Foreign object height measuring method and charged particle beam device

Abstract

In this foreign body height measuring method for measuring a height of a foreign body on a specimen, from a charged particle image acquired with a specimen stage in an inclined state: dependency data representing a dependency of a calculated value of the height of the foreign body, calculated from a foreign body image extracted from the charged particle image, on an orientation of the foreign body are stored in advance; a foreign body image to be measured, which is an image of a foreign body to be measured, is extracted from the charged particle image; and if the orientation of the foreign body to be measured, detected from the foreign body image to be measured, is determined not to satisfy an allowable error range, on the basis of the dependency data, a measured value of the height of the foreign body to be measured is output together with a warning about reliability, or the height of the foreign body to be measured is measured from a charged particle image acquired with the orientation of the foreign body image to be measured changed by rotating the specimen stage.

Description

[Technical field]

[0001] The present invention relates to a method for measuring the height of a foreign object and a charged particle beam device. [Background technology]

[0002] Patent Document 1 discloses that two SEM (scanning electron microscopy) image signals captured from different viewpoints are combined to generate a stereoscopic SEM image signal, and the depth of a defect on a wafer is determined. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 6,353,222 Summary of the Invention [Problem to be solved by the invention]

[0004] In the manufacturing process of semiconductor devices, the etching process is applied to form patterns on semiconductor wafers, such as electrodes, wiring, and vias that constitute the devices. After the etching process, foreign objects (etching residues) of various shapes that are generated during the etching process remain on the semiconductor wafer. If the height or size of the foreign objects remaining on the semiconductor wafer exceeds a certain level, they can cause initial defects or shorten the lifespan of the manufactured semiconductor devices, resulting in a decrease in yield. For this reason, a technique for measuring the height of foreign objects on semiconductor wafers is important for process management in mass production and screening inspection for initial defects.

[0005] Patent Document 1 makes it possible to measure the height or depth of a defect from a 3D SEM image. However, in order to obtain a 3D SEM image, it is necessary to acquire SEM images from multiple viewpoints and perform image processing, which results in low throughput. In particular, to measure the height of a large number of foreign objects in a mass production process, a technology for measuring the height of foreign objects on a semiconductor wafer with high throughput is required. [Means for solving the problem]

[0006] A foreign particle height measuring method according to one embodiment of the present invention is a method for measuring a height of a foreign particle on a sample from a charged particle image obtained by irradiating a charged particle beam onto the sample while tilting a sample stage on which the sample is placed, the method comprising the steps of: Dependency data indicating the dependency of a calculated value of a height of a foreign object calculated from a foreign object image, which is an image of the foreign object extracted from the charged particle image, on the orientation of the foreign object is stored in advance; A measurement target foreign object image, which is an image of the measurement target foreign object, is extracted from the charged particle image, and if it is determined that the orientation of the measurement target foreign object detected from the measurement target foreign object image does not satisfy the allowable error range based on the dependency data, a measurement value of the height of the measurement target foreign object is output together with a warning about reliability, or the height of the measurement target foreign object is measured from the charged particle image obtained by rotating the sample stage to change the orientation of the measurement target foreign object, The orientation of a foreign particle is defined as the angle between the longest line segment connecting the points of contact between the outline of the foreign particle image and the tilt direction lines, which are two parallel straight lines extending in the tilt direction of the sample stage, and a reference line perpendicular to the tilt direction lines. Effect of the Invention

[0007] This enables measurement of the height of foreign particles on a sample with high throughput.

[0008] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Brief description of the drawings]

[0009] [Figure 1]1 is a configuration example of a charged particle beam device. [Diagram 2] FIG. 13 is a diagram showing how a foreign matter image is extracted from an SEM image. [Diagram 3] FIG. 2 is a diagram showing the positional relationship between a sample and an electron beam when an SEM image is captured. [Figure 4A] 1A and 1B are diagrams showing a bird's-eye view of a cone-shaped foreign matter when an SEM image is acquired, and a foreign matter image extracted from the SEM image, with respect to the cone-shaped foreign matter; [Figure 4B] 1A and 1B are diagrams showing a bird's-eye view of a tapered cylindrical foreign matter when an SEM image is acquired, and a foreign matter image extracted from the SEM image. [Diagram 5] FIG. 2 is a diagram for explaining a first definition of the orientation of a foreign object. [Figure 6] FIG. 13 is a diagram showing the dependency of the calculated value of the foreign object height on the orientation of the foreign object. [Figure 7] 11 is a flowchart for measuring the height of a foreign object. [Figure 8A] This is an example where the orientation of the foreign object is different. [Figure 8B] FIG. 13 is a diagram for explaining a second definition of the orientation of a foreign object. [Figure 9] 11 is a flowchart for measuring the height of a foreign object. [Figure 10] 13 is an example of a GUI screen for setting measurement conditions. [Figure 11] 1 is an example of a data structure of measurement data. [Figure 12] 1 is an example of a wafer heat map. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Figure 1 shows an example of the configuration of a charged particle beam device that measures the height of a foreign particle on a semiconductor wafer. Here, a scanning electron microscope is taken as an example to generate an image based on signal electrons emitted from the surface of a sample by scanning an electron beam over the sample. The scanning electron microscope 100 mainly comprises elements that constitute a typical scanning electron microscope, such as an electron optical system, a stage mechanism system, a detection system, a control system, and a signal processing system. Figure 1 shows a schematic diagram of only the basic elements that constitute the scanning electron microscope 100.

[0011] The electron optical system is a mechanism for forming the electron beam 102 into a minute spot and scanning it on the sample 120, and is composed of an electron source, a focusing lens, an aperture, an objective lens, a deflector, etc. Here, the electron source 101 is shown as a representative example.

[0012] The stage mechanism system has the functions of stably supporting the sample 120 to be inspected, and of moving, rotating, and tilting the sample 120 in the horizontal and vertical directions. Shown here are a sample stage 126 on which the sample is placed, and a stage driver 125 having the functions of tilting the sample stage 126 about a rotation axis T so that the electron beam 102 is incident on the sample 120 at a predetermined incident angle, and rotating the sample stage 126 about a rotation axis R perpendicular to the sample placement surface of the sample stage 126.

[0013] The detection system includes a detector that detects signal electrons generated when the sample 120 is irradiated with the electron beam 102. Here, a BSE detector 110a that detects backscattered electrons (BSE) 103 and a secondary electron detector 110b that detects secondary electrons 104 are shown. In this embodiment, an example is shown in which the height of a foreign particle is measured from an SEM image (charged particle image) based on the detected secondary electrons 104, but the present invention is not limited to this.

[0014] The control system controls the electron optical system, stage mechanism system, and detection system to detect signal electrons and generate an SEM image. Here, the control unit 130 includes individual control units that control the individual elements included in the electron optical system, stage mechanism system, and detection system, and an overall control unit that sets the operation of the individual elements so that these individual elements work together to perform the desired operation.

[0015] The signal processing system measures the height of the foreign matter by performing image processing on the SEM image generated by the control system. The image processing unit 131 executes the image processing for this purpose.

[0016] The functions of the overall control unit in the control unit 130 and the functions of the image processing unit 131 are executed by an information processing device (computer) equipped with input devices such as a keyboard, a pointing device, etc., and an output device such as a display, etc. A single information processing device may be used, but the calculation load of the information processing device may be distributed by connecting to a plurality of information processing devices and data storages via a network.

[0017] First, a method for measuring the height of a foreign object 121 on a sample 120 such as a semiconductor wafer will be described. An SEM image obtained by irradiating an electron beam from directly above the sample 120 does not include information about a direction perpendicular to the sample surface. For this reason, in this embodiment, as shown in FIG. 1, an image of the foreign object 121 is captured with the sample stage 126 tilted by a predetermined tilt angle by a stage driving unit 125. Next, as shown in FIG. 2, a foreign object image 202 is extracted by image processing of an SEM image 201. For example, the foreign object image 202 can be extracted from the extracted contour line by binarizing the SEM image 201. Note that this is not limited to this method, and any known method for extracting a foreign object image from an SEM image by image processing may be applied. For example, images of a plurality of foreign objects may be registered in advance and extracted by matching. Since an image of the foreign object 121 is captured by tilting the sample 120, the foreign object image 202 includes information about the bottom surface and the top or top surface of the foreign object 121. Therefore, the height of the foreign matter 121 is calculated using information on the bottom surface and the apex or top surface contained in the foreign matter image 202 .

[0018] 3 shows the positional relationship between the sample 120 and the electron beam (optical axis) 102 when an SEM image is captured. With the sample 120 tilted around a rotation axis T extending in the Y direction, the electron beam 102 scans a scanning range 200 to obtain an SEM image. The angle between the electron beam (optical axis) 102 and the surface of the sample 120 viewed from the Y direction when obtaining an SEM image (the angle between the optical axis of the electron beam (optical axis) 102 and the X axis in FIG. 3) is called the tilt angle α (α<90°).

[0019] A method for calculating the height of a cone-shaped foreign matter that imitates needle-like residues generated in an etching process and a tapered cylindrical foreign matter will be described with reference to FIGS. 4A and 4B.

[0020] FIG. 4A shows a bird's-eye view of a cone-shaped contaminant when an SEM image is acquired, and a contaminant image extracted from the SEM image. The height of the contaminant is H. Two parallel straight lines are defined as a tilt direction line 210 extending in the tilt direction of the sample in the contaminant image. In this example, the contaminant is tilted in the X direction when the SEM image is acquired, so the tilt direction line 210 is also a straight line extending in the X direction. The tilt direction line 210 on the contaminant image can be determined based on the tilt direction of the sample stage 126 and the scanning direction of the electron beam 102 by the electron optical system. Next, a line segment 221 where the tilt direction line 210 and the contour of the contaminant image are tangent is extracted. As shown in the bird's-eye view, the line segment 221 is a line segment that passes through the center of the bottom surface of the contaminant and extends in the Y direction. Next, line segments 222a and 222b that approximate the contour from both end points of the line segment 221 are extracted, and an intersection point 223 between them is obtained. The distance between intersection 223 and line segment 221 is assumed to be h. Here, the contour from which an approximating line segment is extracted is the contour located in the X+ direction with respect to line segment 221. This is because the apex of the foreign object is located on the X+ side of line segment 221 as shown in the bird's-eye view. Since line segment 221, line segment 222a, line segment 222b, and intersection 223 have the relationship shown in the bird's-eye view, the height H of the foreign object is H=h / sinα It is required as follows.

[0021] FIG. 4B shows a bird's-eye view of a tapered cylindrical foreign object when an SEM image is acquired, and a foreign object image extracted from the SEM image. The height of the foreign object is H. Similarly, a line segment 231 where the inclination direction line 210 and the contour of the foreign object image are intersected is extracted. As shown in the bird's-eye view, the line segment 231 is a line segment that passes through the center of the bottom surface of the foreign object and extends in the Y direction. Next, line segments 232a and 232b that approximate the contour from both end points of the line segment 231 are extracted, and a line segment 233 that intersects with the line segments 232a and 232b, is parallel to the line segment 231, and is located at the farthest position from the line segment 231 is obtained. The distance between the line segment 233 and the line segment 231 is h. Here again, the contour from which the approximating line segment is extracted is a contour located in the X+ direction with respect to the line segment 231. This is because the line segment that passes through the center of the upper surface of the foreign object and extends in the Y-axis direction is located on the X+ side of line segment 231 as shown in the bird's-eye view. Since line segment 231, line segment 232a, line segment 232b, and line segment 233 have the relationship shown in the bird's-eye view, the height H of the foreign object is H=h / sinα It is required as follows.

[0022] 4A-B show relatively simple shapes of foreign objects, but if the foreign object has a complex shape, there may be multiple inclination direction lines that are in contact with the outline of the foreign object image. In this case, the longest line segment among the line segments connecting the points of contact with the inclination direction lines is extracted as the line segment indicating the bottom surface position.

[0023] The foreign object shapes shown in Figs. 4A and 4B for explaining the foreign object height calculation method are both axially symmetric, so the shape seen from the side does not change regardless of the direction from which the sample is tilted. In this case, the same foreign object image is obtained regardless of the direction in which the sample is tilted, so the calculation accuracy of the foreign object height does not change. However, foreign objects generated in the etching process are often not axially symmetric, for example, with a distorted bottom surface (e.g., elliptical) or with an inclined side surface. In this case, the obtained foreign object image changes depending on the shape of the foreign object and the direction in which the sample is tilted, and the calculation accuracy changes.

[0024] Therefore, the orientation of the foreign matter is defined based on the inclination direction line described above (first definition). The first definition of the orientation of the foreign matter will be described with reference to FIG. 5. Residues generated in the etching process are basically tapered conical or cylindrical. For this reason, the foreign matter image has a shape extending in the X+ direction. The longest line segment 241 connecting the contact points between the inclination direction line 210 and the outline of the foreign matter image is a line segment that crosses the bottom surface of the foreign matter, so the direction opposite to the line segment 241 is defined as the front surface of the foreign matter. Here, a reference line 240 perpendicular to the inclination direction line 210 is defined, and the angle β between the line segment 241 and the reference line 240 is defined as the orientation of the foreign matter (first definition). If the foreign matter has an axisymmetric shape, the orientation β is always 0, but if not, the orientation β takes various values, and the value of the height H calculated according to the orientation β varies.

[0025] FIG. 6 shows the dependency of the calculated value of the foreign object height H on the foreign object orientation. The horizontal axis is the orientation β (deg), and the vertical axis shows the ratio of the calculated value of the height H when the orientation β is a predetermined value to the calculated value when the orientation β is 0. FIG. 6 is a graph based on the actual measurement value when the foreign object has a predetermined shape. The values ​​of the graph change depending on the shape of the foreign object, but the ratio of the calculated values ​​has a minimum value when the orientation β is 0, and the tendency that the ratio of the calculated values ​​increases as the deviation from the orientation β=0 increases remains unchanged. As can be seen from the graph in FIG. 6, the deviation of the calculated foreign object height H is kept relatively small in the vicinity of the orientation β=0. Therefore, in the measurement of the foreign object height in this embodiment, the user is allowed to set an allowable error in calculating the height H. If the allowable error is exceeded, the direction of the inclination is changed, specifically, the sample stage 126 is rotated by the stage driving unit 125 and remeasured, or an alarm is issued to notify the user that the allowable error has been exceeded. As described above, the graph in FIG. 6 depends on the shape of the foreign object. For this reason, image processing unit 131 creates and stores dependency data of the calculated value of foreign object height H on foreign object orientation β for typical examples of foreign object shapes anticipated in advance by actual measurement or simulation. Based on the stored dependency data, image processing unit 131 can determine the allowable magnitude of β (±εdeg or less) depending on the foreign object shape, and can correct foreign object height H calculated from distance h and tilt angle α depending on the magnitude of foreign object orientation β, specifically, convert it into an estimated value when orientation β=0 and output it as a measured value.

[0026] FIG. 7 shows a flow chart for measuring the height of a foreign object. This flow chart is executed by the control unit 130. First, a measurement tolerance for the height of a foreign object is set (S01). As described later, a user can set the tolerance on a GUI screen. Next, a charged particle image of the foreign object is acquired at a predetermined rotation and tilt angle (S02). The initial rotation angle and tilt angle of the sample stage 126 are set by the user as desired. A foreign object image is extracted from the charged particle image (S03), and as described in FIG. 5, an angle β between a line segment connecting horizontal end points of the outline of the foreign object image and a reference line is calculated (S04). In the following description, the direction in which the inclination direction line 210 extends may be referred to as the vertical direction, and the direction perpendicular to the inclination direction line 210 may be referred to as the horizontal direction.

[0027] It is determined whether the orientation β of the foreign object satisfies the allowable error range (S05). As shown in Fig. 6, the image processing unit 131 determines in advance the allowable orientation range (0±ε [deg]) from the dependency data of the foreign object and the set allowable error, and compares the magnitude of the orientation β obtained in step S04 with the allowable orientation ε, thereby determining whether the orientation β of the foreign object satisfies the allowable error range.

[0028] If the foreign object orientation β satisfies the allowable error range, the distance h between the bottom surface and the apex or top surface of the foreign object image is measured (S06), and the foreign object height H is calculated based on the distance h and the inclination angle α (S07). At this time, if the foreign object orientation β is not 0, the foreign object height H may be converted to the value when β=0 using the dependency data on the foreign object orientation (see FIG. 6) to use as the measured value of the foreign object height. On the other hand, if the foreign object orientation β does not satisfy the allowable error range, it is determined whether or not to perform remeasurement (S08). If remeasurement is to be performed, the rotation angle of the sample stage 126 is changed (S09), and a charged particle image is acquired again (S02). If remeasurement is not to be performed, the foreign object height H is calculated in the same manner (S06, S07), and the measurement result of the height H and the reliability of the measurement are output (S10). As information on the reliability of the measurement, a warning may be given to the effect that the foreign object height has been calculated in a state where the allowable error has been exceeded. This allows the user to evaluate the measurement result including its reliability.

[0029] Here, when the orientation β of the foreign object does not satisfy the allowable error range and the rotation angle of the sample stage 126 is changed (S09), it is preferable that the image processor 131 calculates a desirable rotation angle. Furthermore, even if the orientation β of the foreign object satisfies the allowable error range, there may be another orientation in which the measurement error is smaller depending on the shape of the foreign object. For example, assume that the bottom surface of the foreign object is elliptical. In this case, as shown in FIG. 8A, the bottom surface 250 may be located vertically (case A) or horizontally (case B) with respect to the inclination direction line 210, and in each case, the orientation may satisfy the allowable error range based on the orientation β of the foreign object. However, according to the study by the inventors, the foreign object height H calculated in the horizontal state (case B) can be expected to have higher accuracy than the foreign object height H calculated in the vertical state (case A).

[0030] Therefore, the orientation of the foreign object is defined based on the overall shape of the foreign object image (second definition). In this case, the orientation that is expected to allow calculation of the foreign object height with high accuracy is defined as the front of the foreign object. The second definition of the foreign object orientation will be described with reference to FIG. 8B. The foreign object image is approximated as an ellipse, and a first axis 261 and a second axis 262 of the approximated ellipse 260 are obtained. Here, the first axis 261 is an axis that intersects with the reference line 240 at an acute angle, and the second axis 262 is an axis that intersects with the reference line 240 at an obtuse angle. In the second definition of the foreign object orientation, the angle γ between the major axis of the approximated ellipse 260 and the reference line 240 is defined as the orientation of the foreign object. In this example, as shown in FIG. 8B, it is the angle between the first axis 261 and the reference line 240.

[0031] The aspect ratio of the foreign object image is defined using an approximation ellipse 260. As shown in the figure, the length of the first axis 261 is a, and the length of the second axis 262 is b. The aspect ratio of the foreign object image is (b / a), which is defined based on the approximation ellipse. In this example, the first axis 261 is the major axis of the ellipse, and the second axis 262 is the minor axis of the ellipse, so the aspect ratio of the foreign object image (b / a)<1, which corresponds to the horizontally elongated state (case B) in FIG. 8A. In contrast, when the aspect ratio of the foreign object image (b / a)>1, it corresponds to the vertically elongated state (case A) in FIG. 8A.

[0032] Fig. 9 shows a flowchart for measuring the height of a foreign object. This flowchart includes a flow for determining the orientation of a foreign object and performing remeasurement in order to accommodate various foreign object shapes. This flowchart is entirely executed by the control unit 130. The same steps as those in the measurement flowchart of Fig. 7 are given the same reference numerals, and duplicated explanations will be omitted.

[0033] Steps S01 to S05 are the same as those in the measurement flowchart of Fig. 7. Note that step S05 is for determining whether the allowable error range is satisfied based on the foreign matter orientation β, and therefore the flowchart clearly indicates that this is a determination of the foreign matter orientation according to the first definition.

[0034] As shown in Fig. 8B, the foreign object image is approximated by an ellipse, and the length a of the first axis and the length b of the second axis of the approximate ellipse are obtained (S11), and if the determination of the foreign object orientation according to the first definition is within the allowable error range, the aspect ratio (b / a) of the foreign object image is determined (S12). If the aspect ratio (b / a) of the foreign object image is 1 or less, the foreign object is horizontally elongated, and the foreign object height H can be expected to be calculated with high accuracy using the measurement method of this embodiment. In this case, the foreign object height H is calculated as is (S06, S07), and the foreign object height measurement result is output (S13).

[0035] On the other hand, if the aspect ratio (b / a) of the foreign object image is greater than 1, the foreign object is vertically long, and the foreign object height H calculated by the measurement method of this embodiment may be less accurate. In this case, the sample stage 126 is rotated 90° (S19), a charged particle image is acquired again (S02), and the foreign object height H is calculated based on the reacquired charged particle image. Note that if the aspect ratio (b / a) of the acquired foreign object image is determined to be greater than 1 even after the sample stage 126 is rotated 90° and re-imaging is performed, the accuracy of the foreign object height H calculated from the foreign object images before and after rotation is considered to be approximately the same. Therefore, it is advisable to calculate the foreign object height H from the foreign object images before and after rotation, and obtain the measurement result of the foreign object height H based on the average value (S20).

[0036] On the other hand, if it is determined that the foreign object orientation according to the first definition does not satisfy the allowable error range, the angle γ between the major axis of the approximate ellipse and the reference line is calculated (S14) as shown in FIG. 8B. Then, it is determined whether the foreign object orientation γ according to the second definition satisfies the allowable error range (S15). As shown in FIG. 6, the image processing unit 131 determines in advance the allowable orientation range (0±ε [deg]) from the foreign object dependency data and the set allowable error, and compares the magnitude of the orientation γ obtained in step S14 with the allowable orientation ε to determine whether the foreign object orientation γ satisfies the allowable error range. If the foreign object orientation γ according to the second definition satisfies the allowable error range, it is considered that the calculation accuracy of the foreign object height H is unlikely to improve even if the sample stage 126 is rotated to change the foreign object orientation. Therefore, the foreign object height H is calculated without remeasurement (S06, S07), and the measurement result of the height H is output (S10).

[0037] On the other hand, if the foreign object orientation γ according to the second definition does not satisfy the tolerance, a decision is made as to whether or not to perform remeasurement (S16), and if remeasurement is to be performed, the sample stage 126 is rotated by -γ° (S17) and a charged particle image is acquired again (S02). This allows a charged particle image to be acquired with the front of the foreign object according to the second definition facing the reference line, thereby obtaining a more accurate calculation value for the foreign object height. If remeasurement is not to be performed, the foreign object height H is calculated as is (S06, S07).

[0038] It is also possible to always perform remeasurement without making the judgment based on the second definition (S15).In addition, in step S13, it is desirable to output not only the measurement result of the foreign object height but also the reliability of the measurement in the same manner as in the measurement flowchart of FIG.

[0039] FIG. 10 shows an example of a GUI screen for setting the measurement conditions of the scanning electron microscope 100. The GUI screen is displayed on an output device of an information processing device. The measurement condition setting screen 300 includes an apparatus condition setting section 310 for setting the measurement conditions of the scanning electron microscope 100, a measurement content setting section 320 for setting the measurement content, an allowable error setting section 330 for setting the measurement allowable error, and a remeasurement necessity setting section 340 for setting whether or not remeasurement is necessary. The apparatus condition setting section 310 includes a tilt angle setting section 311 for setting the tilt angle of the sample stage 126, and a rotation angle setting section 312 for setting the initial rotation angle of the sample stage 126. A charged particle image of the foreign object is acquired at the tilt angle and initial rotation angle set by these. The measurement content setting section 320 determines the content to be measured for the sample. Measurements other than the foreign object height H can also be performed. Based on the value set by the allowable error setting section 330, it is determined whether the orientation of the foreign object satisfies the allowable error range. When the remeasurement necessity setting unit 340 is set to yes, remeasurement is performed if the orientation of the foreign matter does not satisfy the allowable error range, and when the remeasurement necessity setting unit 340 is set to no, recapturing of the charged particle beam image by rotating the sample stage 126 is not performed. The measurement conditions set on the measurement condition setting screen 300 are confirmed by pressing the decision button 350.

[0040] FIG. 11 shows an example of a data structure of measurement data showing the measurement results of the scanning electron microscope 100. The measurement data is stored in a storage device of an information processing device. Each record of the measurement data 400 shows the measurement results of a foreign object extracted from a captured charged particle image (SEM image). The image list field 401 has a file name that identifies the SEM image registered. In this example, three measurement item fields are included, such as the height, orientation, and area of ​​the foreign object. The height field 402 has the height H (calculated value) of the foreign object calculated based on the distance h and the tilt angle α registered, the orientation field 403 has the orientation of the foreign object used to calculate the height registered, and the area field 404 has the area of ​​the foreign object (which may be the area of ​​an approximate ellipse) registered. The measurement reliability field 405 has the measurement reliability determined based on whether the orientation of the foreign object satisfies the allowable error range registered. If the orientation of the foreign object satisfies the allowable error range, the measurement reliability is registered as high, and if the orientation of the foreign object does not satisfy the allowable error range, the measurement reliability is registered as low. The estimated value field 406 has the height of the foreign object corrected based on the dependency data registered. The value in the estimated value column 406 is treated as the measured value. In the remarks column 407, any special notes that arise during the measurement are registered.

[0041] To display the measurement results of the scanning electron microscope 100 to the user, the measurement data in Fig. 11 may be displayed as a table, or the occurrence of anomalies may be displayed in association with the positions at which the anomalies were detected as a wafer heat map as shown in Fig. 12, which is useful for understanding the anomalies. For example, a wafer 501 may be divided into a number of sections 502, and information such as whether the occurrence frequency of foreign matter of a predetermined height or more is equal to or exceeds a reference value for each section may be displayed.

[0042] The present invention is not limited to the above-mentioned embodiment, and various modifications are included. For example, the above-mentioned embodiment has been described in detail to easily explain the present invention, and is not necessarily limited to those having all the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace other configurations with respect to a part of the configuration of each embodiment. For example, in order to detect the orientation of a foreign object, the image processing unit 131 may store a classification learning device that has previously been trained using teacher data that is a set of multiple charged particle images captured by changing the orientation of a foreign object and the orientation of the foreign object in the charged particle image, and detect the orientation of the foreign object from the foreign object image using the classification learning device. [Explanation of symbols]

[0043] 100: scanning electron microscope, 101: electron source, 102: electron beam, 103: backscattered electrons, 104: secondary electrons, 110a: BSE detector, 110b: secondary electron detector, 120: sample, 121: foreign matter, 125: stage drive unit, 126: sample stage, 130: control unit, 131: image processing unit, 200: scanning range, 201: SEM image, 202: foreign matter image, 210: tilt direction line, 221, 222a, 222b: line segment, 223: intersection, 231, 232a, 232b, 233: line segment, 240: reference line, 241: line segment, 25 0: bottom surface, 260: approximation ellipse, 261: first axis, 262: second axis, 300: measurement condition setting screen, 310: device condition setting section, 311: tilt angle setting section, 312: rotation angle setting section, 320: measurement content setting section, 330: tolerance setting section, 340: remeasurement necessity setting section, 350: decision button, 400: measurement data, 401: image list column, 402: height column, 403: orientation column, 404: area column, 405: measurement reliability column, 406: estimated value column, 407: remarks column, 500: wafer heat map, 501: wafer, 502: section.

Claims

1. A foreign particle height measuring method for measuring a height of a foreign particle on a sample from a charged particle image obtained by irradiating a charged particle beam onto the sample while tilting a sample stage on which the sample is placed, comprising: storing in advance dependency data indicating the dependency of a calculated value of a height of a foreign object, which is calculated from a foreign object image that is an image of the foreign object extracted from the charged particle image, on an orientation of the foreign object; extracting a measurement target foreign object image, which is an image of the measurement target foreign object, from the charged particle image; when it is determined that the orientation of the measurement target foreign object detected from the measurement target foreign object image does not satisfy the allowable error range based on the dependency data, outputting the measurement value of the height of the measurement target foreign object together with a warning about reliability, or rotating the sample stage to change the orientation of the measurement target foreign object and measuring the height of the measurement target foreign object from the acquired charged particle image; a foreign object height measuring method, characterized in that the orientation of the foreign object is defined by the angle between the longest line segment among the line segments connecting the points of contact between the outline of the foreign object image and a tilt direction line, which is two parallel straight lines extending in the tilt direction of the sample stage, and a reference line perpendicular to the tilt direction line.

2. In claim 1, the dependence data is a ratio of a calculated value of the height of the foreign object when the orientation of the foreign object is 0 to a calculated value of the height of the foreign object when the orientation of the foreign object is a predetermined value; a calculated value of the height of the foreign object to be measured, calculated from the image of the foreign object to be measured, is converted into a calculated value of the height of the foreign object to be measured when the orientation of the foreign object to be measured is 0, based on the detected orientation of the foreign object to be measured and the dependency data, and output as a measured value of the height of the foreign object to be measured.

3. In claim 2, a distance between the apex or top surface of the foreign particle to be measured and the longest line segment among the line segments connecting the tangent points of the contour of the foreign particle image to the tilt direction line and an approximation line segment that approximates the contour of the foreign particle image to be measured extending from each of the tangent points, which are the end points of the line segment, in the tilt direction of the sample stage; and a tilt angle, which is the angle between the surface of the sample and the optical axis of the charged particle beam, the foreign particle height measurement method comprising the steps of: determining a calculated value of the height of the foreign particle to be measured;

4. In claim 1, Regarding two axes of an ellipse obtained by elliptical approximation of the image of the measurement target foreign substance, the axis that intersects with the reference line at an acute angle is defined as a first axis, and the other axis is defined as a second axis, a height measuring method for measuring the height of the foreign object to be measured, the height being measured from the charged particle image acquired by rotating the sample stage by 90° when the orientation of the foreign object to be measured detected from the image of the foreign object to be measured is determined to satisfy the allowable error range based on the dependent data, and when the length of the second axis relative to the length of the first axis exceeds 1, the height being measured from the charged particle image acquired by changing the orientation of the foreign object to be measured.

5. In claim 1, a height measuring method for measuring the height of the foreign particle to be measured, the height being measured from a charged particle image obtained by rotating the sample stage to change the orientation of the foreign particle to be measured in accordance with an angle between the reference line and a major axis of an ellipse obtained by elliptical approximation of the image of the foreign particle to be measured, when the orientation of the foreign particle to be measured detected from the image of the foreign particle to be measured is determined not to satisfy the allowable error range based on the dependent data.

6. In claim 1, a measurement result of the height of the foreign particle on the sample and the measurement position of the sample are displayed in relation to the measurement result;

7. In claim 1, storing a classification learning device that has previously been trained using training data that includes a plurality of charged particle images captured by changing the orientation of a foreign object and the orientation of the foreign object in the charged particle image; a classification learning device for detecting an orientation of the foreign particle to be measured from the image of the foreign particle to be measured, the classification learning device being used to detect an orientation of the foreign particle to be measured from the image of the foreign particle to be measured.

8. In claim 1, The method for measuring the height of a foreign particle, wherein the foreign particle is an etching residue.

9. a sample stage on which a sample is placed and which can rotate and tilt; a charged particle optical system for irradiating the sample with a charged particle beam; a detection system for detecting signal electrons generated when the sample is irradiated with the charged particle beam; a control unit that controls the sample stage, the charged particle optical system, and the detection system, and acquires a charged particle image based on signal electrons detected by the detection system; an image processing unit for measuring a height of a foreign particle on the sample from the charged particle image; the image processing unit stores in advance dependency data indicating dependency of a calculated value of a height of a foreign object, the calculated value being calculated from a foreign object image, which is an image of the foreign object extracted from the charged particle image, on an orientation of the foreign object; the image processing unit extracts a measurement target foreign object image, which is an image of the measurement target foreign object, from the charged particle image, and when it is determined that the orientation of the measurement target foreign object detected from the measurement target foreign object image does not satisfy the allowable error range based on the dependency data, outputs the measurement value of the height of the measurement target foreign object together with a warning about reliability, or measures the height of the measurement target foreign object from the charged particle image obtained by rotating the sample stage to change the orientation of the measurement target foreign object; a charged particle beam device characterized in that the orientation of the foreign particle is defined by the angle between the longest line segment connecting the points of contact between the contour of the foreign particle image and a tilt direction line, which is two parallel straight lines extending in the tilt direction of the sample stage, and a reference line perpendicular to the tilt direction line.

10. In claim 9, the image processing unit stores, as the dependency data, a ratio of a calculated value of the height of the foreign object when the orientation of the foreign object is 0 to a calculated value of the height of the foreign object when the orientation of the foreign object is a predetermined value; the image processing unit outputs, as a measurement value of the height of the foreign object to be measured, a calculated value of the height of the foreign object to be measured calculated from the image of the foreign object to be measured, converted into a calculated value of the height of the foreign object to be measured when the orientation of the foreign object to be measured is 0, based on the detected orientation of the foreign object to be measured and the dependency data.

11. In claim 10, the image processing unit calculates a height of the foreign object to be measured based on a distance to a vertex or top surface of the foreign object to be measured, which is determined based on the longest line segment among the line segments connecting the tangent points of the contour of the image of the foreign object to the inclination direction line and an approximation line segment that approximates the contour of the image of the foreign object to be measured extending from each of the tangent points, which are the end points of the line segment, in the inclination direction of the sample stage, and on a tilt angle, which is the angle between the surface of the sample and the optical axis of the charged particle beam.

12. In claim 9, Regarding two axes of an ellipse obtained by elliptical approximation of the image of the measurement target foreign substance, the axis that intersects with the reference line at an acute angle is defined as a first axis, and the other axis is defined as a second axis, A charged particle beam device characterized in that when the orientation of the target foreign object detected from the image of the target foreign object is determined to satisfy the allowable error range based on the dependency data, and the length of the second axis relative to the length of the first axis exceeds 1, the image processing unit rotates the sample stage 90 degrees to change the orientation of the target foreign object and measures the height of the target foreign object from the charged particle image acquired.

13. In claim 9, a charged particle beam device according to claim 1, wherein when it is determined that the orientation of the foreign particle detected from the image of the foreign particle to be measured does not satisfy the allowable error range based on the dependency data, the image processing unit measures the height of the foreign particle to be measured from the charged particle image obtained by changing the orientation of the foreign particle to be measured by rotating the sample stage in accordance with an angle between the reference line and the major axis of an ellipse obtained by elliptical approximation of the image of the foreign particle to be measured.

14. In claim 9, The image processing unit is a charged particle beam device that displays a measurement result of the height of a foreign object on the sample in relation to a measurement position on the sample.

15. In claim 9, the image processing unit stores a classification learning device that has previously been trained using training data that includes a plurality of charged particle images captured by changing the orientation of a foreign object and the orientation of the foreign object in the charged particle image; The charged particle beam device according to claim 1, wherein the image processing unit detects a direction of the foreign matter to be measured from the image of the foreign matter to be measured by using the classification learning device.

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