can be arbitrarily changed by adjusting the variable speed reduction power supply 14.

An aperture 15 is arranged between the first converging lens 8 and the crossover 10, and an aperture 41 is arranged between the crossover 10 and the electron beam scanning deflector 16. The diaphragm 15 and the diaphragm 41 block extra electrons and serve to determine the aperture angle of the electron beam 36.

An electron beam scanning deflector 16 is disposed between the crossover 10 and the objective lens 9, and has a function of deflecting the electron beam 36 so that the sample 13 is scanned by the focused electron beam 36. Have. The electron beam scanning deflector 16 is provided in the objective lens 9 so that its deflection fulcrum substantially coincides with the center of the magnetic pole gap of the objective lens 9, thereby reducing deflection distortion. be able to.

Between the aperture 15 and the electron beam scanning deflector 16, a blanking connected to the scanning signal generator 24 deflects and blanks the electron beam 36 at a position where the crossover 10 is formed. A deflector 17 is arranged.

An astigmatism correction coil 81 and an astigmatism correction coil 82 having six poles or more are provided inside the converging lens 8. When the electron source 2, the extraction electrode 3, the converging lens, and the like are not axially symmetric, the cross section of the electron beam applied to the sample 13 may be a triangle instead of a circle. Therefore, an astigmatism correction coil 81 and an astigmatism correction coil 82 are provided in the portion of the converging lens 8 to correct the triangle of the electron beam into a circle. As a result, a high-resolution image can be obtained, and a minute defect can be detected.

FIG. 4 is a plan view showing the arrangement of the astigmatism correction coil 81 and the astigmatism correction coil 82. Astigmatism correction coil 8
1. If the astigmatism correction coil 82 has four poles, for example, a force acts to extend the electron beam in the X direction and contract it in the Y direction. When the shape of the electron beam is a triangle, the triangle does not become a circle when the shape is corrected in the X and Y directions. Therefore, as shown in FIG. 4, if the astigmatism correction coil 81 and the astigmatism correction coil 82 are made to have six poles so that a force extending to three sides of the triangle and a force shrinking to three vertices are applied, the triangle becomes a circle. Can be modified. The larger the number of poles of the astigmatism correction coil 81 and the number of poles of the astigmatism correction coil 82, the more accurately the circle can be corrected. Is done.

FIG. 5 is a flowchart showing a procedure for inspecting a circuit pattern formed on a semiconductor wafer using the inspection apparatus according to the present invention.

First, the sample 13 is placed on the sample stage 12.
Is mounted, the sample stage 12 moves into the container 41, the sample inspection chamber in the container 41 is evacuated, and a retarding voltage is applied.

When the sample 13 is scanned with the converged electron beam 36, the secondary electrons 3, which are charged particles, are emitted from the sample 13.
3 and reflected electrons are generated. The secondary electrons 33 are defined as having an energy of 50 eV or less.

The retarding voltage with respect to the electron beam 36 for irradiating the sample 13 acts as an accelerating voltage since the generated secondary electrons have opposite positive and negative directions.
Therefore, the generated secondary electrons 33 are accelerated by the retarding voltage, so that the directions thereof are almost uniform and become almost parallel beams, and the E × B (E-crossing) arranged between the sample 13 and the objective lens 9 is used. B) The light enters the deflector 18.

The E × B deflector 18 is a type of deflector known as a Wien filter, includes a deflection electric field generator for generating a deflection electric field for deflecting the secondary electrons 33, and also irradiates the sample 13 with electrons. And a deflection magnetic field generator for generating a deflection magnetic field orthogonal to the deflection electric field, which cancels the deflection of the beam by the deflection electric field. This deflecting magnetic field has a deflecting action on the secondary electrons 33 in the same direction as the deflecting electric field. Therefore, the deflection electric field and the deflection magnetic field generated by the E × B deflector 18 deflect the accelerated secondary electrons 33 without affecting the electron beam irradiating the sample 13.

In order to keep this deflection angle almost constant,
The deflection electric field and the deflection magnetic field generated by the E × B deflector 18 can be changed in conjunction with the change of the retarding voltage. Since the E × B deflector 18 generates a deflection electric field and a deflection magnetic field, it may be called a deflection electric field and a deflection magnetic field generator.

The secondary electrons 33 deflected by the deflection electric field and the deflection magnetic field of the E × B deflector 18 bombard or irradiate the conductive secondary electron generator 19. Secondary electron generator 19
Is arranged around the axis of the electron beam between the objective lens 9 and the E × B deflector 18, and has a conical shape diverging toward the electron gun 1 along the axis. The secondary electron generator 19 is made of CuBeO, and has a secondary electron generating ability of about five times the number of incident electrons.
Second secondary electrons 20 generated from secondary electron generator 19
(Which has an energy of 50 eV or less) is detected by the charged particle detector 21 and converted into an electric signal.

The height of the sample 13 is measured in real time by the optical sample height measuring device 22, and the measurement result is fed back from the correction control circuit 23 to the lens power supply 7, whereby the focal length of the objective lens 9 is dynamically adjusted. Is corrected to The sample irradiation position of the electron beam is detected by the position monitoring length measuring device 11, and the result is fed back from the correction control circuit 23 to the scanning signal generator 24, whereby the sample irradiation position of the electron beam is controlled. .

FIG. 6 is a plan view of a semiconductor wafer 44 as an example of the sample 13 as viewed from above, and FIG. 7 is an enlarged view of a part thereof. The wafer 44 is continuously moved by a stage driving device (not shown) in the y direction of the xy coordinate as indicated by an arrow y, while scanning of the wafer 44 by the electron beam 36 is indicated by an arrow x in the x direction. As described above, the scanning and the blanking deflection are alternately repeated while the wafer 44 is moving.

In order to make the irradiation of the wafer 44 with the electron beam 36 uniform over time and space, the electron beam 36 is drawn so that the electron beam 36 is not directed to the wafer 44 during the retrace period of each scan. The light is deflected by the blanking deflector 17 shown in FIG.

The scanning by the electron beam 36 is performed by A in FIG.
The process is performed up to the point B starting from the point. During this scanning, the wafer 44 moves in the y direction together with the sample stage 12. The electron beam 36 is blanked between the point B and the point A 'as shown by a broken line in FIG. 7, and scanning is started again from the point A' to the point B '. As described above, the scanning and the blanking are alternately repeated while the wafer 44 is moving, and the scanning from the point C to the point D is performed.

The wafer 44 is moved from the start point A to the end point D.
After the continuous movement to the point, the wafer 44
6, the wafer 44 is moved in the x direction by an amount corresponding to the width w, and then the continuous movement of the wafer 44 in the -y direction is resumed, and the wafer 44 is moved from the current start point C to the end point F, and then continuously. During the movement, scanning of the wafer 44 by the electron beam 36 in the x direction and blanking are alternately repeated.

By repeating such an operation, scanning of the entire surface of the wafer 44 by the electron beam 36 is completed.

FIG. 8 shows a conceptual diagram of the form of blanking of the electron beam 36 shown in FIG. In this embodiment, FIG.
8B, the beam is deflected by blanking with the crossover 10 of the electron beam 36 as a fulcrum, and this is shown in FIG. If the electron beam 36 is deflected with a point other than the crossover 10 as a fulcrum for blanking deflection, the electron beam irradiation position on the wafer 44 moves during the deflection. Further, as shown in FIG. 8B, when the electron beam 36 is a parallel beam, there is an electron beam which cannot be cut off by the diaphragm 15 and the diaphragm 41 during blanking when the electron beam 36 is deflected by blanking. A small area is irradiated slightly. As described above, during the period from the start of blanking deflection to the completion thereof, a part which is not preferably irradiated with the electron beam 36 is an electron beam 36.
In particular, when the resolution is increased, it is a problem that an erroneous image is obtained due to this.

On the other hand, in the embodiment of the present invention, at the time of blanking deflection, the electron beam 36
The electron beam is not deflected with the fulcrum as a fulcrum, so that the electron beam does not irradiate the adjacent region, the change of the irradiation position of the electron beam on the wafer 44 can be avoided, and highly accurate defect detection becomes possible.

The electron beam 3 on the sample 13 or the wafer 44
In the scanning by 6, the electron beam 36 is deflected in the x direction while the wafer 44 is continuously moved in the y direction, but the scanning may be reciprocated instead of alternately repeating the scanning and the blanking deflection. In this case, the scanning speed at the time of going deflection and the scanning speed at the time of returning deflection are made the same. In this way, the blanking deflector 17 can be omitted, and the blanking time can be saved. However, in this case, it is necessary to pay attention to the following.

FIG. 9 is an enlarged view of a part of the wafer 44 showing the scanning direction of the electron beam 36 on the wafer 44 as in FIG. The point B at the end of the reciprocal deflection of the electron beam 36 and the point B 'at the beginning of the wafer 44 are intensively irradiated by the electron beam 36 in a short time. That is, for example,
In the case of scanning from left to right in the x direction, the electron beam stops moving in the x direction at the end point B of the irradiation area, and the wafer 44
Is moved by the scanning width in the y-direction and comes to the first point B ', and then the next column is moved from right to left in the x-direction and scanned. While waiting for movement in the y direction between the points B and B ', irradiation between the region centered on the end point B of the wafer 44 and the region centered on the point B' is performed in the y direction. You can continue. Therefore, in the case of a sample having a very short time constant of the charging phenomenon, when the image is obtained, the brightness of the image becomes non-uniform. Therefore, in order to make the irradiation amount of the electron beam 36 substantially the same over the entire surface of the wafer 44, the scanning speed of the electron beam 36 is higher between the points B and B 'than between the points A and B in FIG. It is preferable to control the scanning speed so as to increase the scanning speed.

Next, the image processing unit 42 shown in FIG.
The following describes the image processing performed in step (1).

The image processing unit 42 detects a defect on the sample 13 from an electric signal from the charged particle detector 21. The electric signal obtained by converting the amount of the second secondary electrons 20 detected by the charged particle detector 21 is amplified by the amplifier 25 and digitized by the A / D converter 26. The digitized signal is stored in the storage units 27 and 28 as an image signal. Specifically, first, the secondary electron image signal of the first inspection area is stored in the storage unit 27.

Next, the second of the adjacent same circuit patterns
While storing the secondary electron image signal of the inspection area of the storage area in the storage unit 28, the secondary electronic image signal of the first inspection area of the storage unit 27 is simultaneously compared with the secondary electron image signal. Further, the secondary electron image signal of the third inspection area is overwritten and stored in the storage unit 27, and at the same time, the storage unit 28
Is compared with the image of the second inspection area. Repeat this,
The storage and comparison of image signals are performed for all inspection areas. The image signal stored in the storage unit 28 is displayed on the monitor 32.

The image comparison is performed by the calculation unit 29 and the defect determination unit 30 shown in FIG. That is, with respect to the secondary electron image signals stored in the storage units 27 and 28, various statistical quantities, specifically, the average and variance of image density values, etc., are calculated by the arithmetic unit 29 based on the defect determination conditions already obtained. The statistic, a difference value between neighboring pixels, and the like are calculated. After these processes have been performed, the processed image signal is transferred to the defect determination unit 30, where it is compared and a difference signal is extracted, and the defect signal is determined with reference to the defect determination conditions already obtained and stored. The signal and other signals are separated.

FIGS. 10A and 10B illustrate an example of image comparison using an image 70. FIG. 10A shows a secondary electron image signal stored in the storage unit 27, and FIG. 2
This is the next electronic image signal. When the difference between the signals of the image 1 of FIG. 1A and the image 2 of FIG. 2B is obtained, a difference image as shown in FIG. 2C is obtained, which is displayed as a defect.

Also, the secondary electronic image signal of the inspection area of the standard circuit pattern is stored in the storage unit 27 in advance,
The secondary electron image signal of the inspection area of the circuit pattern of the sample 13 may be stored in the storage unit 28 and compared with the stored image signal of the storage unit 27. That is, first, the inspection area and the inspection conditions for the non-defective semiconductor device are input from the control unit 31 in advance, the non-defective inspection is executed based on the data, and the secondary electronic image signal of the desired area is fetched into the storage unit 27. Remember. Next, the sample 13 to be inspected is inspected by the same method, and the secondary electron image is taken into the storage unit 28 and stored. At the same time, this and the storage unit 27
After the registration with the non-defective secondary electron image stored in the storage device, the defect is detected only by comparing the positions.

At this time, as a non-defective semiconductor device, a non-defective part of the sample 13 or a non-defective wafer or chip different from the sample 13 is used. For example, sample 13
In such a case, when a circuit pattern is formed, a defect may occur as if the lower layer pattern and the upper layer pattern were misaligned. If the comparison target is a circuit pattern in the same wafer or in the same chip, the above-mentioned defect which occurs similarly on the entire wafer is overlooked, but a good image signal is stored in advance, and the image signal of the sample 13 is stored. By comparing the above, it is possible to detect the above-described overall failure.

The operation command and the condition setting for each part of the inspection apparatus are performed from the control unit 31 in FIG. Therefore, conditions such as acceleration voltage, deflection width (or scanning width) and deflection speed (or scanning speed) of the electron beam, moving speed of the sample stage, and timing for capturing the output signal of the detector are input to the controller 31 in advance. I have.

Next, a description will be given of how an inspection apparatus using an electron beam according to the present invention (hereinafter abbreviated as the present inspection apparatus) differs from a conventional scanning electron microscope (hereinafter abbreviated as an SEM).

The SEM is an apparatus for observing a very limited area, for example, an area of several tens of μm square at high magnification over time. Even a scanning electron microscope for length measurement (hereinafter abbreviated as SEM), which is one of the semiconductor inspection devices, performs observation and measurement of only a limited plurality of points on a wafer at a high magnification. On the other hand, the present inspection apparatus is an apparatus that targets a sample such as a wafer and searches for a defect.
Therefore, the inspection must be performed over a very wide area, so that the inspection speed is extremely important.

FIG. 11 shows the relationship between the image acquisition time per 1 cm ² and the measurement time of one pixel (one pixel). FIG. 12 shows the relationship between the image acquisition time per 1 cm ² and the electron beam current.

In general, the S / N ratio in an electron beam image has a correlation with the value of the square root of the number of irradiation electrons per unit pixel of the electron beam irradiating the sample. The defect to be detected on the sample is a minute defect for which inspection by pixel comparison is desirable. When the resolution required for the inspection apparatus is set to about 0.1 μm based on the size of the pattern to be inspected, the pixel size becomes From this point of view and from the experience of the inventors, it is desirable that the S / N ratio of the raw image after being detected by the charged particle detector and before image processing is 10 or more. . On the other hand, general inspection time required for inspection of the circuit pattern of the wafer is approximately 200 sec / cm ² or so, assuming that about half 100 sec / cm ² about the inspection time the time required for image acquisition only, in FIG. 11 As shown, the required time per pixel is 10 nsec or less.
Further, the required number of electrons per pixel is about 6000, and it can be seen from FIG. 12 that the electron beam current needs to be 100 nA or more. In FIG. 12, S
In the case of EM or SEM, the electron beam current is several hundred pA, since there is no practical problem even if the image acquisition time per cm ² is slow.
The following low values have been adopted:

In consideration of the above, in the embodiment of the present invention, the electron beam current for irradiating the sample is set to 100 n.
A, the pixel size is 0.1 μm, the spot size of the electron beam on the sample is 0.08 μm which is 0.01 μm or less,
The continuous moving speed of the sample stage 12 is set to 10 mm / sec, and under these conditions, the same region of the sample is scanned 200 sec / c only once without scanning the same region with the electron beam a plurality of times.
m ² about which enables a high-speed inspection.

In the conventional SEM and the measurement SEM, the electron beam current for irradiating the sample is about several pA to several hundred pA, so that the inspection time per cm ² is several hundred hours. It is practically impractical to use an SEM in a manufacturing process for inspecting an entire surface of a wafer or the like.

In the embodiment of the above specification, a diffusion-supply type thermal field emission electron source or a Schottky type is used as the electron source 2 of the electron gun 1 so that a large current electron beam can be obtained and high-speed inspection can be performed. Used. Furthermore, a required time per pixel of 10 nsec corresponds to an image sampling time of 100 MHz, and therefore, the charged particle detector 21 needs to have a corresponding fast response speed. is there. In order to satisfy this condition, it is desirable to use a semiconductor detector as the charged particle detector 21.

In the case of a sample having low or no conductivity, the sample is charged by being irradiated with an electron beam. This charge amount depends on the acceleration voltage of the electron beam,
It is solved by lowering its energy. However, in an electron beam inspection apparatus based on image comparison, 1
Since a high current electron beam of 00 nA is used, when the acceleration voltage is reduced, aberrations, that is, the spread of the electron beam in the radial direction increase due to the space charge effect, and 0.08.
It becomes difficult to obtain an electron beam spot size of μm on the sample, and therefore, a decrease in resolution is inevitable.

FIG. 13 shows the relationship between the electron beam diameter and the acceleration voltage when the beam current is 100 nA and the sample irradiation energy is 0.5 keV. In the embodiment of the present invention, as shown in FIG. 13, the acceleration voltage Vacc is set to prevent the reduction and change of the resolution due to the space charge effect and to stably obtain the electron beam spot size of 0.08 μm on the sample. It is set constant at 10 kV.

The quality of the image obtained by the inspection apparatus is as follows.
It depends greatly on the energy of the electron beam irradiating the sample. The energy varies depending on the type of sample. The energy is increased when the contrast of the image is emphasized for a sample that is difficult to be charged or for which the edge of the circuit pattern is to be particularly known, and the energy is reduced for a sample that is easily charged. For this reason, it is necessary to find and set the optimum electron beam irradiation energy every time the type of the sample to be inspected changes.

In the embodiment of the present invention, the optimum irradiation energy of the electron beam for irradiating the sample is set by changing the negative voltage applied to the sample 13 without changing the acceleration voltage Vacc, ie, changing the retarding voltage. You. This retarding voltage can be changed by the variable deceleration power supply 14.

FIG. 14 shows the relationship between the secondary electron detection efficiency (unit%) and the retarding voltage (unit kV). The curve (1) in the figure is based on the long focus method according to the embodiment of the present invention, and the curve (2) is based on the TTL method. As described above, the retarding voltage should be changed depending on the type of the sample. Also, the retarding voltage has the effect of accelerating secondary electrons. In FIG. 14, 2
The secondary electron detection efficiency can be calculated by changing the retarding voltage.
In the case of the TL system, it changes greatly, whereas in the embodiment of the present invention, it does not change much. In the case of the TTL method, the retarding voltage needs to be 5 kV or more. In the case of the TTL system, secondary electrons generated from the sample are converged through the magnetic field of the objective lens, and the convergence position in the axial direction changes by changing the retarding voltage. This is the main cause that greatly changes the secondary electron detection efficiency. On the other hand, in the embodiment of the present invention, since the secondary electrons 33 do not pass through the magnetic field of the objective lens 9, the influence is small. Therefore, in the long focal point method according to the embodiment of the present invention, since the rotation of the image is small and the fluctuation of the secondary electron detection efficiency is small, there is an advantage that the inspection image is stabilized.

As described above, the secondary electrons 33 generated from the sample 13 spread as they are, but are accelerated by the retarding voltage and become almost parallel beams, so that the collection efficiency of the secondary electrons 33 is improved. . The secondary electrons 33 are further deflected by a certain angle, for example, 5 ° with respect to the center axis of the electron beam 36 by the deflection electric field and the deflection magnetic field of the E × B deflector 18, and impact the secondary electron generator 19. Accordingly, a large amount of the second secondary electrons 20 are generated. As described above, the detection efficiency of the secondary electrons is greatly improved by the impact of the parallel beam and the secondary electron generator 19.

As described above, the method of detecting the charged particles generated from the sample 13 after passing through the objective lens 9 is as follows.
It is called TTL method. According to the TTL method, the aberration of the electron beam can be reduced and the resolution can be increased by operating the objective lens with a short focus. On the other hand, in the embodiment of the present invention, as shown in FIG.
Charged particles 33 generated from 3 are detected under the objective lens 9. Therefore, the focal length of the objective lens 9 is TTL
It is set longer than the method. That is, the conventional T
In the TL system, the focal length of the objective lens is about 5 mm, whereas in the embodiment of the present invention, the value is set to about 40 mm. In order to reduce the aberration of the electron beam, a high acceleration voltage of 10 kV is employed as described above. Therefore, according to the embodiment of the present invention, the sample 13
The deflection width of the electron beam 36, which is performed to acquire the image, that is, the scanning width by the electron beam 36 can be increased. For example, while the beam deflection width of the conventional TTL system is about 100 μm, it can be set up to 500 μm in the embodiment of the present invention.

Since the surface of the sample 13 is not a perfect plane, the height of the sample changes as the region to be inspected moves.
Therefore, it is necessary to change the excitation of the objective lens 9 to always focus on the surface of the sample 13. In the conventional TTL method, strong excitation is performed so that the objective lens works with a short focus. However, in the case of a strongly excited objective lens, the flow of the electron beam rotates in the horizontal direction with a change in the height of the sample, and as a result, the rotation of the obtained image occurs. Required. On the other hand, in the embodiment of the present invention, the objective lens 9 is weakly excited so as to be operated at the long focus. For example, if I is the current value of the objective lens (unit A), N is the number of turns of the coil of the objective lens, and E is the energy of the electron beam (unit eV), IN /
It is excited to about ９E = 9. For this reason, even if the focus is finely adjusted in accordance with the change in the height of the sample 13, the rotation of the electron beam 36 and the rotation of the obtained image are substantially negligible, and the correction is not performed. Not required.

In the above-described embodiment of the present invention, the secondary electrons 33 generated from the sample 13 are used for image formation. However, the reflected electrons backscattered from the sample by the irradiation of the electron beam 36 are removed. The same effect can be obtained even if an image is formed by using the same. As described in the description of FIGS. 13 and 14, the retarding voltage should be changed depending on the sample. In the case of the embodiment of the present invention, when the sample irradiation energy is 0.5 keV and the acceleration voltage is 10 kV,
The retarding voltage is 9.5 kV. In FIG. 1, this retarding voltage is applied to a sample 13 from a variable deceleration power supply 14 via a sample stage 12. FIG.
FIG. 5 shows a cross-sectional view around the sample stage 12 of the container 43 shown in FIG. An alternate long and short dash line indicates a moving range of the sample stage 12. As shown in FIG. 15, the sample stage 12 to which the retarding voltage 9.5 kV is applied is housed inside the shield frame 83 which is grounded inside the container 43. Not only reduces the effect of the retarding voltage, but also reduces the sample 13
Of the electric field on the surface and noise.

FIG. 16 shows the sample stage 1 shown in FIG.
2 shows the result of simulation of the discharge limit of a part of No. 2 by calculation. The horizontal axis is the retarding voltage, and the vertical axis is the end portion 12a of the sample stage 12 and the shield frame 8 inside the container 43.
3 is a gap dimension H between the third end 83a. In FIG. 16, when the retarding voltage, which is the condition for the embodiment of the present invention, is 9.5 kV, the end 1 of the sample stage 12
2a and the end 83a of the shield frame 83 inside the container 43 generate a discharge H between the two shown in FIG.
It can be seen that it can be prevented if is 3.5 mm or more. In an actual device design, the gap size H is set to be larger than the gap size H at the discharge generation limit. In the case of the embodiment of the present invention, the design upper limit of the retarding voltage applied to the sample stage 12 is 1
It is 2 kV. As shown in FIG. 16, the gap dimension H at this time is 4.5 mm, which has a margin of 1 mm with respect to the actual limit value of 3.5 mm.

As a result of the above simulation, as shown in FIG. 15, when the gap dimension H is 4.5 mm, the diameter is 300 mm.
The movement dimension L of the sample stage 12 on which the wafer can be mounted is
1141 mm, the width dimension M of the shield frame 83 is 35 mm due to its strength
Therefore, the width W of the container 43 in which the sample stage 12 is incorporated is 1220 mm. Actually, the shield frame 83 is not exposed, and the shield frame 8 is not exposed.
Since the enclosure 84 is provided on the outer circumference of the device 3, for example, about 40 mm outside, the outside dimension of the actual apparatus is larger than the width dimension W of 1220 mm and becomes 1300 mm.

The size of the sample stage 12 changes depending on the size of the wafer to be mounted, and as a result, the moving size also changes. In the case of a wafer having a diameter of 200 mm, for example, the movement dimension L is 941 mm, so that the width dimension W of the container 43 in which the sample stage 12 is incorporated is 1020 mm. For example, the outer dimension of the apparatus including the enclosure is 1100 mm.

As described above, the end portion 12 of the sample stage 12
a and a gap H capable of preventing discharge occurring between the end portion 83a of the shield frame 83 inside the container 43 and the end portion 83a, the size of the apparatus could be reduced to the limit. In the case of the embodiment of the present invention, as described above, the minimum size of the device capable of preventing the occurrence of discharge is that the size W of the portion surrounded by the shield frame 83 when the diameter of the wafer is 300 mm is 1220.
mm and the diameter of the wafer was 200 mm, the dimension W of the portion surrounded by the shield frame 83 was 1020 mm. The sample stage 12 can move in a two-dimensional direction, and the amount of movement is shown in FIG.
Is measured by the position-monitoring device 11 for position monitoring as shown in FIG. For this, an interferometer using laser light is used.
This interferometer irradiates a mirror provided on the sample stage 12 with laser light, detects reflected light, and measures a minute movement amount by using light interference.

FIG. 17 is a perspective view of the sample stage 12 to which the mirror 85 is attached, and FIG. 18 is a perspective view of the mirror 85. Since a retarding voltage is applied to the sample stage 12 and the mirror 85 is glassy, its end 8
There is a problem that the electric field concentrates on 5a and generates discharge with other grounded members such as the shield frame 83. Therefore, as shown in FIG. 18, the end is covered with a metal cover 86 so that the electric field does not concentrate on the end. As a result, the electric field concentrates on the end portion 85a, and the occurrence of discharge with other members can be prevented.

As described above, the discharge of the sample stage to which the retarding voltage is applied and the discharge of the mirror can be prevented, the dimensions of the apparatus can be minimized, and the apparatus can be installed in a clean room where the semiconductor manufacturing process is limited. The device can be easily installed.

[0082]

As described above, according to the present invention, it is possible to obtain an inspection method and an inspection apparatus using an electron beam which can increase the resolution, increase the speed, improve the reliability, and reduce the size. .

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing a configuration of an inspection apparatus using an electron beam according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a procedure of a general semiconductor device manufacturing process.

FIG. 3 is a diagram showing an example of an image obtained by observing a circuit pattern on a semiconductor wafer in a manufacturing process of the semiconductor wafer by SEM.

FIG. 4 is a plan view showing an arrangement of astigmatism correction coils.

FIG. 5 is a flowchart showing an inspection procedure of a circuit pattern formed on a semiconductor wafer.

FIG. 6 is a plan view of the wafer as viewed from above.

FIG. 7 is an enlarged view of a part of the wafer of FIG. 6;

FIG. 8 is a conceptual diagram showing a form of blanking of an electron beam.

FIG. 9 is an enlarged view of a part of the wafer as in FIG. 7;

FIG. 10 is an image diagram showing an example of image comparison.

FIG. 11 is a diagram showing the relationship between the image acquisition time per 1 cm ^{2 of the} sample surface and the measurement time of one pixel.

FIG. 12 is a diagram showing the relationship between the image acquisition time per 1 cm ^{2 of the} sample surface and the electron beam current.

FIG. 13 is a diagram illustrating a relationship between an electron beam diameter and an acceleration voltage.

FIG. 14 is a relationship diagram between secondary electron detection efficiency and retarding voltage.

FIG. 15 is a transverse cross-sectional view around a sample stage of the container.

FIG. 16 is a relationship diagram showing a result of simulation of a discharge limit by calculation.

FIG. 17 is a perspective view of a sample stage.

FIG. 18 is a perspective view of a mirror.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron gun, 2 ... Electron source, 4 ... Acceleration electrode, 6 ... Acceleration power supply, 8 ... First converging lens, 9 ... Objective lens, 10 ... Crossover, 11 ... Position monitor length measuring device, 12 ... Sample stage , 13: sample, 14: variable deceleration power supply, 15: aperture, 16: electron beam scanning deflector, 17: blanking deflector, 18: E × B deflector, 19: secondary electron generator, 20 ... 2nd secondary electron, 21 ... charged particle detector, 2
2. Optical sample height measuring device 23. Correction control circuit 2
4 scanning signal generator, 29 arithmetic unit, 30 defect determination unit, 31 control unit, 33 secondary electron, 36 electron beam, 81, 82 astigmatism correction coil, 83 shield frame,
85: mirror, 86: metal cover.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G06T 7/00 G06F 15/62 405A (72) Inventor Hiroyoshi Mori 882-Momo, Oaza-shi, Ichiba, Hitachinaka-shi, Ibaraki Pref. (72) Inventor, Mitsuru Sato 882-Chair, Oaza-shi, Hitachinaka-shi, Ibaraki Co., Ltd.Incorporated within Hitachi, Ltd.-Measurement Instrument Group (72) Yasutsugu Usami 882-Chair, Ichimo, Hitachinaka-shi, Ibaraki Hitachi, Ltd.Measurement Instruments Group (72) Inventor Mikio Ichihashi, Ibaraki Prefecture, Hitachinaka City, Oji, 882 Co., Ltd. Hitachi, Ltd. Instrumentation Group (72) Inventor Satoru Fukuhara, Ibaraki, Hitachinaka City, Oaza, 882 Ichimo (72) Inventor Hiroyuki Shinada Kokubunji, Tokyo 1-280 Koigakubo, Hitachi, Ltd., Central Research Laboratories, Ltd. (72) Inventor Yutaka Kaneko 1-280 Higashi Koikekubo, Kokubunji, Tokyo, Japan, (72) Inventor Atsuko Takato 1-280, Higashi Koikebo, Kokubunji, Tokyo Address Central Research Laboratory, Hitachi, Ltd. (72) Hiroshi Toyama, Inventor Hiroshi Tougai Kubo 1-280, Kokubunji, Tokyo, Japan Inside Central Research Laboratory Hitachi, Ltd. (72) Katsuya Sugiyama 1-280, Higashi Koikebo, Kokubunji, Tokyo, Hitachi, Ltd. Inside the Central Research Laboratory

Claims (17)

[Claims] A sample is mounted on a sample stage surrounded by a shield frame whose dimensions between the sample stage and the sample stage are determined based on a limit of a discharge generated between the sample stage and the sample stage.
A voltage is applied to the sample through the sample stage, an electron beam is converged on the sample and scanned, and the sample stage is continuously moved during the scanning to detect charged particles generated from the sample. An inspection method using an electron beam, wherein a defect of the sample is detected by using the method. 2. The method according to claim 1, wherein an outer dimension of the shield frame is determined at least based on a limit of the discharge, between the sample stage and the shield frame, and movement of the sample stage. An inspection method using an electron beam, wherein the inspection method is determined from a distance and a width of a member of the shield frame. 3. The inspection method according to claim 2, wherein an outer dimension of the shield frame is 1300 mm or less and 1020 mm or more. 4. A sample is mounted on a sample stage, a voltage is applied to the sample via the sample stage, an electron beam is focused on the sample and scanned, and the sample stage is continuously moved during the scanning. In an inspection method using an electron beam that moves and detects charged particles generated from the sample to detect a defect in the sample, a magnitude of a voltage applied to the sample is determined according to a type of the sample. Inspection method using an electron beam. 5. An electron beam for converging and scanning an electron beam on a sample, continuously moving the sample during the scanning, detecting charged particles generated from the sample, and detecting an electron beam for detecting a defect of the sample. An inspection method using an electron beam, wherein the sectional shape of the electron beam is corrected by a coil having at least six poles. 6. An electron beam that converges on a sample and scans the sample, continuously moves the sample during the scan, and detects charged particles generated from the sample to detect a defect in the sample. An inspection method using an electron beam, wherein the electron beam is blanked and deflected using the crossover of the electron beam as a fulcrum of blanking. 7. The method according to claim 6, wherein the charged particles generated from the sample are detected and converted into an electric signal, information contained in the electric signal is stored, and the sample is used by using the stored information. An inspection method using an electron beam, characterized by detecting a defect of the object. 8. A method for converging an electron beam on a sample to scan a first region of the sample, continuously moving the sample during the scan, and using the crossover of the electron beam as a fulcrum of blanking. The electron beam is blanked and deflected, detects a first charged particle generated from the first region, converts it into a first electric signal, and stores the first information that the first electric signal has, The second region of the sample is scanned with the electron beam, the sample is continuously moved during the scanning, and the electron beam is crossed with the electron beam as a fulcrum of blanking during the movement of the sample. Deflect blanking,
Detecting the second charged particles generated from the second area and converting it into a second electric signal, comparing the second information of the second electric signal with the stored first information An inspection method using an electron beam, wherein a defect of the sample is detected based on the comparison result. 9. An electron source for generating an electron beam, a converging lens for converging the electron beam generated by the electron source on a sample, and a method for scanning the sample with the electron beam converged by the converging lens. A sample stage that continuously moves the sample, a voltage application device that applies a voltage to the sample via the sample stage, and a detector that detects charged particles generated from the sample and detects a defect in the sample. In the inspection apparatus using an electron beam, a shield frame surrounding the sample stage and having a dimension between the sample stage and the sample stage is determined based on a limit of a discharge generated between the sample stage and the sample stage. An inspection apparatus using an electron beam, characterized by the following. 10. The method according to claim 9, wherein an outer dimension of the shield frame is determined at least based on a limit of the discharge, between the sample stage and the shield frame, and movement of the sample stage. An inspection apparatus using an electron beam, which is determined based on a distance and a width of a member of the shield frame. 11. An inspection apparatus using an electron beam according to claim 10, wherein an outer dimension of said shield frame is 1300 mm or less and 1020 mm or more. 12. An electron source for generating an electron beam, a converging lens for converging an electron beam generated by the electron source on a sample, and a method for scanning the sample with the electron beam converged by the converging lens. A sample stage that continuously moves the sample, a voltage application device that applies a voltage to the sample via the sample stage, and a detector that detects charged particles generated from the sample and detects a defect in the sample. An inspection apparatus using an electron beam, wherein a magnitude of a voltage applied to the sample by the voltage application device is determined according to a type of the sample. 13. An electron source for generating an electron beam, a converging lens for converging an electron beam generated by the electron source on a sample, and a method for scanning the sample with the electron beam converged by the converging lens. A sample stage that continuously moves the sample stage, a voltage application device that applies a voltage to the sample through the sample stage, and a mirror that is provided on the sample stage and reflects light that measures the movement of the sample stage. In an inspection device using an electron beam, comprising a measurement device and a detector that detects charged particles generated from the sample and detects a defect of the sample, a metal cover is provided at an end of the mirror. Inspection equipment using an electron beam. 14. An electron source for generating an electron beam, a converging lens for converging the electron beam generated by the electron source on a sample, and continuously scanning the sample while scanning the sample with the converged electron beam. In an inspection apparatus using an electron beam comprising a sample stage to be moved and a detector for detecting charged particles generated from the sample to detect a defect of the sample, at least six poles for correcting a cross-sectional shape of the electron beam An inspection apparatus using an electron beam, comprising: a coil; 15. An electron source for generating an electron beam, a converging lens for converging the generated electron beam on a sample, and a sample for continuously moving the sample while scanning the sample with the converged electron beam. A stage and an inspection apparatus using an electron beam comprising a charged particle detector for detecting charged particles generated from the sample and detecting a defect of the sample, wherein a crossover of the electron beam is used as a fulcrum of blanking. An inspection apparatus using an electron beam, comprising a blanking deflector for blanking and deflecting the electron beam. 16. The apparatus according to claim 15, further comprising: a memory for storing information obtained by said charged particle detector; and defect detecting means for detecting a defect of said sample using said stored information. An inspection apparatus using an electron beam, characterized by the following. 17. An electron source for generating an electron beam, a converging lens for converging the generated electron beam on a sample, and a sample for continuously moving the sample while scanning the sample with the converged electron beam. In the inspection apparatus using an electron beam, comprising a stage and a defect detector that detects charged particles generated from the sample and detects a defect in the sample, scans a first region of the sample with the electron beam. A memory for storing first information obtained by detecting the first charged particles generated by the detection of the second charged particles generated by scanning the second region of the sample with the electron beam. Comparing means for comparing the obtained second information with the first information stored in the memory, wherein the defect detector detects a defect of the sample based on a comparison result by the comparing means. To detect Inspection apparatus using an electron beam to symptoms.