Pattern inspection device

Abstract

A pattern inspection apparatus according to one embodiment includes: a stage on which a sample is placed; a light source that irradiates the sample with light; an imaging means for acquiring an inspection image of the sample on the basis of the light; the workbench control circuit is used for controlling the position of the workbench; a comparison circuit that compares the inspection image acquired by the imaging mechanism with a reference image or another inspection image based on data describing a pattern of the sample; and a control unit that maintains a state in which the light does not continuously irradiate the same position of the sample during a period from the end of the acquisition of the inspection image of the first region of the sample on the stage controlled to the predetermined position by the stage control circuit to the start of the acquisition of the inspection image of the second region of the sample.

Description

Technical Field

[0001] Embodiments of the present invention relate to a pattern inspection apparatus. Background Art

[0002] In the manufacturing process of semiconductor devices, an exposure apparatus is used to transfer a pattern onto a photosensitive material layer (resist) formed above a semiconductor substrate (also referred to as a “wafer”). By using an etching process using the photosensitive material layer, fine patterns such as insulators and conductive bands are formed. For the transfer, a mask or an intermediate mask is used. The mask has an original pattern of the pattern to be transferred onto the insulator and the conductor. In order to form fine patterns on the insulator and the conductor, it is required that the original pattern of the mask is also fine. Therefore, it is required that the pattern inspection apparatus of the mask can detect defects in the fine original pattern.

[0003] As an inspection method, the following methods are known: comparing an optical image obtained by photographing a pattern formed on a specimen such as a photolithography mask at a prescribed magnification using a magnifying optical system with design data, or comparing the optical image with another optical image obtained by photographing the same pattern on the specimen, thereby performing the inspection. For example, as a pattern inspection method, there are “die to die” inspection and “die to database” inspection. In the die to die inspection, optical image data obtained by photographing the same pattern at different positions on the same mask are compared with each other. In the die to database inspection, drawing data (design data) obtained by converting CAD (Computer-Aided Design) data defining the pattern of the mask into a device input format input to a drawing device when drawing the pattern on the mask is input to the inspection apparatus, a design image (reference image) is generated based on the design data, and the reference image and the optical image of the photographed pattern are compared.

[0004] In the inspection method of this inspection apparatus, the specimen is placed on a worktable, and the beam scans the specimen by moving the worktable to perform the inspection. The beam is irradiated onto the specimen through a light source and an illumination optical system. The light transmitted through the specimen or reflected by the specimen forms an image on a sensor via an optical system. The image captured by the sensor is sent to a comparison circuit as measurement data. In the comparison circuit, a plurality of regions defined by virtually dividing the entire inspection target region of the specimen are used. For each such region, photographing and comparison are performed, inspection images of the plurality of regions are sequentially acquired, and comparison of the acquired inspection images is sequentially performed. In addition, photographing and comparison can be performed in parallel for a plurality of regions. After the images are aligned with each other, the measurement data and the reference data are compared according to an appropriate algorithm, and if it does not fall within the allowable range, it is determined that the pattern has a defect.

[0005] The shooting of the mask here also includes irradiating while scanning the mask with light on one side and detecting the light transmitted through the mask.

[0006] Prior art documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2021-110556 Summary of the invention

[0009] Technical problems to be solved by the invention

[0010] Depending on the state of the pattern inspection device, it may be necessary to stop the light scanning. In this case, during the period until the light scanning starts again, the light continues to irradiate the same position of the specimen. This may cause damage to the position of the specimen that continuously receives light. In addition, the light source cannot perform the following operations: after being turned off in a short time to stop irradiating the specimen with light, it starts emitting light again while being turned on.

[0011] Therefore, a pattern inspection device that suppresses damage to the specimen due to the light continuously irradiating the same position of the specimen is needed.

[0012] Means for solving the technical problems

[0013] According to one embodiment, a pattern inspection device includes: a workbench for placing a specimen; a light source for irradiating the specimen with light; an imaging mechanism for obtaining an inspection image of the specimen based on the light; a workbench control circuit for controlling the position of the workbench; a comparison circuit for comparing the inspection image obtained by the imaging mechanism with a reference image based on data describing the pattern of the specimen or another inspection image; and a control unit for maintaining a state where the light does not continuously irradiate the same position of the specimen during the period from the end of obtaining the inspection image of the first region of the specimen on the workbench controlled to a specified position by the workbench control circuit to the start of obtaining the inspection image of the second region of the specimen. Description of the drawings

[0014] Figure 1 Shows the components of the pattern inspection device according to the first embodiment.

[0015] Figure 2 Shows an example of the region of the specimen inspected by the pattern inspection device according to the first embodiment.

[0016] Figure 3 Shows the components of the comparison circuit of the pattern inspection device according to the first embodiment.

[0017] Figure 4 Shows the inspection process of the pattern inspection device according to the first embodiment.

[0018] Figure 5 Shows the object to be compared by the comparison circuit of the pattern inspection apparatus according to the first embodiment.

[0019] Figure 6 Shows a part of the flow of the operation during the acquisition of the inspection image by the pattern inspection apparatus according to the first embodiment.

[0020] Figure 7 Shows a first example of a part of the flow of the operation during the acquisition of the inspection image by the pattern inspection apparatus according to the first embodiment.

[0021] Figure 8 Shows a second example of a part of the flow of the operation during the acquisition of the inspection image by the pattern inspection apparatus according to the first embodiment.

[0022] Figure 9 Shows a third example of a part of the flow of the operation during the acquisition of the inspection image by the pattern inspection apparatus according to the first embodiment. Detailed Description of the Invention

[0023] Hereinafter, embodiments will be described with reference to the accompanying drawings. For a plurality of constituent elements having substantially the same functions and structures in some embodiments, in order to distinguish them from each other, sometimes further numbers or characters are appended to the end of the reference numerals.

[0024] 1. First Embodiment

[0025] The pattern inspection apparatus according to the first embodiment will be described. Hereinafter, a case where the pattern inspection apparatus according to the first embodiment acquires an optical image using a light receiving element (photodiode) as an inspection image will be described. However, the pattern inspection apparatus may also acquire an electron beam image using a scanning electron microscope (SEM) as an inspection image. The pattern inspection apparatus according to the first embodiment can be applied to either die-to-die inspection or die-to-database inspection.

[0026] Figure 1 Shows the constituent elements (structure) of the pattern inspection apparatus 1 according to the first embodiment. As Figure 1 shown, the pattern inspection apparatus 1 includes an imaging mechanism 10 and a control mechanism 20.

[0027] The imaging mechanism 10 irradiates light onto the specimen 5 and detects the light transmitted through the specimen 5, thereby acquiring an image of the specimen 5. The control mechanism 20 controls the imaging mechanism 10.

[0028] The specimen 5 has a plate-like shape and has a geometric pattern (figure). Examples of the specimen 5 include a mask, a wafer (semiconductor substrate), and a substrate used in a liquid crystal display device.

[0029] The photographing mechanism 10 includes a workbench 100, a light source 101, a workbench driving mechanism 102, a shutter 103, a shutter driving mechanism 104, lenses 107 and 108, a photodiode array 112, a sensor circuit 113, a laser length measuring system 114, and an automatic loader 115.

[0030] A specimen 5 is placed on the workbench 100. The workbench 100 can move along the x-axis and y-axis that are parallel to and orthogonal to each other with respect to the surface of the workbench 100 (the surface on which the specimen 5 is placed) while substantially horizontally holding the specimen 5. The workbench 100 can also move along the z-axis perpendicular to the surface of the workbench 100. The workbench 100 may also be able to rotate about the z-axis in the xy-plane.

[0031] The workbench driving mechanism 102 is a mechanism for moving the workbench 100 along the x-axis and y-axis. The workbench driving mechanism 102 includes an x-axis motor 120 and a y-axis motor 121. The x-axis motor 120 moves the workbench 100 along the x-axis. The y-axis motor 121 moves the workbench 100 along the y-axis.

[0032] The light source 101 emits light. The light is, for example, ultraviolet light.

[0033] The shutter 103 can block the light from the light source 101. The shutter 103 has, for example, a plate-like shape and is made of a light-absorbing material. The shutter 103 is located in the region between the light source 101 and the lens 107 described later, and can move along the x-axis and (or) y-axis. The shutter 103 can open and close. That is, the shutter 103 can move along the x-axis and (or) y-axis between a position intersecting the optical path of the light from the light source 101 and a position not intersecting the optical path of the light from the light source 101. During the period when the shutter 103 is closed, the shutter 103 is located between the light source 101 and the lens 107, blocking the light. During the period when the shutter 103 is open, the shutter 103 is not located at a position intersecting the optical path of the light from the light source 101, and the light reaches the lens 107. On the other hand, during the period of acquiring an image of the specimen 5, the shutter 103 is open.

[0034] The shutter driving mechanism 104 moves the shutter 103 along the x-axis and (or) y-axis.

[0035] The lens 107 converges the light from the light source 101 onto the surface of the specimen 5 (the surface facing the light source 101). The lens 107 is located between the light source 101 and the workbench 100.

[0036] The lens 108 forms an image of the light transmitted through the specimen 5 on the photodiode array 112. The lens 108 is located between the workbench 100 and the photodiode array 112.

[0037] The photodiode array 112 generates an analog electrical signal based on the received light. The photodiode array 112 sends the generated electrical signal to the sensor circuit 113. Specifically, the photodiode array 112 includes an image sensor. Examples of the image sensor include a linear sensor, which includes a CCD (Charge-coupled Device) camera arranged in a column. Examples of the linear sensor include a TDI (Time Delay Integration) sensor.

[0038] The sensor circuit 113 converts the analog electrical signal received from the photodiode array 112 into a digital signal. The sensor circuit 113 generates data representing the optical image (optical image data) based on the digital signal. The sensor circuit 113 outputs the optical image data. The optical image is based on the pattern of the specimen 5. The optical image represents the brightness of each pixel obtained by dividing the region (imaging region) of the object from which the optical image is acquired along the xy plane, in terms of gray values. For example, when the gray value is represented by 8-bit data, the pixel value of each pixel has a gray value in the range of 0 or more and 255 or less. Hereinafter, the optical image of the specimen 5 may sometimes be referred to as an inspection image.

[0039] The laser length measurement system 114 measures the position on the x-axis and the position on the y-axis of the worktable 100. Hereinafter, the position on the x-axis and the position on the y-axis of the worktable 100 may sometimes be referred to as the worktable position. The laser length measurement system 114 outputs data representing the worktable position (worktable position data).

[0040] The automatic loader 115 holds a plurality of specimens 5 and moves one specimen 5 to be inspected onto the worktable 100. In addition, the automatic loader 115 moves the specimen 5 for which the acquisition of the inspection image has been completed from the worktable 100 into the automatic loader 115.

[0041] The control mechanism 20 includes a control computer (control unit) 200, a storage device 201, a display device 202, an input device 203, a communication device 204, an automatic loader control circuit 205, a light source control circuit 206, a shutter control circuit 207, a worktable control circuit 208, a reference image generation circuit 209, a comparison circuit 210, and a position circuit 211. They are interconnected via a bus.

[0042] One or more of the automatic loader control circuit 205, light source control circuit 206, shutter control circuit 207, workbench control circuit 208, reference image generation circuit 209, comparison circuit 210, and position circuit 211 may also be constituted by a program executed by the control computer (control unit) 200. That is, one or more of these circuits are implemented by executing the program by the control computer (control unit) 200. The automatic loader control circuit 205, light source control circuit 206, shutter control circuit 207, workbench control circuit 208, reference image generation circuit 209, comparison circuit 210, and position circuit 211 can be implemented by the hardware or firmware provided in the control computer (control unit) 200, or can be implemented by a separate circuit controlled by the control computer (control unit) 200. The following description is based on an example in which these circuits implement their functions based on the program executed by the control computer (control unit) 200.

[0043] The control computer (control unit) 200 controls the entire pattern inspection apparatus 1. More specifically, the control computer (control unit) 200 controls the storage device 201, display device 202, input device 203, communication device 204, automatic loader control circuit 205, light source control circuit 206, shutter control circuit 207, workbench control circuit 208, reference image generation circuit 209, comparison circuit 210, and position circuit 211.

[0044] The control computer (control unit) 200 controls the imaging mechanism 10 to acquire an optical image of the specimen 5. The control computer (control unit) 200 controls the control mechanism 20 to generate a reference image. The control computer (control unit) 200 compares the optical image with the reference image to inspect the pattern of the specimen 5.

[0045] The control computer (control unit) 200 includes a standby time measurement circuit 2001 and a comparison circuit determination circuit 2002. The standby time measurement circuit 2001 measures time, for example, measures the time from the start of interruption of processing. The comparison circuit determination circuit 2002 determines whether the comparison circuit 210 is in an available state.

[0046] The control computer (control unit) 200 includes, for example, a CPU (Central Processing Unit). The CPU executes, for example, the inspection program 223 described later. The control computer (control unit) 200 can be, for example, a CPU device such as a microprocessor, or a computer device such as a personal computer. At least a part of the functions of the control computer (control unit) 200 can also be performed by other integrated circuits such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or a graphics processing unit (GPU).

[0047] The storage device 201 stores information related to pattern inspection. Specifically, the storage device 201 stores data such as design data 220, inspection conditions 221, inspection data 222, and inspection program 223. The storage device 201 includes a ROM (Read Only Memory), a RAM (Random Access Memory), and / or a non-volatile storage medium. The storage device 201 can also include various one or more storage devices such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive) as an external memory.

[0048] The inspection conditions 221 can include inspection-related conditions such as inspection parameters and filter coefficients, and the shooting conditions of the shooting mechanism 10.

[0049] The inspection data 222 includes a reference image, an optical image, and data related to the detected defects. The data related to the defects includes information such as the coordinates and dimensions of the defects.

[0050] The inspection program 223 is a program for performing inspections. For example, the inspection program 223 is stored by the storage device 201 using a non-volatile storage medium.

[0051] The display device 202 is a device for displaying information. Examples of the display device 202 include a CRT (Cathode-ray Tube) monitor, a liquid crystal display, and an organic EL (electroluminescence) display. The display device 202 can also include a device for outputting sound.

[0052] The input device 203 is a device for receiving an external input from the pattern inspection device 1. Examples of the input device 203 include a keyboard, a mouse, a touch panel, and a button switch.

[0053] The communication device 204 connects the pattern inspection device 1 to the network in order to transmit and receive data between the pattern inspection device 1 and a device outside the pattern inspection device 1. The communication device 204 can use any communication standard. For example, the communication device 204 receives design data from an external device and sends the result of pattern inspection to the external device.

[0054] The loader control circuit 205 controls the operation of the loader 115. The loader control circuit 205 operates the loader 115 to move the specimen 5 to be inspected onto the workbench 100. In addition, the loader control circuit 205 operates the loader 115 to move the specimen 5 from the workbench 100.

[0055] The light source control circuit 206 controls the light source 101.

[0056] The shutter control circuit 207 controls the shutter drive mechanism 104. Specifically, the shutter control circuit 207 performs drive control on the shutter drive mechanism 104 to move the shutter 103 to a desired position.

[0057] The workbench control circuit 208 controls the workbench drive mechanism 102. More specifically, the workbench control circuit 208 obtains workbench position data from the laser length measuring system 114 via the position circuit 211. The workbench control circuit 208 performs drive control on the workbench drive mechanism 102 based on the workbench position data.

[0058] The reference image generation circuit 209 generates a reference image based on the design data 220 that describes the pattern formed on the specimen 5. For example, the reference image generation circuit 209 receives the design data 220 from the storage device 201, expands the design data 220 into data for each pattern, and interprets the code representing the shape of the pattern included in the expanded data and the dimensions of the pattern, etc. The reference image generation circuit 209 expands (transforms) the design data 220 into a binary or multi-valued (e.g., 8-bit) image (expanded image) configured as a pattern within a grid of a specified grid unit. The reference image generation circuit 209 calculates the ratio of the figure occupancy for each pixel of the expanded image. The calculated figure occupancy within each pixel functions as the gray value of that pixel. The reference image generation circuit 209 generates a reference image based on the gray values of the pixels according to the pattern of the expanded image. The reference image generation circuit 209 sends the generated reference image to the comparison circuit 210 and the storage device 201.

[0059] The comparison circuit 210 inspects the pattern of the specimen 5. That is, in the case of die-database inspection, the comparison circuit 210 receives the data of the inspection image from the sensor circuit 113. In addition, the comparison circuit 210 receives a reference image from the reference image generation circuit 209, and the reference image is obtained from the design data that defines (describes) the pattern of the area in the specimen 5 from which the inspection image is acquired. The comparison circuit 210 compares the inspection image and the reference image using a certain algorithm. In the case where there are pixels in which the difference between the gray value of the optical image and the gray value of the reference image exceeds a preset threshold value, the comparison circuit 210 determines that there is a defect at the position in the specimen 5 corresponding to the pixel. Hereinafter, the reference image obtained from the design data that defines the pattern of the area in the specimen 5 from which the inspection image is acquired is sometimes referred to as the reference image "corresponding" to the inspection image.

[0060] In the case of die-die inspection, the comparison circuit 210 receives, for example, from the storage device 201, an inspection image of the area in the specimen 5 that includes the area having the same pattern as the pattern of the area from which the inspection image is acquired. Hereinafter, the acquired inspection image of the area having the same pattern as the pattern of the area from which the inspection image is acquired is sometimes referred to as the comparison target image. The comparison circuit 210 compares the inspection image and the comparison target image using a certain algorithm. In the case where there are pixels in which the difference between the gray value of the optical image and the gray value of the comparison target image exceeds a preset threshold value, the comparison circuit 210 determines that there is a defect at the position in the specimen 5 corresponding to the pixel.

[0061] The position circuit 211 receives the stage position data from the laser length measuring system 114, and based on the stage position data, generates position data related to the coordinates on the x-axis and the y-axis of the stage 100.

[0062] Figure 2 An example of the area of the specimen 5 inspected by the pattern inspection device 1 of the first embodiment is shown. The specimen 5 has a pattern (not shown). As Figure 2 shown, the inspection target area of the specimen 5 has a plurality of strips SP and is virtually divided into a plurality of strips SP. Figure 2 An example in which the specimen 5 has N + 1 strips SP_0 - SP_N is shown. N is a positive even number. The strip SP has a quadrilateral shape extending along the y-axis and is distributed over the xy plane of the specimen 5. The strips SP_0 - SP_N are arranged in the direction (-y direction) with a smaller coordinate on the y-axis in this order. Each strip SP extends near each of the two ends (left end and right end) arranged along the x-axis of the specimen 5. The strips SP arranged along the y-axis are adjacent to each other.

[0063] An image of the specimen 5 is acquired for each strip SP. Figure 2An example of the order of acquiring images of the acquisition strip SP is shown by thick lines. First, an image of the strip SP_0 is acquired. Second, an image of the strip SP_1 is acquired. Hereinafter, similarly, images are acquired in the order of the strips SP_2 - SP_N. Let n be an integer greater than or equal to 0 and less than or equal to N. For example, in the strip SP_n where n is even, image acquisition is performed in the +x direction. In the strip SP_n where n is odd, image acquisition is performed in the -x direction. For example, each strip SP is virtually divided into a plurality of rectangular regions RA arranged in the direction in which the strip SP extends, and inspection images can be generated for each part of the rectangular region RA in the image that can be acquired for the strip SP.

[0064] The change of the region of the object of image acquisition is performed by relative movement based on the movement of the workbench 100. That is, when the image acquisition direction is the +x direction, the workbench 100 moves in the -x direction, and when the image acquisition direction is the -x direction, the workbench 100 moves in the +x direction.

[0065] Figure 3 The components of the comparison circuit 210 of the pattern inspection device 1 according to the first embodiment are shown. As Figure 3 shown, the comparison circuit 210 includes J + 1 comparison sub - circuits 2100_0 - 2100_J, where J is an integer greater than or equal to 2 and less than or equal to N.

[0066] The comparison sub - circuits 2100 can work independently of each other or in parallel. Each comparison sub - circuit 2100 compares the inspection image with a reference image or a comparison object image to detect defects. That is, the comparison circuit 210 receives the data of the inspection image from the sensor circuit 113. In addition, in the case of die - database inspection, the comparison circuit 210 receives a reference image from the reference - image generation circuit 209, and this reference image is obtained from the design data that defines the pattern of the region in the specimen 5 from which the inspection image is acquired. The comparison circuit 210 receives a comparison object image in the case of die - die inspection. The comparison sub - circuit 2100 compares the inspection image and the reference image or the comparison object image using a certain algorithm. When there are pixels where the difference between the gray - scale value of the optical image and the gray - scale value of the reference image or the comparison object image exceeds a preset threshold, the comparison sub - circuit 2100 determines that there is a defect at the position (the workbench positions on the x - axis and y - axis) in the specimen 5 corresponding to this pixel.

[0067] Figure 4 The inspection process of the pattern inspection device 1 according to the first embodiment is shown. Figure 4 The process is performed under the control of the control computer 200. As Figure 4As shown, the control computer 200 controls the imaging mechanism 10 to perform calibration (S1). Through calibration, the gray value of the optical image obtained in the sensor circuit 113 is adjusted.

[0068] The control computer 200 acquires an inspection image of a certain area of the inspection object of the specimen 5 (S2). The acquired inspection image is sent to the comparison circuit 210.

[0069] The reference image generation circuit 209 generates a reference image based on the design data 220 (S3). More specifically, the reference image generation circuit 209 reads out the design data 220 stored in the storage device 201 and expands the read design data 220 into an expanded image. The reference image generation circuit 209 generates a reference image based on the generated expanded image. Step S3 is performed in the case of die-database inspection and skipped in the case of die-die inspection.

[0070] The comparison circuit 210 performs comparison (S4). Specifically, the comparison circuit 210 first performs alignment of the inspection image with the reference image or the comparison object image, and performs alignment of the patterns in the inspection image with the patterns in the reference image. Secondly, the comparison circuit 210 compares the inspection image with the reference image or the comparison object image. The comparison circuit 210, for example, calculates the difference in gray value of each pixel between the inspection image and the reference image or the comparison object image, and determines that there is a defect in the pixels where the difference is greater than or equal to a preset threshold.

[0071] The control computer 200 determines whether the inspection of all areas of the inspection object is completed (S5). If the inspection of all areas of the inspection object is not completed (S5_ NO), the process proceeds to step S2. Steps S2 to S4 are performed on the areas where the inspection is not completed.

[0072] If the inspection of all areas of the inspection object is completed (S5_ YES), the process proceeds to step S6. The control computer 200 outputs the comparison result (inspection data) (S6). The control computer 200 stores the inspection result in the storage device 201. The control computer 200 can display the inspection result on the display device 202 or output it to an external device (e.g., a browsing device, etc.) via the communication device 204.

[0073] Alternatively, multiple sets of the processes of steps S2 - S4 for multiple areas can be performed in parallel.

[0074] Figure 5 Shows the comparison object of the comparison circuit 210 of the pattern inspection device 1 according to the first embodiment. As Figure 5As shown, each comparison sub-circuit 2100 compares a strip SP. Multiple comparison sub-circuits 2100 compare each strip SP in parallel. That is, a certain first comparison sub-circuit 2100 receives each inspection image of multiple rectangular regions RA of the first strip SP that is the object of comparison by the first comparison sub-circuit 2100, and then compares each inspection image with the reference image or comparison object image corresponding to the inspection image. Then, during the period when the first comparison sub-circuit 2100 compares the inspection image of the first strip SP with the corresponding reference image or comparison object image, it acquires the inspection image of the rectangular region RA of another second strip SP. Then, during the period when the first comparison sub-circuit 2100 compares the inspection image of the first strip SP with the corresponding reference image or comparison object image, the second comparison sub-circuit 2100 compares the inspection image of the second strip SP with the corresponding reference image or comparison object image. Similarly, multiple comparison sub-circuits 2100 compare each strip SP in parallel.

[0075] If the overall comparison of the strip SP that is the object of comparison by each comparison sub-circuit 2100 is completed, the comparison sub-circuit 2100 sends a signal notifying the completion to the control computer 200. The signal notifying the completion is received by the comparison circuit judgment circuit 2002. When the comparison circuit judgment circuit 2002 receives the signal notifying the completion from a certain comparison sub-circuit 2100, the control computer 200 assigns the comparison sub-circuit 2100 to the comparison of another strip SP. When the comparison of a certain strip SP is completed, the comparison sub-circuit 2100 that is not assigned to any strip SP (i.e., available) is assigned to the next strip SP. The state where there is no available comparison sub-circuit 2100 is the state where the comparison circuit 210 cannot perform the comparison.

[0076] Figure 5 An example of the assignment of the comparison sub-circuit 2100 to the strip SP in the pattern inspection device of the first embodiment is shown. As Figure 5 shown, the comparison sub-circuits 2100_0 - 2100_J compare the strips SP_0 - SP_J respectively. If the comparison of the strip SP_0 is completed, the control computer 200 assigns the comparison sub-circuit 2100_0 to the comparison of the strip SP_J + 1.

[0077] At the moment when the acquisition of the inspection image for a certain strip SP is completed, in the case where there is no available (idle) comparison sub-circuit 2100, a standby time may be generated until an available comparison sub-circuit 2100 is generated. However, by having a sufficient number of comparison sub-circuits 2100 in the pattern inspection device 1, the generation of the standby time can be prevented. That is, based on the speed of acquisition (optical scanning) of the inspection image and the speed of comparison of each comparison sub-circuit 2100, the number of comparison sub-circuits 2100 is set such that the following situation can be achieved: at the moment when the acquisition of the inspection image for a certain strip SP is completed, there can be an available comparison sub-circuit 2100 for the next strip SP. On the other hand, it is not realistic to set a number of comparison sub-circuits 2100 that can achieve a large margin. Therefore, based on the speed of acquisition of the inspection image and the speed of comparison of each comparison sub-circuit 2100, the number of comparison sub-circuits 2100 is set such that the following situation can be achieved: at the moment when the acquisition of the inspection image for a certain strip SP is completed, there can be one idle comparison sub-circuit 2100.

[0078] The comparison sub-circuit 2100 may malfunction or have an abnormal condition. In this case, the malfunctioning or abnormally conditioned comparison sub-circuit 2100 is not used. Alternatively, another comparison sub-circuit 2100 is used. As a specific example, in the case where the comparison sub-circuit 2100_1 cannot operate, the comparison sub-circuits 2100_2, …, 2100_J are respectively assigned to the strips SP_1, …, SP_J-1. When the comparison of the strip SP_0 is completed, the comparison sub-circuit 2100_0 is assigned to the strip SP_J.

[0079] When there is a non-operating comparison sub-circuit 2100, a time may be generated waiting for an available (unassigned) comparison sub-circuit 2100 to be generated. That is, as described above, the number of comparison sub-circuits 2100 is set such that the following situation can be achieved: at the moment when the acquisition of the inspection image for a certain strip SP is completed, there can be an available comparison sub-circuit 2100. In other words, if such a number of comparison sub-circuits 2100 can operate, then at the moment when the acquisition of the inspection image for a certain strip SP is completed, the acquisition of the inspection image for the next strip SP and the subsequent comparison of the available comparison sub-circuit 2100 can be immediately started. Therefore, no time is generated waiting for an available comparison sub-circuit 2100 to be generated. On the other hand, in the case where there is a non-operating comparison sub-circuit 2100, at the moment when the acquisition of the inspection image for a certain strip SP is completed, there is no available comparison sub-circuit 2100. Therefore, the control computer 200 stops the acquisition of the inspection image until an available comparison sub-circuit 2100 is generated.

[0080] Figure 6Shows a part of the process during the acquisition of the inspection image by the pattern inspection apparatus 1 of the first embodiment. Specifically, Figure 6 Shows the process from the completion of the acquisition of the inspection image of a certain strip SP to the start of the acquisition of the inspection image of the next strip SP. Figure 6 The process starts when the acquisition of the inspection image of a certain strip SP is completed and there is a predetermined next strip SP for which the inspection image is to be acquired. Figure 6 The process occurs, for example, under the control of the control computer 200.

[0081] As Figure 6 shown, when the process starts, the control computer 200 uses the comparison circuit determination circuit 2002 to determine whether there is an available (unassigned) comparison sub-circuit 2100 (S11). The existence of an available comparison sub-circuit 2100 has the same meaning as making a comparison with the comparison circuit 210. In the case where there is an available comparison sub-circuit 2100 (S11_yes), the control computer 200 starts the acquisition of the inspection image of the next strip SP (S19). At the same time, the available comparison sub-circuit 2100 is assigned for the comparison of the next strip SP. When step S19 ends, Figure 6 the process ends.

[0082] In the case where there is no available comparison sub-circuit 2100 (S11_no), the control computer 200 stands by for a certain period of time (S12). During step S12, for example, the control computer 200 maintains the workbench 100 at the position before step S12. The workbench 100 may not stay at a fixed position. When starting to standby, the control computer 200 starts the measurement of time by the standby time measurement circuit 2001 to measure the duration of the standby (standby time).

[0083] As step S12, after the control computer 200 stands by for a certain period of time, it determines whether the accumulated standby time since the start of the Figure 6 process is above a threshold value (S13). The accumulated standby time depends on the number of times step S12 is performed. In the case where the accumulated standby time is not above the threshold value (S13_no), the control computer 200 executes step S11, that is, determines whether there is an available comparison sub-circuit 2100. In this way, the control computer 200 repeatedly determines whether there is an available comparison sub-circuit 2100 regularly until the accumulated standby time reaches above the threshold value through the loop of steps S11, S12, and S13.

[0084] When the cumulative standby time is above the threshold (S13_Yes), the control computer 200 controls the computer 200 to take measures to maintain the state where light is not continuously irradiated onto the same part of the specimen 5 or to prevent light from irradiating onto the same part of the specimen 5 (S14). Specific examples of step S14 will be described later. The state formed by the measures taken in step S14 continues until the subsequent step S18.

[0085] The control computer 200 uses the comparison circuit determination circuit 2002 to determine whether there is an available comparison sub-circuit 2100 (S16). When there is no available comparison sub-circuit 2100 (S16_No), the control computer 200 stands by for a certain period of time (S17). During step S16, for example, the control computer 200 does not move the workbench 100 and maintains the workbench 100 at the current position. Step S17 continues to step S16. That is, it is periodically determined whether an available comparison sub-circuit 2100 is generated, and before an available comparison sub-circuit 2100 is generated, the state formed by the measures taken in step S14 continues.

[0086] When there is an available comparison sub-circuit 2100 (S16_Yes), the control computer 200 restores the state before step S14 (S18). That is, the state formed by the measures taken in step S14 ends. Depending on the type of measures taken in step S14, instead of performing step S18, when there is an available comparison sub-circuit 2100 (S16_Yes), the control computer 200 performs step S19.

[0087] The control computer 200 starts scanning the next strip SP (S19). Thus, Figure 6 the process ends.

[0088] Refer to Figures 7 - 9 to describe specific examples of step S14. Figures 7 - 9 The first example, the second example, and the third example of the operation process of the first embodiment are respectively shown.

[0089] As Figure 7As shown, in the first example, as step S14, the control computer 200 provides an instruction to the shutter control circuit 207 to close the shutter 103. The shutter control circuit 207 controls the shutter drive mechanism 104 according to the instruction content to close the shutter 103 (S14_1). Until the available comparison sub-circuit 2100 is generated through the loop of steps S16 and S17, the shutter 103 remains closed. Thus, until the available comparison sub-circuit 2100 is generated through the loop of steps S16 and S17, light does not reach the specimen 5. As step S18, the control computer 200 provides an instruction to the shutter control circuit 207 to open the shutter 103. The shutter control circuit 207 controls the shutter drive mechanism 104 according to the instruction content to open the shutter 103 (step S18_1).

[0090] As Figure 8 shown, in the second example, as step S14, the control computer 200 provides an instruction to the stage control circuit 208 to randomly move the stage 100. The stage control circuit 208 controls the stage drive mechanism 102 according to the instruction content to randomly move the stage 100 (S14_2). For example, the control computer 200 provides an instruction to randomly move the stage 100 within an area centered on the position of the stage 100 immediately before the start of step S14. Examples of randomly moving the stage 100 include continuously moving the stage 100 randomly and randomly moving the stage 100 intermittently within a certain or random period. The control computer 200 provides an instruction to continuously move or intermittently repeat the movement of the stage 100 until the available comparison sub-circuit 2100 is generated through the loop of steps S16 and S17. Thus, until the available comparison sub-circuit 2100 is generated through the loop of steps S16 and S17, light is prevented from reaching the same part of the specimen 5. In the second example, step S18 is not performed.

[0091] As Figure 9 shown, in the third example, as step S14, the control computer 200 provides an instruction to the stage control circuit 208 to move the stage 100 to a position outside the area where light irradiates the specimen 5. The stage control circuit 208 controls the stage drive mechanism 102 based on the instruction content to move the stage 100 to a position outside the area where light irradiates the specimen 5 (S14_3). Until the available comparison sub-circuit 2100 is generated through the loop of steps S16 and S17, the position of the stage is maintained. In the third example, step S18 is not performed.

[0092] According to the first embodiment, as described below, damage to the specimen 5 can be suppressed. As referred to above Figure 5As described above, a situation may occur where the comparison sub-circuit 2100 is waiting for availability. In this case, the acquisition of the inspection image for the next stripe SP cannot be started. Therefore, the workbench 100 cannot move to the position for acquiring the inspection image of the next stripe SP, and during the period until the available comparison sub-circuit 2100 is generated, the light from the light source 101 continues to irradiate the specimen 5. This may cause damage to the specimen 5. For example, if the position of the workbench 100 is simply maintained during the period until the available comparison sub-circuit 2100 is generated, the light may continue to irradiate the same part.

[0093] In the pattern inspection device 1 of the first embodiment, if the state where there is no available comparison sub-circuit 2100 continues for a certain period of time or more at the moment when the acquisition of the inspection image of a certain stripe SP is completed, the state where the light does not continuously irradiate the same position of the specimen 5 is maintained. Moreover, if an available comparison sub-circuit 2100 is generated, the control computer 200 releases the state where the light does not continuously irradiate the same position of the specimen 5 as needed, and starts the acquisition of the inspection image of the next stripe SP. Therefore, it is possible to suppress or prevent the specimen 5 from being damaged by the light irradiating the part that does not require light irradiation during the period until the available comparison sub-circuit 2100 is generated.

[0094] 2. Others

[0095] Reference Figure 1 , an example in which the pattern inspection device 1 acquires an optical image based on the light transmitted through the specimen 5 is described. The pattern inspection device 1 may also acquire an optical image of the light reflected by the specimen 5. Additionally, the pattern inspection device 1 may also acquire both an optical image based on the light reflected by the specimen 5 and an optical image based on the light transmitted through the specimen 5.

[0096] Furthermore, so far, an example in which the pattern inspection device 1 acquires an optical image of the specimen 5 has been described. The pattern inspection device 1 may also use an electron beam to acquire the inspection image. In this case, an electron gun is included instead of the light source 101.

[0097] Several embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and its equivalent scope.

Claims

1. A pattern inspection device, comprising: A workbench for placing a specimen; A light source for irradiating the specimen with light; An imaging mechanism for obtaining an inspection image of the specimen based on the light; A workbench control circuit for controlling the position of the workbench; A comparison circuit for comparing the inspection image obtained by the imaging mechanism with a reference image based on data describing the pattern of the specimen or another inspection image; and A control unit for maintaining a state in which the light does not continuously irradiate the same position of the specimen during the period from the end of obtaining the inspection image of the first region of the specimen on the workbench controlled to a specified position by the workbench control circuit to the start of obtaining the inspection image of the second region of the specimen.

2. The pattern inspection device according to claim 1, wherein: After the end of obtaining the inspection image of the first region of the specimen, when maintaining a state in which the comparison circuit cannot start comparison throughout a first period, the control unit starts the state in which the light does not continuously irradiate the same position of the specimen.

3. The pattern inspection device according to claim 1, wherein: It further comprises a shutter located between the light source and the workbench, During the period of the state in which the light does not continuously irradiate the same position of the specimen, the control unit controls the shutter to maintain the shutter between the light source and the workbench.

4. The pattern inspection device according to claim 1, wherein: The workbench control circuit causes the workbench to continuously or intermittently move during the period of the state in which the light does not continuously irradiate the same position of the specimen.

5. The pattern inspection device according to claim 1, wherein: The workbench control circuit maintains the workbench at a position outside the area where the light continuously irradiates the specimen during the period of the state in which the light does not continuously irradiate the same position of the specimen.

6. The pattern inspection device according to claim 1, wherein: During the period from the end of obtaining the inspection image of the first region of the specimen to the state in which the comparison circuit becomes capable of starting comparison, the control unit maintains the state in which the light does not continuously irradiate the same position of the specimen.

7. The pattern inspection device according to claim 6, wherein: After the end of obtaining the inspection image of the first region of the specimen, when maintaining a state in which the comparison circuit cannot start comparison throughout a first period, the control unit starts the state in which the light does not continuously irradiate the same position of the specimen.

8. The pattern inspection device according to claim 6, wherein: It further comprises a shutter located between the light source and the workbench, During the period of the state in which the light does not continuously irradiate the same position of the specimen, the control unit controls the shutter to maintain the shutter between the light source and the workbench.

9. The pattern inspection device according to claim 6, wherein: The workbench control circuit causes the workbench to continuously or intermittently move during the period of the state in which the light does not continuously irradiate the same position of the specimen.

10. The pattern inspection apparatus according to claim 6, wherein the stage control circuit maintains the stage at a position where the light continuously irradiates the outside of the specimen during a state in which the light does not continuously irradiate the same position of the specimen.

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