Pattern inspection device

Abstract

Provided is a pattern inspection device capable of performing focus adjustment without depending on illumination conditions or a pattern formed on a sample. A pattern inspection device according to one embodiment of the present invention is provided with: an imaging sensor having: a plurality of first detection elements for detecting light beams transmitted or reflected by a sample illuminated by inspection light and imaging a pattern image of the sample; and a plurality of second detection elements which are disposed adjacent to the plurality of first detection elements, detect a light beam that shifts the focal position of the light beam back and forth, and capture an image for focus detection. An adjustment mechanism that adjusts the focal position of the light beam using the focus adjustment images captured by the plurality of second detection elements; and a comparison circuit that compares the pattern image captured by the plurality of first detection elements with a predetermined reference image.

Description

[0001] This application has priority to Japanese Patent Application No. 2024-135117 (Filing date: August 13, 2024). The entire contents of the base application are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to a pattern inspection apparatus. For example, it relates to a pattern apparatus that inspects a pattern defect of a mask for exposure used in semiconductor manufacturing, and a focus position adjustment method of the apparatus. BACKGROUND

[0003] In recent years, with high integration and large capacity of large scale integrated circuits (LSIs), circuit line widths required for semiconductor elements are becoming narrower and narrower. These semiconductor elements are manufactured by forming a circuit by using a photomask pattern (also referred to as a mask or an intermediate mask, hereinafter collectively referred to as a mask) on which a circuit pattern is formed, and transferring the pattern to a wafer by a reduction projection exposure apparatus called a so-called stepper.

[0004] Furthermore, for the manufacture of LSIs which cost a large amount of manufacturing cost, improvement of yield is indispensable. As one of the main reasons for lowering the yield, a pattern defect of a mask used when a super-fine pattern is exposed and transferred on a semiconductor wafer by a lithography technique can be cited. In recent years, with miniaturization of the size of an LSI pattern formed on a semiconductor wafer, the size to be detected as a pattern defect has become extremely small. Therefore, high accuracy of a pattern inspection apparatus for inspecting a defect of a transfer mask used for LSI manufacturing is required.

[0005] As an inspection method, for example, there are "die to die inspection" in which optical image data of the same pattern on different sites on the same mask are compared with each other, and "die to database inspection" in which CAD data of a pattern design is converted into drawing data (design data) in a device input format input to a drawing device when a pattern is drawn on a mask, and a reference image is generated on the basis of this, and an optical image of measurement data obtained by photographing a pattern is compared.

[0006] In this inspection apparatus, it is necessary to clearly acquire a pattern image on a mask which is an inspection object. However, since there is a limited depth of focus in the optical system of the inspection apparatus, it is necessary to continuously hold the inspection surface of the inspection object within the depth of focus of the optical system in the inspection. In other words, it is required to hold the contrast of the photographed image within an allowable range.

[0007] Therefore, in the inspection apparatus, in addition to the inspection optical system for image capturing, an autofocus mechanism that detects displacement of the inspection object in the height direction with respect to the inspection optical system and adjusts the height position is employed.

[0008] With recent micropatterning, shortening of the wavelength of the inspection light is progressing. Along with this, the depth of focus of the inspection optical system is becoming shallower. Therefore, the precision of the measurement system of the independent autofocus mechanism that was conventionally provided in the vicinity of the inspection optical system was sufficient, but without performing in-situ measurement using the inspection optical system itself, it was not possible to detect various fluctuation factors (temperature / mechanical deformation dependency) possessed by the inspection optical system, and high-precision focus adjustment was not possible. Therefore, as the autofocus mechanism, a method of utilizing a part of the inspection optical system was employed (for example, refer to Japanese Patent Application Publication No. 2020-125941).

[0009] In this autofocus mechanism, an autofocus image is projected near the scanning direction of the inspection field of view of transmission inspection or / and reflection inspection, an autofocus signal indicating focus shift of the autofocus image is fed back, and the stage height is adjusted in a manner focused. However, this method has a problem that there is a possibility that precision is insufficient due to the illumination condition or the pattern formed on the sample. SUMMARY

[0010] One embodiment of the present application provides a pattern inspection apparatus capable of performing focus adjustment regardless of the illumination condition or the pattern formed on the sample.

[0011] The pattern inspection apparatus of one embodiment of the present application includes a stage on which a sample on which a pattern is formed is placed and which is movable; a camera sensor including a plurality of first detection elements that detect a light beam transmitted or reflected by the sample illuminated with inspection light and capture a pattern image of the sample, and a plurality of second detection elements that are arranged adjacent to the plurality of first detection elements, detect a light beam in which a focal position of the light beam is shifted, and capture an image for focus detection; an adjustment mechanism that adjusts the focal position of the light beam using an image for focus adjustment captured by the plurality of second detection elements; and a comparison circuit that compares the pattern image captured by the plurality of first detection elements with a predetermined reference image. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a structural diagram showing the structure of the pattern inspection apparatus in Embodiment 1.

[0013] Figure 2 is a conceptual diagram for explaining the inspection region in Embodiment 1.

[0014] Figure 3 is a diagram showing an example of each region in the substrate surface in Embodiment 1.

[0015] Figure 4 is a view showing an example of arrangement of detection elements of an image pickup sensor in Embodiment 1.

[0016] Figure 5 is a sectional view showing an example of structure of an optical mechanism for focus detection and an example of image pickup sensor in Embodiment 1.

[0017] Figure 6 is a view for explaining an example of method of focus detection in Embodiment 1.

[0018] Figure 7 is a view showing an example of structure in a case where simultaneous inspection of a plurality of regions is performed in Embodiment 1.

[0019] Figure 8 is a view showing an example of internal structure of a comparison circuit in Embodiment 1.

[0020] Figure 9 is a view showing an example of internal structure of an autofocus control circuit in Embodiment 1.

[0021] Figure 10 is a view for explaining a filter processing in Embodiment 1.

[0022] Figure 11 is a structural view showing a structure of a pattern inspection apparatus in Embodiment 2.

[0023] Figure 12 is a view showing an example of field stop image of inspection light and measurement light in Embodiment 2.

[0024] Figure 13 is a view for explaining arrangement positions of front-side focus illumination pattern and back-side focus illumination pattern in Embodiment 2.

[0025] Figure 14 is a view showing an example of front view of front-side focus illumination pattern and back-side focus illumination pattern in Embodiment 2. DETAILED DESCRIPTION

[0026] Embodiment 1.

[0027] Figure 1 is a structural view showing a structure of a pattern inspection apparatus in Embodiment 1. In Figure 1 , an inspection apparatus 100 which inspects a defect of a pattern formed on an inspection target substrate such as a mask is provided with an optical image acquisition mechanism 150 and a control system circuit 160.

[0028] The optical image acquisition mechanism 150 has a light source 103, a reflection illumination optical system 171, a movably configured XYθ stage 102, an objective lens 104, a beam splitter 174, a first imaging lens 175, a separation mirror 177, a detection optical system 176, an autofocusing mechanism 131, an image pickup sensor 105, a sensor circuit 106, a strip pattern memory 123, a laser length measuring system 122, and an automatic loader 130. In the case of performing transmission inspection using transmitted light, a transmission illumination optical system 170 is further provided.

[0029] The detection optical system 176 has, for example, a collimator lens 178 and an imaging lens 179.

[0030] In the case of performing reflection inspection using reflected light only without performing transmission inspection, the transmission illumination optical system 170 can be omitted. In the case of performing both transmission inspection and reflection inspection, the detection optical system, the image pickup sensor, the sensor circuit, and the strip pattern memory described later are further added, and the image pickup sensor 105 is configured to capture an image for reflection inspection, and the added image pickup sensor is configured to capture an image for transmission inspection.

[0031] The autofocusing mechanism 131 includes a focusing optical system 180, a light amount sensor 185 (first light amount sensor), a light amount sensor 187 (second light amount sensor), a Z drive mechanism 132, and a position sensor 134. The focusing optical system 180, the light amount sensor 185, and the light amount sensor 187 constitute a part of a confocal sensor.

[0032] The focusing optical system 180 includes an imaging optical system 181, a beam splitter 182, a slit plate 184, and a slit plate 186. The focusing optical system 180 guides a light beam transmitted or reflected by the substrate 101 to the light amount sensor 185 and the light amount sensor 187 when the substrate 101 is irradiated with measurement light using a part of light generated from the light source. The beam splitter 182 is disposed at a position closer to the designed focal position. The slit plate 184 is disposed at a front focal position (front-side focal position) and receives light transmitted by the beam splitter 182. The light amount sensor 185 measures the amount of light passing through the slit plate 184 disposed at the front focal position (front-side focal position). The slit plate 186 is disposed at a rear focal position (rear-side focal position) and receives light branched by the beam splitter 182. The light amount sensor 187 measures the amount of light passing through the slit plate 186 disposed at the rear focal position (rear-side focal position).

[0033] A substrate 101, which is carried from an automatic loader 130, is arranged on an XYθ stage 102 (an example of a stage). As the substrate 101, for example, a photomask for exposure to transfer a pattern to a semiconductor substrate such as a wafer is included. Further, a plurality of pattern figures, which are the inspection targets, are formed on the photomask. The substrate 101 is arranged on the XYθ stage 102, for example, in a manner that a pattern formation surface faces a lower side. The XYθ stage 102 is an example of a stage.

[0034] As the imaging sensor 105, a line sensor or a two-dimensional sensor is used. For example, a TDI (Time Delay Integration) sensor is preferably used.

[0035] Further, the optical mechanism 35 is arranged near the end of the optical axis direction of the plurality of detection elements of the imaging sensor 105.

[0036] In the control system circuit 160, the control computer 110, which controls the entire inspection apparatus 100, is connected to the position circuit 107, the comparison circuit 108, the reference image making circuit 112, the automatic loader control circuit 113, the stage control circuit 114, the automatic focusing control circuit 140, the disk device 109, the memory 111, the tape device 115, the floppy disk device (FD) 116, the CRT 117, the pattern monitor 118, and the printer 119 via the bus 120. Further, the imaging sensor 105 is connected to the strip pattern memory 123, which is connected to the comparison circuit 108. Further, the reference image making circuit 112 is connected to the comparison circuit 108. Further, the comparison circuit 108 is preferably arranged in plurality, such as the comparison circuit 108a, the comparison circuit 108b, and the like.

[0037] The position sensor 134 measures the height position of the reference surface (for example, a glass substrate surface) of the pattern formation surface of the substrate 101. The measured height position of the back surface of the XYθ stage 102 is preferably adjusted to be the same height as the reference surface of the pattern formation surface of the substrate 101 when the substrate 101 is placed on the XYθ stage 102. Thus, the position sensor 134 can also measure the height position of the reference surface of the pattern formation surface of the substrate 101 by measuring the height position of the back surface of the XYθ stage 102.

[0038] The output of the position sensor 134 is connected to the automatic focusing control circuit 140. Further, the outputs of the light quantity sensors 185 and 187 are connected to the automatic focusing control circuit 140.

[0039] Furthermore, the series of circuits including position circuit 107, comparison circuit 108, image creation circuit 112, autoloader control circuit 113, stage control circuit 114, and autofocus control circuit 140 has a processing circuit. This processing circuit includes electrical circuits, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor device. Each circuit can be constructed using the same processing circuit (one processing circuit) or different processing circuits (separate processing circuits). For example, the series of circuits including position circuit 107, comparison circuit 108, image creation circuit 112, autoloader control circuit 113, stage control circuit 114, and autofocus control circuit 140 can also be constructed and executed by a control computer 110. The input data or calculation results required by position circuit 107, comparison circuit 108, image creation circuit 112, autoloader control circuit 113, stage control circuit 114, and autofocus control circuit 140 are stored each time in a memory (not shown) or memory 111 within each circuit. The input data or calculation results required to control the computer 110 are stored in a memory (not shown) or memory 111 within the control computer 110 each time. The program that causes the processor to execute can be recorded on a recording medium such as a disk drive 109, magnetic tape drive 115, FD 116, or ROM (read-only memory).

[0040] In the inspection apparatus 100, a reflective inspection optical system and / or a transmissive inspection optical system are mounted as the inspection optical system. A high-magnification reflective inspection optical system is constructed from a light source 103, a reflective illumination optical system 171, a beam splitter 174, an objective lens 104, an XYθ stage 102, and a detection optical system 176. Alternatively, a high-magnification transmissive inspection optical system is constructed from a light source 103, a transmissive illumination optical system 170, an XYθ stage 102, an objective lens 104, and a detection optical system (not shown).

[0041] Furthermore, the XYθ stage 102 is driven by the stage control circuit 114 under the control of the control computer 110. It can move using a drive system such as a three-axis (XY-θ) motor that drives along the X, Y, and θ directions. These X, Y, and θ motors can be, for example, stepper motors. The XYθ stage 102 can move horizontally and in the rotational direction using the motors on each of the X, Y, and θ axes. The XYθ stage 102 is an example of a stage. The position of the substrate 101 disposed on the XYθ stage 102 is measured by the laser length measuring system 122 and supplied to the position circuit 107. Additionally, the transfer of the substrate 101 from the autoloader 130 to the XYθ stage 102, and the transfer of the substrate 101 from the XYθ stage 102 to the autoloader 130, are controlled by the autoloader control circuit 113.

[0042] In addition, the XYθ stage 102 is driven in the z direction by a Z drive mechanism 132 controlled by an autofocus control circuit 140. As the Z drive mechanism 132, for example, a piezoelectric element or a stepping motor is preferably used. In addition, the height position of the pattern formation surface (glass substrate surface) of the substrate 101 measured by a position sensor 134 is output to the autofocus control circuit 140.

[0043] Also, a drive mechanism 135 controlled by the autofocus control circuit 140 moves at least one of the collimator lens 178 and the imaging lens 179 in the optical axis direction.

[0044] Drawing data (design data) that is the basis of pattern formation of the substrate 101 that is the inspection target is input from the outside of the inspection device 100 and saved in the disk device 109. A plurality of graphic patterns are defined in the drawing data, and each graphic pattern is generally composed of a combination of a plurality of element graphics. In addition, there can be a graphic pattern composed of one graphic. On the substrate 101 to be inspected, based on each graphic pattern defined in the drawing data, a corresponding pattern is formed.

[0045] Here, in Figure 1 , the structural parts required for the embodiment 1 are described. For the inspection device 100, of course, other structures necessary can also be included as usual.

[0046] Figure 2 is a conceptual view for explaining the inspection region in the embodiment 1. As shown in Figure 2 , the inspection region 10 (entire inspection region) of the substrate 101 is hypothetically divided into a plurality of inspection strips 20 (strip regions) in a long strip shape of a width W in the Y direction, for example. The width W is preferably set to the scan width of the group of detection elements of the imaging sensor 105 that captures the inspection image. Then, in the inspection device 100, an image (strip region image) is acquired for each inspection strip 20. For each inspection strip 20, an image of the graphic pattern arranged in the inspection strip 20 is captured in the long side direction (X direction) of the inspection strip 20 using laser light (inspection light). In addition, in order to prevent omission of the image, the plurality of inspection strips 20 are preferably set so that the adjacent inspection strips 20 overlap each other by a prescribed margin width.

[0047] By the movement of the XYθ stage 102, the imaging sensor 105 continuously moves in the X direction while capturing the optical image. The imaging sensor 105 continuously captures the optical image while moving in the X direction as shown in Figure 2The optical images of the width W are shown. In Embodiment 1, after the optical images in one inspection strip 20 are photographed, the position of the next inspection strip 20 is moved in the Y direction, and the optical images of the width W are continuously photographed again this time while moving in the opposite direction. That is, the photographing is repeated in the forward (FWD) - backward (BWD) direction toward the opposite direction in the forward and backward directions.

[0048] In addition, at the time of actual inspection, as shown in Figure 2 The strip area images of each inspection strip 20 are divided into images of a plurality of frame areas 30 in a rectangular shape. Then, each image of the frame area 30 is inspected. For example, the division is performed in a size of 512 x 512 pixels. Therefore, the reference image compared with the frame image 31 of the frame area 30 is also made for each frame area 30.

[0049] Here, the direction of the photographing is not limited to the repetition of the forward (FWD) - backward (BWD). The photographing can be performed from one direction. For example, it can be FWD-FWD repetition. Or, it can be BWD-BWD repetition.

[0050] As described above, the inspection device 100 has the autofocusing mechanism 131 that detects the displacement of the substrate 101 as the inspection object in the height direction with respect to the inspection optical system in addition to the inspection optical system (the reflection inspection optical system or / and the transmission inspection optical system).

[0051] Figure 3 is a diagram showing an example of each area in the substrate surface in Embodiment 1. In Figure 3 In the case where the scanning operation of each inspection strip is performed, the substrate is irradiated with each inspection light in a manner that the reflection field of view (field stop image) of the inspection light for reflection inspection and the AF image for autofocusing (AF) are arranged in the scanning direction. In the case where the transmission inspection is performed, the substrate is further irradiated with each inspection light in a manner that the transmission field of view (field stop image) of the inspection light for transmission inspection is arranged side by side with the reflection field of view in the scanning direction. At this time, it is preferable that the AF image for autofocusing (AF) is arranged near the front in the scanning direction with respect to each inspection field of view.

[0052] Further, the width of each inspection strip 20 is formed to be slightly smaller than the long side direction size of each inspection field of view. The image of the light beam portion transmitted or reflected in the substrate 101 by irradiating the inspection field of view portion outside the inspection strip 20 is photographed as the image for focus detection in Embodiment 1.

[0053] Figure 4 is a diagram showing an example of the arrangement of the detection elements of the imaging sensor in Embodiment 1. In Figure 4In the example of FIG. 2, a case where a TDI sensor is used as the image pickup sensor 105 (205) is shown. The TDI sensor has a plurality of detection elements 1 (photoelectric sensor elements) arranged in two dimensions. Each detection element 1 is set to a prescribed image accumulation time when an image is captured. In the TDI sensor, the outputs of the plurality of detection elements 1 arranged in the scanning direction are integrated and output. The plurality of detection elements 1 arranged in the scanning direction capture the same pixel while being shifted in time in accordance with the movement of the XYθ stage 102. In the case where a line sensor is used as the image pickup sensor 105, the plurality of detection elements are arranged in a direction orthogonal to the scanning direction.

[0054] In addition, the image pickup sensor 205 is used in the case of transmission inspection.

[0055] The plurality of detection elements 1 of the image pickup sensor 105 have a plurality of detection elements 2 (first detection elements) that capture a pattern image of the substrate 101, and a plurality of detection elements 3 (second detection elements) that are arranged adjacent to the plurality of detection elements 2 and capture an image for focus detection. The plurality of detection elements 2 arranged in the inspection region detect a light beam transmitted or reflected by the substrate 101 (sample) illuminated by the inspection light, and capture a pattern image of the substrate 101. The plurality of detection elements 3 arranged in the focus detection region detect a light beam having a focal position shifted forward or backward, and capture an image for focus detection.

[0056] In the case where the TDI sensor is used as the image pickup sensor 105 (205), the image pickup sensor 105 (205) uses a time delay integration (TDI) method, and has a plurality of detection elements 3 at the end portion in a direction orthogonal to the TDI accumulation direction. The number of the plurality of detection elements 3 is smaller than the number of the plurality of detection elements 2. In the case where the line sensor is used as the image pickup sensor 105, the plurality of detection elements 3 are arranged in a direction orthogonal to the scanning direction. Figure 4 In the example of FIG. 2, a case where 2 to 10 or so, for example, 6 detection elements are used as the detection elements 3 from the end portion in a direction orthogonal to the TDI accumulation direction is shown. The number of detection elements in the TDI accumulation direction is the same as the number of detection elements 2.

[0057] Figure 5 is a cross-sectional view showing an example of the structure of the optical mechanism for focus detection in Embodiment 1 and an example of the image pickup sensor. In Figure 5In the present embodiment, the optical mechanism 35 (25) is disposed near the optical axis direction of the plurality of detection elements 3 of the imaging sensor 105 (205). The optical mechanism 35 (25) has a half mirror 6, a mirror 7, and a glass block 8. The optical mechanism 35 (25) moves the focal point position of a light beam that irradiates the area for focus detection of the imaging sensor 105 (205) to the front side and the rear side. Specifically, it functions as follows. A light beam that irradiates the area for focus detection of the imaging sensor 105 (205) is incident on the half mirror 6. The light beam reflected by the half mirror 6 is reflected by the mirror 7 toward the detection element 3. At this time, the optical axis is lengthened by the distance between the half mirror 6 and the mirror 7, and thus a focal point is formed at the front side focal point position (front focal point position) that is closer to the front than the designed focal point position (detection element 2 surface). Therefore, the detection element 3 detects a front side focal point image (front focal point image) that passes through the front side focal point position. The light beam that passes through the half mirror 6 is incident on the glass block 8. The refractive index changes during the passage through the glass block 8, and the incident light beam advances in a state close to parallel light. Therefore, the light beam that passes through the glass block 8 forms a focal point at the rear side focal point position (rear focal point position) that is farther to the rear than the designed focal point position (detection element 2 surface). Therefore, the detection element 3 that is different from the detection element 3 that captures the front side focal point image detects a rear side focal point image (rear focal point image) that reaches immediately before the rear side focal point position. Thus, the plurality of detection elements 3 for focus detection of the imaging sensor 105 (205) can capture a front focal point image and a rear focal point image. When viewed from the detection surface of the imaging sensor 105 (205) that is the designed focal point position, the front side focal point position and the rear side focal point position are preferably configured to be formed at the same distance.

[0058] The plurality of detection elements 2 and the plurality of detection elements 3 are irradiated with a light beam by the same detection optical system 176. Therefore, the image for focus adjustment captured by the plurality of detection elements 3 can use the same image as the pattern image that becomes the inspection image of the substrate 101 in terms of numerical aperture (NA).

[0059] Figure 6 is a diagram for explaining an example of a method of focus detection in Embodiment 1. In Figure 6In the example of FIG. 10, a case where the edges of the captured pattern are shown. In a case where the focal point position of the light beam incident on the image pickup sensor 105 (205) is the position of the detection surface of the image pickup sensor 105 (205) (in-focus), the blur amount of the front-side focal point image and the blur amount of the rear-side focal point image become the same size. In other words, the rising angle (or falling angle) of the edge of the front-side focal point image and the rising angle (or falling angle) of the edge of the rear-side focal point image are the same angle. In contrast, in a case where the focal point position of the light beam incident on the image pickup sensor 105 (205) is a position close to the front-side focal point, the blur amount of the front-side focal point image is smaller than the blur amount of the rear-side focal point image. In other words, the front-side focal point image becomes an image having a steep edge rise, while the rear-side focal point image becomes an image having a gentle edge rise. In contrast, in a case where the focal point position of the light beam incident on the image pickup sensor 105 (205) is a position close to the rear-side focal point, the blur amount of the rear-side focal point image is smaller than the blur amount of the front-side focal point image. In other words, the rear-side focal point image becomes an image having a steep edge rise, while the front-side focal point image becomes an image having a gentle edge rise. Therefore, by adjusting the rising distance Sf (or falling distance) of the edge of the front-side focal point image and the rising distance Sr (or falling distance) of the edge of the rear-side focal point image to be the same, the focal point position can be made to coincide with the detection surface of the image pickup sensor.

[0060] Next, the specific operation of the inspection apparatus 100 will be described.

[0061] As the optical image acquisition process, the optical image acquisition mechanism 150 acquires an optical image of the substrate 101. The image pickup sensor 105 receives a light beam (first light beam) transmitted or reflected in a region (first region) of the substrate 101 (sample). In the example of FIG. 10, the first light beam is transmitted in the first region of the substrate 101. The image pickup sensor 105 converts the received light beam into an electrical signal, and outputs the electrical signal to the image processing mechanism 160. Figure 1 and Figure 3In the example of FIG. 1, the imaging sensor 105 receives a light beam (first light beam) reflected in a reflection field region (first region) of the substrate 101 (sample). Specifically, the following operation is performed. In the pattern formed in the substrate 101, a portion of laser light of a wavelength of 400 nm or less (for example, DUV light) generated from the light source 103 is irradiated to the beam splitter 174 as inspection light through the reflection illumination optical system 171. The irradiated inspection light is reflected by the beam splitter 174 and is irradiated to the substrate 101 through the objective lens 104. Here, the inspection light of the above-described reflection field is irradiated to the substrate 101. A light beam corresponding to the inspection light reflected from the substrate 101 enters the split mirror 177 through the objective lens 104, the beam splitter 174, and the first imaging lens 175. Then, a portion of the light beam is imaged by the detection optical system 176 to be incident to the imaging sensor 105 through a gap of the split mirror 177, and an optical image for reflection inspection is captured. In the detection optical system 176, the collimator lens 178 guides the incident light beam to the imaging lens 179. Then, the imaging lens 179 images the incident light beam on the imaging sensor 105.

[0062] In this case, a plurality of detection elements 3 for focus detection among the plurality of detection elements 1 of the imaging sensor 105 receive a portion of the light beam imaged by the detection optical system 176 through the optical mechanism 35, and an optical image for focus detection is captured.

[0063] The image of the pattern imaged on the imaging sensor 105 is photoelectrically converted by each detection element 1 of the imaging sensor 105, and is further A / D (analog / digital) converted by the sensor circuit 106. Then, data of pixel values of the kth (n=k) inspection strip 20 of the measurement object captured by the plurality of detection elements 2 of the inspection region and optical image data for focus adjustment captured by the plurality of detection elements 3 of the focus adjustment region are stored in the strip pattern memory 123. These measurement data (pixel data) are, for example, 8-bit unsigned data representing the level (light amount) of the brightness of each pixel. The data of the pixel values of the inspection strip 20 of the measurement object and the optical image data for focus adjustment are output to the comparison circuit 108 (for example, the comparison circuit 108a) together with the positional information measured by the position circuit 107.

[0064] In addition, at the same time, another part of the laser light generated from the light source 103 is irradiated to the beam splitter 174 as measurement light through the reflected illumination optical system 171. The irradiated measurement light is reflected by the beam splitter 174 and is irradiated to the substrate 101 through the objective lens 104. Here, on the substrate 101, the measurement light of the above-described autofocusing image is irradiated to an autofocusing field region adjacent to the reflected field region. The light flux corresponding to the measurement light reflected from the substrate 101 passes through the objective lens 104, the beam splitter 174, and the first imaging lens 175, and enters the separation mirror 177. Then, it is reflected by the separation mirror and enters the focusing optical system 180. Then, the light amount data measured by the light amount sensors 185, 187 is output to the autofocusing control circuit 140.

[0065] In the case where the transmission inspection is performed at the same time, the operation is further performed as follows.

[0066] Figure 7 is a view showing an example of the structure in the case where the simultaneous inspection of a plurality of regions is performed in Embodiment 1. In Figure 7 In the example of , an example in the case where the reflection inspection and the transmission inspection are performed at the same time is shown. The combination is not limited to this, and the simultaneous inspection of the reflection inspection and the reflection inspection can be performed. Alternatively, the simultaneous inspection of the transmission inspection and the transmission inspection can be performed.

[0067] In the case where the transmission inspection is performed at the same time in addition to the reflection inspection, in the structure of Figure 1 In the structure of Figure 7 , for the transmission inspection, a detection optical system 276, an imaging sensor 205, a sensor circuit 206, a strip pattern storage 223, and an optical mechanism 25 are further provided as shown in

[0068] The imaging sensor 205 receives a light flux (second light flux) transmitted or reflected in a region (second region) of the substrate 101 (sample) at the same timing as the imaging sensor 105. In Figure 7 and Figure 3 In the example of , the imaging sensor 205 receives a light flux 19-2 (second light flux) transmitted in a transmission field region (second region) of the substrate 101 (sample). As Figure 4As described above, the imaging sensor 205 has a plurality of detection elements 2 (third detection elements) that capture an image of a pattern of the transmission field region (second region) of the substrate 101 and a plurality of detection elements 3 (fourth detection elements) that capture an image for focus detection. The plurality of detection elements 2 capture an image of a pattern of the transmission field region (second region) of the substrate 101 at the same timing as the imaging sensor 105, by detecting a light beam 19-2 (second light beam) that has transmitted through the transmission field region (second region) of the substrate 101 (sample). The plurality of detection elements 3 are arranged adjacent to the plurality of detection elements 2 and capture an image for focus detection by detecting a light beam in which the focal position of the light beam 19-2 is shifted. Specifically, the operation is performed as follows.

[0069] In Figure 7 In the example, when the substrate 101 is illuminated with the inspection light 14 for reflection inspection, the light beam 19-1 reflected on the substrate 101 is incident on the detection optical system 176, for example, through a gap between two mirrors of the split mirror 177.

[0070] When the substrate 101 is illuminated with the measurement light 16 for autofocusing, the light beam 19-3 reflected on the substrate 101 is incident on the focusing optical system 180, for example, by being reflected by one of the two mirrors of the split mirror 177.

[0071] In addition, another portion of the laser light generated from the light source 103 is irradiated to the substrate 101 as the inspection light 15 for transmission inspection through the transmission illumination optical system 170. Here, on the substrate 101, the inspection light 15 of the above-described transmission field is irradiated to a transmission field region adjacent to the reflection field region. The light beam 19-2 corresponding to the inspection light 15 that has transmitted through the substrate 101 is incident on the imaging sensor 205 by being reflected by the split mirror 177 and imaged as an optical image by the detection optical system 276, to capture an optical image for transmission inspection.

[0072] In this case, the plurality of detection elements 3 for focus detection among the plurality of detection elements 1 of the imaging sensor 205 receive a portion of the light beam imaged by the detection optical system 276 through the optical mechanism 25, to capture an optical image for focus detection.

[0073] The image of the pattern imaged on the image pickup sensor 205 is photoelectrically converted by each detection element 1 of the image pickup sensor 105, and then A / D (analog / digital) converted by the sensor circuit 106. Then, the data of the pixel values of the kth (n=k) inspection strip 20 of the measurement object photographed by the plurality of detection elements 2 of the inspection region and the optical image data for focus adjustment photographed by the plurality of detection elements 3 of the focus adjustment region are stored in the strip pattern memory 123. These measurement data (pixel data) are, for example, 8-bit unsigned data representing the gradation (light quantity) of the brightness of each pixel. The data of the pixel values of the inspection strip 20 of the inspection object and the optical image data for focus adjustment are output to the comparison circuit 108 (for example, the comparison circuit 108b) together with the positional information measured by the position circuit 107.

[0074] Figure 8 is a view showing an example of the internal structure of the comparison circuit in Embodiment 1. In Figure 8 In the comparison circuit 108, a storage device 70, 72, 73, 76, a frame image making section 74, an alignment section 78, and a comparison processing section 79 are arranged. The frame image making section 74, the alignment section 78, and the comparison processing section 79 have a processing circuit. The processing circuit includes an electrical circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor device. In addition, the respective sections can use a common processing circuit (the same processing circuit). Alternatively, different processing circuits (different processing circuits) can be used. The input data required for the frame image making section 74, the alignment section 78, and the comparison processing section 79 or the results of the calculation are stored in a memory not shown in the drawing or the memory 111 in the comparison circuit 108 each time. In the case where a plurality of comparison circuits 108a, 108b are arranged, the structures can be all the same, for example.

[0075] The strip data (strip region image) of the inspection strip 20 of the inspection object input to the comparison circuit 108 is stored in the storage device 70. The optical image data for focus adjustment is stored in the storage device 73. Furthermore, the optical image data for focus adjustment is output to the auto focus control circuit 140.

[0076] Figure 9 is a view showing an example of the internal structure of the auto focus control circuit in Embodiment 1. In Figure 9 In the auto focus control circuit 140, a storage device 51, 55, 61, a determination section 50, a focus signal processing section 52 (focus signal calculation section), an auto focus processing section 54, an image data processing section 56, and an auto focus processing section 58 are arranged.

[0077] The series of "sections" of the determination section 50, the focus signal processing section 52, the auto focus processing section 54, the image data processing section 56, and the auto focus processing section 58 have processing circuits. The processing circuits include electrical circuits, computers, processors, circuit boards, quantum circuits, or semiconductor devices, and the like. In addition, the respective "sections" can use common processing circuits (the same processing circuit). Alternatively, different processing circuits (different processing circuits) can be used. The input data required for the determination section 50, the focus signal processing section 52, the auto focus processing section 54, the image data processing section 56, and the auto focus processing section 58, or the results of the calculations are stored in a memory or the memory 111, not shown, within the auto focus control circuit 140 each time.

[0078] In the case where transmission inspection is performed at the same time, a storage device 65, an image data processing section 66, and an auto focus signal processing section 68 are also provided.

[0079] The front side focus image data and the rear side focus image data for focus adjustment, which are captured by the imaging sensor 105, are stored in the storage device 55.

[0080] First, the determination section 50 determines whether the image pair focus detection captured by the plurality of detection elements 3 of the focus adjustment region is valid. Specifically, the determination section 50 reads out the front side focus image data and the rear side focus image data for focus adjustment from the storage device 55, and determines whether the two images are valid in focus detection. As explained in Figure 6 As explained in the above, by adjusting the rising distance Sf (or the falling distance) of the edge of the front side focus image for focus detection and the rising distance Sr (or the falling distance) of the edge of the rear side focus image to be the same, the focus position can be made to coincide with the detection surface of the imaging sensor. Therefore, in the case where a region without a pattern is captured, or in the case where a solid region that does not cross the edge of a pattern is captured, the determination becomes difficult. In the case where the image is a region for which the determination is difficult, the determination is made to be invalid for focus detection. In the case where a region that crosses the edge of a pattern is captured, the determination is made to be valid for focus detection.

[0081] The auto focus control circuit 140 controls the driving mechanism 135 and the auto focus mechanism 131 so that, in the case where the image pair focus detection captured by the plurality of detection elements 3 is valid, focus adjustment of the light beam 19-1 is performed by the driving mechanism 135 (adjustment mechanism) controlled by the auto focus processing section 58, and, in the case where the image pair focus detection captured by the plurality of detection elements 3 is invalid, focus adjustment of the reflected light (light beam 19-3) for auto focus is performed by the auto focus mechanism 131 controlled by the auto focus processing section 54. Specifically, the operation is performed as follows.

[0082] As the image data processing procedure for focus adjustment, the image data processing section 56 first extracts an edge profile indicating a pair of edge positions from the front-side focus image data and the rear-side focus image data taken by the imaging sensor 105, in the case where it is determined that the focus detection is effective.

[0083] Next, the image data processing section 56 calculates the rising distance Sf (or the falling distance) of the edge of the front-side focus image and the rising distance Sr (or the falling distance) of the edge of the rear-side focus image.

[0084] The image data processing section 56 calculates the amount of movement of, for example, the collimator lens 178 for aligning the focus position with the detection surface of the imaging sensor 105, from the difference between the rising distance Sf (or the falling distance) of the edge of the front-side focus image and the rising distance Sr (or the falling distance) of the edge of the rear-side focus image. The relationship between the difference between the rising distance Sf (or the falling distance) of the edge of the front-side focus image and the rising distance Sr (or the falling distance) of the edge of the rear-side focus image and the amount of movement of the collimator lens 178 can be calculated in advance through experiments or simulations, or the like.

[0085] As the focus adjustment procedure, the auto focus processing section 58 controls the driving mechanism 135. Then, the driving mechanism 135 (adjusting mechanism) adjusts the focus position of the light beam 19-1 using the images for focus adjustment taken by the plurality of detection elements 3 of the imaging sensor 105. In other words, the focus position of the light beam 19-1 is adjusted using the images projected to the plurality of detection elements 3 at the end portion of the imaging sensor 105. Specifically, the driving mechanism 135 (adjusting mechanism) moves the collimator lens 178 by the calculated amount of movement, thereby adjusting the focus position of the light beam 19-1 incident to the imaging sensor 105.

[0086] In addition, in the example of Figure 1 The driving mechanism 135 (adjusting mechanism) adjusts the focus position of the light beam 19-1 by moving at least one of the imaging lens 179 and the collimator lens 178 in the optical axis direction in real time. For example, the focus position of the light beam 19-1 incident to the imaging sensor 105 can be adjusted by moving the imaging lens 179. Alternatively, the focus position of the light beam 19-1 incident to the imaging sensor 105 can be adjusted by moving both the collimator lens 178 and the imaging lens 179.

[0087] In the case where the transmission inspection is performed simultaneously, the focus position of the light beam 19-2 incident to the imaging sensor 205 is adjusted separately in parallel with the reflection inspection. Specifically, the operation is performed as follows.

[0088] First, the front-side focus image data and the rear-side focus image data for focus adjustment taken by the imaging sensor 205 are stored in the storage device 65.

[0089] As the image data processing procedure for focus adjustment, in a case where it is determined that the focus detection is effective, the image data processing section 66 first extracts the edge profile indicating the paired edge positions from the front-side focus image data and the rear-side focus image data taken by the imaging sensor 205.

[0090] Next, the image data processing section 66 calculates the rising distance Sf (or the falling distance) of the edge of the front-side focus image and the rising distance Sr (or the falling distance) of the edge of the rear-side focus image.

[0091] The image data processing section 66 calculates the amount of movement of, for example, the collimator lens 278 for aligning the focus position with the detection surface of the imaging sensor 205, from the difference between the rising distance Sf (or the falling distance) of the edge of the front-side focus image and the rising distance Sr (or the falling distance) of the edge of the rear-side focus image. The relationship between the difference between the rising distance Sf (or the falling distance) of the edge of the front-side focus image and the rising distance Sr (or the falling distance) of the edge of the rear-side focus image and the amount of movement of the collimator lens 278 can be calculated in advance by experiment or simulation, or the like.

[0092] As the focus adjustment procedure, the auto focus processing section 68 controls the driving mechanism 235. Also, the driving mechanism 235 (adjustment mechanism) adjusts the focus position of the light beam 19-2 using the images for focus adjustment taken by the plurality of detection elements 3 of the imaging sensor 205. In other words, the focus position of the light beam 19-2 is adjusted using the images projected to the plurality of detection elements 3 at the end portion of the imaging sensor 205. The adjustment method is the same as in the case of the imaging sensor 105.

[0093] Also, the case where the collimator lens 278 is moved is described, but the same as in the case of the focus adjustment of the imaging sensor 105, it is not limited thereto. For example, the focus position of the light beam 19-2 incident to the imaging sensor 205 can also be adjusted by moving the imaging lens 279. Or, the focus position of the light beam 19-2 incident to the imaging sensor 205 can also be adjusted by moving both the collimator lens 278 and the imaging lens 279.

[0094] In a case where it is determined that the images taken by the plurality of detection elements 3 are not effective for focus detection, the focus adjustment is performed by the auto focus mechanism 131. The auto focus mechanism 131 detects the reflection light for auto focus reflected by the substrate 101 irradiated with the measurement light 16 for auto focus, and adjusts the focus of the reflection light for auto focus by adjusting the height position of the pattern formation surface of the substrate 101. Specifically, it acts as follows.

[0095] The light beam incident to the focusing optical system 180 is refracted by the imaging optical system 181 toward a condensing direction, and irradiates the beam splitter 182. The light transmitted through the beam splitter 182 is partially restricted by the slit plate 184 of the front focal position (front focal point position), and the light quantity of the light passing through the slit plate 184 is measured by the light quantity sensor 185. A part of the light branched by the beam splitter 182 is restricted by the slit plate 186 of the rear focal position (rear focal point position), and the light quantity of the light passing through the slit plate 186 is measured by the light quantity sensor 187. Thus, the light quantity at the front focal point position and the light quantity at the rear focal point position can be measured. The respective light quantity data (light intensity data) of the light quantity at the front focal point position and the light quantity at the rear focal point position measured in the scanning are output to the autofocus control circuit 140, and stored in the storage device 51. In addition, the information (z data) of the height position of the pattern formation surface of the substrate 101 measured by the position sensor 134 is stored in the storage device 61.

[0096] As the focus signal calculation process, the focus signal processing section 52 calculates a focus signal using the light quantity at the front focal position and the light quantity at the rear focal position measured. The focus signal (f) is defined by the following equation (1) using the light quantity A at the front focal position and the light quantity B at the rear focal position.

[0097] (1) f = (A - B) / (A + B)

[0098] As the autofocus process, under the control of the autofocus processing section 54, the height position of the XYθ stage 102 is variably driven by the Z driving mechanism 132 so as to make the focus signal (f) be, for example, zero, whereby the autofocus operation is performed.

[0099] As described above, the scanning of each inspection strip 20 is performed while the focus of the light beam 19-1 toward the imaging sensor 105 is directly adjusted in real time by the driving of the detection optical system 176. In addition, in a case where the focus adjustment based on the driving of the detection optical system 176 cannot be performed, the height position of the XYθ stage 102 is variably driven by the autofocus mechanism 131, whereby the focus of the light beam 19-1 toward the imaging sensor 105 is indirectly adjusted in real time. In addition, the imaging sensor 105 is designed to be arranged in a manner conjugate to the focal position of the substrate 101 side of the objective lens 104. Thus, if the height position of the pattern formation surface of the substrate 101 is in focus, the focal position of the light beam 19-1 is designed to be in focus on the inspection surface of the imaging sensor 105. However, since there is actually a deviation, the adjustment is directly performed with high precision in principle by using the driving of the detection optical system 176.

[0100] As a reference image production process, the reference image production circuit 112 produces a reference image as a reference using the graphic pattern data (design data). The production of the reference image is implemented in parallel with the scanning operation of each inspection strip 20. Specifically, the operation is performed as follows. The reference image production circuit 112 inputs the graphic pattern data (design data) with respect to each frame region 30 of the inspection strip 20 that becomes the object, and converts each graphic pattern defined in the graphic pattern data into binary or multivalued image data.

[0101] The graphic defined in the graphic pattern data is, for example, a graphic in which a rectangle or a triangle is the basic graphic, and for example, graphic data is stored which defines the shape, size, position, etc. of each pattern graphic using information such as the coordinates (x, y) at the reference position of the graphic, the length of the side, the graphic code as an identifier that distinguishes the graphic type such as a rectangle or a triangle.

[0102] When the design pattern data that becomes the graphic data is input to the reference image production circuit 112, the data is expanded to each graphic, and the graphic code, the graphic size, etc. that represent the graphic shape of the graphic data are interpreted. Then, as a pattern that is arranged in a square that is a unit of a grid in a prescribed quantization size, the design pattern image data that is expanded to binary or multivalued is output. In other words, the design data is read in, with respect to each square that is obtained by virtually dividing the frame region into grids in a prescribed size, the occupancy rate of the graphic in the design pattern is calculated, and n-bit occupancy rate data (design image data) is output. For example, it is preferable to set one square to one pixel. Also, if one pixel is given a resolution of 1 / 2 8 (= 1 / 256), a small region of 1 / 256 of the region amount of the graphic arranged in the pixel is allocated to calculate the occupancy rate in the pixel. Then, 8-bit occupancy rate data is generated. The square (inspection pixel) can coincide with the pixel of the measurement data.

[0103] Next, the reference image production circuit 112 performs a filter process on the design image data of the design pattern of the image data as a graphic using a filter function.

[0104] Figure 10 is a diagram for explaining the filter process in Embodiment 1. The pixel data of the optical image taken from the substrate 101 is in a state of being subjected to the filter, in other words, in a continuously changing analog state, according to the resolution characteristics, etc. of the optical system used for the imaging, and therefore, for example, as shown in Figure 10As shown, the image intensity (shading value) is different from the developed image (design image) of the digital value. On the other hand, in the graphic pattern data, as described above, it is defined by the graphic code or the like, and thus in the developed design image, the image intensity (shading value) sometimes becomes the digital value. Therefore, the reference image production circuit 112 performs image processing (filtering process) on the developed image, and produces a reference image close to the optical image. Thereby, it is possible to make the design side image data, i.e., the design image data, in which the image intensity (shading value) is the digital value, coincide with the image generation characteristics of the measurement data (optical image). The generated reference image is output to the comparison circuit 108. The reference image data input to the comparison circuit 108 is stored in the storage device 72.

[0105] As the comparison process, the comparison circuit 108 (comparison section) compares the pattern image photographed by the plurality of detection elements 2 of the imaging sensor 105 with the corresponding reference image. Specifically, it operates as follows.

[0106] In the comparison circuit 108, first, the frame image generation unit 74 generates a plurality of frame images 31 in which the strip region image (optical image) is divided at a predetermined width, and specifically, as shown in Figure 2 the strip region image is divided into a plurality of frame regions 30 of rectangular frame images. For example, it is divided into a size of 512 x 512 pixels. The data of each frame region 30 is stored in the storage device 76.

[0107] Next, the alignment unit 78 reads out the corresponding frame image 31 and the corresponding reference image from the storage devices 72, 76 for each frame region 30, and performs alignment of the frame image 31 and the corresponding reference image using a predetermined algorithm. For example, the alignment is performed using the least square method.

[0108] Then, the comparison processing unit 79 (another example of the comparison section) compares the frame image 31 and the reference image corresponding to the frame image 31. For example, it compares them for each pixel. Here, according to a predetermined determination condition, it compares both for each pixel, and for example, determines the presence or absence of defects such as shape defects. As the determination condition, for example, according to a predetermined algorithm, it compares both for each pixel, and determines the presence or absence of defects. For example, it calculates the difference value of the pixel values of both images for each pixel, and determines that the case where the difference value is greater than a threshold Th as a defect. Also, the comparison result is output to, for example, the disk device 109, the tape device 115, the floppy disk device (FD) 116, the CRT 117, the pattern monitor 118, or from the printer 119.

[0109] In the above-described example, the die-database inspection case is explained, but it can also be a die-die inspection. In this case, the comparison circuit 108 uses the frame image (optical image) of the die 2 acquired for the region of one of the frame regions 30 each other for which die-die inspection is performed as a reference (reference image) for the frame regions each other for which die-die inspection is performed. First, the alignment section 78 reads out the frame image 31 of the die 1 and the frame image of the die 2 corresponding to each frame region 30 for which die-die inspection is performed from the storage device 76, and performs alignment of the frame image 31 of the die 1 and the frame image of the die 2 using a prescribed algorithm. For example, alignment is performed using the least square method. Then, the comparison processing section 79 (comparison section) compares the frame image 31 of the die 1 and the frame image of the die 2 for each pixel for each frame region 30 for which die-die inspection is performed.

[0110] In the case of performing transmission inspection at the same time, the strip data for transmission inspection is output to a comparison circuit 108b different from the comparison circuit 108a for reflection inspection, for example. The reference image is also further output to the comparison circuit 108b differently from that for reflection inspection. Then, comparison processing is performed as with the above-described content, and the comparison result is output.

[0111] As described above, according to Embodiment 1, the focus adjustment image using the same imaging conditions as the inspection image is used, and the focus position of the light beam 19-1 (19-2) is adjusted directly to the detection surface of the imaging sensor 105 (205) by the detection optical system 176 (276). In addition, even in the case of simultaneous inspection of reflection inspection / transmission inspection, simultaneous inspection of reflection inspection / reflection inspection, or simultaneous inspection of transmission inspection / transmission inspection, focus adjustment can be performed separately independently in units of imaging sensors. Therefore, focus adjustment can be performed without depending on the illumination conditions, the pattern formed on the inspected substrate 101.

[0112] Embodiment 2

[0113] In Embodiment 1, the structure in which the focus position of the light beam before entering the imaging sensor 105 (205) is shifted forward and backward using the optical mechanism 35 (25) is explained, but the method of generating the image for focus adjustment is not limited thereto. In Embodiment 2, a structure in which the inspection light 14 before irradiating the substrate 101 is processed is explained. Hereinafter, the content other than the point specifically described is the same as Embodiment 1.

[0114] Figure 11 is a structural view showing the structure of the pattern inspection apparatus in Embodiment 2. In Figure 11 , the same as Figure 1 is explained except that the optical mechanism 35 is deleted.

[0115] Figure 12 is a view showing an example of the field stop image of the inspection light and the measurement light in Embodiment 2. As shown in the view, the inspection light 14 for reflection inspection illuminates the entire field stop opening 47 formed in the field stop plate 46, thereby limiting the passing light flux and forming a field stop image of the reflection field of the inspection light 14. Similarly, the measurement light 16 for autofocusing illuminates the entire field stop opening 48 formed in the field stop plate 46, thereby limiting the passing light flux and forming an autofocusing image of the autofocusing field of the measurement light 16. Then, the field stop image of the reflection field of the inspection light 14 and the autofocusing image of the autofocusing field of the measurement light 16 are irradiated on the substrate 101 through the magnifying optical system 194. In the case of performing transmission inspection, the inspection light 15 for transmission inspection is also similarly. Figure 12

[0116] Here, in Embodiment 2, the front-side focal point illumination pattern 40 and the rear-side focal point illumination pattern 42 are arranged in a manner not overlapping in the front and rear of the optical axis direction with respect to a part of the field stop opening 47.

[0117] Figure 13 is a view for explaining the arrangement positions of the front-side focal point illumination pattern and the rear-side focal point illumination pattern in Embodiment 2.

[0118] Figure 14 is a view showing an example of the front view of the front-side focal point illumination pattern and the rear-side focal point illumination pattern in Embodiment 2.

[0119] The front-side focal point illumination pattern 40 is arranged at a front-side focal point position closer to the front in the optical axis direction than the focal point position of the field stop image formed by the field stop opening 47. The rear-side focal point illumination pattern 42 is arranged at a rear-side focal point position closer to the rear in the optical axis direction than the focal point position of the field stop image formed by the field stop opening 47. The front-side focal point illumination pattern 40 and the rear-side focal point illumination pattern 42 are each formed of, for example, a line and space pattern. When imaging is performed by the imaging sensor 105, it is preferable that the line and space pattern be repeatedly arranged in a direction orthogonal to the TDI accumulation direction. The front-side focal point illumination pattern 40 and the rear-side focal point illumination pattern 42 are arranged at positions overlapping with the region of the end portion of the field stop opening 47.

[0120] ​The light beam portions transmitted or reflected by the substrate 101 illuminated by the inspection light portions of the remaining portions of the field stop image of the inspection light 14 are detected by the plurality of detection elements 2 of the image pickup sensor 105, and become the optical image of the inspection object.

[0121] Thus, by disposing the front-side focal point illumination pattern 40 and the rear-side focal point illumination pattern 42 in front of and behind the illumination field stop, even if the optical mechanism 35 is not disposed in the vicinity of the image pickup sensor 105, the front-side focal point image and the rear-side focal point image can be captured.

[0122] Further, by illuminating the substrate 101 with the image of the front-side focal point illumination pattern 40 and the image of the rear-side focal point illumination pattern 42, even if there is no pattern at the illuminated position of the substrate 101, the image for focal point adjustment can be captured by the image pickup sensor 105. The method of focal point adjustment using the obtained image is the same as in Embodiment 1.

[0123] Therefore, the determination by the determination section 50 performed in Embodiment 1 can be omitted, and the image for focal point adjustment using the same imaging conditions as the inspection image can be used at all times, and the focal point position of the light beam 19-1 (19-2) is directly adjusted to the detection surface of the image pickup sensor 105 (205) by the detection optical system 176 (276).

[0124] In the case of performing transmission inspection at the same time, by disposing the front-side focal point illumination pattern 40 and the rear-side focal point illumination pattern 42 in front of and behind the field stop opening, the focal point adjustment of the inspection light 15 for transmission inspection can also be performed in the same manner.

[0125] Further, the period and phase of the illumination pattern are known, and thus can be distinguished from the substrate pattern. Further, in the case where a substrate pattern similar to the illumination pattern is continuous over a long area, the focal point error can be reduced by a method of providing a plurality of different periods or the like to the illumination pattern.

[0126] As described above, according to Embodiment 2, the same effects as in Embodiment 1 can be obtained. Further, even if there is no pattern at the illuminated position of the substrate 101, the image for focal point adjustment can be captured by the image pickup sensor 105, and thus the autofocus mechanism 131 can also be omitted.

[0127] The embodiments have been described above with reference to specific examples. However, the present application is not limited to these specific examples.

[0128] Further, the description of the present application does not directly require the description of the device structure, the control method, and the like, and the description thereof is omitted. However, the device structure, the control method, and the like required can be appropriately selected and used. For example, the control section structure for controlling the inspection device 100 is omitted from the description, but the control section structure required can be appropriately selected and used.

[0129] Further, all the inspection devices having the elements of the present application and being appropriately designed and changed by those skilled in the art are included in the scope of the present application.

Claims

1. A pattern inspection apparatus comprising: a stage on which a sample formed with a pattern is placed and which is movable; an imaging sensor having a plurality of first detection elements that detect a light beam transmitted or reflected by the sample illuminated with an inspection light and that capture a pattern image of the sample, and a plurality of second detection elements that are arranged adjacent to the plurality of first detection elements, that detect a light beam in which a focal position of the light beam is shifted forward or backward, and that capture an image for focus adjustment; an adjustment mechanism that adjusts the focal position of the first light beam using the image for focus adjustment captured by the plurality of second detection elements; and a comparison circuit that compares the pattern image captured by the plurality of first detection elements with a predetermined reference image.

2. The pattern inspection apparatus according to claim 1, wherein the image for focus adjustment captured by the plurality of second detection elements is an image having the same numerical aperture as the pattern image of the sample.

3. The pattern inspection apparatus according to claim 1, wherein the imaging sensor has the plurality of second detection elements at end portions in a direction orthogonal to a TDI accumulation direction using a time delay integration (TDI) method, and adjusts the focal position of the light beam using an image of the plurality of second detection elements projected to the end portions.

4. The pattern inspection apparatus according to claim 1, further comprising: an imaging lens that images the light beam on the imaging sensor; and a collimator lens that guides the light beam to the imaging lens, wherein the adjustment mechanism adjusts the focal position of the first light beam by moving at least one of the imaging lens and the collimator lens in an optical axis direction in real time.

5. The pattern inspection apparatus according to claim 1, wherein the imaging sensor receives a first light beam transmitted or reflected by a first region of the sample as a first imaging sensor, and the pattern inspection apparatus further comprises a second imaging sensor having a plurality of third detection elements that detect a second light beam transmitted or reflected by a second region of the sample at the same timing as the first imaging sensor and that capture a pattern image of the second region of the sample, and a plurality of fourth detection elements that are arranged adjacent to the plurality of third detection elements, that detect a light beam in which a focal position of the second light beam is shifted forward or backward, and that capture an image for focus adjustment.

6. The pattern inspection apparatus according to claim 1, further comprising: a field stop aperture plate that forms a field stop aperture opening through which the inspection light is illuminated to form a field stop image of the inspection light as a whole; and a front pattern and a rear pattern that are arranged not to overlap in a front-rear direction of an optical axis with respect to a partial region of the field stop aperture opening, wherein a light beam portion transmitted or reflected by the sample illuminated by a portion of the inspection light of the field stop image of the inspection light that has passed through the front pattern and the rear pattern is detected by the plurality of second detection elements, and a light beam portion transmitted or reflected by the sample illuminated by a portion of the inspection light of the field stop image of the inspection light that has not passed through the front pattern and the rear pattern is detected by the plurality of first detection elements. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 7. The pattern inspection apparatus according to claim 1, wherein Further comprising: an optical mechanism configured to move a focal point position of the light beam to a front side and a back side, in a direction of an optical axis of the plurality of second detection elements.

8. The pattern inspection apparatus according to claim 7, wherein Further comprising: an auto-focusing mechanism configured to detect an auto-focusing-use reflected light reflected by the sample illuminated with an auto-focusing-use measurement light, and to perform a focal point adjustment of the auto-focusing-use reflected light by adjusting a height position of a pattern forming surface of the sample; a determination circuit configured to determine whether or not an image focus detection is valid for an image captured by the plurality of second detection elements; and a control circuit configured to control the adjustment mechanism and the auto-focusing mechanism such that, in a case where the image focus detection is valid for the image captured by the plurality of second detection elements, the focal point adjustment of the light beam is performed by the adjustment mechanism, and in a case where the image focus detection is not valid for the image captured by the plurality of second detection elements, the focal point adjustment of the auto-focusing-use reflected light is performed by the auto-focusing mechanism.

9. The pattern inspection apparatus according to claim 1, wherein a number of the plurality of second detection elements is less than a number of the plurality of first detection elements.

10. The pattern inspection apparatus according to claim 7, wherein the optical mechanism has a half mirror, a mirror, and a glass block. ​

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