JP2011129458A - Scanning electron microscope, and imaging method of scanning electron microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten operating time with high operating efficiency by enabling to precisely and automatically image a preset area in a specified condition. <P>SOLUTION: The scanning electron microscope 10 is provided with a driving control portion 50 for driving an electron-optical system 30 and a sample stage 40 and an automatic imaging device 60. The automatic imaging device 60 is provided with an image specifying module 61 carrying out specifying of one or a plurality of imaging areas inside a current visual field picture area and setting of imaging conditions of a specified area, a storage module 62 storing position information, imaging conditions and visual field pictures of the imaging area specified, a superposing display 63 for displaying pictures displaying the current imaging area and pictures displaying imaging conditions superposed on the current visual field pictures, and a position adjustment module 64 for comparing the current imaging picture imaged on the basis of the position information inputted with the current visual field picture stored and for outputting a corrected imaging position from a volume of positional shift of the both pictures, and obtains a final imaging picture at the corrected imaging position found by the position adjustment module on the basis of the imaging conditions stored. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a scanning electron microscope and an imaging method of the scanning electron microscope, and more particularly to an imaging of a scanning electron microscope and a scanning electron microscope capable of accurately and easily imaging a plurality of designated areas under designated conditions. Regarding the method.

  A scanning electron microscope generates an electron beam from an electron gun by irradiating the sample by two-dimensional scanning with the scanning means while converging the electron beam from the electron gun onto the sample by a focusing means such as an objective lens. The detected secondary electrons and the like are detected by a detector, and the detection signal is supplied to display means synchronized with the scanning of the electron beam to obtain a scanned image of the sample.

  When observing an image of a sample using such a scanning electron microscope, the sample stage on which the sample is placed is mechanically moved in the XY direction or rotated around a predetermined axis to An image of a desired area is observed. Moreover, the movement and rotation of the observation range of the sample are not only mechanical, but also an image shift function for controlling the deflection range of the electron beam and a scan rotation for electrically rotating the direction of the two-dimensional scanning of the electron beam. Also by function. Furthermore, when imaging each area, the voltage conditions of the convergence means and the scanning means are individually specified so that the imaging conditions can be specified in detail.

  When using a scanning electron microscope to image a plurality of regions of the same material under a predetermined condition, the image information includes information such as the coordinate information of the imaging region and the voltage conditions at which the image was captured. Sometimes stored with relevance.

  In Patent Document 1, in the visual field search mode, a plurality of video signals of different visual fields on the sample are stored together with position information of the respective samples, and a plurality of sample images are simultaneously displayed based on the stored video signals of the plurality of visual fields. When a sample image is selected from a plurality of displayed sample images, the sample is automatically moved to the sample position corresponding to the selected sample image.

  In Patent Document 2, a plurality of microscopic images with different observation positions and observation conditions are displayed in one display device, and the microscopic image display device is provided with a plurality of microscopic images in order to enable appropriate selection and observation. And a display means for displaying the microscopic images stored in the plurality of frame memories simultaneously or in a switched manner.

  Further, in Patent Document 3, at least the spot size of the electron beam on the sample, the acceleration voltage, the type of detector, the position of the sample, and the observation magnification are set as image observation conditions, and an observation image is captured. A plurality of different image observation conditions are automatically set, a plurality of observation images are picked up based on the set image observation conditions, and the plurality of observation images picked up by the observation image acquisition means are displayed on the second display unit. An electron microscope is described in which a desired observation image is selected from a plurality of observation images displayed at the same time and displayed on the second display unit, and the selected observation image is enlarged and displayed on the first display unit.

Japanese Patent Laid-Open No. 2000-357481 JP-A-5-258705 Japanese Patent No. 4014917

  By the way, in the conventional scanning electron microscope, when imaging a plurality of areas of the same sample, the position setting of the imaging area and the subsequent positioning operation are performed manually by the operator. There is a problem that work efficiency is poor and it takes time and effort. Such a problem becomes more prominent when imaging is performed by changing the tilt angle because an image obtained by the tilt is deformed. Also, when multiple images are taken, they are not associated with multiple image files that have been acquired and stored, and when shooting multiple different areas, the same place was taken at different magnifications. In this case, when images are taken at different inclination angles, the user has to observe a plurality of images and visually determine the location, magnification, inclination angle, etc., and the determination takes time or is inaccurate. There is a problem that.

  Accordingly, the present invention can accurately and automatically image a set area under a specified condition when imaging a plurality of areas of the same material under a specified condition, and can reduce work time with high work efficiency. An object of the present invention is to provide a scanning electron microscope and an imaging method of the scanning electron microscope that can easily and accurately determine an imaging location and imaging conditions.

  According to a first aspect of the present invention, there is provided a scanning electron microscope that scans an electron beam with an electron optical system to obtain a sample image of a sample placed on a sample stage. An area is designated as an imaging area, its position is designated, and an imaging setting means for setting an imaging condition for each designated imaging area, position information for the designated imaging area, imaging conditions for each imaging area, and the current A storage means for storing a field-of-view image; an image for displaying a position of the designated imaging area when an imaging area and imaging conditions are set by the imaging setting means; and an image for displaying an imaging condition of each imaging area A superimposed display means for displaying the image on the field-of-view image, and a current captured image captured based on the designated position are compared with the stored current field-of-view image to obtain a positional deviation amount between both images. A position correcting unit that outputs a corrected imaging position that designates a new imaging region based on the amount of positional deviation, and an imaging control unit that captures an image with the stored imaging condition at the corrected imaging position to obtain a corrected captured image. And a scanning electron microscope.

  According to a second aspect of the present invention, in the scanning electron microscope according to the first aspect, the position correcting means compares the corrected captured image acquired based on the current captured image with the current visual field image as the current captured image, This process is repeated until the amount of image displacement becomes a predetermined value or less.

  According to a third aspect of the present invention, in the scanning electron microscope according to the first or second aspect, the position correcting means compares the current captured image with the current visual field image, and calculates a magnification of the current captured image. It is characterized by being changed.

  According to a fourth aspect of the present invention, in the scanning electron microscope according to any one of the first to third aspects, the imaging condition includes an inclination angle of the electron beam with respect to the sample at the time of imaging, and the position correcting means is The current captured image at each tilt until reaching the specified tilt angle is compared with the previous captured image, and the corrected captured position at the tilt angle at the next imaging is output. It is characterized in that imaging is performed by tilting the electron beam tilt angle by a predetermined number of times by a predetermined number of times until the specified tilt angle is reached.

  According to a fifth aspect of the present invention, in the scanning electron microscope according to any one of the first to fourth aspects, the superimposed display means is unable to capture an image of a designated area and performs imaging in the vicinity of the area. In this case, it is characterized in that information about a region actually captured is displayed.

  The invention according to claim 6 is the scanning electron microscope according to any one of claims 1 to 5, wherein the current field image and the finally obtained captured image of each acquired area are stored. A storage unit, generating a region image indicating which region in the visual field image the imaging region of the finally obtained captured image corresponds to, and an imaging condition image that displays the imaging condition; Imaging condition display means for displaying the region image and the imaging condition image in a superimposed manner.

  The invention according to claim 7 is an imaging method of a scanning electron microscope that scans an electron beam with an electron optical system to obtain a sample image of a sample placed on a sample stage, and displays 1 in a region of a displayed current visual field image. Or specifying a position of a plurality of areas as imaging areas, setting imaging conditions of each of the designated imaging areas, position information of the designated imaging areas, imaging conditions of the imaging areas, and the A step of storing a current field-of-view image; an image displaying a position of the designated imaging region when setting an imaging region and imaging conditions by the imaging setting unit; and an image displaying an imaging condition of each imaging region A step of superimposing and displaying on the field-of-view image, and comparing the currently captured image captured based on the designated position with the stored current field-of-view image to determine the amount of positional deviation between both images. Therefore, the method includes a step of outputting a corrected imaging position that designates a new imaging region based on the amount of positional deviation, and a step of capturing a captured image at the corrected imaging position under the stored imaging conditions. This is an imaging method for a scanning electron microscope.

  According to the present invention, since a plurality of regions designated by a user in a field-of-view image are automatically imaged under a predetermined imaging condition, work time can be shortened with high work efficiency. In addition, since the display can easily understand the relationship between the images, the imaging location and the imaging conditions can be determined easily and accurately.

It is a schematic diagram which shows the basic structure of a scanning electron microscope. It is a block diagram which shows the structure of the control system of the scanning electron microscope which concerns on an Example. It is a flowchart which shows operation | movement of the scanning electron microscope which concerns on an Example. It is a schematic diagram which shows a present visual field image. It is a schematic diagram which shows the designation | designated state of the imaging area in a current visual field image. It is a schematic diagram which shows the imaged visual field image. It is a schematic diagram which shows the captured image of the designated area | region (PointA). It is a schematic diagram which shows the captured image of the designated area | region (PointB). It is a flowchart which shows the position alignment procedure of imaging. It is a schematic diagram which shows the state of the alignment of imaging. It is a flowchart which shows the procedure of the modification of the position alignment of imaging. It is a flowchart which shows the procedure of the inclination angle adjustment of imaging. It is a schematic diagram which shows the procedure of the inclination angle adjustment of imaging.

  The present invention relates to a scanning electron microscope that scans an electron beam with an electron optical system and obtains a sample image of a sample placed on a sample stage, and displays one or more regions in a region of a displayed current field image. An imaging setting means for specifying the position as the imaging area and setting the imaging condition of each designated imaging area, position information of the designated imaging area, imaging conditions of each imaging area, and the current visual field image A storage means for storing the image, and an image for displaying the position of the designated imaging area and an image for displaying the imaging condition of each imaging area when the imaging area and imaging conditions are set by the imaging setting means. The superimposed display means for displaying the image on the upper side, and the current captured image captured based on the designated position is compared with the stored current visual field image to obtain a positional deviation amount between the two images. A position correcting unit that outputs a corrected imaging position that designates a new imaging region based on a shift amount; and an imaging control unit that captures an image with the stored imaging condition at the corrected imaging position and acquires a corrected captured image. Is. According to the scanning electron microscope according to the present example, it is possible to automatically capture a plurality of regions designated by the user in the field-of-view image under predetermined imaging conditions, and to shorten the work time with high work efficiency.

  Further, the position correcting means of the scanning electron microscope according to the present invention compares a corrected captured image acquired based on the current captured image as the current captured image with the current visual field image, and a deviation amount between both images is equal to or less than a predetermined value. This process is repeated until. According to the scanning electron microscope according to the present example, the correction of the imaging position is repeated based on the new corrected imaging position until the deviation amount becomes a predetermined value or less. Can be acquired.

  The position correcting means of the scanning electron microscope according to the present invention compares the current captured image with the current visual field image by changing the magnification of the current captured image. According to the scanning electron microscope according to the present example, pattern matching is performed with an intermediate image having an intermediate magnification between the imaging magnification and the field-of-view image magnification, so that the alignment accuracy can be increased.

  In addition, the imaging condition according to the present invention includes an inclination angle of the electron beam with respect to the sample at the time of imaging, and the position correcting unit displays a current captured image at each inclination until the designated inclination angle is reached. Compared with the previous captured image, the corrected imaging position at the inclination angle at the next imaging is output, and the drive control means sets the electron beam inclination angle to a predetermined number until the specified inclination angle is reached. Imaging is performed by tilting the divided angles over the predetermined number of times. According to the scanning electron microscope according to this example, the imaging position is corrected for a while in consideration of the deformation of the image due to the angle tilt, so that it is possible to prevent the shift of the imaging position due to the tilt angle setting.

  In addition, the superimposed display means of the scanning electron microscope according to the present invention displays information about the actually imaged area when the specified area cannot be imaged and is imaged in the vicinity of the area. is there. According to the scanning electron microscope according to the present example, a region actually captured can be displayed in the current visual field image.

  Further, the present invention relates to an image storage means for storing the current visual field image and the finally acquired captured image of each acquired area, and the imaging region of the finally acquired captured image is the visual field image. Imaging condition display means for generating an imaging condition image for displaying an area image corresponding to which area in the imaging area and the imaging condition, and displaying the area image and the imaging condition image on the current visual field image. It is to be prepared. According to the scanning electron microscope of the present example, the region image corresponding to the region in the field-of-view image corresponding to the imaging region in which the captured image is captured and the imaging condition are displayed in the displayed image. The operator can grasp at a glance the relevance between each captured image and the field-of-view image in the displayed image.

  And this invention relates to the imaging method of the scanning electron microscope which scans an electron beam with an electron optical system, and acquires the sample image of the sample arrange | positioned on the sample stand, and 1 or in the area | region of the displayed current visual field image Designating positions of a plurality of areas as imaging areas, setting imaging conditions for the designated imaging areas, position information of the designated imaging areas, imaging conditions for the imaging areas, and the current A step of storing a field-of-view image, and an image for displaying a position of the designated imaging region and an image for displaying the imaging condition of each imaging region when the imaging region and the imaging condition are set by the imaging setting unit. A step of superimposing the image on the image, and comparing the currently captured image captured based on the designated position with the stored current field-of-view image to obtain a positional deviation amount between the images. A step of outputting a corrected imaging position for designating a new imaging region based on the amount of positional deviation; and a step of acquiring a corrected captured image by imaging at the corrected imaging position under the stored imaging conditions. is there. According to the imaging method of the scanning electron microscope according to the present example, it is possible to automatically capture a plurality of regions designated by the user in the field-of-view image under predetermined imaging conditions, and to shorten the work time with high work efficiency. .

  Hereinafter, a scanning electron microscope according to an embodiment will be described with reference to the drawings. First, the basic configuration of the scanning electron microscope 10 will be described. FIG. 1 is a schematic diagram showing the basic structure of a scanning electron microscope. In the scanning electron microscope 10 according to the embodiment, the electron beam 13 generated from the electron beam source 12 in the upper part of the lens barrel 11 is converged by the condenser lens 14, deflected by the deflection coil 15, converged by the objective lens 16, and By adjusting the focus and scanning the sample chamber 17 in the sample chamber 17, the charged particles 19 such as secondary electrons and reflected electrons generated from the sample chamber 17 are detected by the detector 20, and the display unit 52 (FIG. 2) display the sample image.

  In this embodiment, in order to control the scanning electron microscope 10, the following control system is provided in this embodiment. FIG. 2 is a block diagram illustrating a configuration of a control system of the scanning electron microscope according to the embodiment. The electron beam system 30 including the electron beam 13, the condenser lens 14, the deflection coil 15, and the objective lens 16 and the sample stage 40 on which the sample 18 is placed are driven and controlled by a drive control unit 50. Here, the sample stage 40 can be moved and tilted in the X and Y directions, and the scanning electron microscope 10 can be imaged by a normal operation by the drive control unit 50. The drive control unit 50 is provided with an input unit 51 such as a keyboard for inputting imaging conditions and imaging positions, a touch panel, and a display unit 52 such as a CRT or LCD for displaying captured images.

  In this example, an automatic imaging device 60 is connected to the drive control unit 50, and automatic imaging of a plurality of areas designated by controlling the drive control unit 50 is performed. The automatic imaging device 60 includes an imaging designation unit 61, a storage unit 62, a superimposed display unit 63, a position correction unit 64, an image storage unit 65, an imaging information image generation unit 66, and an imaging control unit 67, an input unit 68, a display The unit 69 is connected.

  The imaging designation means 61 designates one or a plurality of imaging areas in the area of the currently displayed visual field image area and sets the imaging conditions for the designated area. The setting is performed from the input unit 68 while the operator observes the current visual field image displayed on the display unit 69. The storage unit 62 stores position information of the designated imaging region, imaging conditions, and the current visual field image. The superimposing display unit 63 displays the image for displaying the imaging region and the image for displaying the imaging condition on the current view image and displays them on the display unit 69. The position correcting unit 64 compares the current image captured based on the input position information with the stored current visual field image, and outputs a corrected imaging position from the amount of positional deviation between both images. The imaging control unit 67 drives the sample stage 40 and the electron optical system 30 based on the stored imaging conditions at the corrected imaging position obtained by the position correcting unit 64 to acquire a final captured image.

  In addition, the position correcting unit 64 compares the image captured at the corrected imaging position output based on the current captured image again with the current visual field image as the current captured image, and the positional deviation amount of both images is equal to or greater than a predetermined value. A new corrected imaging position is output. Further, the position correcting means 64 compares the current captured image with the reference image by changing the magnification of the current image.

  Further, in the scanning electron microscope 10 according to this example, the imaging condition includes an inclination angle of the electron beam with respect to the sample at the time of imaging, and the position correcting unit is configured to perform each inclination until the specified inclination angle is reached. The current image at the time is compared with the current visual field image, and the corrected imaging position at the inclination angle at the time of the next imaging is output, and the drive control means has the electron beam inclination angle until the specified inclination angle is reached. Is imaged by tilting the image by a predetermined number of angles divided by a predetermined number of times, and imaging at the specified angle is performed.

  The superimposing display means 63 displays information about the actually imaged area when the specified area cannot be imaged and is imaged in the vicinity of the area. Further, the image storage means 65 stores the current visual field image and the captured image finally obtained for each acquired area.

  In addition, the imaging information image generation unit 66 generates an imaging condition image that displays an area image indicating which area the imaging area in which the captured image is captured corresponds to in the current visual field image and the imaging conditions, The region image and the imaging condition image are superimposed on the current view image and displayed on the display unit 69.

  The automatic image pickup device 60 including these means can be configured by a computer having a CPU, HDD, RAM, ROM, and various IO interfaces, and the software stored in the HDD and ROM is a CPU using the RAM as a work area. The functions of the respective means are realized by executing the above. The storage means and the image storage means are realized by the HDD and RAM.

  Next, the operation of the scanning electron microscope 10 according to the present embodiment will be described. The scanning electron microscope 10 according to this example automatically adjusts the range, magnification, scan rotation, and tilt angle specified by the operator from the display unit 69 with the automatic imaging device 60 in the field of view currently displayed on the input unit 68. Then image.

  First, the entire process will be described. FIG. 3 is a flowchart illustrating the operation of the scanning electron microscope according to the embodiment, FIG. 4 is a schematic diagram illustrating a current visual field image, and FIG. 5 is a schematic diagram illustrating a designated state of an imaging region in the current visual field image. First, by the operator's operation, the sample stage is driven to move the sample 18 and move to the imaging location (step SA1). In this scanning, the operator moves the sample 18 to the imaging region by driving the sample stage, and is the same as the operation performed conventionally.

  Thereby, for example, as shown in FIG. 4, an image in which the patterns 120 and 130 are arranged on the substrate 110 is displayed on the display unit 69 as the current visual field image. The operator designates a plurality (for example, n) of imaging regions from the input unit 68 while observing the current visual field image displayed on the display unit 69, and sets the imaging conditions of each region (step SA2). Examples of the imaging conditions include the cumulative number, scan speed, imaging range (magnification), scan rotation, and tilt angle.

  The storage means 62 stores position information (coordinates) for specifying the position of the area to be imaged, and the automatic imaging process is executed thereafter (step SA3). For example, if it is specified that the pattern 120 of the substrate 110 is to be imaged at an inclination angle of 0 ° and the pattern 130 is at an inclination angle, as shown in FIG. A frame 121 is displayed as a graphic, and a pattern 132 is displayed on the pattern 130 to indicate that the image is captured with the frame 131 and an inclination angle. At this time, the character string “Point A” can be set in the image capturing area of the pattern 120 and the character string “Point B” can be set in the image capturing area of the pattern 130, and the character strings 122 and 133 are also displayed on the display unit 52. The An arbitrary name can be set for the imaging region name, and this character string is also stored in the storage means 62.

  In the automatic imaging process, first, the current visual field is imaged and stored in the storage unit 62 as a current visual field image. This current visual field image is used as a reference image for position correction. Next, the sample stage 40 and the electron optical system 30 are driven, the scanning area of the electron beam is moved to the first designated area (step SA5), image adjustment is performed according to designated imaging conditions, and alignment is executed. (Step SA6). Then, the position correction means 64 determines whether the image adjustment and position of the acquired image are appropriate (step SA7), and if this is appropriate, the area is imaged as a success (step SA8). On the other hand, if this is inappropriate, predetermined error processing is performed as a failure (step SA10).

  The processing from step SA5 to step SA8 is performed for all the designated areas, and the automatic imaging ends. By this automatic photographing process, the image storage means 65 stores the current visual field image and each captured image. In this example, an image showing the current visual field image and images of two imaging areas are stored. This image is displayed on the display unit 69 by designation from the input unit 68.

  FIG. 6 is a schematic diagram showing a captured field-of-view image, FIG. 7 is a schematic diagram showing a captured image of a specified area (Point A), and FIG. 8 is a schematic diagram showing a captured image of a specified area (Point B). . As shown in FIG. 6, pattern images 220 and 230 are displayed on the substrate image 210, and the frame image 221 and the characters “Point A” are displayed on the substrate image 210 as a graphic indicating the imaging region. The column 222 is superimposed on the pattern image 230, and a frame 231 and a graphic 232 indicating that the image is captured with an inclination angle and a character string 233 “Point B” are displayed as a graphic indicating the imaging region. The frame, the figure, and the character string are displayed on a layer that is generated by the imaging information image generation unit 66 based on the input position information and imaging conditions and is superimposed on the layer on which the substrate image 210 of the current visual field image is displayed. Is done. Note that by selecting the layer to be displayed, it is possible to display only the substrate image 210 and the like without displaying graphics such as a frame.

  In addition, in the image of “Point A” in the image of the designated area, a frame 242 and a character string 243 are displayed on the enlarged image 240 including the pattern image 241 as shown in FIG. Similarly, in the “Point B” image, a frame 252 and a character string 253 are displayed on the enlarged image 250 including the pattern image 251 as illustrated in FIG. 8. Since the enlarged image 250 is captured at an inclination angle, the projection of the pattern image 251 is emphasized more than the pattern image 230 of the current visual field image. Further, it can be shown that the inclination angle is set with the color of the frame 252 being different from the color of the “Point A” frame 242. Also in each of these enlarged images, the frame, the figure, and the character string are superimposed on the layer on which the enlarged image is displayed by the imaging information image generating unit 66 based on the input position information and imaging conditions. It is possible to display only a magnified image without displaying a figure or the like.

  Next, the automatic imaging process will be described in detail. First, a case where no tilt angle is provided, that is, the same tilt angle as that of the current visual field image will be described. As described above, when the imaging location is designated based on the current visual field image and moved to the designated location, a deviation may occur between the designated position and the actual movement position due to the accuracy of visual field movement. Therefore, in this example, the image of the specified magnification acquired in the specified area is changed to the magnification corresponding to the selection range, the image is reduced by the ratio of the magnification before and after the change, and pattern matching is performed to align the selection range. And take an image.

FIG. 9 is a flowchart showing an imaging alignment procedure, and FIG. 10 is a schematic diagram showing an imaging alignment state. First, the operator designates an imaging region and an imaging magnification from the input unit 68 while observing the current visual field image displayed on the display unit 69 (step SB1). In this example, it is assumed that the current visual field image is captured at X1 magnification, and “Point A” is captured at X2 magnification. By this operation, as shown in FIG. 10A, the “Point A” area is designated from the current visual field image. Next, based on this designation, the sample stage is driven to take an image (step SB2). Thereby, the image shown in FIG. 10B is obtained. This image may deviate from the designated region due to the relationship such as the accuracy of movement of the sample stage (FIG. 10B). For this reason, the magnification of the captured image is changed and compared with the reference image. First, the acquired image is reduced to match the magnification of the reference image. In this example, the acquired image is changed to the magnification (X1 / X2) (step SB3). Here, the magnification is changed by a well-known method, but it is preferable to change the magnification based on the following equation. Here, M is a matrix, I 'when calculating the = MI and (multiplying M to I), the image I is m _x times in the transverse direction, the longitudinal direction is m _y times, the image I' is obtained . This calculation is numerically executed by a computer constituting the automatic imaging device 60.

  Next, template matching is performed to compare the acquired image for which the magnification has been changed with the reference image (step SB4). Template matching is performed by comparing the image with the changed magnification (FIG. 10D) with a reference image (FIG. 10C) in the vicinity of the imaging region of the current visual field image. Template matching is performed, for example, by evaluating the degree of similarity using a normalized correlation expressed by the following equation and regarding a position with a high degree of similarity as the same point. For example, in an image of image size NxM, when f [x, y] is an original image and s [x, y] is a template image, a position where the value R of the following equation is the largest is a position with a high degree of similarity. It is regarded as the same point of the original image and the template image. For evaluation of the similarity, a known method such as one using the above formula in addition to the above formula can be used.

  Thereby, the amount of displacement of the imaging region is calculated (step SB5), and it is determined whether the amount of displacement is equal to or less than a predetermined value (step SB6). If it is less than the reference value, the final imaging is performed under the imaging conditions specified in the area. If the amount of positional deviation exceeds the reference value, the sample stage 40 is driven based on the amount of positional deviation to Position alignment is performed (step SB7), and imaging is performed again at the magnification X2 (step SB8).

  Then, the acquired image is reduced (step SB9), the reduced image is template-matched with the reference image (step SB10), the positional deviation amount is calculated (step SB11), and the positional deviation amount is determined (step SB12). Do. If the amount of positional deviation is less than or equal to the reference value in this determination, final imaging is performed under the imaging conditions specified in the area (step SB13). When the positional deviation amount exceeds the reference value, the operations of Steps SB9 to SB12 are repeated until the positional deviation amount becomes equal to or less than the reference value, and final imaging is performed in a state where the positional deviation amount becomes equal to or less than the reference value (Step SB13). ).

  In the above example, the operation is repeated until the positional deviation amount is equal to or less than a predetermined reference value. However, for simplicity, the positional deviation amount is calculated by one template matching, and the positional deviation amount is calculated based on the positional deviation amount. The final imaging can be performed only by performing the alignment.

  As a modified example of this embodiment, at the time of alignment, alignment accuracy is obtained by pattern matching at an intermediate magnification (X3: X1 <X3 <X2) between the final imaging magnification (for example, X2) and the magnification (X1) of the current visual field image. Can be increased. In this case, follow the procedure below. FIG. 11 is a flowchart showing the procedure of a modified example of the alignment of imaging. In this example, the acquired image is imaged at an intermediate magnification (for example, X2) (step SC1), the template matching is performed (step SC2), and this is repeated a predetermined number of times (for example, m times), and then a desired magnification (X2) (Step SC3) and template matching is performed (step SC4).

  When the sample stage is not moved accurately or when imaging is performed in the designated imaging area due to the limit of the moving range, the position of the frame displaying the imaging area is adjusted to be the actual imaging position. be able to. In addition, before and after pattern matching, image adjustment such as focus adjustment and histogram adjustment is automatically performed as necessary. In this example, the change of the imaging region can be set to a mode in which the user automatically moves to the next imaging region and a mode in which the user views the captured image and moves to the next imaging region. If only the mode of moving automatically is used, if the image obtained with the set imaging region and imaging conditions is different from the user's assumption, it is necessary to redo all the processes, which takes time and effort. In this example, in order to prevent such a situation, a mode is provided in which the user moves to the next imaging point after the user's judgment.

  Next, the case where the inclination angle at the time of imaging differs between the current visual field image and the designated imaging area will be described. FIG. 12 is a flowchart showing a procedure for adjusting the tilt angle of imaging, and FIG. 13 is a schematic diagram showing a procedure for adjusting the tilt angle of imaging.

  As described above, when the inclination angle of the current visual field image and the imaging position is set to be different, pattern matching between the current visual field image and the imaging location cannot be executed. This is because if the image is tilted at a specified angle at a time, the acquired image has a large distortion due to the tilt.

  Therefore, in this example, after aligning the image of the designated area acquired at the same magnification as the reference image, the image is tilted little by little to perform pattern matching with the original image. At this time, the one-time inclination is set to an angle that allows pattern matching, and the position is aligned by inclining a plurality of times and pattern matching with the image obtained at the previous inclination angle each time. This is repeated until the specified inclination angle is reached.

  The procedure will be described below. In this example, the tilt angle of the electron beam with respect to the sample is θ, and the tilt angle is θ / t (t is an integer of 1 or more). First, the operator designates the imaging region in the current visual field image displayed on the display unit 69 and the values of the inclination angles θ and t from the input unit 68 (step SD1). For example, as shown in FIG. 13A, setting is performed to capture Point B in the current visual field image at an inclination angle θ. Next, the image is moved to a position to acquire an image, and the area is imaged at the same magnification inclination 0 ° as that of the current visual field image to acquire “image before alignment (0 °)” (see step SD2, FIG. 13B). .

  Next, this “pre-position image (0 °)” is template-matched with the current visual field image to perform the first position correction (step SD3). And after moving based on the said correction | amendment, imaging is performed and the "post-positioning image (0 degree)" is acquired (step SD4). Next, the electron beam is tilted (θ / t) with respect to the sample, and a “pre-positioning image (θ / t)” is acquired (step SD5).

  Further, the “image before alignment (θ / t)” and the “image after alignment (0 °)” are template-matched, and the next position correction is performed (step SD6). Then, Step SD5 and Step SD6 are repeated t times (Step SD7, Step SD8). The inclination angle is changed while correcting the position of the imaging area, and when the inclination angle becomes θ, the imaging area shown in FIG. The image of the designated inclination angle of the imaging area finally designated is acquired.

  The above processing is performed for each designated image area as required, and the current visual field image and each captured image are stored in the image storage unit 65 as described above.

DESCRIPTION OF SYMBOLS 10 Scanning electron microscope 11 Lens tube 12 Electron beam source 13 Electron beam 14 Condenser lens 15 Deflection coil 16 Objective lens 17 Sample chamber 18 Sample 19 Charged particle 20 Detector 30 Electron optical system 40 Sample stage 50 Drive control unit 51 Input unit 52 Display unit 60 Automatic imaging device 61 Imaging designation unit 62 Storage unit 63 Overlay display unit 64 Position correction unit 65 Image storage unit 66 Imaging information image generation unit 67 Imaging control unit 68 Input unit 69 Display unit 110 Substrate 120 Pattern 121 Frame 130 Pattern 131 Frame 132 figure 133 character string 122,
210 substrate image 220 pattern image 221 frame 222 character string 230 pattern image 231 frame 232 figure 233 character string 240 enlarged image 241 pattern image 242 frame 243 character string 250 enlarged image 251 pattern image 252 frame 253 character string

Claims (7)

In a scanning electron microscope that scans an electron beam with an electron optical system and acquires a sample image of a sample placed on a sample stage,
An imaging setting means for designating a position of one or a plurality of areas in the displayed area of the current visual field image as an imaging area, and setting an imaging condition for each of the designated imaging areas;
Storage means for storing position information of the designated imaging area, imaging conditions of each imaging area and the current visual field image;
An image for displaying the position of the designated imaging area and an image for displaying the imaging condition of each imaging area when the imaging area and imaging conditions are set by the imaging setting unit are superimposed on the current view image. Display means;
A correction for comparing the current captured image captured based on the specified position with the stored current field-of-view image to determine the amount of positional deviation between both images, and specifying a new imaging area based on the amount of positional deviation Position correcting means for outputting an imaging position;
An imaging control unit that captures an image at the corrected imaging position under the stored imaging condition to obtain a corrected captured image;
A scanning electron microscope comprising:   The position correcting means compares the corrected captured image acquired based on the current captured image as the current captured image with the current visual field image, and repeats this process until the positional deviation amount of both images becomes a predetermined value or less. The scanning electron microscope according to claim 1.   3. The scanning electron microscope according to claim 1, wherein the position correction unit compares the current captured image with the current visual field image by changing a magnification of the current captured image. 4. . The imaging condition includes an inclination angle of the electron beam with respect to the sample at the time of imaging,
The position correction means compares the current captured image at each tilt until reaching the specified tilt angle with the previous captured image, and outputs a corrected capture position at the tilt angle at the next imaging,
2. The image pickup apparatus according to claim 1, wherein the drive control unit performs imaging by tilting the electron beam tilt angle by a predetermined number of times by a predetermined number of times until the specified tilt angle is reached. The scanning electron microscope according to claim 3.   5. The superimposing display unit displays information about an actually imaged area when the specified area cannot be imaged and is imaged in the vicinity of the area. A scanning electron microscope according to any one of the above. Image storage means for storing the current field-of-view image and the finally obtained captured image of each acquired area;
A region image indicating which region in the field-of-view image corresponds to the imaging region of the finally obtained captured image and an imaging condition image that displays the imaging condition are generated, and the region image is displayed on the current field-of-view image And imaging condition display means for displaying the imaging condition image in an overlapping manner,
The scanning electron microscope according to any one of claims 1 to 5, further comprising: In an imaging method of a scanning electron microscope that scans an electron beam with an electron optical system and acquires a sample image of a sample placed on a sample stage,
Designating the position of one or a plurality of areas in the displayed area of the current visual field image as an imaging area, and setting imaging conditions for each of the designated imaging areas;
Storing the position information of the designated imaging region, the imaging condition of each imaging region, and the current visual field image;
A step of displaying an image displaying the position of the designated imaging region and an image displaying the imaging condition of each imaging region on the current visual field image when the imaging region and imaging conditions are set by the imaging setting unit. When,
A correction for comparing the current captured image captured based on the specified position with the stored current field-of-view image to determine the amount of positional deviation between both images, and specifying a new imaging area based on the amount of positional deviation Outputting an imaging position;
Capturing at the corrected imaging position under the stored imaging conditions to obtain a corrected captured image;
An imaging method for a scanning electron microscope, comprising: