JP2020194864A - Imaging apparatus and imaging method - Google Patents

Abstract

To provide an imaging apparatus and an imaging method capable of easily and appropriately correcting shading.SOLUTION: An imaging apparatus 100 according to an embodiment includes a stage 30 on which a sample 20 is placed, a light source 10 that generates illumination light L1 for illuminating the sample 20, a detector 11 that detects light from the sample 20 illuminated by the illumination light in order to image the sample 20, a calibration data generation unit 52 that generates calibration data on the basis of peripheral data obtained by detecting light from a peripheral portion 30a outside the sample 20 by the detector 11 in the stage 30 on which the sample 20 is placed, and a correction unit 53 that corrects the shading of the captured image of the sample 20 on the basis of the calibration data.SELECTED DRAWING: Figure 1

Description

The present invention relates to an imaging device and an imaging method thereof.

Patent Document 1 discloses an inspection device that captures an image of a semiconductor wafer, a liquid crystal substrate, or the like. In Patent Document 1, the holder member includes a reference plane provided in addition to the contact portion with the substrate in order to correct shading on the diffracted image.

Specifically, the inspection device includes a holder member that vacuum-sucks the substrate. The holder member is formed with irregularities for adsorbing the substrate. The convex portion of the holder member serves as a contact portion in contact with the substrate, and the bottom surface of the concave portion serves as a reference plane (paragraph 0027). Alternatively, in the holder member, the surface opposite to the surface on which the substrate is attracted is the reference plane. Further, Patent Document 2 discloses a substrate holding device that adsorbs a substrate.

Japanese Unexamined Patent Publication No. 2005-10073 Japanese Unexamined Patent Publication No. 2012-241357

In Patent Document 1, the concave portion directly below the sample or the surface opposite to the suction surface of the holder member is used as a reference plane. Therefore, in order to measure the reference plane, it is necessary to carry out the substrate from the holder member. That is, the reference flat is measured while the substrate is not held by the holder member.

The present disclosure has been made against the background of such circumstances, and provides an imaging device and an imaging method capable of easily and appropriately correcting shading.

The image pickup apparatus according to one aspect of the present embodiment is illuminated by a stage on which the sample is placed, a light source that generates illumination light for illuminating the sample, and the illumination light for imaging the sample. Calibration data based on the detector that detects the light from the sample and the peripheral data that the detector detects the light from the peripheral part outside the sample on the stage on which the sample is placed. It is provided with a calibration data generation unit for generating the sample, and a correction unit for correcting the shading of the captured image of the sample based on the calibration data.

In the above imaging device, the stage is a chuck stage that sucks and holds the sample, and the chuck stage has a stage stand provided with an exhaust port for sucking and holding the sample, and projects upward from the stage stand. A seal portion located below the peripheral portion of the sample and a support pin arranged on the center side of the sample with respect to the seal portion and in contact with the sample are provided, and the peripheral portion is the seal portion. May include a portion protruding from the sample.

In the above image pickup apparatus, the seal portion is provided with a seal pin protruding upward, and the calibration is performed using peripheral data excluding the portion corresponding to the seal pin in the peripheral image obtained by imaging the peripheral portion. Operation data may be generated.

The imaging method according to one aspect of the present embodiment is illuminated by a stage on which the sample is placed, a light source that generates illumination light for illuminating the sample, and the illumination light for imaging the sample. This is an imaging method in an imaging device equipped with a detector for detecting light from a sample, and on a stage on which the sample is placed, light from a peripheral portion outside the sample is detected by the detector. It includes a step of generating calibration data based on the peripheral data detected by the sample, and a step of correcting the shading of the captured image of the sample based on the calibration data.

In the above imaging method, the stage is a chuck stage that sucks and holds the sample, and the chuck stage has a stage stand provided with an exhaust port for sucking and holding the sample, and projects upward from the stage stand. A seal portion located below the peripheral portion of the sample and a support pin arranged on the center side of the sample with respect to the seal portion and in contact with the sample are provided, and the peripheral portion is the seal portion. May include a portion protruding from the sample.

In the above imaging method, the seal portion is provided with a seal pin protruding upward, and calibration is performed using peripheral data excluding the portion corresponding to the seal pin in the peripheral image obtained by imaging the peripheral portion. Data may be generated.

According to the present disclosure, it is possible to provide an image pickup apparatus and an image pickup method capable of performing shading correction easily and appropriately.

It is a schematic diagram which shows the whole structure of the image pickup apparatus which concerns on this embodiment. It is a graph which shows the profile of a sample data. It is a graph which shows the profile of a sample data. It is a graph which shows the change rate of the profile of a sample data. It is a graph which shows the change rate of the profile of the peripheral data. It is a graph which shows the profile which canceled the shading of a sample data using the peripheral data. It is a flowchart which shows the image pickup method of the image pickup apparatus which concerns on this embodiment. It is a top view which shows typically the structure of a stage 30. It is a side sectional view schematically showing the structure of a stage 30. It is a figure which shows the image of the peripheral part of a stage 30.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following description shows preferred embodiments of the present invention, and the scope of the present invention is not limited to the following embodiments. In the following description, those having the same reference numerals indicate substantially the same contents.

The image pickup apparatus according to the present embodiment captures a sample. Here, the inspection device is an inspection device that performs an inspection based on an image obtained by the imaging device (hereinafter, also referred to as a sample image). The inspection device is a macro inspection device that inspects a sample such as a semiconductor wafer on which a fine pattern is formed. The inspection device performs a macro inspection based on the reflected brightness value of the sample image. For example, the inspection device detects defects by thresholding the reflection luminance value of the sample image or comparing the sample image with another image. In the following description, a semiconductor wafer on which an image sensor chip such as a CCD (Charge-Coupled Device) sensor or a CMOS (Complementary metal-oxide-semiconductor) sensor is formed is used as a sample.

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The image pickup apparatus and the image pickup method according to the present embodiment will be described with reference to FIG. FIG. 1 is a diagram schematically showing an overall configuration of an imaging device. The image pickup apparatus 100 includes a light source 10, a detector 11, a filter 13, a filter 14, a stage 30, and a processing apparatus 50. An optical element other than the configuration shown in FIG. 1, for example, a lens or a mirror may be appropriately provided in the optical system. Further, when the monochromatic light source 10 is used, the filter 13 and the filter 14 are unnecessary.

FIG. 1 shows a three-dimensional Cartesian coordinate system of XYZ for the sake of clarity. The Z direction is the vertical direction, which is parallel to the thickness direction of the sample 20. The Z direction is the normal direction of the pattern forming surface of the sample 20. The X direction and the Y direction are horizontal directions, which are parallel to the pattern forming direction of the sample 20.

A sample 20 to be imaged is placed on the stage 30. As described above, the sample 20 is a patterned wafer. The stage 30 is, for example, a chuck stage, and holds the sample 20 by vacuum adsorption. The stage 30 has a size larger than that of the sample 20. Therefore, a part of the stage 30 protrudes to the outside of the sample 20. In the stage 30, the portion outside the sample 20 is referred to as the peripheral portion 30a. That is, even when the sample 20 is placed on the stage 30, the peripheral portion 30a of the stage 30 is a region that can be imaged by the detector 11.

A light source 10 and a detector 11 are arranged on the sample 20. The light source 10 is, for example, a linear light source that generates a linear illumination light L1. The illumination light uniformly illuminates a line-shaped illumination region along the Y direction on the surface of the sample 20. Alternatively, the light source 10 may irradiate ring-shaped or planar illumination light. The illumination light L1 from the light source 10 may be focused on the surface of the sample 20 by a lens. The light source 10 irradiates illumination light L1 such as visible light, ultraviolet light, or infrared light.

The light source 10 illuminates the sample 20 in an oblique direction, that is, in a direction inclined from the Z axis. Alternatively, the light source 10 may illuminate the sample 20 from a direction parallel to the Z axis. In the XZ plane, the angle formed by the optical axis of the illumination light L1 and the Z axis is the illumination angle α. The incident angle of the illumination light L1 on the optical axis is the illumination angle α. The illumination light L1 illuminates the sample 20 from a direction inclined by an illumination angle α from the Z axis. The optical system of the illumination light L1 may be provided with a lens, an optical scanner, a mirror, a beam splitter, and the like.

The illumination light L1 from the light source 10 forms a line-shaped illumination region on the surface of the sample 20. For example, the illumination light L1 may be focused on the pattern surface of the sample 20 by a lens (not shown). The illumination light L1 is reflected on the surface of the sample 20.

The detector 11 detects the detection light L2 from the illumination region. The detector 11 is a line sensor camera in which light receiving pixels are arranged in the Y direction. In the line sensor, a plurality of light receiving pixels are arranged in a row. For example, the detector 11 images the sample 20 using a CCD line sensor or the like. Of course, the detector 11 is not limited to the line sensor, and may be a two-dimensional array sensor in which a plurality of light receiving pixels are arranged in an array. Further, a lens (not shown) may image the detection light L2 on the light receiving surface of the detector 11.

The detector 11 detects the detection light L2 from an oblique direction, that is, a direction inclined from the Z axis. The angle of the detector 11 with respect to the sample 20 is defined as the detection angle β. The angle formed by the Z axis and the optical axis of the detector 11 is the detection angle β. The detection light L2 may be specularly reflected light reflected by the sample 20 or diffusely reflected light diffusely reflected by the surface of the sample 20. That is, the illumination angle α and the detection angle β may have the same value or different values. Further, the detection light L2 may be diffracted light diffracted by the pattern of the sample 20. The illumination angle α and the detection angle β may coincide with each other at 0 °. In this case, the optical path of the illumination light L1 and the detection light L2 may be split by the beam splitter of the half mirror.

Then, the detector 11 takes an image of the sample 20 while changing the relative positions of the sample 20 and the illumination region. Specifically, the stage 30 is movable in the X direction. While moving the stage 30 in the X direction, the detector 11 detects the detection light L2 from the illumination region illuminated by the light source 10. Then, the detection data corresponding to the brightness of the detection light L2 detected by the detector 11 is input to the processing device 50. Further, the processing device 50 controls the drive of the stage 30. Then, the processing device 50 visualizes the change in the brightness of the detection light L2 detected by the detector 11. By doing so, an image of the entire surface of the sample 20 can be obtained.

In this way, the processing apparatus 50 acquires a two-dimensional image of the sample 20 as a sample image. The processing device 50 performs an inspection based on the acquired sample image. When the sample 20 is defective, the intensity of the detection light L2 changes, so that the brightness of the sample image changes. For example, the brightness of the sample image becomes low in the defective portion. Alternatively, the brightness of the sample image is increased at the defective portion. Therefore, defects can be detected according to the change in the brightness of the sample image.

The processing device 50 corrects the shading of the detector 11. It should be noted that shading corresponds to variations in the detection sensitivity of the light receiving pixels. The processing device 50 uses the calibration data to correct variations in the detection sensitivity of the light receiving pixels of the detector 11. For example, in the calibration data, a coefficient is set for each light receiving pixel. The processing device 50 stores the calibration data in a memory or the like. The processing device 50 corrects the shading by multiplying the coefficient by the output value of each light receiving pixel. The processing device 50 performs the inspection based on the shading-corrected image.

Further, the processing device 50 updates the calibration data for shading correction. For example, when ultraviolet light is used as the illumination light L1, the detector 11 deteriorates in a short period of time. Further, the degree of deterioration is different for each light receiving pixel of the detector 11. The shading profile changes due to the deterioration of the detector 11. That is, the shading amount of the detector 11 changes with the passage of time. Therefore, in the present embodiment, the processing device 50 repeatedly acquires the calibration data. The processing device 50 performs shading correction based on the latest calibration data. The shading correction process by the processing device 50 will be described later.

A filter 13 is arranged between the light source 10 and the sample 20. Further, a filter 14 is arranged between the sample 20 and the detector 11. The filter 13 and the filter 14 are wavelength selection filters such as a bandpass filter and the like. Actually, a plurality of filters 13 and 14 are arranged so as to be removable in the optical path. For example, one bandpass filter selected from a plurality of bandpass filters is inserted into the optical path as the filter 13 or the filter 14. By using a bandpass filter as the filter 13 or the filter 14, the detected light can be made monochromatic.

By inserting and removing the filters 13 and 14, the illumination wavelength or the detection wavelength can be selectively extracted. Alternatively, the illumination wavelength may be changed by preparing a plurality of light sources 10. That is, a plurality of light sources 10 having different wavelengths may be prepared and the light sources 10 may be switched and used.

Further, the angle between the light source 10 and the detector 11 is variable. For example, the illumination angle α of the illumination light L1 can be changed by rotating the light source 10 around the Y axis (see arrow A in FIG. 1). Further, by rotating the detector 11 around the Y axis, the detection angle β detected by the detector 11 can be changed (see arrow B in FIG. 1).

The angle between the light source 10 and the detector 11 can be adjusted independently. That is, the illumination angle α and the detection angle β can be changed independently. Alternatively, the stage 30 may be tilted around the X-axis or the Y-axis to change the angle of the illumination light and the detector 11. When the light source 10 or the detector 11 is moved to change the detection angle, the filter 13 or the filter 14 also moves.

Hereinafter, the shading correction in the processing device 50 will be described. The processing device 50 includes an image acquisition unit 51, a calibration data generation unit 52, and a correction unit 53.

The image acquisition unit 51 acquires a sample image. That is, the detector 11 detects the detection light L2 from the sample 20 with the sample 20 placed on the stage 30. Then, by moving the stage 30 in the X direction, the image acquisition unit 51 can acquire a two-dimensional image of the sample 20. The sample image may be an entire image of the sample 20 or a partial image. The data of the sample image is used as the sample data. That is, the sample data is the output value of each light receiving pixel when the detection light L2 from the sample 20 is detected by the detector 11. The sample data changes according to the amount of light received by each light receiving pixel of the detector 11. The processing device 50 stores the sample data in a memory or the like.

Further, the image acquisition unit 51 acquires an image of the peripheral portion 30a of the stage 30 (hereinafter referred to as a peripheral image). That is, the detector 11 images the peripheral portion 30a while the sample 20 is placed on the stage 30. The peripheral portion 30a is the upper surface of the stage 30 and is a portion outside the sample 20. Specifically, the light source 10 illuminates the peripheral portion 30a with the illumination light L1. The detector 11 detects the detection light L2 from the illuminated peripheral portion 30a. By moving the stage 30 in the X direction, the image acquisition unit 51 can acquire a two-dimensional image of the peripheral portion 30a. The data of the peripheral image is used as the peripheral data. That is, the peripheral data is an output value when the detection light L2 from the peripheral portion 30a is detected by the detector 11. The processing device 50 stores peripheral data in a memory or the like.

The calibration data generation unit 52 generates calibration data for correcting shading. Specifically, the calibration data generation unit 52 generates calibration data from peripheral data before and after the elapse of a predetermined period. That is, the calibration data generation unit 52 compares the peripheral image captured on the imaging date and time T1 with the peripheral image captured on the imaging date and time T2, and obtains a coefficient according to the degree of deterioration for each light receiving pixel. The calibration data has a coefficient set for the light receiving pixel.

Then, the correction unit 53 corrects the shading of the sample image by using the calibration data. For example, the correction unit 53 corrects the shading of the sample image by multiplying each light receiving pixel by a coefficient. That is, a shading-corrected sample image (also referred to as a corrected image) can be obtained by multiplying the output value of the light receiving pixel by a coefficient. The processing device 50 can inspect the sample 20 more appropriately by performing the inspection based on the corrected image.

2 and 3 are graphs showing sample data (also referred to as bare wafer data) when the bare wafer is used as the sample 20. 2 and 3 are profile data in which the output values of the light receiving pixels of the detector 11 are plotted. The horizontal axis is the pixel address of the detector 11, and the vertical axis is the output value of the normalized pixel.

Here, a bare wafer is used as a reference sample. In the bare wafer, since the pattern is not formed, the output values of the light receiving pixels should be the same in the ideal state without shading. In other words, when there is shading, even if the light receiving amount of the light receiving pixels is the same, the output values of the light receiving pixels are different as shown in FIGS. 2 and 3.

FIG. 2 is bare wafer data of the bare wafer image captured at the imaging date and time T1, and FIG. 3 is bare wafer data of the bare wafer image captured at the imaging date and time T2. The imaging date and time T1 and the imaging date and time T2 are different by one week. That is, the imaging date and time T2 is a date and time one week after the imaging date and time T1. 2 and 3 show sample data measured under the same imaging conditions using the same bare wafer and the same detector 11. By comparing the bare wafer data of FIGS. 2 and 3, the degree of deterioration of each light receiving pixel of the detector 11 after one week has passed can be obtained. Further, FIGS. 2 and 3 show data standardized so that the average value of the output values of the light receiving pixels is the same value.

FIG. 4 is a graph showing the rate of change of the profile obtained by comparing the bare wafer data of FIGS. 2 and 3. As shown in FIG. 2, the rate of change is different for each light receiving pixel. The amount of shading changes by about 1% at the maximum.

The processing device 50 performs shading correction so as to cancel the change in the profile shown in FIG. FIG. 5 is a diagram showing the rate of change of the profile of the peripheral image at the same imaging date and time as in FIG. That is, FIG. 5 is a graph obtained by comparing the peripheral data of the peripheral image of the imaging date and time T1 with the peripheral data of the peripheral image of the imaging date and time T2. Note that FIG. 5 shows a moving average value for 200 pixels.

The rate of change in the shading amount of the peripheral data (FIG. 5) and the rate of change in the shading amount of the bare wafer data (FIG. 4) are almost the same. When the data of FIG. 4 is A and the data of FIG. 5 is B, the profile of A / B is shown in FIG. As shown in FIG. 6, the rate of change of the profile can be reduced. Specifically, the change in shading amount, which was about 1% at the maximum in FIG. 4, is reduced to about 0.3% at the maximum in FIG. In this way, by using the peripheral data, it is possible to cancel the change in the shading amount between the imaging date and time T1 and the imaging date and time T2. The processing device 50 can correct the shading amount of the sample image by using the rate of change of the profile of the peripheral data. Specifically, the calibration data generation unit 52 generates calibration data using peripheral data of peripheral images having different imaging dates and times.

The image acquisition unit 51 acquires a sample image and a peripheral image. The calibration data generation unit 52 generates calibration data based on the peripheral data of the imaging date / time T1 and the imaging date / time T2. In the calibration data, a coefficient for canceling shading is set for each light receiving pixel. Then, the correction unit 53 corrects the shading of the sample image using the calibration data. The correction unit 53 corrects the sample data by multiplying each light receiving pixel by a coefficient. This makes it possible to capture a sample image (also referred to as a corrected image) in which shading is appropriately corrected.

Further, in the present embodiment, the detector 11 images the peripheral portion 30a protruding from the sample 20 at the stage 30. Then, the calibration data generation unit 52 generates the calibration data based on the two peripheral images. That is, the coefficient is obtained by comparing the peripheral data of two peripheral images having different imaging dates and times for each light receiving pixel.

By doing so, calibration data can be easily created. That is, the calibration data can be updated without using a calibration sample such as a bare wafer. That is, since it is not necessary to transport the bare wafer to the stage 30, it is possible to suppress an increase in the tact time.

Further, even when the sample 20 is arranged, the peripheral portion 30a can be imaged. Therefore, the sample 20 can be immediately imaged after the peripheral portion 30a is imaged. Alternatively, after imaging the sample 20, the peripheral portion 30a can be imaged immediately. Therefore, the calibration data generation unit 52 can generate the calibration data based on the peripheral data of the peripheral image captured immediately after or immediately before the imaging of the sample 20. Since the peripheral image can be captured immediately before or immediately after the sampling of the sample 20, there is almost no difference in the amount of shading between the time of capturing the peripheral image and the time of capturing the sample image. Thereby, the shading of the sample image can be appropriately corrected.

For example, the processing device 50 may update the calibration data every time a patterned wafer as a sample 20 is placed. The image pickup apparatus 100 can update the calibration data by taking an image of the peripheral portion 30a. As a result, even if the light receiving pixels of the detector 11 deteriorate with the passage of time, the shading can be appropriately corrected. Further, the calibration data can be updated without transporting the calibration sample such as a bare wafer to the stage 30. Therefore, the processing device 50 can easily and appropriately correct the shading of the sample image.

An example of generating calibration data will be described below. The corrected luminance value C2 can be obtained by the following equation (1).
C2 = S2 x (W0 / W1) x (P1 / P2) ... (1)

W0 and W1 are bare wafer data when the sample 20 is a bare wafer. Specifically, W0 is bare wafer data in the initial state (hereinafter, referred to as initial bare wafer data W0). The initial bare wafer data W0 is bare wafer data at the imaging date and time T0. W1 is bare wafer data at the imaging date and time T1 after the imaging date and time T0.

S2 is the sample data of the sample 20 to be inspected, and is the sample data at the imaging date and time T2. That is, S2 is the output value of the detector 11 when the sample 20 is imaged. P1 and P2 are peripheral data. P1 is peripheral data at the imaging date and time T1. P2 is peripheral data at the imaging date and time T2. The calibration data generation unit 52 may smooth the peripheral data P1 and P2 by obtaining the moving average in the Y direction.

(W0 / W1) × (P1 / P2) is a coefficient for shading correction of the sample image. Then, the correction unit 53 corrects the shading of the sample image by multiplying the sample data S2 by the coefficient for each light receiving pixel. As a result, the correction unit 53 can calculate a corrected image that has been appropriately shaded and corrected. Then, the processing device 50 performs an inspection based on the corrected image.

Here, the peripheral data P1 is measured immediately before the start of measurement of the bare wafer data W1. That is, the peripheral data P1 is peripheral data of the peripheral image captured with the bare wafer mounted on the stage 30. The peripheral data P2 is measured immediately before the start of measurement of the sample data S2. That is, the peripheral data P2 is peripheral data of the peripheral image captured with the sample 20 mounted on the stage 30. Specifically, the peripheral portion 30a is imaged at the start of scanning for capturing a sample image or a bare wafer image. After capturing the peripheral image of the peripheral portion 30a, the stage 30 is driven to image the bare wafer or the sample 20. In other words, the stage 30 scans the bare wafer or the entire sample 20 after scanning the peripheral portion 30a.

As described above, the calibration data generation unit 52 generates the calibration data by using the peripheral data and the sample data when the stage 30 adsorbs the sample 20 to be imaged. Further, the calibration data generation unit 52 may generate calibration data by using the peripheral data and the sample data when the bare wafer is placed on the stage 30 as the sample 20. By doing so, shading correction can be performed with higher accuracy.

Hereinafter, the imaging method according to the present embodiment will be described with reference to FIG. 7. FIG. 7 is a flowchart showing an imaging method. Note that FIG. 7 shows an example in which a bare wafer is imaged every predetermined period (for example, one week) to generate calibration data.

First, the initial bare wafer data W0 is acquired (S10). As described above, the initial bare wafer data W0 is the data of the bare wafer image in the initial state. That is, at the imaging date and time T0, the bare wafer is placed on the stage 30, and the detector 11 images the sample 20. As a result, the initial bare wafer data at the imaging date and time T0 is acquired.

Next, the bare wafer and the peripheral portion 30a are imaged to acquire the bare wafer data W1 and the peripheral data P1 (S11). That is, at the imaging date and time T1, the bare wafer, which is the sample 20, is placed on the stage 30, and the detector 11 images the bare wafer image and the peripheral image. As a result, the bare wafer data W1 and the peripheral data P1 at the imaging date and time T1 are acquired. The order in which the bare wafer image and the peripheral image are captured is not particularly limited. The bare wafer image may be captured before the peripheral image is captured, or the bare wafer image may be captured after the peripheral image is captured. Alternatively, the peripheral image may be captured during the imaging of the bare wafer image. Peripheral images may be captured before and after imaging the bare wafer image.

The sample 20 and the peripheral portion 30a are imaged to acquire the sample data S2 and the peripheral data P2 (S12). That is, at the imaging date and time T2, the sample 20 to be inspected is placed on the stage 30, and the detector 11 images the sample image and the peripheral image. As a result, the sample data S2 at the imaging date and time T2 and the peripheral data P2 are acquired. The order in which the sample image and the peripheral image are captured is not particularly limited. The sample image may be captured before the peripheral image is captured, or the sample image may be captured after the peripheral image is captured. Alternatively, the peripheral image may be captured during the imaging of the sample image. Peripheral images may be captured before and after imaging the sample image.

Next, the calibration data generation unit 52 generates calibration data (S13). Then, the correction unit 53 corrects the calibration of the sample image using the calibration data (S14). That is, the processing device 50 corrects the shading of the sample image by using the above formula (1). The calibration data generation step S13 and the shading correction step S14 may be performed substantially at the same time, or may be performed in order.

Next, the processing device 50 determines whether or not a predetermined period (for example, one week) has elapsed from the previous imaging date and time T1 of the bare wafer (S15). When a predetermined period has elapsed from the imaging date and time T1 of the bare wafer (YES in S15), the bare wafer is conveyed to the stage 30 and S11 is performed again. As a result, P1 and W1 are updated.

When a predetermined period has not elapsed from the imaging date and time T1 of the bare wafer (NO in S15), the next sample 20 is conveyed to the stage 30 to perform the processes S13 to S15. As a result, the peripheral data P2 is updated. That is, the calibration data generation unit 52 updates the calibration data using the newly acquired peripheral data P2. The correction unit 53 can obtain the correction image of the next sample 20. By doing so, it is possible to generate appropriate calibration data without frequently transporting the bare wafer to the stage 30. Therefore, shading correction can be performed easily and appropriately.

In the above description, the peripheral data P2 is acquired every time the sample 20 is transported to the stage 30, but the acquisition timing of the peripheral data P2 is not particularly limited. For example, when the time change of the shading amount is small, the acquisition timing of the peripheral data P2 can be reduced. For example, the peripheral data P2 may be updated every 20 or more samples, or every predetermined time.

Further, the frequency of placing the bare wafer on the stage 30 can be reduced. For example, the bare wafer can be imaged about once a week. Therefore, it is possible to prevent an increase in takt time. The frequency of imaging the bare wafer may be less than the frequency of imaging the sample 20 to be inspected.

Random noise can be reduced by measuring the peripheral data for calculating the calibration data a plurality of times. For example, the peripheral image may be captured a plurality of times and the integrated value may be used. Alternatively, the scanning speed of the peripheral portion 30a may be slower than the scanning speed of the sample 20. By doing so, the S / N ratio can be improved. Shading can be corrected more accurately.

Peripheral images may be captured before and after imaging the sample image. Calibration data may be generated by using the peripheral data after imaging of the peripheral data before imaging the sample image. By comparing the peripheral data before and after the imaging of the sample image, it is possible to evaluate the change in the shading amount during the imaging of the sample image, that is, during the scanning of the stage 30. Therefore, the shading amount of the sample image can be corrected more appropriately.

Next, an example of the stage 30 will be described with reference to FIGS. 8 and 9. FIG. 8 is a top view showing the configuration of the stage 30. FIG. 9 is a side sectional view showing the configuration of the stage 30. The stage 30 has, for example, the same configuration as the substrate holding device shown in Patent Document 2.

The stage 30 includes a seal portion 31, a seal pin 33, a support pin 35, a suction space 36, an exhaust port 38, and a stage stand 39. In the following description, the direction perpendicular to the sample 20 is defined as the Z direction, and the plane of the sample 20 perpendicular to the Z direction is defined as the XY plane.

The stage base 39 is a disk-shaped pedestal and has an outer shape larger than that of the sample 20. The stage base 39 is provided with an exhaust port 38 for sucking and fixing the sample 20. The exhaust port 38 is a suction hole that penetrates the stage base 39. The exhaust port 38 is connected to a vacuum pump or the like (not shown). The exhaust port 38 exhausts the suction space 36.

A seal portion 31 is provided on the stage base 39. The seal portion 31 is formed by a convex portion protruding upward from the surface of the stage base 39. The seal portion 31 is continuously formed in the vicinity of the outer peripheral edge of the sample 20. Sample 20 is a semiconductor wafer having a substantially circular outer shape. Therefore, the seal portion 31 is formed in an annular shape along the outer peripheral edge of the sample 20. The seal portion 31 is arranged directly below the peripheral edge portion of the sample 20.

The outer shape of the seal portion 31 is larger than the outer shape of the sample 20. Therefore, since the seal portion 31 protrudes to the outside of the sample 20, a part of the seal portion 31 becomes a peripheral portion 30a. Since the top surface 31a of the seal portion 31 has a high flatness, it is suitable for acquiring peripheral data. Further, by setting the seal portion 31 as the peripheral portion 30a, the peripheral image can be easily captured.

On the stage table 39, the space inside the seal portion 31 is the suction space 36. The seal portion 31 serves as an outer peripheral wall that separates the suction space 36 and the external space (the space outside the suction space 36).

A plurality of support pins 35 are provided in the suction space 36. The support pin 35 projects upward from the surface of the stage base 39. In the XY plane, the plurality of support pins 35 are arranged on the stage table 39 at substantially regular intervals. That is, the distance between the adjacent support pins 35 is almost constant. The plurality of support pins 35 are provided at substantially the same height and at substantially the same diameter.

A plurality of seal pins 33 are provided on the top surface 31a of the seal portion 31. The seal pin 33 projects upward from the top surface 31a of the seal portion 31. In the XY plane, the plurality of seal pins 33 are arranged on the seal portion 31 at substantially regular intervals. That is, the distance between the adjacent seal pins 33 is almost constant. The plurality of seal pins 33 are provided at substantially the same height and substantially the same diameter. Further, the seal pin 33 is provided not only directly under the sample 20 but also outside the outer shape of the sample 20 in consideration of the misalignment during the transportation of the sample 20.

The height of the top surface of the seal pin 33 is almost the same as the height of the top surface of the support pin 35. Therefore, the sample 20 comes into contact with the support pin 35 and the seal pin 33. The top surface of the seal pin 33 may be lower than the top surface of the support pin 35.

The peripheral portion 30a includes a seal portion 31 and a seal pin 33. That is, the region including the seal portion 31 and the seal pin 33 is the peripheral portion 30a. Then, the detector 11 detects the detection light from the seal portion 31 and the seal pin 33, so that the peripheral portion 30a is imaged.

FIG. 10 shows an example of a peripheral image obtained by capturing the peripheral portion 30a. In FIG. 10, the sample 20 is a bare wafer. In FIG. 9, the horizontal axis is the Y direction, that is, the arrangement direction of the light receiving pixels of the detector 11, and the vertical direction is the scanning direction by the stage 30. Therefore, the two-dimensional image of the peripheral portion 30a becomes the peripheral image.

Here, the calibration data generation unit 52 generates peripheral data by taking an average value of output values (luminance values) for each light receiving pixel of the detector 11. That is, the brightness of a plurality of pixels arranged in the X direction in the two-dimensional image is integrated, and the integrated value is divided by the number of pixels. By doing so, the profile of the peripheral data is calculated.

As shown in FIG. 10, in the peripheral image, the seal pin 33 is darker than the seal portion 31. That is, the pixel that receives the detection light from the seal pin 33 has a smaller luminance value than the pixel that receives the detection light from the seal portion 31. Therefore, the calibration data generation unit 52 generates the calibration data by using the peripheral data of only the region of the seal unit 31 in the peripheral image. That is, the calibration data is generated by excluding the peripheral data of the portion corresponding to the seal pin 33.

For example, in the peripheral image, when the XY address of the portion corresponding to the seal pin 33 is known, the portion corresponding to the seal pin 33 is masked. Alternatively, the calibration data generation unit 52 may specify the pixel address to be the seal pin 33 by performing image processing on the peripheral image. The calibration data generation unit 52 obtains peripheral data of the average value of the brightness values of the pixels in only the seal unit 31. The calibration data generation unit 52 may obtain the average value of the brightness values for each Y address in the band-shaped region 61 between the seal pin 33 and the seal pin 33. By doing so, more accurate shading correction becomes possible.

A part or all of the processing of the processing apparatus 50 described above may be executed by a computer program. The programs described above can be stored and supplied to a computer using various types of non-transitory computer readable media. Non-transitory computer-readable media include various types of tangible storage media (tangible storage media). Examples of non-temporary computer-readable media include magnetic recording media (eg, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (eg, magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / W, semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory)) is included. The program may also be supplied to the computer by various types of temporary computer readable media (transitory computer readable media). Examples of temporary computer-readable media include electrical, optical, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

Although the embodiments of the present invention have been described above, the present invention includes appropriate modifications that do not impair its purpose and advantages, and is not limited by the above embodiments.

100 Imaging device 10 Light source 11 Detector 13 Filter 14 Filter 20 Sample 30 Stage 30a Peripheral part 50 Processing device 51 Image acquisition unit 52 Calibration data generation unit 53 Correction unit W0 Initial bare wafer data W1 Bare wafer data P1 Peripheral data P2 Peripheral data S2 sample data

Claims (6)

The stage on which the sample is placed and
A light source that generates illumination light for illuminating the sample,
A detector that detects light from a sample illuminated by the illumination light in order to image the sample.
In the stage on which the sample is placed, a calibration data generation unit that generates calibration data based on the peripheral data detected by the detector for light from a peripheral portion outside the sample.
An imaging device including a correction unit that corrects shading of an captured image of the sample based on the calibration data. The stage is a chuck stage that adsorbs and holds the sample.
The chuck stage is
A stage stand provided with an exhaust port for adsorbing and holding the sample, and
A seal portion that protrudes upward from the stage table and is located below the peripheral edge portion of the sample.
It is provided with a support pin which is arranged on the center side of the sample from the seal portion and comes into contact with the sample.
The imaging device according to claim 1, wherein the peripheral portion includes a portion of the seal portion protruding from the sample. The seal portion is provided with a seal pin that projects upward.
The imaging device according to claim 2, wherein the calibration data is generated by using the peripheral data excluding the portion corresponding to the seal pin in the peripheral image obtained by capturing the peripheral portion. The stage on which the sample is placed and
A light source that generates illumination light for illuminating the sample,
An imaging method in an imaging apparatus including a detector that detects light from a sample illuminated by the illumination light in order to image the sample.
In the stage on which the sample is placed, a step of generating calibration data based on the peripheral data detected by the detector for light from a peripheral portion outside the sample.
An imaging method including a step of correcting shading of an captured image of the sample based on the calibration data. The stage is a chuck stage that adsorbs and holds the sample.
The chuck stage is
A stage stand provided with an exhaust port for adsorbing and holding the sample, and
A seal portion that protrudes upward from the stage table and is located below the peripheral edge portion of the sample.
It is provided with a support pin which is arranged on the center side of the sample from the seal portion and comes into contact with the sample.
The imaging method according to claim 4, wherein the peripheral portion includes a portion of the seal portion protruding from the sample. The seal portion is provided with a seal pin that projects upward.
The imaging method according to claim 5, wherein calibration data is generated by using peripheral data excluding the portion corresponding to the seal pin in the peripheral image obtained by imaging the peripheral portion.