JP2015161578A - Wafer inspection method and charged particle beam device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer inspection method for doing inspection by comparing die images, the method eliminating, for high-accuracy wafer inspection, the effects due to the overlapping of image-capturing regions by taking into account the overlapping of image-capturing regions during the image-capture.SOLUTION: Provided is a wafer inspection method for acquiring a reference image to be compared with from a certain die, comparing the reference image with a plurality of inspection images each acquired from each of a plurality of other dies, and performing inspection, wherein a region group to be image-captured at a time in a die from which the reference image is acquired is determined on the basis of the overlapping of image-capture regions in a plurality of dies when the image-capture regions are placed on top of a prescribed die.

Description

  The present invention relates to a wafer inspection method and a charged particle beam apparatus using a charged particle beam.

  A semiconductor device such as a memory or a microcomputer used in a computer or the like is manufactured by repeating a process of transferring a pattern such as a circuit formed on a photomask by exposure processing, lithography processing, etching processing, or the like. In the manufacturing process of a semiconductor device, the presence or absence of defects such as the quality of lithography processing, etching processing, other processing results, and the generation of foreign matter greatly affects the yield of semiconductor devices. Therefore, in order to improve the yield, pattern inspection on the semiconductor wafer is performed at the end of each manufacturing process, and the occurrence of abnormality or defect is detected early or in advance.

  The inspection apparatus used in the above-described processes is required to perform high-throughput and high-precision inspection following the increase in wafer diameter and circuit pattern miniaturization. Therefore, it is often performed that the entire surface of the wafer is inspected by an inspection device, coordinate data of detected defects is transferred to a review device, and high magnification data is acquired by an electron microscope based on the coordinate data. At that time, for defect detection image processing, a defect image obtained by capturing an image of the defect position and a reference image obtained by imaging the same coordinate position in another die (Die) for comparison are captured for each defect. Then, the detected defect is imaged at a higher magnification. A method of acquiring a reference image from an adjacent die every time a defect image is acquired is often used. However, as described in Patent Document 1, all reference images are acquired in advance from one or more dies. Then, a method of capturing a defect image is also considered. In the latter case, it is possible to shorten the moving distance and time to each imaging location at the time of acquiring a reference image, which is an effective method for high throughput.

JP 2000-30652 A

  On the other hand, the latter method of acquiring all reference images with one or a plurality of dies in advance has another problem. When the imaging locations are close, for example, the range 203 is imaged after imaging the range 202 of the on-wafer pattern 201 in FIG. In this case, the contamination formed when the range 202 is imaged, that is, the mark to which the hydrocarbon or the like formed when the electron beam is irradiated appears as the region 204 when the range 203 is imaged. The degree varies depending on the acceleration voltage and current amount of the electron beam, the cumulative number, the atmosphere in the sample chamber, and the like, but it remains as a trace on the image and affects image processing such as defect detection. For example, there is a problem that detection accuracy is deteriorated such that an image of a portion where contamination is formed becomes black and erroneously detected as a pattern defect or particle (foreign matter).

  The size of the die on the wafer is generally several millimeters to several tens of millimeters, but the number of review points per wafer is several hundreds at most. In general, the probability that an imaging location is close as shown in FIG. 2 is low even when considering observation at an imaging magnification (FOV: Field-Of-View) of several μm to several tens μm. However, systematic defects due to potential causes of the design pattern itself or mask defects often occur at specific locations within the die. When superposed on one die, the situation as shown in FIG. 2 is fully conceivable. Compared with randomly generated defects, capturing the cause of a systematic defect is likely to greatly contribute to improving the yield, and it is important to capture an accurate image.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a high-accuracy wafer inspection method that prevents the influence of overlapping imaging ranges by performing imaging in consideration of overlapping imaging ranges in a wafer inspection method that performs inspection by comparing die images. Is to provide.

  Another object of the present invention is to prevent the influence of overlapping imaging ranges by performing imaging in consideration of overlapping imaging ranges in a charged particle beam apparatus that performs inspection by image comparison of dies. An object of the present invention is to provide a charged particle beam apparatus capable of wafer inspection.

  In order to solve the above-described problem, the present invention acquires a reference image to be compared from a certain die and compares the plurality of inspection images acquired from other dies with the reference image for inspection. A method for inspecting a wafer, wherein an image is obtained at a time in a die for obtaining the reference image based on an overlap of the imaging regions when the imaging regions in the plurality of dies are superimposed on a predetermined die. A region group to be acquired is determined.

  The present invention also provides a charged particle beam apparatus that irradiates a wafer with a charged particle beam, detects secondary electrons or reflected electrons emitted from the wafer, and captures an image of the wafer. And comparing a stage for controlling the irradiation position of the charged particle beam on the wafer, a reference image to be compared obtained from one die, and a plurality of inspection images respectively obtained from other dies. An image processing unit that performs an operation, and the image processing unit acquires the reference image based on an overlap of the imaging regions when the imaging regions in the plurality of dies are superimposed on a predetermined die. And a reference image acquisition region determination unit that determines a region group for acquiring images at a time in the die.

  According to the present invention, in a wafer inspection method in which inspection is performed by die image comparison, imaging is performed in consideration of overlapping imaging ranges, thereby preventing the influence of overlapping imaging ranges, and high-accuracy wafer inspection can be performed. It becomes possible.

  Moreover, in charged particle beam equipment that performs inspection by comparing die images, charged particle beams that enable high-accuracy wafer inspection by preventing the influence of overlapping imaging ranges by performing imaging in consideration of overlapping imaging ranges An apparatus can be realized.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is a figure showing the whole charged particle beam device concerning one embodiment of the present invention. It is a figure explaining duplication of an imaging range. It is a flowchart explaining operation | movement of the charged particle beam apparatus which concerns on one Embodiment of this invention. It is a conceptual diagram of the data conversion which concerns on one Embodiment of this invention. It is a figure explaining the imaging range duplication determination which concerns on one Embodiment of this invention. It is a figure explaining the imaging range duplication determination which concerns on one Embodiment of this invention. It is a figure explaining the imaging range duplication determination which concerns on one Embodiment of this invention. It is a figure explaining the imaging range duplication determination which concerns on one Embodiment of this invention. It is a figure explaining the imaging range duplication determination which concerns on one Embodiment of this invention. It is a figure explaining the imaging range duplication determination which concerns on one Embodiment of this invention. It is a figure explaining expansion imaging range determination concerning one embodiment of the present invention. It is a figure explaining expansion imaging range determination concerning one embodiment of the present invention. It is a figure explaining expansion imaging range determination concerning one embodiment of the present invention. It is a figure explaining expansion imaging range determination concerning one embodiment of the present invention. It is a figure explaining expansion imaging range determination concerning one embodiment of the present invention. It is a figure explaining expansion imaging range determination concerning one embodiment of the present invention. It is a figure explaining expansion imaging range determination concerning one embodiment of the present invention. It is a figure explaining extraction of a reference picture from an enlarged picked-up picture concerning one embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the following description, examples of the present invention will be described using examples of a defect inspection apparatus and a defect inspection method for detecting defects on the surface of a semiconductor wafer, but these are only examples of the present invention, and However, the present invention is not limited to these examples. For example, the defect inspection apparatus referred to here widely refers to a device that acquires an image and determines the presence or absence of a defect from the image. Some charged particle beam devices such as review devices are equipped with defect inspection means such as means for inspecting a predetermined position on a sample for fixed-point observation and process monitoring. Of course, the present invention can also be applied to a line device, and the defect inspection device described below includes these devices. Fixed point observation means to specify a place to be managed in the process, such as a place where defects in the chip are likely to occur, and to take an image of that part. Process monitoring means pattern processing, cleaning, etc. This means that the number of defects on the wafer, its increase / decrease, location, etc. are inspected and managed to determine whether an abnormality has occurred in each semiconductor manufacturing process.

  In this embodiment, an example of a defect inspection apparatus that extracts defect candidates from a comparative image of a portion corresponding to an image to be inspected and displays defect candidates included in a designated area as a defect will be described.

  FIG. 1 shows an overall outline of a defect inspection apparatus, that is, a charged particle beam apparatus in the present embodiment. The defect inspection apparatus in this embodiment includes an electron gun 101 that emits an electron beam 107, a lens 102 that converges the electron beam 107, a deflector 103 that controls deflection of the electron beam 107, an objective lens 104 that converges the electron beam 107, and a sample 105. The sample stage 106, the secondary electron detector 122, the backscattered electron detector 123, and the sample stage 106 that detect secondary electrons 108 and backscattered electrons 109 generated by irradiating the sample 105 with the electron beam 107 are moved. A scanning electron microscope (SEM: Scanning-Electron-Microscope) including a movable stage 124 to be moved. The backscattered electron detector 123 is installed at a position facing each other on a straight line in order to capture a dual shadow image. These are then placed in a column (not shown) and can be maintained in a vacuum by a vacuum pump (not shown).

  The electron beam 107 radiated from the electron gun 101 is converged by the lens 102, scanned and deflected two-dimensionally by the deflector 103, converged by the objective lens 104, and irradiated onto the sample 105. When the sample 105 is irradiated with the electron beam 107, secondary electrons 108 and reflected electrons 109 corresponding to the shape and material of the sample 105 are generated. The secondary electrons 108 and the reflected electrons 109 are detected by the secondary electron detector 122 or the reflected electron detector 123, amplified by an amplifier (not shown), and then an analog / digital (A / D) converter 113. Is converted to a digital value. The signal from the backscattered electron detector 123 is used to form an L image and an R image that are backscattered electron images, and the signal from the secondary electron detector 122 is used to form an S image that is a secondary electron image. . Hereinafter, signals obtained from samples such as secondary electrons and reflected electrons are collectively referred to as secondary charged particles. Unless otherwise specified, image processing may be performed using an L image, an R image, an S image, or a composite image thereof, and these are collectively referred to as an image in the present specification. The data converted into the digital value is stored in the image memory 115. At this time, the address control circuit 114 generates an address synchronized with the scanning signal of the electron beam 107 as the address of the image data stored in the image memory 115. Further, the image memory 115 transfers the stored image data to the image processing unit 119 as needed.

  The image processing unit 119 sends the sent image data to the display unit 117 such as a display via the control unit 118 and performs arithmetic processing based on the image data to perform processing such as defect extraction. The defect extraction (detection) process here is performed by comparing and calculating the sent image data and other image data obtained from the pattern corresponding to the image data. More specifically, the acquired image to be inspected (also referred to as a defect image) is compared with a predetermined image (hereinafter referred to as a reference image), and the difference between the two is determined as a defect. In this specification, the “defect image” is an image (inspected image) to be subjected to defect inspection, and includes not only a true defect image but also a defect candidate image and a pseudo defect image. The “reference image” is an image used for comparison with a defect image for defect extraction, and is an image of a normal region, that is, a region estimated to have no defect. In the following, an example in which a comparison operation is performed between a reference image to be compared acquired from one die and a plurality of inspection images respectively acquired from a plurality of other dies will be described.

  The lens 102, the deflector 103, and the objective lens 104 are controlled by control signals from the lens control circuit 110, the deflection control circuit 111, and the objective lens control circuit 112, respectively, and the focal position and deflection amount of the electron beam 107 are controlled. Thereby, it can adjust so that the electron beam 107 may be irradiated to an appropriate position with respect to the sample 105. The moving stage 124 on which the sample stage 106 is placed can be translated in two dimensions by a control signal from the mechanism control circuit 116. For this reason, the sample 105 held by the sample stage 106 can also be translated in two dimensions, whereby the position at which the electron beam 107 is scanned with respect to the sample 105 can be controlled. The lens control circuit 110, the deflection control circuit 111, the objective lens control circuit 112, and the mechanism control circuit 116 are all controlled by signals from the control unit 118.

  An input unit 120 including a keyboard and a mouse is used for GUI (Graphic-User-Interface) operations displayed on the display unit 117 for device operation and parameter setting, and an external input / output unit 121 is an HDD (Hard- It is used for exchanging electronic files between an external storage device such as a disk-drive (USB) or a universal-serial-bus (USB) memory and this apparatus. It can also be used as an input / output port for communication means such as a computer network line.

  Further, as will be described below, the image processing unit 119 includes an image data reading unit that reads image data, an image cutting unit that cuts out an image, a defect detection unit that performs defect candidate detection and defect determination, and the like. In addition, as described below with a specific example, the image processing unit 119 performs the reference based on the overlap of the imaging regions when the imaging regions in the plurality of dies are superimposed on a predetermined die. A reference image acquisition region determination unit that determines a region group for acquiring images at once in a die for acquiring images. Each of these functional blocks may be configured by combining arithmetic processing circuits that execute processing of each unit (so-called hardware implementation), or a memory that stores a program corresponding to the processing of each unit is provided in the image processing unit 119. Similarly, the processing flow shown in FIG. 3 may be executed by causing the processor provided in the image processing unit 119 to execute the program. Also, some functional blocks can be realized by a dedicated processing circuit, and the remaining functional blocks can be realized by software using a program and a processor.

  FIG. 3 is a flowchart showing the operation of the defect inspection apparatus, that is, the charged particle beam apparatus of the present embodiment. First, a wafer is loaded into the apparatus (step 301), and the wafer is moved to the moving stage 124. Actually, a transfer robot is used to take out and move the wafer from FOUP (Front-Opening-Unified-Pod), but detailed description thereof is omitted in this embodiment. Next, a recipe that determines inspection conditions prepared in advance in an external storage device or the like is read via the GUI, that is, input of recipe (Recipe) data from the input unit 120 or the external input / output unit 121 (step 302). The recipe describes various information necessary for the automatic operation of the inspection, and includes at least an imaging magnification (FOV), a maximum imaging magnification, and a reference image acquisition die number described in the present embodiment.

  Here, the reference image is an image obtained by imaging the same coordinate position in a die of another die (Die) corresponding to a specific location in the die to be inspected in the comparison inspection by image processing. Further, the maximum imaging magnification is a magnification that can be captured as one image so as to include all of the imaging ranges of a plurality of captured images, and an imaging range captured at that magnification is referred to as a maximum imaging range.

  Next, an electronic file in which defect information such as die coordinates and wafer coordinates is described is input in the same manner as the above recipe (step 303). Here, the coordinates in the die (Die) are, for example, position information in the die defined by the positional relationship in the vertical and horizontal directions of the die when viewed in plan, that is, the position in the die as indicated by the X, Y coordinates. Means information. The wafer coordinates mean, for example, a number for each die in the wafer and position information of the die in the wafer, that is, position information in the wafer as indicated by X and Y coordinates.

  Based on the input defect information, a die (Die) for acquiring a reference image is determined (step 304). This is preferably a die that is close to the center of the wafer and does not include any defects, but a die used for reference image acquisition may be registered in advance in the recipe. Next, a list of in-die coordinates of the defect to be inspected is created (step 305). Normally, the coordinates in a die are often described in advance, so it is only necessary to extract the coordinate values. However, in the case of wafer coordinates, the die information of the wafer (number of vertical and horizontal dies, die -Convert the offset value from the center of the matrix to the coordinate value in the die. Since the list created here contains only the coordinates in the die without the die number, it looks as if all defect coordinates are aggregated on one die as shown in FIG. The circles in FIG. 4 represent defect coordinates, and the rectangles represent dies on the wafer.

  Next, in order to group a group of adjacent defect coordinates from the list created in step 305, the following process is performed to group the list. First, an electron beam scanning range (imaging range) is calculated from certain defect coordinates and imaging magnification (FOV) (step 306). For example, as shown in FIG. 5A, when the center coordinate of the defect 501 is (xi, yi) and the scan range 502 is (Xrange, Yrange), the imaging range is (xi−Xrange / 2 <x <xi + Xrange / 2), (Yi-Yrange / 2 <y <yi + Yrange / 2). This is obtained for defect coordinates of all inspection objects. Next, the number of overlapping imaging ranges is measured for each defect (step 307).

  As shown in FIG. 5B, for a certain defect point (xi, yi) in the scan range 316 and (xj, yj) in another scan range close to the scan range 316, | xi−xj | <Xrange, and When | yi−yj | <YRange, two points (xi, yi) (xj, yj) are regarded as overlapping imaging ranges, and each of the overlapping numbers 1 is counted. By obtaining this for all the defect coordinates of the inspection object, it is possible to count the number of overlapping imaging ranges. At this time, the number (ID) of the defect that has been duplicated is also recorded. Based on this overlapping number, the defect coordinates with overlapping imaging ranges are grouped into defect coordinates that do not overlap (step 308). 5C and 5D are schematic diagrams illustrating this content. 0001 to 0007 and squares in FIG. 5C schematically represent defect IDs and imaging ranges thereof, and FIG. 5D is a table showing a plurality of adjacent defect IDs for each defect ID from the state of FIG. 5C.

  By this processing, the group is divided into overlapping groups (0001, 0002, 0005, 0006), (0002, 0001), (0005, 0001), (0006, 0001) and other 0003, 0004, and 0007. As a result of grouping, there is a case where one ID extends over a plurality of groups. These are grouped together for each overlapping group. One group, for example, (0001, 0002, 0005, 0006) is taken out and IDs included in another group to which the ID included in the group belongs are collected. This is repeated until there are no new IDs.

  In the case of (0001, 0002, 0005, 0006), since all IDs included in the groups of 0002, 0005, 0006 are 0001, there is no additional ID. This is equivalent to finding a whole range by tracing a point where a defect coordinate is a point and connecting points where the imaging ranges are overlapped with a side from one point to the outside. FIG. 5E is a schematic diagram for illustrating the relationship between overlapping imaging ranges in FIG. 5C in a graph. A point represents each defect coordinate, and a side (a line connecting the points) represents an overlapping relationship. For example, from FIG. 5E, since 0001 has sides of 0002, 0005, and 0006, it overlaps with these three imaging ranges. Since 0003, 0004, and 0007 are only points, they do not overlap with any other imaging range.

  By these processes, the defect coordinates are divided into a plurality of groups of inspection points having overlapping ranges, and the entire imaging range becomes the maximum and minimum values of the x-coordinate and y-coordinate of the imaging range of each group. FIG. 5F shows a schematic diagram of the entire imaging range for one group consisting of 0001, 0002, 0005, and 0006 in FIG. 5C.

  Next, the process proceeds to step 309 and step 310, and for each group, the imaging range in the group is scanned based on the maximum imaging range specified by the recipe, and the imaging range dividing method is determined. FIG. 6A schematically shows a defect position 601 and its imaging range 602, as in FIG. 5A. A thick frame 603 in FIG. 6C indicates the maximum imaging range. When the imaging range 604 of all the defects in the group is included in the maximum imaging range as illustrated in FIG. 6B, the ranges are collectively captured as one image as illustrated in FIG. 6C. The imaging range of one group can be determined from the maximum and minimum values of the imaging ranges x and y of individual defects in the group. When the imaging range in the group cannot enclose all within one imaging range, that is, as shown in FIG. 6D or FIG. 6E, as shown in FIG. 6F, images are divided into a plurality of maximum imaging ranges.

  Note that the maximum imaging range can be made variable by adjusting the scanning range of the electron beam. Thus, as shown in FIG. 6G, for example, when the entire range of the group is smaller than the maximum imaging range, the imaging range is changed. The image can be narrowed. This is performed for all groups to determine the imaging range. In addition, about the defect coordinate which does not overlap an imaging range, it images individually in the imaging range defined in the recipe centering on the defect coordinate.

  Next, proceeding to step 311, each group is imaged for the designated reference die within the imaging range designated at step 309 and step 310. The image captured at this time is stored in an external storage device via the image memory in the image processing unit 119 and the external input / output unit 121, and is used when generating a reference image in the next step 312.

  After all the images have been acquired or during the processing of step 311, that is, during image acquisition, a reference image is generated from the acquired images (step 312). As shown in FIG. 7, this is a process of cutting out an imaging range centered on each defect coordinate specified in the recipe and generating a reference image for defect detection. Specifically, a certain defect 701 included in an image of a certain group (701 is a diagram for explaining the defect center and is not included in the captured image) and its center coordinates (xi, yi) are ( Images of xi-Xrange / 2 <x <xi + Xrange / 2) and (yi-Yrange / 2 <y <yi + Yrange / 2) are extracted and set as a reference image 702 in the defect. Xrange and Yrange are the lengths of the imaging range in the X and Y directions, respectively. In step 310, when the images in the group are divided into a plurality of images, the reference image is divided for the defect near the boundary. In this case, the image is extracted from each region and the coordinate value is extracted. Synthesize based on

  Next, in step 313, the defect coordinates to be inspected are moved, and an image at that position (defect image 703 is acquired. This process may be performed in parallel with the reference image generation in step 312. In order to prevent useless stagnation in order to detect a defect immediately after capturing a defect image in step 314 and capture a defect image by changing the imaging magnification (FOV), the reference image generation in step 312 is performed in the order of defect coordinate movement. After acquiring the defect image, the defect position is extracted by comparing with the reference image corresponding to the defect coordinates acquired in advance, and the imaging magnification (FOV) is changed based on the recipe and detected. An image (704 in FIG. 7) with an increased magnification is imaged with respect to the image centered on the defect (step 315) When a plurality of defects are detected, an image may be captured for the plurality of defects. You This is performed for defect coordinates of all inspection targets, and defect detection is performed with defect detection and imaging with a changed imaging magnification (FOV).

  After the imaging is completed, the wafer is unloaded (step 316), returned from the moving stage 124 to the FOUP, and the inspection is completed.

  In this embodiment, when the image is divided into a plurality of imaging ranges in the group, the reference image of the defect coordinates at the boundary is generated and synthesized. However, another die is designated and re-acquired at that location. May be. In addition, when the reference image of the defect included in the die specified for reference image acquisition cannot be acquired, for example, when there is a defect in all the dies, this can also be changed by changing the die as described above. Take an image.

  At this time, it is desirable from the viewpoint of throughput to be adjacent to the reference image acquisition die as much as possible. In addition, the reference image can use a range larger than the range specified in the recipe. Of course, the enlarged imaging range, that is, the maximum imaging range as shown in FIG. 6F and FIG. 6G is limited to a range that does not exceed the imaging range. Can be widened, and the range of defect detection can be expanded. However, since it takes time to calculate as the image becomes larger, it is necessary to select it in consideration of the calculation ability.

  As described above, according to the present embodiment, in the inspection method for inspecting a wafer by die comparison, when inspection is performed by superimposing captured images of a plurality of dies, contamination, that is, electron beam irradiation is performed. This makes it possible to suppress the influence of the mark to which the hydrocarbon or the like formed on the wafer adheres, and to perform highly accurate wafer inspection. Also, in an inspection apparatus that inspects a wafer by die comparison, when performing inspection by superimposing captured images of a plurality of dies, contamination, that is, traces of adhering hydrocarbons or the like that are formed when an electron beam is irradiated Therefore, it is possible to realize a charged particle beam apparatus capable of high-precision wafer inspection such as a pattern inspection apparatus and a defect inspection apparatus.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  DESCRIPTION OF SYMBOLS 101 ... Electron gun, 102 ... Lens, 103 ... Deflector, 104 ... Objective lens, 105 ... Sample, 106 ... Sample stand, 107 ... Electron beam, 108 ... Secondary electron, 109 ... Reflected electron, 110 ... Lens control circuit, DESCRIPTION OF SYMBOLS 111 ... Deflection control circuit, 112 ... Objective lens control circuit, 113 ... Analog / digital converter, 114 ... Address control circuit, 115 ... Image memory, 116: Mechanism control circuit, 117 ... Display part, 118 ... Control part, 119 ... Image processing unit, 120 ... input unit, 121 ... external input / output unit, 122 ... secondary electron detector, 123 ... backscattered electron detector, 124 ... moving stage.

Claims (14)

A wafer inspection method for obtaining a reference image to be compared from a certain die and comparing the plurality of inspection images obtained from other dies with the reference image for inspection.
A region group for acquiring images at a time in the die for acquiring the reference image is determined based on an overlap of the imaging regions when the imaging regions in the plurality of dies are superimposed on a predetermined die. Wafer inspection method.   When each imaging area in the plurality of dies is superimposed on a predetermined die, the overlapping of each imaging area is obtained, and when each imaging area overlaps, at least two imaging areas are included. 2. The wafer inspection method according to claim 1, wherein an imaging region of the reference image is set.   The inspection coordinates that specify the position in the inspection image are converted into in-die coordinates that specify the position in the die of the die from which the reference image is acquired, and each imaging area in the plurality of dies is determined by the in-die coordinates. The wafer inspection method according to claim 1, wherein an overlap of each imaging region is obtained when the is superimposed on a predetermined die.   The reference image of a region having the same size as the inspection image is cut out from the image of the region acquired at one time, and the extracted reference image is compared with the inspection image. Wafer inspection method.   5. The wafer inspection method according to claim 4, wherein the reference image is cut out in the same order as the order in which the inspection images are acquired.   2. A maximum imaging range is set in advance in a recipe that defines inspection conditions for an area to be inspected, and is acquired and determined at a time within a die for acquiring the reference image within a limit not exceeding the maximum imaging range. The wafer inspection method described in 1.   In the case where there are a plurality of area groups to be acquired at one time, and one imaging area straddles the plurality of area groups, a part of the image of the one imaging area is cut out from each area group. The wafer inspection method according to claim 1, wherein a reference image corresponding to the one imaging region is generated by combining. A charged particle beam apparatus that irradiates a wafer with a charged particle beam, detects secondary electrons or reflected electrons emitted from the wafer, and captures an image of the wafer,
A stage for placing the wafer and controlling an irradiation position of the charged particle beam on the wafer;
An image processing unit that performs a comparison operation between a reference image to be compared acquired from a certain die and a plurality of inspection images respectively acquired from a plurality of other dies;
The image processing unit
Reference image acquisition for determining an area group for acquiring images at once in the die for acquiring the reference image based on the overlap of the imaging regions when the imaging regions in the plurality of dies are superimposed on a predetermined die A charged particle beam apparatus comprising an area determining unit.   The reference image acquisition area determination unit obtains an overlap of the imaging areas when the imaging areas in the plurality of dies are superimposed on a predetermined die, and if the imaging areas overlap, at least 2 The charged particle beam apparatus according to claim 8, wherein an imaging region of the reference image is set so as to include two or more imaging regions.   The reference image acquisition region determination unit converts the inspection coordinates that specify the position in the inspection image into the in-die coordinates that specify the position in the die of the die that acquires the reference image. The charged particle beam apparatus according to claim 8, wherein an overlap of each imaging region is obtained when each imaging region is superimposed on a predetermined die in the plurality of dies.   The reference image acquisition region determination unit cuts out a reference image of a region having the same size as the inspection image from the region image acquired at one time, and compares the extracted reference image with the inspection image. 9. The charged particle beam apparatus according to claim 8, wherein   12. The charged particle beam apparatus according to claim 11, wherein the reference image is cut out in the same order as the order in which the inspection images are acquired.   The reference image acquisition area determination unit sets a maximum imaging range in advance in a recipe that defines inspection conditions for an area to be inspected, and is determined to be acquired at a time within a die that acquires the reference image within a limit not exceeding the maximum imaging range. The charged particle beam apparatus according to claim 8, wherein   In the case where there are a plurality of area groups to be acquired at one time, and one imaging area straddles the plurality of area groups, the reference image acquisition area determination unit determines whether the one imaging area from each area group The charged particle beam device according to claim 8, wherein a reference image corresponding to the one imaging region is generated by cutting out and synthesizing a part of each of the images.

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