Pattern inspection method and pattern inspection apparatus

A method according to an embodiment includes: mounting a reference-specimen of a same material as that of a specimen on a support member and creating a map indicating a distortion in a gravity direction of the reference-specimen; mounting the specimen on the support member and irradiating light to the specimen; correcting a linear component of a distortion in a gravity direction of the specimen between a first point on the specimen and a second point located in the first scanning direction on the specimen on a basis of a first difference in the gravity direction between the first and second points in the map, and correcting a secondary component of the distortion in the gravity direction of the specimen using a feedback circuit, when the pattern is imaged; and performing a defect inspection using an image of the pattern.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2018-018275, filed on Feb. 5, 2018, the entire contents of which are incorporated herein by reference.

FIELD

The embodiments of the present invention relate to a pattern inspection method and a pattern inspection apparatus.

BACKGROUND

In recent years, a circuit line width required for semiconductor elements has been more and more narrowed with increase in the density and increase in the capacity of a large-scale integration circuit (LSI). These semiconductor elements are manufactured through circuit formation by exposing or transferring a pattern onto a wafer with a reduced projection exposure device so-called “stepper” using an original image pattern (also “mask” or “reticle”, hereinafter collectively “mask”) that has a circuit pattern formed thereon. Therefore, a pattern drawing device using an electron beam that can draw a fine circuit pattern is used to manufacture a mask for transferring a fine circuit pattern onto a wafer. A pattern circuit is sometimes drawn directly on a wafer using such a pattern drawing device. Alternatively, development of a laser-beam drawing device that draws a pattern using a laser beam rather than an electron beam or a nanoimprint technology of pressing a pattern of a template against a wafer to be transferred thereon is being attempted.

Enhancement of the yield rate is essential to manufacturing of an LSI that involves a considerable manufacturing cost. However, the pattern constituting an LSI has changed from that of the sub-micron order to that of the nanometer order. A pattern defect of a mask to be used when an ultrafine pattern is exposed or transferred onto a semiconductor wafer using a photolithography technique is one of major factors that reduce the yield rate. In recent years, the dimension of a pattern defect to be detected has also become quite small with downscaling of the dimension of an LSI pattern formed on a semiconductor wafer. Accordingly, increase in the accuracy of a pattern inspection apparatus that inspects a defect on a transfer mask to be used for LSI manufacturing is required.

As an inspection method, there is a known method of performing an inspection by comparing an optical image obtained by imaging a pattern formed on a specimen such as a mask using an enlargement optical system at a predetermined magnification with design data or an optical image obtained by imaging the same pattern on the specimen. For example, as a pattern inspection method, there are a “die to die (die-die) inspection” of comparing optical image data obtained by imaging the same patterns at different places on the same mask with each other, and a “die to database (die-database) inspection” of inputting drawing data (design pattern data) obtained by converting CAD (Computer-Aided Design) data of a pattern design to data of a device input format that is input by a drawing device when a pattern is drawn on a mask to an inspection apparatus, generating a design image (a reference image) based on the data, and comparing the reference image with an optical image of a pattern. In the inspection method performed by such an inspection apparatus, a specimen is mounted on a stage, and the specimen is scanned with light flux along with movement of the stage to perform an inspection. The light flux is irradiated to the specimen by a light source and an illumination optical system. Light having transmitted through or reflected from the specimen forms an image on a sensor via an optical system. The image taken by the sensor is sent to a comparison circuit as measurement data. After aligning images with each other, the comparison circuit compares the measurement data and the reference data according to an appropriate algorithm. When the measurement data and the reference data do not match, it is determined that there is a patter defect.

In this pattern inspection apparatus, an image of a pattern formed on the surface of a mask needs to be acquired in a state where the surface of the mask is accurately aligned in an imaging plane of an objective lens. An autofocus function by a slit-projection mask-plane-position measurement device is used to align the surface of the mask with the imaging plane.

During an inspection, the mask is supported on the stage at three or more support points and is sometimes distorted due to the self-weight. This gravitational distortion causes misfocusing during imaging. Therefore, the pattern inspection apparatus corrects the position of the mask in a vertical direction (a Z direction) using the autofocus function.

However, when the inspection speed is increased and the imaging speed becomes faster, the operating speed of a feedback also needs to be faster. The acceleration of the feedback operation is costly and adversely increases the entire cost of the pattern inspection apparatus.

SUMMARY

A pattern inspection method according to an embodiment uses a pattern inspection apparatus comprising a support member configured to support a specimen, an optical system configured to irradiate light from a light source to the specimen, an imaging sensor configured to image a pattern formed on the specimen while relatively moving the specimen in a first scanning direction, an inspection part configured to perform a defect inspection using an image of the pattern, and a feedback circuit configured to correct a position in a gravity direction of the specimen using autofocusing when the pattern is imaged, the method includes:

mounting a reference specimen of a same material as that of the specimen on the support member and creating a map indicating a distortion in a gravity direction of the reference specimen;

mounting the specimen on the support member and irradiating light from the light source to the specimen;

correcting a linear component of a distortion in a gravity direction of the specimen between a first point on the specimen and a second point located in the first scanning direction on the specimen on a basis of a first difference in the gravity direction between the first point and the second point in the map, and correcting at least a secondary component of the distortion in the gravity direction of the specimen using the feedback circuit, when the pattern is imaged while a position of the specimen with respect to light from the light source is relatively moved in the first scanning direction; and

performing a defect inspection using an image of the pattern.

The support member may be moved in a gravity direction to cause a stripe in a surface of the specimen to be substantially horizontal when the pattern is imaged.

The imaging sensor may image the pattern with respect to each of stripes obtained by virtually dividing the specimen in a reed shape when imaging the pattern, and

a linear component of a distortion in a gravity direction of the specimen may be corrected with respect to each of the stripes.

The linear component of a distortion in a gravity direction of the specimen may be corrected with respect to each plurality of the stripes.

The imaging sensor may image the pattern with respect to each of stripes obtained by virtually dividing the specimen in a reed shape when imaging the pattern,

a linear component of a distortion in a gravity direction of the specimen may be corrected using a current correction value for a stripe imaged last time when an error between the current correction value and the first difference in a stripe imaged next is smaller than a predetermined threshold, and

a linear component of a distortion in a gravity direction of the specimen may be corrected using the first difference when an error between the current correction value and the first difference is equal to or larger than the threshold.

The current correction value may be updated with the first difference and a linear component of a distortion in a gravity direction of the specimen may be corrected using the current correction value having been updated when an error between the current correction value and the first difference is equal to or larger than the threshold.

The linear component of a distortion in a gravity direction of the specimen may be corrected when the distortion in the gravity direction of the specimen is larger than a threshold.

The first point may be one end of each of the stripes and the second point may be another end of the corresponding stripe.

The first point may be a highest point in a gravity direction of each of the stripes of the specimen, and the second point may be a lowest point in the gravity direction of the corresponding stripe of the specimen.

The support member may support the specimen at three positions from below in a gravity direction.

A pattern inspection apparatus according to an embodiments includes:

a support member configured to support a specimen;

an optical system configured to irradiate light from a light source to the specimen;

an imaging sensor configured to image a pattern formed on the specimen while relatively moving the specimen in a first scanning direction;

an inspection part configured to perform a defect inspection using an image of the pattern;

a feedback circuit configured to correct a position in a gravity direction of the specimen using autofocusing when the pattern is imaged;

a storage part configured to store therein a map indicating a distortion in a gravity direction of a reference specimen of a same material as that of the specimen; and

a controller configured to correct a linear component of a distortion in a gravity direction of the specimen between a first point and a second point on a surface of the specimen on a basis of a first difference in the gravity direction between the first point and the second point in the map and to correct at least a secondary component of the distortion in the gravity direction of the specimen using the feedback circuit, when the pattern is imaged while a position of the imaging sensor with respect to the specimen is moved from a position corresponding to the first point to that corresponding to the second point.

DETAILED DESCRIPTION

Embodiments will now be explained with reference to the accompanying drawings. The present invention is not limited to the embodiments. The drawings are schematic or conceptual, and the ratios and the like among respective parts are not necessarily the same as those of actual products. In the present specification and the drawings, elements identical to those described in the foregoing drawings are denoted by like reference characters and detailed explanations thereof are omitted as appropriate.

First Embodiment

FIG. 1is a configuration diagram illustrating an example of a pattern inspection apparatus in a first embodiment. An inspection apparatus100includes an optical-image acquisition part150that inspects a defect on a pattern formed on a specimen101, and a control system circuit160.

The optical-image acquisition part150includes an optical system20, an imaging part30, a stage102, an imaging sensor31(an example of the imaging part30), a sensor circuit106, a laser-length measurement system122, and an autoloader130.

The stage102serving as a support member on which the specimen101is mounted includes an XY stage (210inFIG. 3) movable in a horizontal direction (an X direction and a Y direction) and a Z stage (220inFIG. 3) movable in a vertical direction (a Z direction). The XY stage is movable also in a rotation direction (a θ direction). The XY stage can be an air slider driven by a stage control circuit114under control of a control calculator110. The XY stage and the Z stage (hereinafter, also “XYZ stage”) can be moved by a driving system such as four axis motors that are driven in the θ direction, the X direction, the Y direction, and the Z direction. For example, liner motors or step motors can be used as the θ motor, the X motor, the Y motor, and the Z motor. A movement position of the specimen101placed on the XYZ stage is measured by the laser-length measurement system122and is transferred to a position circuit107.

The specimen101is placed on the XYZ stage and the specimen101moves with the XYZ stage. The specimen101includes, for example, an exposure photomask for transferring a pattern onto a wafer or a template used in a NIL (Nano-Imprint Lithography) technology. A pattern composed of a plurality of graphics as an inspection target is formed on a photomask or a template. The specimen101is placed on the XYZ stage, for example, with a pattern formation surface down. By moving the XY stage in the X direction and the Y direction within a substantially horizontal plane, the specimen101on the XY stage can be relatively scanned with light from the optical system20.

The optical system20includes a light source21, a polarizing beam splitter22, a half-wave plate23, an objective lens25, a beam splitter26, and an autofocus part27. The light source21generates light to be irradiated to the specimen101. The polarizing beam splitter22reflects the light from the light source21toward the specimen101and transmits reflection light reflected from the specimen101to the imaging part30. The half-wave plate23applies a phase difference to a polarization plane of the light from the specimen101. The light having passed through the half-wave plate23is focused on the specimen101and is irradiated to the specimen101. Light having reflected on the specimen101passes through the objective lens25, the half-wave plate23, the polarizing beam splitter22, and the beam splitter26to be received by the imaging part30. A part of the light travels from the beam splitter26to the autofocus part27and is received by the autofocus part27. The autofocus part27measures a light intensity via a plurality of slits and outputs information of the light intensity to a focal-position detection circuit128. The focal-position detection circuit128receives the information of the light intensity from the autofocus part27, computes the ratio of the light intensities from the slits, and feeds back the light intensity ratio to the control calculator110. The control calculator110controls the stage control circuit114on the basis of the light intensity ratio and adjusts the position of the XYZ stage to adapt the focal position of light to the surface of the specimen101. In this way, the inspection apparatus100can align the focal position with the specimen101using the autofocus function.

The inspection apparatus100is a reflective inspection apparatus in which reflection light from the specimen101is received by the imaging part30to obtain an optical image. However, the inspection apparatus100can be a transmissive inspection apparatus in which light having transmitted through the specimen101is received by the imaging part30to obtain an optical image.

The imaging part30includes the sensor31and the sensor circuit106and receives the light from the specimen101to acquire an image of the specimen101. The sensor31receives the light from the optical system20and converts an optical signal to an electrical signal (photoelectric conversion). The sensor31can be, for example, a line sensor including imaging elements such as photodiodes arrayed in a line, or an area sensor including imaging elements arranged two-dimensionally in a plane. For example, a TDI (Time Delay Integration) sensor can be used as a line sensor. The sensor31can be, for example, a CCD (Charge Coupled Device). The sensor circuit106performs A/D (Analogue-to-Digital) conversion of the electrical signal from the sensor31to obtain an optical image. This image is transmitted to a comparison circuit108via the position circuit107and is used for comparison processing at the time of detection of a defect on the specimen101.

The sensor circuit106performs A/D conversion of the pattern image received from the sensor31and sends image data of the pattern image to the position circuit107. The image data obtained by the A/D conversion is, for example, 8-bit data with no sign and represents tones of brightness of respective pixels of the sensor31.

The autoloader130is driven by an autoloader control circuit113under control of the control calculator110to automatically mount the specimen101as an inspection target on the stage102and automatically carry the specimen101out of the stage102after the inspection ends. When the specimen101is mounted on the stage102, light is irradiated from the optical system20located below the stage102to the pattern formed on the specimen101. Light reflected on the specimen101forms an image on the sensor31included in the imaging part30. The inspection apparatus100can have a configuration to introduce light transmitted through the specimen101to the sensor31. When this configuration and the configuration illustrated inFIG. 1are both used at the same time, optical images respectively produced by the transmission light and the reflection light can be acquired simultaneously.

In the control system circuit160, the control calculator110serving as a computer is connected to the position circuit107, the comparison circuit108, an expansion circuit111, a reference circuit112, the autoloader control circuit113, the stage control circuit114, the focal-position detection circuit128, a storage part109, a display117, a pattern monitor118, and a printer119via a bus120. The control system circuit160can be constituted of a single CPU (Central Processing Unit) or a plurality of CPUs.

Format data stored in the storage part109contains design pattern data. The design pattern data is read by the expansion circuit111from the storage part109through the control calculator110. The expansion circuit111converts the design pattern data to image data (bit pattern data). The image data converted by the expansion circuit111is sent to the reference circuit112and is used for generation of a reference image. The reference image generated by the reference circuit112is sent to the comparison circuit108and is compared with an optical image of the specimen101as an inspection target.

Meanwhile, an optical image of the specimen101is imaged by the sensor31, is subjected to the A/D conversion, and is sent to the position circuit107in the manner described above. In order to obtain an optical image suitable for an inspection, it is important to accurately detect the focal position of the light irradiated to the specimen101and perform focusing. The autofocus function is used to align the surface of the specimen101(a surface on which the pattern is formed: hereinafter, also “pattern surface”) with the focal position of the optical system20.

The control calculator110controls the stage control circuit114on the basis of the information from the focal-position detection circuit128to move the Z stage in the Z direction (a height direction) in such a manner that the detected focal position is located on the pattern surface of the specimen101as described above. This adjusts the pattern surface of the specimen101to be aligned with the focal position. The adjustment of the focal position is performed by relatively moving the position of the pattern surface of the specimen101and the focal position. Therefore, while the adjustment of the focal position can be performed by moving the focal position itself, the adjustment can be performed by moving the Z stage as in the present embodiment.

When the pattern surface of the specimen101is aligned with the focal position of the optical system20, the sensor31takes an optical image of the pattern of the specimen101. Practically, the sensor31images the pattern of the specimen101sequentially with respect to each of stripes as illustrated inFIG. 2. Therefore, determination of reliability of the autofocus function is performed nearly in real time immediately before imaging of the pattern. The optical image is subjected to A/D conversion by the sensor circuit106and is sent to the comparison circuit108with the data indicating the position of the specimen101on the stage102and output from the position circuit107.

The comparison circuit108compares the optical image data and the reference image data with each other using an appropriate comparison determination algorithm as described above. When a result of the comparison indicates that a difference between both data is above a predetermined threshold, that place is determined as a defect.

FIG. 1illustrates constituent parts necessary for explanation of the first embodiment. It goes without saying that other constituent parts generally required for the inspection apparatus100can be included. Respective circuits in the sensor circuit106, the autoloader control circuit113, the stage control circuit114, the focal-position detection circuit128, the expansion circuit111, the reference circuit112, the comparison circuit108, and the position circuit107can be constituted of electrical circuits or can be realized as software that can be operated by a computer such as the control calculator110. These circuits can be implemented by a combination of hardware and software or a combination with firmware.

FIG. 2is a conceptual diagram illustrating imaging of an inspection region. An inspection region R10of the specimen101is, for example, virtually divided into a plurality of inspection stripes R20of a reed shape having a scanning width W in the Y direction. The inspection apparatus100acquires an image (a stripe region image) of each of the inspection stripes R20. Laser light is used to each of the inspection stripes R20to take an image of a pattern formed in the relevant stripe region in a longitudinal direction (the X direction) of the stripe region. The sensor31acquires an optical image while continuously relatively moving in the X direction with movement of the XY stage. The sensor31sequentially takes optical images with the scanning width W as illustrated inFIG. 2. In other words, the sensor31takes an optical image of the pattern formed on the specimen101using inspection light while moving relatively to the XY stage. In the present embodiment, after taking an optical image of one inspection stripe (first stripe) R20, the sensor31moves to the position of the next inspection stripe (second stripe) R20in the Y direction and then continuously takes an optical image with the scanning width W in the same manner while moving in the reverse direction. That is, imaging is repeated in a forward (FWD)-backward (BWD) direction where the direction of an outward path and the direction of a return path are opposite to each other. For example, the image of the first stripe corresponds to an image acquired in an outward path of the XY stage and the image of the second stripe corresponds to an image acquired in a return path of the XY stage. The image of the first stripe can correspond to an image acquired in a return path of the XY stage and the image of the second stripe can correspond to an image acquired in an outward path of the XY stage.

As described above, at the time of imaging the pattern, the sensor31alternately acquires, for example, images of first stripes taken while relatively moving in a direction D1inFIG. 4and images of second stripes taken while relatively moving in a direction D2opposite to the direction D1. This enables the sensor31to image the entire pattern surface of the specimen101.

The direction of the imaging is not limited to repetition of forward (FWD)-backward (BWD) and the imaging can be performed in one direction. For example, the imaging can be performed by repetition of FWD-FWD. Alternatively, the imaging can be performed by repetition of BWD-BWD.

In this way, the imaging part30acquires an image of the pattern on the specimen101while the specimen101is scanned with the light from the optical system20.

The configuration of the stage102is explained below in more detail.

FIGS. 3A and 3Bare front and plan views illustrating an example of the configuration of the stage102, respectively. As illustrated inFIG. 3A, the stage102includes a surface plate200, the XY stage210, and the Z stage220. The surface plate200is fixed substantially horizontally to the body of the inspection apparatus100. The XY stage210is provided on the surface plate200.

The XY stage210can move substantially in parallel to a substantially-horizontal surface (an XY plane) of the surface plate200. The XY stage210has three support shafts211to213as illustrated inFIG. 3B. Each of the support shafts211to213is extendable in a substantially vertical direction (Z direction). The Z stage220is provided on the support shafts211to213of the XY stage210.

The Z stage220can be moved in the substantially vertical direction (Z direction) by an extending operation of the support shafts211to213of the XY stage210. The support shafts211to213can extend by the same amounts, respectively, to move the Z stage220in parallel to the XY plane. Only one or two of the support shafts211to213can extend to incline the Z stage220with respect to the XY plane.

The Z stage220has an opening OP as illustrated inFIG. 3A. The opening OP is provided above the objective lens25to enable light from the objective lens25to be irradiated to the specimen101. That is, as illustrated inFIG. 3B, the opening OP is provided to overlap with the objective lens25and the specimen101when viewed from above in the Z direction. The opening OP is substantially similar to the outline of the specimen101and is slightly larger than the specimen101. The Z stage220has three support parts221to223on an internal side surface of the opening OP and supports the specimen101from vertically below. The specimen101is adsorptively immobilized on the support parts221to223and can move within the XY plane according to an operation of the XY stage210and move in the Z direction according to an operation of the Z stage220. The objective lens25is provided right below the specimen101and light from the objective lens25is irradiated to the specimen101. InFIGS. 3A and 3B, the specimen101is indicated with a broken line.

The specimen101is supported at three positions by the support parts221to223within the opening OP. Other part of the specimen101than contact portions with the support parts221to223is in a floating state due to the opening OP as illustrated inFIG. 3A. Therefore, the specimen101has slightly different height positions in the Z direction between support regions supported by the support parts221to223and a floating region other than the support regions due to the self-weight, and has a distortion in the Z direction.

FIG. 4is a perspective view illustrating a distortion of the specimen101on the Z stage220. InFIG. 4, the distortion of the specimen101is drawn in a manner easy to understand. Arrows A221, A222, and A223denote places supported by the support parts221to223on the bottom surface of the specimen101, respectively. With the support of the support parts221to223, the places of the specimen101denoted by the arrows A221, A222, and A223are located at relatively high positions. Meanwhile, the specimen101falls vertically downward (in a −Z direction) due to the self-weight to cause a distortion as the distance from the places denoted by the arrows A221, A222, and A223is increased.

Such a distortion of the specimen101leads to a deviation of the focal position of the light from the objective lens25. The focal position can generally be corrected by a feedback circuit using the autofocus part27, the focal-position detection circuit128, the stage control circuit114, motors M, and the stage102. However, as described above, when the imaging speed of the imaging part30(that is, the scanning speed) is increased, increase in the operating speed of the feedback is required to follow the increased imaging speed. The acceleration of the feedback operation requires increase in an operation speed of the feedback circuit and weight reduction of the object controlled on the stage102. Accordingly, the cost of the pattern inspection apparatus inevitably increases. On the other hand, a feedback circuit that is inexpensive and has a low speed cannot follow the imaging speed and the imaging part30performs imaging in a state where the focal position is deviated from the pattern surface of the specimen101due to the distortion of the specimen101. This prevents the inspection apparatus100from accurately inspecting a defect of the pattern.

In order to solve this problem, the inspection apparatus100according to the present embodiment previously creates a map (hereinafter, also “distortion map”) indicating a distortion in the gravity direction (the Z direction) of the specimen101using a reference mask, and corrects a linear component (that is, a primary component) of the distortion in the gravity direction of the specimen101on the basis of the distortion map. Secondary and higher-order components of the distortion of the specimen101are corrected using the feedback circuit (27,128,114, M, and102). Accordingly, while the pattern surface is scanned with the light from the optical system20, the position of the specimen101in the Z direction is controlled so as to cause a part of the pattern surface irradiated with the light to have substantially uniform heights. That is, while the position of the specimen101in the Z direction is controlled so as to cancel the distortion in the Z direction of the specimen101, the pattern surface of the specimen101is scanned with the light from the optical system20. Because the linear component of the distortion is already corrected on the basis of the distortion map in the present embodiment, feedback control of the secondary and higher-order components can be performed using the autofocus function. Therefore, even a low-speed feedback circuit can follow the imaging speed of the pattern surface.

A pattern inspection method according to the present embodiment is explained below in more detail.

FIGS. 5A and 5Bare flowcharts illustrating an example of the pattern inspection method according to the first embodiment.

First, a distortion map is previously created using a reference specimen (Step S10). The reference specimen is a specimen of the same material and the same size as those of the specimen101as an inspection target and can be considered as the specimen101before formation of a pattern. In order to distinguish the reference specimen from the specimen101, the reference specimen is hereinafter denoted by101ref. The reference specimen101ref is mounted on the stage102and is irradiated with light from the optical system20similarly to the specimen101illustrated inFIGS. 3A and 3B. The surface of the reference specimen101ref is scanned with light in the manner as described with reference toFIG. 2. At this time, the surface of the reference specimen101ref is scanned with light while the focal position is aligned with the surface of the reference specimen101ref using the autofocus function. The position in the Z direction (the height) of the Z stage220at a time when the focal position is aligned with the surface of the reference specimen101ref is stored in the storage part109. When the height of the Z stage220is stored in the storage part109for the entire surface of the reference specimen101ref, a distortion map indicating a distortion in the gravity direction of the reference specimen101ref is completed.

Because the reference specimen101ref is of the same material, the same size, and the same thickness as those of the specimen101, a distortion occurring in the specimen101when the specimen101is mounted on the stage102can be substantially reproduced. This distortion map of the reference specimen101ref can be regarded as indicating the distortion of the specimen101. At the time of creation of the distortion map, the surface of the specimen101ref is scanned with light at a speed that can be sufficiently followed by the feedback circuit. That is, because focusing is performed using the autofocus function, the creation speed of the distortion map using the reference specimen101ref is lower than the inspection speed of the specimen101. However, this enables the distortion map to have information of the distortion of the specimen101almost accurately. The distortion map can be stored in the storage part109or can be managed outside the inspection apparatus100. The distortion map can be used commonly for a plurality of specimens101as long as the specimens101are the same as the reference specimen101ref.

After the reference specimen101ref is removed from the stage102, the method proceeds to an inspection of the pattern on the specimen101. In the inspection of the pattern, the specimen101is first mounted on the stage102(Step S20).

Next, as explained with reference toFIG. 2, the XYZ stage210,220is moved while the light from the optical system20is irradiated to the specimen101, and the imaging part30images the pattern on the specimen101with respect to each of the inspection stripes R20. For example, numbers 1 to n (n is an integer equal to or larger than 2 and indicates the last stripe) are respectively assigned to the inspection stripes in the inspection order. In this case, the optical system20scans the first inspection stripe to the nth inspection stripe with the light in the ascending order and the imaging part30follows the scan and images patterns on the first inspection stripe to the nth inspection stripe in the ascending order. The first and second inspection stripes can correspond to the first and second stripes described above, respectively.

The inspection apparatus100according to the present embodiment corrects (cancels) the linear component of the distortion in the gravity direction (the Z direction) of the specimen101using the distortion map described above, without using the feedback circuit, at the time of imaging of the pattern.

The control calculator110or the stage control circuit114calculates a correction value with respect to each of the inspection stripes (Step S22). For example, at the time of imaging of a kth (1≤k≤n) inspection stripe, the control calculator110or the stage control circuit114can calculate a difference (a first difference) ΔZk in the height between one of ends of the kth inspection stripe in the X direction and the other end as a correction value. Alternatively, the control calculator110or the stage control circuit114can calculate a difference ΔZk between the maximum value (a highest point) in the Z direction of the kth inspection stripe and the minimum value (a lowest point) thereof as a correction value. The initial value of k is 1.

In correction of the linear component of the distortion, the control calculator110or the stage control circuit114corrects the Z stage220to cause a straight line connecting one of the ends of the kth inspection stripe in the X direction and the other end to be substantially parallel to an X-Y plane (substantially horizontal) (that is, to cause the difference ΔZk to be 0 (zero)). Alternatively, the control calculator110or the stage control circuit114corrects the Z stage220to cause a straight line connecting the maximum value in the X direction of the kth inspection stripe and the minimum value thereof to be substantially parallel to the X-Y plane (substantially horizontal) (that is, to cause the difference ΔZk to be 0).

Along with the correction of the linear component of the distortion of the specimen101, the inspection apparatus100corrects (cancels) secondary and higher-order components of the distortion in the Z direction of the specimen101using the feedback circuit (Step S30).

Correction processing for the linear component of the distortion of the specimen101is explained in more detail.

FIGS. 6A to 6Care graphs illustrating linear components of the distortion of the specimen101in certain inspection stripes R20, respectively. The vertical axis represents the displacement in the gravity direction (the Z direction) of the pattern surface of the specimen101. The horizontal axis represents the position in the X direction on the inspection stripe R20.

For example,FIG. 6Aillustrates a linear component of a distortion in an inspection stripe R20located near the arrow A223(the support part223) inFIG. 4. Because the specimen101is supported at the arrow A223, the specimen101falls vertically downward (in the −Z direction) with an increasing distance from the arrow A223in the +X direction (the direction D2).

For the inspection stripe near the arrow A223inFIG. 4, the pattern is imaged while the position of the light is moved from a first point P1aon the pattern surface of the specimen101to a position corresponding to a second point P2alocated in the direction D2.

At the time of imaging of the pattern, the stage control circuit114moves the Z stage220to correct the linear component of the distortion in the gravity direction of the specimen101between the first point P1aand the second point P2aby a difference (ΔZa inFIG. 6A) in the Z direction between the first point P1aand the second point P2ain the distortion map. That is, the linear component of the distortion of the specimen101is canceled based on the distortion map (Step S32). The first point P1aand the second point P2acan be any different two points in the inspection stripe of the specimen101. However, to correct the linear component of the distortion more accurately, it is preferable that the first point P1aand the second point P2aare one end (an inspection start point) of an inspection stripe and the other end (an inspection end point) thereof. Alternatively, to correct the linear component of the distortion accurately, the first point P1aand the second point P2acan be the maximum value (a highest point) and the minimum value (a lowest point) in the Z direction of an inspection stripe of the specimen101.

Correction of the linear component of the distortion can be performed by changing the lengths in the Z direction of the support shafts211to213illustrated inFIG. 3B. For example, at the time of imaging an inspection stripe near the arrow A223inFIG. 4, the stage control circuit114decreases the extension length of the support shaft211to be shorter than those of the other support shafts212and213because the second point P2ais lower than the first point P1a. It suffices to cause the support shaft211to be lower than the support shafts212and213by the difference ΔZa inFIG. 6Awhile the inspection stripe is scanned with light from one end to the other end. This lowers the first point P1aand can correct the linear component of the distortion illustrated inFIG. 6Ato be substantially horizontal. That is, the difference ΔZa is canceled.

The stage control circuit114can alternatively increase the extension lengths of the two support shafts212and213to be longer than that of the support shaft211to correct the linear component of the distortion. However, control on one support shaft211is more accurate and easier than control on the two support shaft212and213. Therefore, it is preferable that the linear component of the distortion is corrected by control on the support shaft211.

Meanwhile, along with the correction of the linear component by the stage control circuit114using the distortion map, the feedback circuit (27,128,114, M, and102) having the autofocus function corrects (cancels) secondary and higher-order components of the distortion in the Z direction of the specimen101using the autofocus function (Step S34). At this time, the inspection apparatus100corrects the secondary and higher-order components of the distortion of the specimen101by feedback control in a state where the distortion of the linear component has been eliminated. Therefore, the feedback circuit does not require a very high speed operation. An existing control method can be applied to the feedback control. Therefore, detailed descriptions of the feedback control are omitted here.

FIG. 6Billustrates a linear component of a distortion in an inspection stripe R20located near the arrow A221(the support part221) inFIG. 4. Because the specimen101is supported at the arrow A221, the specimen101falls vertically downward (in the −Z direction) with an increasing distance from the arrow A221in the −X direction (the direction D1).

For the inspection stripe near the arrow A221inFIG. 4, the pattern is imaged while the position of the light is moved from a first point P1bon the pattern surface of the specimen101to a position corresponding to a second point P2blocated in the direction D2.

At the time of imaging of the pattern, the stage control circuit114moves the Z stage220to correct the linear component of the distortion in the gravity direction of the specimen101between the first point P1band the second point P2bby a difference (ΔZb inFIG. 6B) in the Z direction between the first point P1band the second point P2bin the distortion map. That is, the linear component of the distortion of the specimen101is canceled based on the distortion map (Step S32). The first point P1band the second point P2bcan also be any different two points in the corresponding inspection stripe. However, the first point P1band the second point P2bcan be one end (an inspection start point) and the other end (an inspection end point) of the corresponding inspection stripe, or can be the maximum value and the minimum value in the Z direction of the inspection stripe.

Correction of the linear component of the distortion can be performed by changing the lengths in the Z direction of the support shafts211to213illustrated inFIG. 3B. For example, at the time of imaging an inspection stripe near the arrow A221inFIG. 4, the stage control circuit114increases the extension length of the support shaft211to be longer than those of the other support shafts212and213because the first point P1bis lower than the second point P2b. While the inspection stripe is scanned with light from one end to the other end, it suffices to cause the support shaft211to be higher than the support shafts212and213by the difference ΔZb inFIG. 6B. This causes the first point P1bto be higher and can correct the linear component of the distortion illustrated inFIG. 6Bto be substantially horizontal. That is, the difference ΔZb is canceled.

Meanwhile, along with the correction of the linear component by the stage control circuit114using the distortion map, the feedback circuit (27,128,114, M, and102) cancels secondary and higher-order components of the distortion in the Z direction of the specimen101using the autofocus function (Step S34). At this time, the inspection apparatus100can correct the secondary and higher-order components of the distortion of the specimen101by the feedback control in a state where the distortion of the linear component has been eliminated. Therefore, the feedback circuit does not require a very high speed operation.

FIG. 6Cillustrates a linear component of a distortion in an inspection stripe R20located near the arrow A222(the support part222) inFIG. 4. Because the specimen101is supported at the arrow A222, the specimen101falls vertically downward (in the −Z direction) with an increasing distance from the arrow A222in the +X direction (the direction D2).

For the inspection stripe near the arrow A222inFIG. 4, the pattern is imaged while the position of the light is moved from a first point P1con the pattern surface of the specimen101to a position corresponding to a second point P2clocated in the direction D2.

At the time of imaging of the pattern, the stage control circuit114moves the Z stage220to correct the linear component of the distortion in the gravity direction of the specimen101between the first point P1cand the second point P2cby a difference (ΔZc inFIG. 6C) in the Z direction between the first point P1cand the second point P2cin the distortion map. That is, the linear component of the distortion of the specimen101is canceled based on the distortion map (Step S32). The first point P1cand the second point P2ccan also be any different two points in the corresponding inspection stripe. However, the first point P1cand the second point P2ccan be one end (an inspection start point) and the other end (an inspection end point) of the corresponding inspection stripe, or can be the maximum value and the minimum value in the Z direction of the inspection stripe.

Correction of the linear component of the distortion can be performed by changing the lengths in the Z direction of the support shafts211to213illustrated inFIG. 3B. For example, at the time of imaging of an inspection stripe near the arrow A222inFIG. 4, the stage control circuit114decreases the extension length of the support shaft211to be shorter than those of the other support shafts212and213because the second point P1cis lower than the first point P1c. It suffices to cause the support shaft211to be lower than the support shafts212and213by the difference ΔZc inFIG. 6Cwhile the inspection stripe is scanned with light from one end to the other end. This lowers the first point P1cand the linear component of the distortion illustrated inFIG. 6Ccan be corrected to be substantially horizontal. That is, the difference ΔZc is canceled.

Meanwhile, along with correction of the linear component by the stage control circuit114using the distortion map, the feedback circuit (27,128,114, M, and102) cancels secondary and higher-order components of the distortion in the Z direction of the specimen101using the autofocus function (Step S34). At this time, the inspection apparatus100can correct the secondary and higher-order components of the distortion of the specimen101by the feedback control in a state where the distortion of the linear component has been eliminated. Therefore, the feedback circuit does not require a very high speed operation. The imaging part30can image the pattern surface of the specimen101while thus correcting the distortion of the specimen101.

The image of the pattern of the specimen101is transmitted to the position circuit107and the comparison circuit108and is used for an inspection of the pattern.

Inspection processing on the pattern is explained next. In an inspection of the pattern, an inspection according to the die-database method or the did-die method is performed (Step S40). An inspection method according to the die-database method is described below as an example. In the die-database method, a reference image to be compared with an optical image as an inspection target is a reference image generated from the design pattern data. In the case of the die-die method, a reference image is an optical image of another region having the same pattern as that of the inspection target. It is needless to say that the present embodiment can be applied to the die-die method.

The design pattern data is stored in the storage part109and is read with progression of the inspection to be sent to the expansion circuit111. The storage part109can be a storage device such as an HDD (Hard Disk Drive) and an SSD (Solid State Drive).

CAD data created by a user is converted to design intermediate data of a hierarchized format. The design intermediate data includes design pattern data created for each layer and formed on a specimen. Generally, an inspection apparatus is not configured to be capable of reading design intermediate data directly. Therefore, the design intermediate data is converted for each layer to format data unique to each inspection apparatus and is then input to the inspection apparatus. The format data can be data unique to an inspection apparatus or can alternatively be data compatible to a drawing device used to draw a pattern on a specimen.

The format data having been used at the time of pattern formation of the specimen101is stored in the storage part109. Graphics included in the design pattern are graphics created using a rectangle, a triangle, and the like as basic graphics. Graphic data that is information such as the coordinates at a reference position of a graphic, the lengths of the sides, a graphic code being an identifier for identifying the graphic type such as a rectangle or a triangle and that defines the shape, the size, the position, and the like of each pattern graphic is stored.

The format data stored in the storage part109contains the design pattern data. The design pattern data is read from the storage part109by the expansion circuit111through the control calculator110.

The expansion circuit111converts the design pattern data to image data (bit pattern data). That is, the expansion circuit111expands the design pattern data in data of each graphic and interprets the graphic code indicating the graphic shape of the graphic data, the graphic dimension, and the like. The data is expanded in binary or multi-valued image data as a pattern arranged within squares having grids of a predetermined quantization dimension as units. An occupancy of a graphic in the design pattern with respect to each region (square) corresponding to a sensor pixel is computed and the graphic occupancy in each pixel becomes a pixel value.

The image data converted by the expansion circuit111is sent to the reference circuit112serving as a reference image generator and is used for generation of a reference image.

The optical image of the specimen101output from the sensor circuit106is sent to the comparison circuit108with data indicating the position of the specimen101on the stage102and output from the position circuit107. The reference image described above is also sent to the comparison circuit108.

At this time, the inspection stripes R20inFIG. 2are each divided into an appropriate size as sub-stripes. A sub-stripe clipped from the optical image and a sub-stripe clipped from the corresponding reference image are input to a comparison unit in the comparison circuit108. Each of the input sub-stripes is further divided into rectangular small regions called “inspection frame” and comparison in units of frames is performed in the comparison unit to detect a defect. Several dozen comparison units are installed in the comparison circuit108to enable a plurality of inspection frames to be simultaneously processed in parallel. Each of the comparison units captures an unprocessed frame image immediately after processing of one inspection frame ends. Accordingly, many inspection frames are sequentially processed. The comparison circuit108compares the optical image of the specimen101and the reference image with each other using an appropriate comparison determination algorithm. When a difference therebetween is larger than a predetermined threshold as a result of the comparison, that place is determined to be a defect.

Until imaging and inspections on all stripes of the pattern on the specimen101are completed, processes at Steps S22to S40are repeated. For example, the control calculator110or the stage control circuit114determines whether k has reached n (Step S50). When k has not reached n (NO at Step S50), the control calculator110or the stage control circuit114increases k (that is, substitutes k+1 for k) (Step S52) and repeatedly performs the processes at Steps S22to S50.

When k has reached n (YES at Step S50), it is determined that imaging and inspections on all the stripes of the pattern on the specimen101are completed. Accordingly, the inspection of the specimen101ends and the specimen101is carried out of the stage102(Step S60).

As described above, while correcting a linear component of a distortion of the specimen101using the distortion map, the inspection apparatus100corrects secondary and higher-order components of the distortion by feedback control using the autofocus function. Accordingly, even when the inspection speed is increased and the imaging speed of the sensor31becomes faster, the Z stage220can be corrected in the Z direction to move the pattern surface of the specimen101to be substantially horizontal. The feedback circuit (27,128,114, M, and102) does not need to correct the linear component of the distortion of the specimen101and it suffices that the feedback circuit corrects the secondary and higher-order components. Therefore, the operating speed of the autofocus function or the feedback circuit does not need to be so high. Accordingly, the inspection apparatus100can image the pattern on the specimen101at a high speed while suppressing the cost.

The stage102supports the specimen101at three positions (A221to A223) from below in the gravity direction. Therefore, the inclination of the linear component of the distortion varies according to the positions of the inspection stripes R20in the Y direction as illustrated inFIGS. 6A to 6C. The linear component of the distortion can be corrected based on the distortion map with respect to each of the inspection stripes R20. In this case, each time the XY stage210is reciprocated in the direction D1or D2to image an inspection stripe R20, the control calculator110and the stage control circuit114correct the linear component of the distortion of the specimen101. The number of the support parts on the specimen101is not limited to three and can be four or more. Also in this case, the linear component of the distortion of the specimen101can be obtained.

Second Embodiment

In the first embodiment, the linear component of the distortion of the specimen101is corrected with respect to each of the inspection stripes R20. That is, the control calculator110or the stage control circuit114calculates a correction value for each inspection stripe and adjusts the height of the Z stage220with the correction value. In the second embodiment, in contrast thereto, the linear component of the distortion of the specimen101is corrected every plural adjacent inspection stripes. That is, the correction value is the same for plural adjacent inspection stripes and is computed for plural inspection stripes.

Other operations in the second embodiment can be identical to those in the first embodiment. Therefore, also in the case of the second embodiment, the sensor31acquires images of the first and second stripes alternately while the XY stage210is reciprocated in the directions D1and D2similarly in the first embodiment.

FIG. 7is a flowchart illustrating an operation example of the inspection apparatus100according to the second embodiment. InFIG. 7, the control calculator110or the stage control circuit114changes the correction value every A (2≤A≤n) inspection stripes.

First, the processes at Steps S10to S22are performed similarly to those in the first embodiment. The initial value of k is 1. The initial value of B is A.

Next, the control calculator110or the stage control circuit114determines whether k has reached B+1 (Step S25). That is, it is determined whether k has exceeded B. When k has not reached B+1 (NO at Step S25), the processes at Steps S30to S52are performed.

When k has not reached n at Step S50(NO at Step S50), the process returns to Step S25. Therefore, the processes at Steps S25to S52are repeatedly performed without updating the correction value until k exceeds B. That is, the correction value calculated at Step S22is maintained until k reaches B+1.

On the other hand, when k has reached B+1 (YES at Step S25), the control calculator110or the stage control circuit114substitutes B+A for B (Step S27) and calculates the correction value for the kth inspection stripe at that time (Step S22). The correction value is thus updated. The value of B at Step S25is reset with increase of A. Accordingly, the correction value is updated every A inspection stripe. That is, the control calculator110or the stage control circuit114corrects adjacent A inspection stripes with the same correction value and recalculates the correction value every A inspection stripe. The control calculator110or the stage control circuit114repeatedly performs the processes at Step S25to S52using the updated correction value.

Thereafter, the processes at Steps S22to S52are repeatedly performed until k reaches n. When k has reached n (YES at Step S50), the inspection of the specimen101ends and the specimen101is carried out of the stage102(Step S60).

When A=2 is established as a specific example, the linear component of the distortion is corrected with respect to each pair of stripes adjacent to each other. At this time, the initial value of B is 2 and the Z stage220is corrected with the correction value for a first inspection stripe when the first inspection stripe and a second inspection stripe are imaged.

When k has reached 3 at Step S25, B is set to B+A=4 (Step S27). The correction value for a third inspection stripe is calculated (Step S22). Therefore, when the third inspection stripe and a fourth inspection stripe are imaged, the Z stage220is corrected with the correction value for the third inspection stripe.

Similarly, when k has reached 5 at Step S25, B is set to B+A=6 (Step S27). The correction value for a fifth inspection stripe is calculated (Step S22). Therefore, when the fifth inspection stripe and a sixth inspection stripe are imaged, the Z stage220is corrected with the correction value for the fifth inspection stripe. Imaging of seventh and subsequent inspection stripes is performed in the same manner.

Correction of the secondary and higher-order components of the distortion of the specimen101can be performed by the feedback circuit (27,128,114, M, and102) with respect to each inspection stripe in the same manner as in the embodiment described above. Furthermore, A can be 3 or more. That is, it is needless to say that the linear component of the distortion can be corrected every three or more inspection stripes.

According to the second embodiment, the same correction value is used for plural adjacent inspection stripes. Therefore, the control calculator110or the stage control circuit114does not need to calculate the correction value for each inspection stripe and load on the control calculator110or the stage control circuit114is reduced. Furthermore, because the stage control circuit114does not need to correct the Z stage220with respect to each inspection stripe, the inspection speed is higher than in a case where the Z stage220is corrected with respect to each inspection stripe.

Third Embodiment

According to a third embodiment, when an error between a difference (a first difference) ΔZk in the Z direction between a first point and a second point in the distortion map of a kth inspection stripe and a current correction value ΔZcrr is equal to or larger than a predetermined threshold, the current correction value ΔZcrr of the linear component of the distortion of the specimen101is updated with ΔZk. When the error between the difference ΔZk and the current correction value ΔZcrr is smaller than the threshold, the control calculator110or the stage control circuit114does not update the current correction value ΔZcrr and corrects the Z stage220using the current correction value ΔZcrr. The current correction value ΔZcrr is a correction value used for an inspection stripe already imaged last time. That is, ΔZcrr is a currently-set correction value. ΔZk is a difference in the Z direction between a first point and a second point of the distortion map in an inspection stripe to be imaged next.

Other operations of the third embodiment can be identical to the operations of the first embodiment. Therefore, in the case of the third embodiment, similarly to the first embodiment, the sensor31acquires images of the first and second stripes alternately while the XY stage210is reciprocated in the directions D1and D2.

FIG. 8is a flowchart illustrating an operation example of the inspection apparatus100according to the third embodiment. InFIG. 8, the control calculator110or the stage control circuit114sets the threshold to S (S is a positive number).

First, similarly to the first embodiment, the processes at Steps S10to S22are performed. The initial value of k is 1.

Next, the control calculator110or the stage control circuit114calculates an error |ΔZk−ΔZcrr| between the difference ΔZk of the kth inspection stripe calculated at Step S22and the current correction value ΔZcrr (Step S23). The initial value of ΔZcrr is 0. Therefore, the error |ΔZ1−ΔZcrr| of the correction value for a first inspection stripe is ΔZ1.

Subsequently, the control calculator110or the stage control circuit114determines whether the error |ΔZk−ΔZcrr| of the correction value calculated at Step S23is equal to or higher than the threshold being S (Step S24). When the error |ΔZk−ΔZcrr| is smaller than the threshold S (NO at Step S24), the control calculator110or the stage control circuit114maintains the current correction value ΔZcrr (Step S26) and performs the processes at Steps S30to S52. When k is 1 being the initial value and |ΔZ1−ΔZcrr| is equal to or smaller than the threshold S, the current correction value ΔZcrr is 0. Therefore, the height of the Z stage220is not corrected.

On the other hand, when the error |ΔZk−ΔZcrr| of the correction value is equal to or larger than the threshold S (YES at Step S24), the control calculator110or the stage control circuit114uses a new correction value ΔZk as the current correction value ΔZcrr (Step S28). That is, when the difference ΔZk in the Z direction in the distortion map is different from the current correction value ΔZcrr having been used until that time by the threshold or a larger value, the control calculator110or the stage control circuit114updates the current correction value ΔZcrr with the correction value ΔZk. That is, the correction value ΔZk is substituted for the current correction value ΔZcrr.

Next, while the Z stage220is corrected with the correction value ΔZcrr, the inspection stripes are imaged and inspected (Steps S30to S52).

Thereafter, the processes at Steps S22to S52are repeatedly performed until k reaches n. When k has reached n (YES at Step S50), the inspection of the specimen101ends and the specimen101is carried out of the stage102(Step S60).

When S=0.5 is established and the correction value ΔZ1for a first inspection stripe is 0.6 as a specific example, the error |ΔZ1−ΔZcrr| of the correction value is 0.6 and is larger than the threshold (YES at Step S24). Therefore, the current correction value ΔZcrr is updated with ΔZ1=0.6 (Step S28). The control calculator110or the stage control circuit114corrects the height of the Z stage220using 0.6 as the current correction value ΔZcrr (Step S30).

Next, when the correction value for a second inspection stripe is 0.4, the error |Z2−ΔZcrr| of the correction value is 0.2 (|0.4−0.6|) and is smaller than the threshold (NO at Step S24). Therefore, the current correction value ΔZcrr is not updated and is maintained at 0.6. Also for the second inspection stripe, the control calculator110or the stage control circuit114corrects the height of the Z stage220while maintaining the current correction value ΔZcrr at 0.6.

Next, when the correction value for a third inspection stripe is −0.1, the error |ΔZ3−ΔZcrr| of the correction value is 0.7 (|−0.1−0.6|) and is larger than the threshold (YES at Step S24). Therefore, the current correction value ΔZcrr is updated with ΔZ3=−0.1 (Step S28). The control calculator110or the stage control circuit114corrects the height of the Z stage220using −0.1 as the current correction value ΔZcrr (Step S30). Also in imaging subsequent inspection stripes, the Z stage220is corrected in the same manner.

Correction of the secondary and higher-order components of the distortion of the specimen101can be performed by the feedback circuit (27,128,114, M, and102) with respect to each inspection stripe in the same manner as in the embodiment described.

According to the third embodiment, when the error |ΔZk−ΔZcrr| between the correction value ΔZk for a kth inspection stripe and the current correction value ΔZcrr is equal to or larger than the threshold S, the control calculator110or the stage control circuit114updates the current correction value ΔZcrr with ΔZk. When the error |ΔZk−ΔZcrr| is smaller than the threshold S, the control calculator110or the stage control circuit114uses the current correction value ΔZcrr as it is without updating.

Therefore, the control calculator110or the stage control circuit114does not need to update the correction value with respect to each inspection stripe and load on the control calculator110or the stage control circuit114is reduced. Furthermore, because the stage control circuit114does not need to correct the Z stage220with respect to each inspection stripe, the inspection speed is increased as compared to a case where the Z stage220is corrected with respect to each inspection stripe.

When the difference (the correction value) ΔZa between the first point P1aand the second point P2ain each inspection stripe of the distortion map is smaller than a predetermined threshold, the inspection apparatus100does not perform correction of the linear component based on the distortion map. On the other hand, when the difference (the correction value) ΔZa is equal to or larger than the predetermined threshold, the inspection apparatus100performs correction of the linear component based on the distortion map. The inspection apparatus100can thus perform correction of the linear component based on the distortion map only when the correction value for each inspection stripe is equal to or larger than a predetermined threshold. Even in this modification, the effects of the present embodiment are not lost.

At least a part of the inspection method in the inspection apparatus100according to the present embodiment can be constituted by hardware or software. When it is constituted by software, the inspection method can be configured such that a program for realizing at least a part of the functions of the data processing method is stored in a recording medium such as a flexible disk or a CD-ROM, and the program is read and executed by a computer. The recording medium is not limited to a detachable device such as a magnetic disk or an optical disk, and can be a fixed recording medium such as a hard disk device or a memory. Further, a program for realizing at least a part of the functions of the inspection method can be distributed via a communication line (including wireless communication) such as the Internet. Furthermore, the program can be distributed in an encrypted, modulated, or compressed state via a wired communication line or a wireless communication line such as the Internet, or the program can be distributed as it is stored in a recording medium.