Pattern inspection device

Abstract

To prevent the same position of a sample from being continuously irradiated with light.SOLUTION: A pattern inspection device includes: a stage on which a sample is placed; a light source for applying light toward a sample; a photographing mechanism for acquiring an inspection image of the sample on the basis of light; a stage control circuit for controlling a position of the stage; a comparison circuit for comparing an inspection image acquired by the photographing mechanism with a reference image based on data for describing a pattern that the sample has, or another inspection image; and a control section for maintaining a state in which light does not continue to be applied on the same position of the sample from the time when acquisition of the inspection image is terminated in a first area of the sample on the stage controlled to a predetermined position by the stage control circuit to the time when acquisition of the inspection image in a second area of the sample is started.SELECTED DRAWING: Figure 1

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

[0003] As inspection methods, there are methods of comparing an optical image obtained by imaging a pattern formed on a sample such as a mask for lithography at a predetermined magnification using an enlarged optical system with design data, or comparing the optical image with another optical image obtained by imaging the same pattern on the sample. For example, as pattern inspection methods, there are "die to die inspection" and "die to database inspection". In die to die inspection, optical image data obtained by imaging the same pattern at different locations on the same mask are compared with each other. In die to database inspection, CAD (Computer-Aided Design) data defining the pattern of the mask is converted into a device input format that is input to a drawing device when the pattern is drawn on the mask, and the resulting drawing data (design data) is input to the inspection apparatus. Based on the design data, a design image (reference image) is generated, and the reference image is compared with the optical image obtained by imaging the pattern.

[0004] In the inspection method of such an inspection device, the sample is placed on a stage, and the inspection is performed by scanning the sample with a light beam as the stage moves. The sample is illuminated with a light beam by a light source and an illumination optical system. The light that passes through or reflects off the sample is imaged onto a sensor via the optical system. The image captured by the sensor is sent to a comparison circuit as measurement data. In the comparison circuit, multiple regions are used, defined by virtually dividing the entire area of ​​the sample to be inspected. Image acquisition and comparison are performed for each of these regions, and inspection images of multiple regions are acquired one after another, and comparisons of the acquired inspection images are performed one after another. Furthermore, image acquisition and comparison can be performed in parallel for multiple regions. After the images are aligned, the measurement data and reference data are compared according to an appropriate algorithm, and if they do not fall within the acceptable range, the pattern is determined to have a defect.

[0005] The mask imaging here involves using light, illuminating the mask while scanning it with light, and detecting the light that passes through the mask. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2021-110556 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Depending on the condition of the pattern inspection device, the light scanning may have to be stopped. In this case, light will continue to shine on the same location on the sample until the light scanning is resumed. This can cause damage to the part of the sample that is continuously exposed to light. Furthermore, the light source cannot be turned off for a short period of time to stop irradiating the sample with light, and then immediately turned on to resume emitting light.

[0008] Therefore, there is a need for a pattern inspection device that can suppress damage to the sample caused by light continuously shining on the same spot on the sample. [Means for solving the problem]

[0009] A pattern inspection apparatus according to one embodiment includes a stage on which a sample is placed, a light source that irradiates light toward the sample, an imaging mechanism that acquires an inspection image of the sample based on the light, a stage control circuit that controls the position of the stage, 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 the sample pattern, and the stage control circuit. The above positioning From the end of acquiring the inspection image of the first region of the sample on the stage to the start of acquiring the inspection image of the second region of the sample, the sample In virtually the same location Maintain a state where the above light does not continuously shine on it. And while the above comparison circuit is in a state where it cannot start the comparison, Light does not continue to shine on it Maintain the state, and when the above comparison circuit is ready to start the comparison, Light does not continue to shine on it The state is released and acquisition of the inspection image of the second region described above begins. Control unit and, including The control unit determines whether there is an available comparison subcircuit based on the completion notification of the comparison subcircuit within the comparison circuit, and when there is no available comparison subcircuit after the acquisition of the inspection image of the first region is completed and the cumulative waiting time exceeds a predetermined threshold, it starts maintaining a state in which the light does not continue to shine on substantially the same position on the sample, and when an available comparison subcircuit becomes available, the control unit Light does not continue to shine on it The state is released and acquisition of the inspection image of the second region described above begins. . [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 shows the components of the pattern inspection apparatus according to the first embodiment. [Figure 2] Figure 2 shows an example of a sample region to be inspected by the pattern inspection device of the first embodiment. [Figure 3] Figure 3 shows the components of the comparison circuit of the pattern inspection apparatus according to the first embodiment. [Figure 4] Figure 4 shows the inspection flow using the pattern inspection device of the first embodiment. [Figure 5] Figure 5 shows the objects of comparison by the comparison circuit of the pattern inspection apparatus of the first embodiment. [Figure 6] Figure 6 shows a partial flow of operations during the acquisition of inspection images by the pattern inspection apparatus of the first embodiment. [Figure 7]FIG. 7 shows a first example of a part of the flow of operations during inspection image acquisition by the pattern inspection apparatus according to the first embodiment. [Figure 8] FIG. 8 shows a second example of a part of the flow of operations during inspection image acquisition by the pattern inspection apparatus according to the first embodiment. [Figure 9] FIG. 9 shows a third example of a part of the flow of operations during inspection image acquisition by the pattern inspection apparatus according to the first embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

[0011] Embodiments will be described below with reference to the drawings. For a plurality of components having substantially the same functions and configurations in a certain embodiment, additional numbers or characters may be added to the end of the reference numerals in order to distinguish them from each other.

[0012] 1. First Embodiment The pattern inspection apparatus according to the first embodiment will be described. Hereinafter, the 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 acquire an electron beam image using a scanning electron microscope (SEM: Scanning Electron Microscope) as an inspection image. The pattern inspection apparatus according to the first embodiment can be applied to both die-die inspection and die-database inspection.

[0013] FIG. 1 shows the components (configuration) of the pattern inspection apparatus 1 according to the first embodiment. As shown in FIG. 1, the pattern inspection apparatus 1 includes a photographing mechanism 10 and a control mechanism 20.

[0014] The photographing mechanism 10 irradiates the sample 5 with light and detects the light transmitted through the sample 5 to acquire an image of the sample 5. The control mechanism 20 controls the photographing mechanism 10.

[0015] Sample 5 has a plate-like shape and has a pattern (figure) of a geometric shape. Examples of sample 5 include a mask, a wafer (semiconductor substrate), and a substrate used in a liquid crystal display device.

[0016] The imaging mechanism 10 includes a stage 100, a light source 101, a stage drive mechanism 102, a shutter 103, a shutter drive mechanism 104, lenses 107 and 108, a photodiode array 112, a sensor circuit 113, a laser length measurement system 114, and an autoloader 115.

[0017] Sample 5 is placed on the stage 100. The stage 100 can move along the x-axis and y-axis that are parallel to and perpendicular to each other on the surface of the stage 100 (the surface on which sample 5 is placed) while holding sample 5 substantially horizontally. The stage 100 can also move along the z-axis perpendicular to the surface of the stage 100. The stage 100 may further be able to rotate along the xy plane about the z-axis.

[0018] The stage drive mechanism 102 is a mechanism for moving the stage 100 along the x-axis and y-axis. The stage drive mechanism 102 includes an x-axis motor 120 and a y-axis motor 121. The x-axis motor 120 moves the stage 100 along the x-axis. The y-axis motor 121 moves the stage 100 along the y-axis.

[0019] The light source 101 emits light. The light is, for example, ultraviolet light.

[0020] The shutter 103 can block 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 a region including the space between the light source 101 and the lens 107 (described later), and can move along the x and / or y axes. The shutter 103 can be opened and closed. That is, the shutter 103 can move along the x and / or y axes between a position where it intersects with the optical path of light from the light source 101 and a position where it does not intersect with the optical path of light from the light source 101. While the shutter 103 is closed, it is located between the light source 101 and the lens 107, blocking the light. While the shutter 103 is open, it is not located where it intersects with the optical path of light from the light source 101, and the light reaches the lens 107. On the other hand, while an image of sample 5 is being acquired, the shutter 103 is open.

[0021] The shutter drive mechanism 104 moves the shutter 103 along the x-axis and / or the y-axis.

[0022] The lens 107 focuses the shutter 103 from the light source 101 onto the surface of the sample 5 (the surface facing the light source 101). The lens 107 is positioned between the light source 101 and the stage 100.

[0023] The lens 108 images the light transmitted through the sample 5 onto the photodiode array 112. The lens 108 is located between the stage 100 and the photodiode array 112.

[0024] The photodiode array 112 generates an analog electrical signal based on the light it receives. The photodiode array 112 transmits the generated electrical signal to the sensor circuit 113. Specifically, the photodiode array 112 includes an image sensor. An example of an image sensor is a line sensor that includes a row of CCD (Charge-coupled Device) cameras. An example of a line sensor is a TDI (Time Delay Integration) sensor.

[0025] The sensor circuit 113 converts the analog electrical signal received from the photodiode array 112 into a digital signal. Based on the digital signal, the sensor circuit 113 generates data representing an optical image (optical image data). The sensor circuit 113 outputs the optical image data. The optical image is based on the pattern of the sample 5. The optical image represents the brightness of each pixel obtained by dividing the area of ​​the object from which the optical image was acquired (imaging area) along the xy plane as a grayscale value. For example, if the grayscale value is represented as 8-bit data, the pixel value of each pixel has a grayscale value in the range of 0 to 255. The optical image of sample 5 may hereafter be referred to as the inspection image.

[0026] The laser length measuring system 114 measures the position of the stage 100 on the x-axis and the y-axis. The position of the stage 100 on the x-axis and the y-axis may hereafter be referred to as the stage position. The laser length measuring system 114 outputs data indicating the stage position (stage position data).

[0027] The autoloader 115 holds multiple samples 5 and moves one sample 5 to be inspected onto the stage 100. The autoloader 115 also moves a sample 5 from the stage 100 to the autoloader 115 after the inspection image has been acquired.

[0028] 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 autoloader control circuit 205, a light source control circuit 206, a shutter control circuit 207, a stage control circuit 208, a reference image generation circuit 209, a comparison circuit 210, and a position circuit 211. These are connected to each other via a bus.

[0029] One or more of the autoloader control circuit 205, light source control circuit 206, shutter control circuit 207, stage control circuit 208, reference image generation circuit 209, comparison circuit 210, and position circuit 211 may be configured by a program executed by the control computer (control unit) 200. That is, one or more of these circuits are realized by the execution of a program by the control computer (control unit) 200. The autoloader control circuit 205, light source control circuit 206, shutter control circuit 207, stage control circuit 208, reference image generation circuit 209, comparison circuit 210, and position circuit 211 may be realized by hardware or firmware provided by the control computer (control unit) 200, or by individual circuits controlled by the control computer (control unit) 200. The following description is based on an example in which the functions of these circuits are realized based on a program executed by the control computer (control unit) 200.

[0030] The control computer (control unit) 200 controls the entire pattern inspection device 1. More specifically, the control computer (control unit) 200 controls the storage device 201, display device 202, input device 203, communication device 204, auto loader control circuit 205, light source control circuit 206, shutter control circuit 207, stage control circuit 208, reference image generation circuit 209, comparison circuit 210, and position circuit 211.

[0031] The control computer (control unit) 200 controls the imaging mechanism 10 to acquire an optical image of the sample 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 and the reference image to inspect the pattern of the sample 5.

[0032] 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, the time since the start of the interruption of processing. The comparison circuit determination circuit 2002 determines whether the comparison circuit 210 is in a usable state.

[0033] 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 may be, for example, a CPU device such as a microprocessor, or a computer device such as a personal computer. At least some of the functions of the control computer (control unit) 200 may be carried out by other integrated circuits such as an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Alley (FPGA), or a Graphics Processing Unit (GPU).

[0034] 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 ROM (Read Only Memory), RAM (Random Access Memory), and / or non-temporary storage media. The storage device 201 may include one or more storage devices as external storage, such as HDD (Hard Disk Drive) or SSD (Solid State Drive).

[0035] The inspection conditions 221 may include inspection conditions such as inspection parameters and filter coefficients, as well as conditions for imaging by the imaging mechanism 10.

[0036] Inspection data 222 includes a reference image, an optical image, and data on detected defects. The defect data includes information such as the coordinates and size of the defects.

[0037] The inspection program 223 is a program for performing an inspection. For example, the inspection program 223 is stored by the memory device 201 using a non-temporary storage medium.

[0038] The display device 202 is a device that displays information. Examples of the display device 202 include a CRT (Cathode-ray Tube) display, a liquid crystal display, and an organic EL (electroluminescence) display. The display device 202 may also include a device that outputs sound.

[0039] The input device 203 is a device that receives input from outside the pattern inspection device 1. Examples of input devices 203 include a keyboard, mouse, touch panel, and button switches.

[0040] The communication device 204 connects the pattern inspection device 1 to a network for sending and receiving data between the pattern inspection device 1 and external devices. The communication device 204 can use any communication standard. For example, the communication device 204 receives design data from an external device and transmits the pattern inspection results to the external device.

[0041] The autoloader control circuit 205 controls the operation of the autoloader 115. The autoloader control circuit 205 operates the autoloader 115 to move the sample 5 to be inspected to the stage 100. The autoloader control circuit 205 also operates the autoloader 115 to move the sample 5 from the stage 100.

[0042] The light source control circuit 206 controls the light source 101.

[0043] The shutter control circuit 207 controls the shutter drive mechanism 104. Specifically, the shutter control circuit 207 drives and controls the shutter drive mechanism 104 to move the shutter 103 to a desired position.

[0044] The stage control circuit 208 controls the stage drive mechanism 102. More specifically, the stage control circuit 208 acquires stage position data from the laser length measurement system 114 via the position circuit 211. Based on the stage position data, the stage control circuit 208 drives and controls the stage drive mechanism 102.

[0045] The reference image generation circuit 209 generates a reference image based on design data 220 that describes the pattern formed on the sample 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 indicating the shape of the pattern and the dimensions of the pattern included in the expanded data. The reference image generation circuit 209 expands (converts) the design data 220 into a binary or multi-level (e.g., 8-bit) image (expanded image) as a pattern arranged in a grid of predetermined units. The reference image generation circuit 209 calculates the percentage of the expanded image that is occupied by a shape for each pixel. The calculated shape occupancy rate in each pixel functions as a grayscale value for that pixel. Based on the grayscale value of each pixel, the reference image generation circuit 209 generates a reference image from the pattern of the expanded image. The reference image generation circuit 209 transmits the generated reference image to the comparison circuit 210 and the storage device 201.

[0046] The comparison circuit 210 inspects the pattern of sample 5. In other words, in die-database inspection, the comparison circuit 210 receives inspection image data from the sensor circuit 113. The comparison circuit 210 also receives a reference image from the reference image generation circuit 209, which is obtained from design data that defines (describes) the pattern of the region of sample 5 from which the inspection image was acquired. The comparison circuit 210 compares the inspection image and the reference image using a certain algorithm. If the difference between the grayscale value of the optical image and the grayscale value of the reference image exceeds a preset threshold for any pixel, the comparison circuit 210 determines that there is a defect at the position corresponding to that pixel in sample 5. Hereinafter, the reference image obtained from the design data that defines the pattern of the region of sample 5 from which the inspection image was acquired may be referred to as the reference image "corresponding" to the inspection image.

[0047] In die-die inspection, the comparison circuit 210 receives, for example from the storage device 201, an inspection image of a region in the sample 5 that includes the region from which the inspection image was acquired, and which has the same pattern as the region from which the inspection image was acquired. The acquired inspection image of a region that has the same pattern as the region from which the inspection image was acquired may hereafter be referred to as the comparison target image. The comparison circuit 210 compares the inspection image and the comparison target image using a certain algorithm. If there is a pixel in the sample 5 where the difference between the grayscale value of the optical image and the grayscale value of the comparison target image exceeds a preset threshold, the comparison circuit 210 determines that there is a defect at the position corresponding to that pixel.

[0048] The position circuit 211 receives stage position data from the laser length measurement system 114 and generates position data relating to the x-axis and y-axis coordinates of the stage 100 based on the stage position data.

[0049] Figure 2 shows an example of a region of sample 5 to be inspected by the pattern inspection device 1 of the first embodiment. Sample 5 has a pattern not shown. As shown in Figure 2, the region of sample 5 to be inspected has multiple stripes SP and is virtually divided into multiple stripes SP. Figure 2 shows an example in which sample 5 has N+1 stripes SP_0 to SP_N, where N is a positive even number. The stripes SP have a quadrilateral shape extending along the y-axis and are distributed across the xy-plane of sample 5. The stripes SP_0 to SP_N are arranged in this order, in the direction of the smaller coordinate on the y-axis (-y direction). Each stripe SP extends to the neighborhood of each of the two ends (left end and right end) aligned along the x-axis of sample 5. The stripes SP aligned along the y-axis are touching each other.

[0050] Images of sample 5 are acquired for each stripe SP. Figure 2 shows an example of the order in which images of stripe SPs are acquired, indicated by thick lines. First, the image of stripe SP_0 is acquired. Next, the image of stripe SP_1 is acquired. Similarly, images are acquired in the order of stripe SP_2 to SP_N. Let n be an integer between 0 and N (inclusive). For example, for stripe SP_n where n is even, the image is acquired in the +x direction. For stripe SP_n where n is odd, the image is acquired in the -x direction. For example, each stripe SP can be virtually divided into multiple rectangular regions RA aligned in the direction in which the stripe SP extends, and an inspection image can be generated for each portion of the rectangular region RA from the image acquired for this stripe SP.

[0051] The area targeted for image acquisition is changed by the relative movement of stage 100. That is, if the direction of image acquisition is in the +x direction, stage 100 moves in the -x direction, and if the direction of image acquisition is in the -x direction, stage 100 moves in the +x direction.

[0052] Figure 3 shows the components of the comparison circuit 210 of the pattern inspection device 1 according to the first embodiment. As shown in Figure 3, the comparison circuit 210 includes J comparison subcircuits 2100_0 to 2100_J, where J is an integer between 2 and N.

[0053] The comparison subcircuits 2100 can operate independently of each other and in parallel. Each comparison subcircuit 2100 detects defects by comparing the inspection image with a reference image or a comparison target image. Specifically, the comparison circuit 210 receives inspection image data from the sensor circuit 113. In the case of die-database inspection, the comparison circuit 210 also receives a reference image from the reference image generation circuit 209, which is obtained from design data defining the pattern of the region in the sample 5 from which the inspection image was acquired. In the case of die-die inspection, the comparison circuit 210 receives a comparison target image. The comparison subcircuit 2100 compares the inspection image with the reference image or comparison target image using a certain algorithm. If there is a pixel in the sample 5 where the difference between the grayscale value of the optical image and the grayscale value of the reference image or comparison target image exceeds a preset threshold, the comparison subcircuit 2100 determines that there is a defect at the position (stage position on the x-axis and y-axis) corresponding to this pixel.

[0054] Figure 4 shows the flow of inspection by the pattern inspection device 1 of the first embodiment. The flow in Figure 4 is performed under the control of the control computer 200. As shown in Figure 4, the control computer 200 controls the imaging mechanism 10 to perform calibration (S1). Calibration adjusts the grayscale values ​​of the optical image acquired by the sensor circuit 113.

[0055] The control computer 200 acquires an inspection image of a certain region of the sample 5 to be inspected (S2). The acquired inspection image is transmitted to the comparison circuit 210.

[0056] The reference image generation circuit 209 generates a reference image from the design data 220 (S3). More specifically, the reference image generation circuit 209 reads the design data 220 stored in the memory device 201 and unfolds the read design data 220 into an unfolded image. The reference image generation circuit 209 generates a reference image from the generated unfolded image. Step S3 is performed in the case of die-database inspection, but is skipped in the case of die-die inspection.

[0057] The comparison circuit 210 performs a comparison (S4). Specifically, the comparison circuit 210 first aligns the inspection image with the reference image or the image to be compared, and aligns the pattern in the inspection image with the pattern in the reference image. Next, the comparison circuit 210 compares the inspection image with the reference image or the image to be compared. For example, the comparison circuit 210 calculates the difference in grayscale values ​​for each pixel between the inspection image and the reference image or the image to be compared, and determines that there is a defect in pixels where this difference is greater than or equal to a preset threshold.

[0058] The control computer 200 determines whether the inspection has been completed for all areas to be inspected (S5). If the inspection has not been completed for all areas to be inspected (S5_No), the process proceeds to step S2. Steps S2 to S4 are performed for the areas that have not been inspected.

[0059] If the inspection of all areas to be inspected is complete (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 may display the inspection result on the display device 202, or it may output it to an external device (e.g., a review device) via the communication device 204.

[0060] Multiple sets of steps S2 to S4 for multiple regions may be performed in parallel.

[0061] Figure 5 shows the objects of comparison by the comparison circuit 210 of the pattern inspection device 1 of the first embodiment. As shown in Figure 5, each comparison subcircuit 2100 performs a comparison for one stripe SP. Multiple comparison subcircuits 2100 perform comparisons for their respective stripe SPs in parallel. That is, a certain first comparison subcircuit 2100 receives inspection images of each of the multiple rectangular regions RA of the first stripe SP that the first comparison subcircuit 2100 is comparing, and compares each inspection image with the reference image or comparison target image that corresponds to this inspection image. While the first comparison subcircuit 2100 is comparing the inspection image of the first stripe SP with the corresponding reference image or comparison target image, an inspection image of the rectangular region RA of another second stripe SP is acquired. While the first comparison subcircuit 2100 is comparing the inspection image of the first stripe SP with the corresponding reference image or comparison target image, the second comparison subcircuit 2100 performs a comparison of the inspection image of the second stripe SP with the corresponding reference image or comparison target image. Similarly, multiple comparison subcircuits 2100 perform comparisons on their respective stripe SPs in parallel.

[0062] Each comparison subcircuit 2100 sends a completion signal to the control computer 200 when it has completed comparing the entire stripe SP it is comparing. The completion signal is received by the comparison circuit determination circuit 2002. When the comparison circuit determination circuit 2002 receives a completion signal from a comparison subcircuit 2100, the control computer 200 assigns this comparison subcircuit 2100 to compare another stripe SP. When the comparison for a stripe SP is completed, any comparison subcircuit 2100 that is not assigned to any stripe SP (i.e., available) is assigned to the next stripe SP. The state in which there are no available comparison subcircuits 2100 means that the comparison circuit 210 cannot perform a comparison.

[0063] Figure 5 shows an example of the assignment of the comparison subcircuit 2100 to the stripe SP in the pattern inspection apparatus of the first embodiment. As shown in Figure 5, the comparison subcircuits 2100_0 to 2100_J perform comparisons for stripes SP_0 to SP_J, respectively. Once the comparison for stripe SP_0 is complete, the control computer 200 assigns the comparison subcircuit 2100_0 to the comparison of stripe SP_J+1.

[0064] If, at the time the acquisition of an inspection image for a certain stripe SP is complete, there are no available (empty) comparison subcircuits 2100, a waiting time may occur until an available comparison subcircuit 2100 becomes available. However, by having a sufficient number of comparison subcircuits 2100 in the pattern inspection device 1, it is possible to prevent the occurrence of waiting time. That is, based on the speed of inspection image acquisition (light scanning) and the speed of comparison by each comparison subcircuit 2100, a number of comparison subcircuits 2100 is provided that allows for the existence of an available comparison subcircuit 2100 for the next stripe SP at the time the acquisition of the inspection image for a certain stripe SP is complete. On the other hand, it is impractical to provide a number of comparison subcircuits 2100 that allows for a large margin. Therefore, based on the speed of inspection image acquisition and the speed of comparison by each comparison subcircuit 2100, a number of comparison subcircuits 2100 is provided that allows for the existence of one empty comparison subcircuit 2100 at the time the acquisition of an inspection image for a certain stripe SP is complete.

[0065] The comparison subcircuit 2100 may fail or malfunction. In this case, the faulty or malfunctioning comparison subcircuit 2100 is not used. Instead, another comparison subcircuit 2100 is used. For example, if comparison subcircuit 2100_1 is not operational, comparison subcircuits 2100_2, ... 2100_J are assigned to stripe SP_1, ..., SP_J-1, respectively. Once the comparison for stripe SP_0 is complete, comparison subcircuit 2100_0 is assigned to stripe SP_J.

[0066] If there are non-operating comparison subcircuits 2100, there may be a waiting period until an available (unassigned) comparison subcircuit 2100 becomes available. That is, as described above, a number of comparison subcircuits 2100 are provided that ensure there is at least one available comparison subcircuit 2100 when the acquisition of the inspection image for a certain stripe SP is completed. In other words, if such a number of comparison subcircuits 2100 are operational, as soon as the acquisition of the inspection image for a certain stripe SP is completed, the acquisition of the inspection image for the next stripe SP and subsequent comparison by the available comparison subcircuit 2100 can begin immediately. Therefore, there is no waiting period until an available comparison subcircuit 2100 becomes available. On the other hand, if there are non-operating comparison subcircuits 2100, there are no available comparison subcircuits 2100 when the acquisition of the inspection image for a certain stripe SP is completed. Therefore, the control computer 200 stops acquiring inspection images until an available comparison subcircuit 2100 becomes available.

[0067] Figure 6 shows a portion of the flow during inspection image acquisition by the pattern inspection apparatus 1 of the first embodiment. Specifically, Figure 6 shows the flow from the completion of acquisition of the inspection image of a certain stripe SP until the start of acquisition of the inspection image of the next stripe SP. The flow in Figure 6 starts when the acquisition of the inspection image of a certain stripe SP is completed and there is another stripe SP whose inspection image is scheduled to be acquired. The flow in Figure 6 is brought about, for example, by the control of the control computer 200.

[0068] As shown in Figure 6, when the flow starts, the control computer 200 uses the comparison circuit determination circuit 2002 to determine if there is an available (unassigned) comparison subcircuit 2100 (S11). The presence of an available comparison subcircuit 2100 is equivalent to the comparison circuit 210 being able to perform the comparison. If there is an available comparison subcircuit 2100 (S11_Yes), the control computer 200 starts acquiring the inspection image of the next stripe SP (S19). At the same time, the available comparison subcircuit 2100 is assigned to the comparison of the next stripe SP. When step S19 is completed, the flow in Figure 6 ends.

[0069] If no usable comparison subcircuit 2100 is available (S11_No), the control computer 200 waits for a certain period of time (S12). During step S12, for example, the control computer 200 maintains the stage 100 in the position it was in immediately before step S12. The stage 100 does not have to remain in a fixed position. As soon as the waiting period begins, the control computer 200 starts measuring time using the waiting time measurement circuit 2001 to measure the duration of the waiting period (waiting time).

[0070] The control computer 200, after waiting for a certain period of time as step S12, determines whether the cumulative waiting time since the start of the flow in Figure 6 is equal to or greater than a threshold (S13). The cumulative waiting time depends on the number of times step S12 has been performed. If the cumulative waiting time is not equal to or greater than the threshold (S13_No), the control computer 200 executes step S11, that is, determines whether there is an available comparison subcircuit 2100. In this way, the control computer 200 periodically and repeatedly determines whether there is an available comparison subcircuit 2100 through a loop of the set of steps S11, S12, and S13 until the cumulative waiting time reaches or exceeds the threshold.

[0071] If the cumulative waiting time is greater than or equal to a threshold (S13_Yes), the control computer 200 maintains a state in which light does not continuously shine on the same spot on the sample 5, or takes measures to prevent light from hitting it (S14). A specific example of step S14 will be described later. The state formed by the measures taken in step S14 continues until the subsequent step S18.

[0072] The control computer 200 uses the comparison circuit determination circuit 2002 to determine if there is an available comparison sub-circuit 2100 (S16). If there is no available comparison sub-circuit 2100 (S16_No), the control computer 200 waits for a certain period of time (S17). During step S16, for example, the control computer 200 maintains the stage 100 in its current position without moving it. Step S17 continues to step S16. That is, it is periodically determined whether an available comparison sub-circuit 2100 has become available, and the state formed by the measures taken in step S14 continues until an available comparison sub-circuit 2100 becomes available.

[0073] If a usable comparison subcircuit 2100 exists (S16_Yes), the control computer 200 restores the state immediately before step S14 (S18). That is, the state formed by the action taken in step S14 is terminated. Depending on the type of action taken in step S14, step S18 may not be performed, and if a usable comparison subcircuit 2100 exists (S16_Yes), the control computer 200 performs step S19.

[0074] The control computer 200 begins scanning for the next stripe SP (S19). This completes the flow shown in Figure 6.

[0075] A specific example of step S14 is described with reference to Figures 7 to 9. Figures 7 to 9 show the first, second, and third examples of the operation flow of the first embodiment, respectively.

[0076] As shown in Figure 7, in the first example, in step S14, the control computer 200 instructs the shutter control circuit 207 to close the shutter 103. Based on this instruction, the shutter control circuit 207 controls the shutter drive mechanism 104 to close the shutter 103 (S14_1). The shutter 103 remains closed for the duration until the loop of steps S16 and S17 generates a usable comparison subcircuit 2100. As a result, light does not reach the sample 5 for the duration until the loop of steps S16 and S17 generates a usable comparison subcircuit 2100. In step S18, the control computer 200 instructs the shutter control circuit 207 to open the shutter 103. Based on this instruction, the shutter control circuit 207 controls the shutter drive mechanism 104 to open the shutter 103 (S18_1).

[0077] As shown in Figure 8, in the second example, as step S14, the control computer 200 instructs the stage control circuit 208 to move the stage 100 randomly. Based on this instruction, the stage control circuit 208 controls the stage drive mechanism 102 to move the stage 100 randomly (S14_2). For example, the control computer 200 instructs the stage 100 to move randomly within a region centered on the position of the stage 100 immediately before step S14. Examples of moving the stage 100 randomly include continuously moving the stage 100 randomly and sporadically moving the stage 100 randomly over a fixed or random period of time. The control computer 200 instructs the stage 100 to continue moving or to move sporadically and repeatedly over a period of time until a usable comparison subcircuit 2100 is generated by the loop of steps S16 and S17. This prevents light from reaching the same location on sample 5 during the period until the loop of steps S16 and S17 generates a usable comparison subcircuit 2100. In the second example, step S18 is not performed.

[0078] As shown in Figure 9, in the third example, as step S14, the control computer 200 instructs the stage control circuit 208 to move the stage 100 to a position where the light strikes outside the sample 5. Based on this instruction, the stage control circuit 208 controls the stage drive mechanism 102 to move the stage 100 to a position where the light strikes outside the sample 5 (S14_3). The stage position is maintained for a period of time until a usable comparison subcircuit 2100 is generated by the loop of steps S16 and S17. In the third example, step S18 is not performed.

[0079] According to the first embodiment, damage to the sample 5 is suppressed as described below. As shown above with reference to Figure 5, it may occur that the system waits for a usable comparison subcircuit 2100 to become available. In this case, acquisition of the inspection image of the next stripe SP cannot be started. Therefore, the stage 100 cannot move to a position for acquiring the inspection image of the next stripe SP, and light from the light source 101 continues to shine on the sample 5 until a usable comparison subcircuit 2100 becomes available. This can cause damage to the sample 5. For example, if the position of the stage 100 is simply maintained until a usable comparison subcircuit 2100 becomes available, light may continue to shine on the same spot.

[0080] In the pattern inspection apparatus 1 of the first embodiment, if there are no usable comparison subcircuits 2100 available for a certain period of time after the acquisition of an inspection image of a certain stripe SP is completed, the apparatus maintains a state in which light does not continuously shine on the same position of the sample 5. When a usable comparison subcircuit 2100 becomes available, the control computer 200 releases the state in which light does not continuously shine on the same position of the sample 5 as necessary, and starts acquiring an inspection image of the next stripe SP. Thus, damage to the sample 5 caused by light shining on areas that do not need to be illuminated during the period until a usable comparison subcircuit 2100 becomes available is suppressed or prevented.

[0081] 2. Others Referring to Figure 1, an example is described in which the pattern inspection device 1 acquires an optical image using light transmitted through the sample 5. The pattern inspection device 1 may also acquire an optical image using light reflected by the sample 5. Furthermore, the pattern inspection device 1 may acquire both an optical image using light reflected by the sample 5 and an optical image using light transmitted through the sample 5.

[0082] Furthermore, the above description has shown an example in which the pattern inspection device 1 acquires an optical image of the sample 5. The pattern inspection device 1 may also acquire an inspection image using an electron beam. In this case, an electron gun is included instead of the light source 101.

[0083] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0084] 1…Pattern inspection device, 10…Photography mechanism, 20…Control mechanism, 5…Sample, 100…Stage, 101…Light source, 102…Stage drive mechanism, 103…Shutter, 104…Shutter drive mechanism, 107…Lens, 108…Lens, 112…Photodiode array, 113…Sensor circuit, 114…Laser length measurement system, 115…Auto loader, 120…X-axis motor, 121…Y-axis motor, 200…Control computer (control unit), 201…Storage device, 202…Display device, 203…Input device, 204…Communication device, 205…Auto loader control circuit, 206…Light source control circuit, 207…Shutter control circuit, 208…Stage control circuit, 209…Reference image generation circuit, 210…Comparison circuit, 211…Position circuit,

Claims

1. A stage on which the sample is placed, A light source that irradiates light onto the aforementioned sample, A photographing mechanism that acquires an inspection image of the sample based on the aforementioned light, A stage control circuit controls the position of the aforementioned stage, 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 the pattern of the sample, A control unit maintains a state in which light does not continuously illuminate substantially the same position on the sample from the end of acquiring an inspection image of the first region of the sample on the stage positioned by the stage control circuit until the start of acquiring an inspection image of the second region of the sample, maintains the state in which light does not continuously illuminate the sample while the comparison circuit is in a state where it cannot start the comparison, and releases the state in which light does not continuously illuminate the sample and starts acquiring an inspection image of the second region when the comparison circuit becomes in a state where it can start the comparison, Equipped with, The control unit determines whether there is an available comparison subcircuit based on the completion notification of the comparison subcircuit within the comparison circuit, and when there is no available comparison subcircuit after the acquisition of the inspection image of the first region is completed and the cumulative waiting time exceeds a predetermined threshold, it starts maintaining a state in which the light does not continuously shine on substantially the same position on the sample, and when an available comparison subcircuit becomes available, it releases the state in which the light does not continuously shine and starts acquiring the inspection image of the second region. Pattern inspection device.

2. The control unit starts measuring time when there are no idle comparison subcircuits after the acquisition of the inspection image of the first region is complete, and when the cumulative waiting time exceeds a predetermined threshold as the duration of waiting, it starts maintaining the state in which light does not continuously shine on the area. The pattern inspection apparatus according to claim 1.

3. The system further includes a shutter that can be positioned between the light source and the stage, During periods when the light is not continuously hitting the stage, the control unit controls the shutter to maintain it between the light source and the stage. The pattern inspection apparatus according to claim 1.

4. The stage control circuit moves the stage by continuous or sporadic pseudo-random micro-movements within a predetermined range centered on the position at the end of acquisition of the inspection image of the first region, while the stage is not continuously exposed to light. The pattern inspection apparatus according to claim 1.

5. The stage control circuit maintains the stage in a position where the light continues to shine on the outside of the sample while the light is not continuously shining on it. The pattern inspection apparatus according to claim 1.

6. The first region and the second region are adjacent to each other within the sample region. After the acquisition of the inspection image of the first region is completed, the control unit switches the scanning direction of the stage within a predetermined range centered on the position at the time of completion and starts acquiring the inspection image of the second region. During or immediately after the switching, while the comparison circuit is unable to start the comparison, the light is kept from continuously shining on the same position on the sample. The pattern inspection apparatus according to claim 1.

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