JP3216709B2 - Secondary electron image adjustment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting a secondary electron image in an electron beam tester to be clear.

[0002]

2. Description of the Related Art LS is used for analyzing the cause of a defective LSI.
An electron beam tester is used to irradiate the surface of the I surface with electrons while scanning and obtain a secondary electron image.

[0003] In an electron beam tester, astigmatism (As, etc.) in the focus, vertical and horizontal directions, and oblique directions, which are parameters of the electron optical system, is measured.
By adjusting tigmatism) to an appropriate state, a clear secondary electron image can be obtained. In an electron beam tester, focus and astigmatism in the vertical and horizontal directions and diagonal directions are usually adjusted by changing the current of each excitation coil, and can be controlled by parameters corresponding to each current. Has become.

When the secondary electron image is unclear, the user
By changing the parameter values by trial and error while observing the secondary electron image, the image is made clear. With respect to these parameters, even if only the observation target portion of the LSI is changed, the optimum value changes, and the image becomes unclear, so that the adjustment is frequently required. However, the operation of adjusting the parameters takes time and requires the experience and skill of the user. In order for an inexperienced user to operate the electron beam tester, automation of such a function is desired.

In recent years, an LS using an electron beam tester has been developed.
Attempts have been made to automate the failure analysis of I, but for that purpose automatic adjustment of such parameters is essential.

As a simple method for automatically optimizing such parameters, the overall clarity of an image in each case is evaluated while sequentially changing each parameter.
A simple hill-climbing method in which a parameter that gives the best evaluation value is obtained can be considered. In the case where only the focus is deviated and a clear image can be obtained by adjusting the focus alone, the relationship between the focus control value and the evaluation value of the overall clarity peaks at the optimum value and gradually decreases on both sides. Since it has a simple mountain shape, there is no problem in time to obtain a clear image, and it is easy to realize. Normally, an electron beam tester is provided with an automatic focus adjustment function.

[0007]

However, in the usual case,
As parameters to be adjusted, three-dimensional parameters of focus (one-dimensional) and astigmatism (two-dimensional in vertical and horizontal directions and in oblique directions) need to be targeted. In the case where three parameters are adjusted in this manner, if a simple hill-climbing method in which the best evaluation value is obtained while evaluating only the overall clarity is used, the number of parameters is large, By trial and error for each, it takes time to optimize clarity.

In particular, when trying to optimize the overall clarity by changing the value of a certain parameter, if the other parameter values are not optimal and deviate, the original optimal value In some cases, the overall clarity may be maximized at a value different from the above, and in such a case, it is necessary to optimize again after other shifted parameters are optimized.

For this reason, it is better to change the parameter from a parameter that deviates greatly from the optimum value. However, it is not possible to determine which parameter deviates greatly only by evaluating the overall clarity.

For the above reasons, a method of climbing a hill while evaluating the overall clarity is also possible, but it is necessary to acquire a large number of images and evaluate the overall clarity. It will take.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for optimizing a focus control value and an astigmatism control value more quickly and adjusting the focus control value and the astigmatism control value to a clear secondary electron image.

[0012]

A secondary electron image adjusting method according to the present invention comprises irradiating an LSI surface while scanning an LSI surface with an electron beam.
The secondary electric power obtained for the shape of the LSI surface
Both the presence and absence of the shape flow in the child image
Or one side is read, and the target shape in the secondary electron image is centered.
Line detection and detection by changing the astigmatism control value
Performs line and line extraction image processing to extract lines representing the flow direction.
And the angle of the line representing the direction of flow from 0 degree
By reading in the 180-degree direction range, the flow direction
Obtaining the data and the focus control value or non-
Secondary electron image adjustment method with step of changing astigmatism control value
In the method, changing the astigmatism control value reduces the direction of flow by increasing the oblique astigmatism control value,
If the direction is between 45 degrees and 135 degrees,
The vertical and horizontal astigmatism control value is determined to be smaller than the optimum value, and the vertical and horizontal astigmatism control value is further increased.

[0013] The secondary electron image adjustment method of the present invention, L
Irradiation while scanning the SI surface with an electron beam
The presence or absence of shape flow in the secondary electron image obtained
Focus on both or one of these directions and the image
Result of changing some of the control values or astigmatism control values
Existence and flow of shape flow in the obtained secondary electron image
Read both or one of the directions
Change the astigmatism control value within the range centered on the target shape
Image processing of line detection and line extraction by
Extracting a line representing the direction of flow, and
By reading the angle in the direction range from 0 to 180 degrees,
Obtaining flow direction data and focusing on the data
Changing the control value or the astigmatism control value.
In the secondary electron image adjustment method, the change of the astigmatism control value
Increasing the diagonal astigmatism control value decreases the flow direction, and when the direction is in the range of 45 degrees to 135 degrees, the vertical and horizontal astigmatism control values are smaller than the optimum value. And increasing the vertical and horizontal astigmatism control values.

Further, the astigmatism control value is changed by increasing the oblique astigmatism control value to increase the flow direction. If the direction is in the range of 45 degrees to 135 degrees, It is characterized in that it is determined that the directional astigmatism control value is larger than the optimum value, and the vertical and horizontal astigmatism control values are made smaller.

[0015]

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a flowchart of an embodiment of the present invention, FIG. 2 is a diagram showing a configuration of an electron beam system in an electron beam tester, FIG. 3 is a diagram showing a configuration of a stigmatter in an electron beam tester,
FIG. 4 is a diagram showing examples of focus and astigmatism control values and the presence / absence and direction of the flow of the secondary electron image in the electron beam tester. FIGS. 5 to 7 show display screens of the secondary electron image by the electron beam tester. FIG. 5 shows the case where the focus and astigmatism control values are optimal, FIG. 6 shows the case where there is a flow of the secondary electron image, and FIG. 7 shows the case where there is no flow of the secondary electron image. 9 shows an example of an inappropriate aberration control value.

In the acquisition of a secondary electron image, the surface of the LSI is irradiated with an electron beam while being scanned by the function of an electron beam tester, thereby acquiring a secondary electron image.

Referring to FIG. 2, the electron beam tester includes an electron beam source 21 for generating an electron beam, a converging lens 22 for converging the electron beam, and an objective lens aperture 2.
3, a scan coil 24 for scanning an electron beam on the LSI surface, an objective lens 25 for focusing the electron beam on the LSI surface, a stigmator 26 for controlling astigmatism, and a test object It has an LSI 27 and a secondary electron detector 29 for detecting a secondary electron image.

The operation of the electron beam tester is such that electrons are generated in an electron beam source 21 and the electrons are generated by a focusing lens 22.
The beam becomes a focused beam through the objective lens aperture 23.

The scan coil 24 is a pair of two coils arranged in a direction perpendicular to each other. Each coil pair is a pair of coils that generate a magnetic field in the same direction. By applying horizontal and vertical scanning signals to each coil pair, the electron beam scans a two-dimensional area of the LSI.

The objective lens 25 is a coil for generating a magnetic field in the same direction as the axis of the electron beam, and focuses the electron beam. The focal length changes depending on the applied current. This current is controlled by the focus control value.

The stigmatter 26 is constituted as one unit by a total of four pairs of a pair of coils for generating a magnetic field in opposite directions across the axis of the electron beam and a pair of equivalent coils arranged in a direction perpendicular thereto. ing. FIG. 3 shows the arrangement. Each coil pair is positioned so as to generate a magnetic field either toward the axis of the electron beam or in the opposite direction, and one of the two coil pairs is positioned in the beam axis. When the magnetic field is generated toward the other coil pair, the other coil pair is configured to generate a magnetic field opposite to the beam axis. Each coil is configured so that a current for generating a magnetic field having the same strength flows. These currents are controlled as astigmatism control values. The stigmator 26 controls astigmatism of the electron beam.

The stigmatter 26 installed in the vertical and horizontal directions
If the astigmatism value is further increased, depending on the installation conditions, it acts so that the horizontal focusing of the electron beam is strengthened and at the same time the vertical focusing is weakened. If the astigmatism value is larger than the optimum value, the distance at which the beam is focused in the horizontal direction is shorter than the distance at which the beam is focused in the vertical direction. For this reason, the beam becomes vertically long at the near position, and horizontally at the far position. Conversely, if the astigmatism value is smaller than the optimum value, the distance at which the beam is focused in the horizontal direction is longer than the distance at which the beam is focused in the vertical direction. For this reason, the beam becomes horizontally long at the near position, and vertically at the deep position. A secondary electron image obtained by scanning a horizontally or vertically long beam flows horizontally or vertically.

Such a stigmatter includes a stigmatter 26 for adjusting an electron beam in the vertical and horizontal directions and a stigmatter 27 for adjusting an electron beam in an oblique direction.
Are arranged respectively. The current for each is
It is configured to be controlled by astigmatism control values in the vertical, horizontal, and oblique directions.

Next, the flow of the secondary electron image adjusting method of the present invention will be described with reference to FIG. Initial values of the focus and astigmatism control values are set (step 1). Secondary electrons generated according to the shape and potential of the surface of the LSI by the electrons irradiated on the LSI are detected by the secondary electron detector 29. A secondary electron image is generated by the detected secondary electrons (Step 2). The secondary electron image data is generated as data representing the gradation for each pixel (step 3).

In the evaluation of the clarity of the image and the presence / absence / direction of the image flow, the secondary electron image data is analyzed, and the direction and the clarity of the image flow therein are read (step 4).

The clarity is evaluated by taking the total sum of the differences between adjacent pixels, taking the maximum value or the average value of the gradient of the gradation at several points, and the like.

With respect to the presence / absence / direction of the flow, the presence / absence / direction of the flow is evaluated for a plurality of portions in the secondary electron image, and comprehensive evaluation is performed to perform a more accurate evaluation (step 5). ). Specifically, a point of interest in the secondary electron image is determined, and for a region centered on that point,
A line representing the direction of the flow is extracted by performing image processing of line detection and line extraction. Change the direction of this line from 0 degree to 1
The flow direction data is obtained by reading in the range of 80 degrees. The focus and astigmatism control values are changed based on this data (step 6), and the evaluation of the resulting clarity of the secondary electron image and the presence / absence / direction of the image flow are repeated.
An optimal focus and astigmatism control value is obtained (step 7).

In the evaluation of the flow and its direction, the presence / absence and the direction of the image flow can be read with higher accuracy by reading the presence / absence of the image flow in a portion of the secondary electron image where the high gradation range is small. Usually, in the secondary electron image on the LSI surface,
The outline of the wiring near the surface and the outline of the via (also referred to as a through hole) are observed. In order to read the direction of the flow, the outline of the via having a smaller circular shape than the outline of the linearly extending wiring clearly indicates the direction of the flow. On the other hand, by reading the flow direction, a more accurate evaluation can be performed.

In the evaluation of the flow and its direction, a pixel having the highest gradation within the entire secondary electron image or a part thereof is searched for, and a flow direction having a shape including the pixel is obtained. good. The point of high gradation is basically LS
It corresponds to contour lines such as wiring and vias on the I surface. Further, when the flow is observed in a certain direction, that is, when the electron beam is irradiated while being spread in a certain direction without being well focused, the spread and the contour of the electron beam in the contour line extending in the same direction. Are superimposed, the gradation in the secondary electron image is most emphasized. Therefore, the pixel with the highest gradation within a certain range is often a point emphasized due to the flow.

Alternatively, as another method of evaluating the flow and its direction, edge detection processing of a secondary electron image is performed, a pixel having the highest degree of edge within the entire image or a part of the image is searched for, and its surroundings are determined. It is also good to determine the direction of the flow.

The point with a high edge degree is basically LS
It corresponds to the periphery of the contour line such as wiring and via on the I surface. Further, when there is a flow in a certain direction, that is, when the electron beam is irradiated while being spread in a certain direction without being well focused, the spread and the contour of the electron beam around the contour line extending in the same direction are also considered. Are overlapped with each other, so that the gradation in the secondary electron image is most emphasized, and therefore, the degree of the edge of the peripheral portion is also increased. Therefore, the pixel with the highest edge degree within a certain range is often a point emphasized due to flow.

Further, the flow direction may be read by using an image of the edge detection result instead of the secondary electron image. In the image of the edge detection result, a line representing the direction of flow can be extracted by performing image processing of line detection and line extraction on a region centered on a pixel having a high edge degree. If the direction of this line is read in the range of 0 to 180 degrees, the flow direction can be obtained.

The determination of the presence / absence of a flow is made by examining the gradient of the gradation in the direction considered to be the flow direction and in the direction perpendicular to the flow direction around the place where the flow is read. It is determined that there is a flow if the gradient of the gradation is in the direction considered to be the flow direction, and that there is no flow if the gradation is in the direction perpendicular to the direction in which the gradient of the gradation is considered to be the flow direction. I do. Also, when the directions of the flows checked at a plurality of locations are comprehensively viewed, if there are few coincident directions, it is determined that there is no flow.

The presence / absence, direction, and clarity of the flow can be evaluated by the method described above.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The optimum focus and astigmatism control values are determined based on the focus and astigmatism control values obtained so far and the flow and direction of the target shape in the secondary electron image. Determine the astigmatism value. An example of a method for determining the focus and astigmatism control values will be described below.

FIG. 4 shows a case where a secondary electron image on the LSI surface is observed with an electron beam tester while changing the focus control value, the astigmatism control value in the vertical and horizontal directions, and the astigmatism control value in the oblique direction under a certain condition. 2 shows an example of data on the presence / absence of the flow of the secondary electron image and the direction of the flow. The direction is 0 degree or more and 1
Expressed as less than 80 degrees. Under this condition, the optimal values of the focus control value and the astigmatism control values in the vertical, horizontal, and oblique directions are as follows. Focus control value (optimum value) = 14700 Vertical and horizontal astigmatism control value (optimum value) = 400 Oblique astigmatism control value = −200 FIG. 4 shows, for example, focus control value = 14800 and vertical and horizontal astigmatism control values. = 400, oblique astigmatism control value = -10
When the secondary electron image is acquired at 0, there is a flow, and when the direction is expressed between 0 degree and 180 degrees, it means 135 degrees.

As shown in this table, there are some relationships between the focus control value, the vertical / horizontal astigmatism control value, the oblique astigmatism control value, and the presence / absence and direction of the flow. The following describes how to set the focus and astigmatism control values in order to obtain a clear secondary electron image based on a part of the relationship and the relationship.

First, when the flow direction is close to 0 or 90 degrees, it can be determined that the oblique astigmatism control value is close to the optimum value, and that the vertical and horizontal astigmatism control values deviate from the optimum values.
For example, in FIG. 4, (2) and (8) correspond. In this case, it can be seen that in order to obtain a clearer secondary electron image, the astigmatism control value in the vertical and horizontal directions should be changed.

When the astigmatism control value in the oblique direction is changed, the flow disappears or the flow direction becomes zero.
When the angle becomes 90 degrees or 90 degrees, the oblique astigmatism control value becomes the optimum value. For example, in FIG. 4, (1), (2), (3)
Among them, in (2) in which the oblique astigmatism control value is the optimum value -200, the flow direction is 90 degrees. Therefore, when the oblique direction astigmatism control value is changed, as a set value of the next oblique direction astigmatism control value for obtaining a clearer secondary electron image, there is no flow direction, or What is necessary is just to set the oblique astigmatism control value so that the direction of the flow becomes 0 degree or 90 degrees.

When the flow direction is close to 45 degrees or 135 degrees, it can be determined that the vertical and horizontal astigmatism control values are close to the optimum values, and the oblique astigmatism control values deviate from the optimum values. For example, in FIG. 4, (4) and (6) correspond. In this case, it is understood that the oblique astigmatism control value should be changed in order to obtain a clearer secondary electron image.

When the vertical and horizontal astigmatism control values are changed, the flow direction disappears or the vertical and horizontal astigmatism control values when the flow direction becomes 45 degrees or 135 degrees are optimal. Value. For example, in FIG.
In (4) and (7), the astigmatism control value in the vertical and horizontal directions is the optimum value 400. In (4), the flow direction is 1
35 degrees. Therefore, when the vertical and horizontal astigmatism control values are changed, the next vertical and horizontal astigmatism control values for obtaining a clearer secondary electron image are:
The astigmatism control value in the vertical and horizontal directions may be such that there is no flow direction or the flow direction is 45 degrees or 135 degrees.

In the following, an example is given of the relationship between the change in the flow direction when the focus and astigmatism control values change, and how to set the focus and astigmatism based on this will be described.

When the vertical and horizontal astigmatism control value (300) <optimal value (400), the oblique astigmatism control value is set to-
Increasing from 300 to −100 reduces the flow direction from 120 to 60 for the focus control value of 14600, unless there is no flow direction. Line numbers (1) to (3) are applicable, and the flow direction is centered at 90 degrees, and is from 45 degrees to 1
It is in the range of 35 degrees. In the case of the focus control value of 14800, the flow direction is reduced from 30 to 0 and from 180 to 150. Line numbers (19) to (21) correspond, and the flow direction is centered on 0 degree, and is 45 to 0 degrees and 180 to 13
It is in the range of 5 degrees.

Conversely, astigmatism control value in vertical and horizontal directions (500)>
In the case of the optimal value (400), the oblique astigmatism control value is increased from −300 to −100 except for the case where the focus control value is matched. Increases from 150 to 30. Line numbers (7) to (9) correspond, and the flow direction is in the range of 135 to 45 degrees, centered on 0 degree. In the case of the focus control value of 14800, the flow direction increases from 60 to 120. Line numbers (25) to (27) correspond, and the flow direction is centered at 90 degrees and ranges from 45 degrees to 135 degrees.

When the vertical and horizontal astigmatism control values are close to the optimum value (400), the focus control value is set to the optimum value (14).
Direction is 45 degrees or 1
35 degrees. In FIG. 4, the row numbers (4) to (6) and the row numbers (22) to (24) correspond. If the focus control value is close to the optimal value (14700), no flow will appear. FIG.
Corresponds to row numbers (10) to (18).

From these facts, by increasing the control value of the astigmatism in the oblique direction, the direction of the flow is reduced, and when the direction is in the range of 45 degrees to 135 degrees, the control value of the astigmatism in the vertical and horizontal directions is obtained. Is smaller than the optimal value. Therefore, in such a case, it is understood that the vertical and horizontal astigmatism control values should be further increased as the next focus and astigmatism control values for obtaining a clearer secondary electron image.

Similarly, by increasing the control value of the astigmatism in the oblique direction, the direction of the flow is increased. When the direction is in the range of 45 degrees to 135 degrees, the control value of the astigmatism in the vertical and horizontal directions becomes the optimum value. It can be inferred that this is the case. Therefore, in such a case, it is understood that the vertical and horizontal astigmatism control values should be made smaller as the next focus and astigmatism control values for obtaining a clearer secondary electron image.

Next, how to determine whether the focus control value is larger than the optimum value will be described. Focus control value is optimal 1
If it is smaller than 4700, and if the oblique astigmatism control value is smaller than the optimum value -200, the flow direction is in the range of 90 to 180 degrees, and the row numbers (1), (4),
(7) corresponds to this. Oblique astigmatism control value is optimal-
If it is larger than 200, the flow direction is in the range of 0 to 90 degrees, and the line numbers (3), (6), and (9) correspond.

Conversely, when the focus control value is larger than the optimum value of 14700, the oblique astigmatism control value becomes smaller than the optimum value of -20.
If it is less than 0, the flow direction is in the range of 0 to 90 degrees, and the line numbers (19), (22), and (25) correspond. If the oblique astigmatism control value is greater than the optimal value -200, the flow direction is in the range of 90 degrees to 180 degrees,
Line numbers (21), (24), and (27) correspond.

The control value of the astigmatism in the oblique direction is the optimum value−
When it is closer to 200, the direction is near 90 degrees or 0 degrees, and row numbers (2), (8), (20), and (26) correspond.

Thus, when the control value of the astigmatism in the oblique direction is reduced, the flow direction is in the range of 90 degrees to 180 degrees, and when the control value is increased, the flow direction is changed from 0 degrees to 90 degrees.
If it is in the range of degrees, it can be estimated that the focus control value is smaller than the optimum value. Therefore, it is understood that the focus control value should be further increased at the next focus and astigmatism control value. Conversely, when the oblique astigmatism control value is reduced, the flow direction is in the range of 0 to 90 degrees,
If the direction of the flow is in the range of 90 degrees to 180 degrees when the value is increased, it can be estimated that the focus control value is larger than the optimum value. Therefore, it is understood that the focus control value should be made smaller in the next focus and astigmatism.

The clarity evaluation value is also referred to in addition to the flow, and the focus and astigmatism values are estimated to be improved from the tendency of the clarity change when the focus and astigmatism are changed. An aberration control value may be determined. In particular, when there is no flow, it is necessary to determine the focus and astigmatism control values based on the evaluation value of clarity.

It has been found that, in a particular combination of astigmatism and focus control values in the vertical and horizontal directions, even if the respective control values are changed, the clarity of the combination of the values becomes the best. In this case, that is, when it is determined that the combination of the values is optimal, the combination of the values is determined to be optimal, the optimal value is set, and a series of operations may be terminated.

In the manner described above, the flow and direction of the secondary electron image, or the change in the flow and direction of the secondary electron image when the focus and astigmatism control values are changed, are used. Focus and astigmatism can be introduced to improve the secondary electron image into a clearer image.

According to the secondary electron image adjusting method as described above,
The existence, direction and clarity of the flow of the target shape in the secondary electron image obtained by irradiating the LSI surface with the electron beam while scanning can be evaluated, and based on those, a clearer secondary electron image can be obtained. By changing the focus control value and the astigmatism control value so as to obtain the following, it is possible to efficiently adjust to a clear secondary electron image.

[0056]

According to the method of the present invention, the presence / absence, direction, and clarity of the flow of the target shape in the secondary electron image obtained by irradiating the LSI surface while scanning the electron beam are utilized. Since it is possible to guide the way of changing the focus control value and the astigmatism control value for improving a clearer secondary electron image, the secondary electron is obtained by trial and error using only the clarity of the entire image. It is possible to automatically improve a clear secondary electron image more efficiently than a method for improving the image.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a first embodiment of the present invention.

FIG. 2 shows a configuration of an electron beam system in the electron beam tester.

FIG. 3 shows a configuration of a stigmatter in an electron beam tester.

FIG. 4 is a diagram showing an example of focus and astigmatism control values and data on the presence / absence and direction of a secondary electron image flow in an electron beam tester.

FIG. 5 is an example of a display screen when the focus and astigmatism control values of a secondary electron image by an electron beam tester are optimal.

FIG. 6 is an example of a display screen when there is a flow of a secondary electron image (about 10 degrees) and focus and astigmatism control values are not appropriate.

FIG. 7 is an example of a display screen when a secondary electron image does not flow but focus and astigmatism control values are not appropriate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Focus and astigmatism control value 2 Secondary electron image acquisition 3 Secondary electron image data 4 Flow / direction / clarity evaluation 5 Flow / direction / clarity 6 Change of focus and astigmatism control value 20 Vacuum chamber 21 Electron beam Source 22 Focusing lens 23 Objective lens aperture 24 Scan coil 25 Objective lens 26 Stigmater (vertical and lateral directions) 27 Stigmater (oblique direction) 28 Target LSI 30 Secondary electron detector 31 Excitation coil 32 Magnetic field 33 Electron beam center axis

Claims (8)

(57) [Claims] 1. While scanning the LSI surface with an electron beam
By irradiating, the shape of the LSI surface can be obtained.
Of the shape flow in the secondary electron image and the flow direction
Object in the secondary electron image
Change the astigmatism control value within the range centered on the shape.
Perform line detection and line extraction image processing to display the flow direction.
Extracting a passing line; and
By reading the angle in the direction range from 0 to 180 degrees,
Obtaining flow direction data; and
Changing the focus control value or the astigmatism control value.
In the secondary electron image adjusting method, the change of the astigmatism control value is such that the direction of the flow decreases by increasing the oblique astigmatism control value, and the direction is in a range of 45 degrees to 135 degrees. In this case, it is determined that the vertical and horizontal astigmatism control value is smaller than the optimum value, and the vertical and horizontal astigmatism control value is further increased. 2. While scanning the LSI surface with an electron beam
Of the shape in the secondary electron image obtained by irradiation
Presence or absence of flow and / or flow direction and before
For imaging, one of the focus control values or astigmatism control values
Flow in the secondary electron image obtained as a result of changing the section
Reading the presence or absence and flow direction or both,
Within the range centered on the target shape in the secondary electron image,
Image processing for line detection and line extraction by changing the aberration control value
Extracting a line representing the direction of the flow.
The angle of the line representing these directions is in the direction range of 0 to 180 degrees.
Obtaining flow direction data by reading in box
And the focus control value or astigmatism control based on the data.
In a secondary electron image adjustment method having a step of changing a control value
Te, the change in the astigmatism control value, if the direction of flow is reduced by increasing the oblique direction astigmatism control value, the direction is in the range of 135 degrees from 45 degrees, the vertical and horizontal directions non A secondary electron image adjustment method characterized by determining that the astigmatism control value is smaller than the optimum value, and increasing the astigmatism control value in the vertical and horizontal directions. 3. The method of claim 1, wherein the astigmatism control value is changed by increasing the oblique astigmatism control value so that the flow direction increases, and the direction is in a range of 45 degrees to 135 degrees. 3. The secondary electron image adjustment method according to claim 1, wherein it is determined that the vertical and horizontal astigmatism control value is larger than the optimum value, and the vertical and horizontal astigmatism control value is reduced. 4. The method according to claim 1, wherein the change of the focus control value reduces the oblique direction astigmatism control value.
If the flow direction is in the range of 0 to 90 degrees when the flow direction is in the range of 90 degrees to 180 degrees and the flow direction is increased in the range of 0 to 90 degrees, it is determined that the focus control value is smaller than the optimum value, and the focus control value is 3. The secondary electron image adjusting method according to claim 1, wherein the secondary electron image is adjusted. 5. The method according to claim 1, wherein the change in the focus control value decreases the oblique astigmatism control value so that the flow direction changes from 0 degrees to 90 degrees.
If the flow direction is in the range of 90 degrees to 180 degrees when it is increased, it is determined that the focus control value is larger than the optimum value, and the focus control value is set smaller.
Secondary electron image adjustment method according to claim 1 or 2, wherein the to. 6. A perforated flow shape in the secondary electron image
The reading of both or one of the direction and the direction of the flow is to read the presence or absence of the flow of the shape in the secondary electron image and the direction of the flow by the isolated high gradation point and the surrounding area in the secondary electron image. 3. A method according to claim 1, wherein
The method for adjusting a secondary electron image according to the above. 7. A flow of a shape in said secondary electron image.
The reading of the presence or absence and the flow direction is performed by reading the presence / absence and flow direction of the shape in the secondary electron image by the portion having the highest gradation within the entire secondary electron image or a part thereof. 3. The method for adjusting a secondary electron image according to claim 1, wherein: 8. Flow of shape in said secondary electron image
The reading of both or one of the presence and absence of the flow direction determines the presence or absence and the flow direction of the shape in the secondary electron image by the part where the most prominent edge is obtained within the entire secondary electron image or the part thereof. The secondary electron image adjusting method according to claim 1, wherein reading is performed.