JP2000277046A - Automatic focusing method in scanning electronic microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always obtain a focused point and automatically performs a focus match of a scanning type electronic microscope regardless of the presence of non-point aberra tion and a distribution state of each edge in the sample, etc. SOLUTION: An (x) direction detection value and (y) direction detection value are obtained for a current value of each objective lens by changing the current value of the objective lens (steps S1 to S5). A maximum value of the (x) direction detection value and a maximum value of the (y) direction detection value are detected, then a focused point is obtained based on the maximum value of the (x) direction detection values and the maximum value of the (y) direction detection value (step S6). The focus match is then performed (step S7). The (x) direction detection value is calculated that the (y) direction integration information signal obtained by integrating the information signal along (y) direction is used as a unit information value, by using a predetermined arithmetic equation. The (y) direction detection value is calculated that the (x) direction integration information signal obtained by integrating an information signal along the (x) direction is used as a unit information value, by using a predetermined arithmetic equation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an automatic focusing method for a scanning electron microscope.

[0002]

2. Description of the Related Art Conventionally, automatic focusing in this type of scanning electron microscope has been performed with a configuration as shown in FIG.

In FIG. 9, reference numeral 1 denotes a lens barrel, 2 denotes an electron gun, and electrons emitted from the electron gun 2 are converged by a converging lens 3 and are two-dimensionally scanned by a scanning coil 5 controlled by a scanning circuit 4. And is squeezed by the objective lens 6 and radiated onto the sample 8 as an electron probe 7, whereby secondary electrons are emitted from the sample 8. The secondary electrons emitted from the sample 8 are detected by a detector 9, and a high-frequency component signal is extracted by a high-frequency component extraction filter 10 to obtain a secondary electron image (information signal), and the A / D converter The signal is converted into a digital signal by 11 and stored in the information signal storage unit 12.

The information signal storage unit 12 includes an electronic probe 7
A two-dimensional information signal group for each two-dimensional position (x, y) as shown in FIG. 10 is stored corresponding to each position on the sample 8 scanned by.

[0005] The detection value calculation unit 100 includes an information signal storage unit 1
Based on the two-dimensional information signal group stored in 2, a detection value S (I) for the current I (current objective lens current value) currently supplied to the objective lens 6 is obtained. This operation is
Conventionally, an information signal h (x, y) for each position (x, y) is determined as a unit information value using a predetermined arithmetic expression. As the arithmetic expression, for example, the sum of squares of each unit information value (the following expression (P1)) or the sum of squares of the difference between adjacent unit information values (the following expression (P2) or expression (P3)) Are used.

S (I) = ΣyΣx ｛h (x, y)｝ ² (P1) S (I) = ΣyΣx ｛h (x, y) -h (x−1, y)｝ ² (P2) S (I) = {y} x {h (x, y) -h (x, y-1)} ² (P3)

The detected value S (I) is stored in the detected value storage unit 110 in association with the current objective lens current value I.

When the detected value calculating section 100 obtains a detected value S (I) for one objective lens current value I and stores it in the detected value storage section 110, it controls the objective lens current output circuit 13 to send the objective lens 5 The supplied current value I is changed, and the detected value S (I) for the new objective lens current value I is stored in the detected value storage unit 110 in the same process as described above. Thereafter, the detection value S (I) for each objective lens current value I is stored in the detection value storage unit 110 while sequentially changing the objective lens current value I in the same manner.

The in-focus position determination section 120 determines the in-focus position based on the detected value S (I) for each objective lens current value I stored in the detected value storage section 110. That is, the focal position of the electronic probe 7 changes depending on the difference in the objective lens current value I, and the value of the detection value S (I) changes accordingly.

For example, when there is no astigmatism, FIG.
As shown in (a), when the electron probe 7 converges on P and the focus position of the electron probe 7 is on the sample 8, the diameter of the electron probe 7 on the sample 8 becomes minimum, and at this time, the detection value S ( I) is maximum. That is, the detection value S (I) for each objective lens current value I without astigmatism
12A, as shown in FIG. 12A, the change characteristic of the detection value S (I) with respect to each objective lens current value I shows a unimodal characteristic, and the maximum value of the detection value S (I) is focused. And the objective lens current value If at the in-focus position is obtained.

In a state where there is astigmatism, FIG.
As shown in (b), the electron probes 7 on the u axis parallel to the meridian plane gather at P1 at the meridional image position, and the electron probes 7 on the v axis orthogonal to the u axis gather at P2 at the sagittal image position. The distance between P1 and P2 is called astigmatic difference, and P1
An intermediate position (１ ／ of the astigmatism difference) between P and P2 is the position P of the circle of least confusion, and the position P of the circle of least confusion is the focal point position in a state where there is astigmatism. Here, the detection value S for each objective lens current value I in a state where there is astigmatism
When (I) is graphed, as shown in FIG.
The change characteristic of the detection value S (I) with respect to each objective lens current value I shows a bimodal property in which two peaks corresponding to P1 and P2 are formed. Then, an intermediate point between the two peaks becomes a focal point corresponding to the position P of the circle of least confusion, and the objective lens current value If at the focal point is obtained.

If the objective lens current value If at the in-focus position obtained as described above is output to the objective lens 6, the focus can be adjusted automatically.

[0013]

However, the prior art having such a structure has the following problems. Due to the existence of an edge-like structure on the sample 8, the distribution of the information signal differs between the in-focus state and the out-of-focus state, and this difference is different from the detection value S (I) of the in-focus state. This causes a difference in detection value S (I) from the out-of-focus state.

It has been described that in a state where there is astigmatism, two peaks are formed in the change characteristic of the detection value S (I) with respect to each objective lens current value I. 8, the magnitude of the other peak having a component in the u-axis direction is determined by the amount and magnitude of the edge having a component in the u-axis direction. It depends on the amount and size.

That is, among the edges in the sample 8, u
If the distribution of the amount of the edge having the component in the axial direction and the like and the amount of the edge having the component in the v-axis direction are uniform, two peaks are clearly formed, but the edge having the component in each axial direction If there is a bias in the distribution of the amounts of the two peaks, as shown in FIG. 13, a significant difference occurs in the size of the two peaks, one peak is absorbed by the other peak, and the two peaks are clearly formed. Disappears. In the case of FIG. 13, the detection value S (I)
Is the maximum value of one of the peaks, which is different from the focus position, and the two peaks cannot be detected. Therefore, the intermediate point cannot be detected. As a result, the focus position cannot be obtained. Become.

The present invention has been made in view of such circumstances, and a scanning method capable of always finding a focused position regardless of the presence or absence of astigmatism and the distribution state of each edge in a sample. It is an object of the present invention to provide an automatic focusing method in a scanning electron microscope.

[0017]

The present invention has the following configuration to achieve the above object. That is, according to the present invention, a two-dimensional information signal obtained from a sample based on the irradiation of the electron beam is obtained by converging an electron beam emitted from an electron gun and irradiating the sample with a two-dimensional scan on a sample surface. In an automatic focusing method in a scanning electron microscope for detecting a group and obtaining a focal point position, the two-dimensional information signal group is subjected to x along one direction (x direction) of the two dimensions. The direction detection value is calculated using a predetermined arithmetic expression with a y-direction integrated information signal obtained by integrating information signals along a direction (y direction) orthogonal to the x direction as a unit information value. Assuming that the detected value in the y direction along the direction is calculated using a predetermined arithmetic expression with the x direction integrated information signal obtained by integrating the information signal along the x direction as a unit information value, the objective lens current value is changed. While
The x-direction detection value and the y value for each objective lens current value
A direction detection value is obtained, a maximum value of the x-direction detection value and a maximum value of the y-direction detection value are detected, and a sum is calculated based on the maximum value of the x-direction detection value and the maximum value of the y-direction detection value. It is characterized in that focusing is performed by obtaining a focal position.

[Operation] The operation of the present invention is as follows. The electron beam emitted from the electron gun is converged, two-dimensionally scanned and irradiated onto the sample surface, and a two-dimensional information signal group obtained from the sample based on the irradiation of the electron beam is subjected to the second step. Conventionally, a detected value in the x direction along one direction (x direction) of the dimension is used as a unit information value using a y direction integrated information signal obtained by integrating an information signal along a direction (y direction) orthogonal to the x direction. Calculated using the same arithmetic expression as above, and the y-direction detection value along the y-direction is defined as an x-direction integrated information signal obtained by integrating the information signal along the x-direction as a unit information value. It shall be calculated using an arithmetic expression.

According to the x-direction detection value obtained in this manner, among the blurs in the out-of-focus state, only the x-direction blur can be detected, so that the focus state in the x-direction can be evaluated.
Further, according to the y-direction detection value, among the blurs in the out-of-focus state, only the y-direction blur can be detected, so that the focus state in the y direction can be evaluated.

Then, the x-direction detection value and the y-direction detection value for each objective lens current value are obtained while changing the objective lens current value. Next, the maximum value of the x-direction detection values for each objective lens current value and the maximum value of each y-direction detection value for each objective lens current value are detected. Then, the in-focus position is obtained based on the maximum value of the x-direction detection value and the maximum value of the y-direction detection value, and the focusing is performed by specifying the objective lens current value with respect to the focus position.

Each detected value in the x direction for each objective lens current value indicates a characteristic change of the detected value corresponding to the focus state in the x direction, and each detected value in the y direction for each objective lens current value is
5 shows a characteristic change of a detection value corresponding to a focus state in the y direction.

In a state where there is no astigmatism, the maximum value among the detected values in each x direction for each current value of the objective lens corresponds to the focal position in the x direction, and each y value for each current value of the objective lens.
The maximum value of the direction detection values corresponds to the focus position in the y direction. Further, when there is no astigmatism, the focus position in the x direction and the focus position in the y direction are the same, so the maximum value position of the detected value in the x direction (the objective lens current value corresponding to) and the y direction It is the same as the maximum value position of the detection value (the objective lens current value corresponding to the position).

In the state where there is astigmatism, the maximum value among the x-direction detection values for each objective lens current value is one of two focal positions equidistant with respect to the in-focus position. And the maximum value of the detected values in the y direction for each objective lens current value appears at a position corresponding to the other of the two focal positions. Then, an intermediate position (objective lens current value corresponding to) between the maximum value position of the x-direction detection value (objective lens current value corresponding to) and the maximum value position of the y-direction detection value (objective lens current value corresponding to). Corresponds to the in-focus position.

Accordingly, the result of adding the maximum value position of the x-direction detection value (objective lens current value corresponding to) and the maximum value of the y-direction detection value (objective lens current value corresponding to) is 2
By dividing by, the in-focus position (the objective lens current value corresponding to) can be calculated regardless of the presence or absence of astigmatism.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an apparatus configuration for realizing an automatic focusing method in a scanning electron microscope according to one embodiment of the present invention.

In FIG. 1, components denoted by reference numerals 1 to 13 are the same as those of the conventional apparatus (FIG. 9). In this embodiment, the detection value calculation unit 100 and the detection value storage unit 11 of the conventional device are used.
0, instead of the in-focus position determination section 120, the x-direction detection value calculation section 20, the y-direction detection value calculation section 21, the x-direction detection value storage section 22, the y-direction detection value storage section 23, and the in-focus position determination section 24. In addition, one objective lens current value I
X-direction detection value Sx (I) and y-direction detection value Sy
(I) are obtained, and the x-direction detection value storage unit 22
And the y-direction detection value storage unit 23, the current value I supplied from the objective lens current output circuit 13 to the objective lens 5
Is configured to change.

The x-direction detection value calculation section 20 is a two-dimensional information storage group stored in the information signal storage section 12 (see FIG. 10).
As shown in FIG. 2, first, for each x-coordinate, a y-direction integrated information signal Ry (x) (= Σy [h (x, x, y) obtained by integrating the information signal h (x, y) along the y-direction. y)]), and using the y-direction integral information signal Ry (x) as a unit information value, the same arithmetic expression as in the past, for example, each unit information value Ry
Using the sum of squares of (x) (formula (1) below) or the like, the x-direction detection value Sx (I) for one objective lens current value I
Get.

Sx (I) = {x ｛Ry (x)｝ ² = {x ｛Σy [h (x, y)]｝ ² (1)

The x-direction detection value Sx thus obtained
According to (I), among the blurs in the out-of-focus state, the blur in only the x direction can be detected, so that the focus state in the x direction can be evaluated.

As shown in FIG. 3, the y-direction detection value calculating section 21 first obtains information along the x-direction for each y coordinate from the two-dimensional information storage group stored in the information signal storage section 12, as shown in FIG. An x-direction integration information signal Rx obtained by integrating the signal h (x, y)
(Y) (= Σx [h (x, y)]) is obtained, and this x-direction integral information signal Rx (y) is used as a unit information value, and the same arithmetic expression as in the past, for example, each unit information value Rx (y) The y-direction detection value Sy (I) for one objective lens current value I is obtained using the sum of squares of the following (formula (2) below).

Sy (I) = {y ｛Rx (y)｝ ² = Σy ｛Σx [h (x, y)]｝ ² (2)

The y-direction detection value Sy thus obtained is
According to (I), among the blurs in the out-of-focus state, only the blur in the y direction can be detected, so that the focus state in the y direction can be evaluated.

In the x-direction detection value storage section 22, the x-direction detection value Sx (I) for each obtained objective lens current value I is associated with the objective lens current value I while sequentially changing the objective lens current value I. The y-direction detection value storage unit 23 stores the obtained y-direction detection value Sy (I) for each objective lens current value I in association with the objective lens current value I while sequentially changing the objective lens current value I. It is memorized.

Each detected value Sx (I) in the x direction for each objective lens current value I indicates a characteristic change of the detected value corresponding to the focus state in the x direction.
The direction detection value Sy (I) indicates a characteristic change of the detection value corresponding to the focus state in the y direction.

FIG. 4 is a graph showing each detected value in the x direction Sx (I) and each detected value in the y direction Sy (I) with respect to each objective lens current value I in a state where there is no astigmatism.

As shown in FIG. 4, when there is no astigmatism, each x-direction detection value Sx for each objective lens current value I
The maximum value of (I) corresponds to the focal position in the x direction,
Each y direction detection value Sy for each objective lens current value I
The maximum value in (I) corresponds to the focus position in the y direction. Further, in a state where there is no astigmatism, the focus position in the x direction and the focus position in the y direction are the same, so that the objective lens current value corresponding to the maximum value position of the x direction detection value Sx (I) ( Ix = If) and the maximum value position (corresponding to the objective lens current value Iy = If) of the y-direction detection value Sy (I) are the same.

FIG. 5 is a graph showing an example of each detected value Sx (I) in the x direction and each detected value Sy (I) in the y direction with respect to each current value I of the objective lens in a state where there is astigmatism.

As shown in FIG. 5, when there is astigmatism, each x-direction detection value Sx for each objective lens current value I
The maximum value of (I) appears at a position corresponding to one of two focal positions (P1 and P2 in FIG. 11B) equidistant from the in-focus position. The maximum value of the y-direction detection values Sy (I) for the objective lens current value I appears at a position corresponding to the other of the two focal positions. Then, the x direction detection value Sx
Objective lens current value I corresponding to the maximum value position (I)
An intermediate position (corresponding to the objective lens current value If) corresponding to the maximum value position (corresponding to the objective lens current value Iy) of the x-direction detection value Sy (I) corresponds to the in-focus position.

Here, the focal positions P1, P in FIG.
The peak corresponding to 2 is formed when the diameter Du of the electron probe 7 in the u-axis direction becomes minimum and when the diameter Dv of the electron probe 7 in the v-axis direction becomes minimum. On the other hand, the uv coordinates and the xy coordinates do not always match. Since the x direction detection value Sx (I) is obtained by integrating the information signal along the y direction, its peak is formed at a position where the width Dx of the electron probe 7 in the x direction becomes minimum. Since the y-direction detection value Sy (I) is obtained by integrating the information signal along the x-direction, its peak is the width Dy of the electron probe 7 in the y-direction.
Is formed at the position where the minimum value is obtained. For example, as shown in FIG. 7A, when the uv coordinate and the xy coordinate coincide with each other, as shown in FIG. 5, like the two peaks obtained by the conventional method (see FIG. 12B). The x-direction detection value Sx
The position where the maximum value of (I) appears, and the y-direction detection value Sy
The position where the maximum value of (I) appears is the position farthest from the focal point position. Also, as shown in FIG.
When the coordinates and the xy coordinates are shifted by 45 °, Dx and Dy
Is always equal, in this case, as shown in FIG. 6, the position where the maximum value of the x-direction detection value Sx (I) appears,
The position where the maximum value of the y-direction detection value Sy (I) appears coincides with the in-focus position. Then, the x direction detection value Sx
The position where the maximum value of (I) appears, and the y-direction detection value Sy
The position where the maximum value of (I) appears is a position between the position shown in FIG. 5 and the position shown in FIG. 6 according to the deviation angle between the uv coordinate and the xy coordinate. Also, no matter what angle the uv coordinate and the xy coordinate are shifted, the x direction detection value Sx
The position where the maximum value of (I) appears, and the y-direction detection value Sy
The position where the maximum value of (I) appears is always equidistant from the in-focus position.

Based on the above, the in-focus position calculating section 24
First, the maximum value (corresponding to the objective lens current value Ix) of each x-direction detection value Sx (I) for each objective lens current value I stored in the x-direction detection value storage unit 22 and the y-direction detection value The maximum value (corresponding to the objective lens current value Iy) of the respective y-direction detection values Sy (I) for each objective lens current value I stored in the storage unit 23 is detected. And
As shown in the following equation (3), the x-direction detection values Sx
The result of adding the maximum value of (I) (the objective lens current value Ix corresponding to) and the maximum value of the y-direction detection value Sy (I) (the objective lens current value Iy) is divided by two, The in-focus position (object lens current value If corresponding to) is calculated.

If = (Ix + Iy) / 2 (3)

According to the above equation (3), for example, as shown in FIGS. 4 and 6, the maximum value (corresponding to the objective lens current value Ix) of the x-direction detection value Sx (I) and the y-direction detection value Value S
Maximum value of y (I) (objective lens current value Iy corresponding to)
Even if and coincides with the in-focus position (the objective lens current value If corresponding to), the in-focus position (the objective lens current value If corresponding to) can be obtained.

If (the objective lens current value If corresponding to) is obtained, the objective lens current value If is output to the objective lens 6, the focus can be adjusted automatically.

FIG. 8 shows the processing procedure of the above embodiment. In addition, as a processing procedure, the step width of step S5 is
Initially, a large step width is set, and coarse focusing is performed while sequentially changing the objective lens current value I with the large step width. As a result, about the objective lens current value If determined to be the in-focus position, By performing detailed focusing while sequentially changing the objective lens current value I with a small step width, the accuracy of focusing can be improved.

As described above, according to this embodiment, the focus state is evaluated separately for the focus state in the x direction and the focus state in the y direction, and in a state where there is astigmatism, the focus state is sandwiched. Since the peaks corresponding to the two equidistant focal positions (P1, P2) are separately detected, the distribution of each edge in the sample 8 is biased, and the difference between the two peaks is significantly different. Occurs, and even if one peak is smaller than the other peak, two peaks can be detected and the objective lens current value I corresponding to the in-focus position (
f) can be determined. Further, even when there is no astigmatism, the in-focus position can be obtained by the same processing as when there is no astigmatism. Therefore, regardless of the presence or absence of astigmatism and the distribution state of each edge in the sample 8, the in-focus position can always be obtained, and the in-focus position can always be obtained by the same processing.

In the above embodiment, the x-direction detection value Sx
The sum of squares of each unit information value (Ry (x), Rx (y)) was used as an arithmetic expression for calculating (I) and the y-direction detection value Sy (I). For example, the following expression (4) , (5), the sum of squares of the differences between adjacent unit information values (Ry (x), Rx (y)) may be used, or the detection value S (I)
May be used.

Sx (I) = {x ｛Ry (x) −Ry (x−1)｝ ² Σx ｛Σy [h (x, y)] − Σy [h (x−1, y)]｝ ² ... ( 4) Sy (I) = Σy {Rx (y) -Rx (y-1)} 2 Σy {Σx [h (x, y)] -? x [h (x, y-1)]} ² (5 )

In the configuration of FIG. 1, the information signal storage unit 1
After storing the digitized two-dimensional information signal group into two, the x direction detection value Sx (I) and the y direction detection value Sy (I)
However, the present invention is not limited to this configuration.

For example, if the two-dimensional scanning of the electronic probe 7 is performed while sequentially changing the position of the electronic probe 7 in the y direction while changing the position in the x direction, the integration information in the y direction is obtained for each scanning in the y direction. The signal Ry (x) can be determined by an analog signal, and the x-direction detection value Sx (I) can also be determined by an analog signal. Further, if the two-dimensional scanning of the electronic probe 7 is performed while changing the position of the electronic probe 7 in the x direction sequentially in the y direction, the x direction integration information signal Rx ( y) can be obtained from an analog signal, and furthermore, the y-direction detection value Sy
(I) can also be obtained from an analog signal. Therefore,
For one objective lens current value I, in the first scan,
The electronic probe 7 scans along the y direction while sequentially changing the position in the x direction. In the second scan, the electronic probe 7 scans along the x direction while sequentially changing the position in the y direction. If two-dimensional scanning of the electronic probe 7 is performed twice for one objective lens current value I while changing the scanning direction, the x-direction detection value Sx (I) for one objective lens current value I is obtained. The method according to the present invention can also be realized with a configuration in which a circuit for obtaining the y-direction detection value Sy (I) with an analog signal is incorporated.

The information signal is not limited to secondary electrons, and the method of the present invention can be similarly applied to other information signals obtained from the sample 8 such as reflected electrons.

[0051]

As is apparent from the above description, according to the present invention, the focus state is evaluated separately for the focus state in the x direction and the focus state in the y direction. Since the peaks corresponding to the two focal positions equidistant from the focal position are separately detected, the in-focus position can be obtained even if the distribution of each edge in the sample is biased. Further, according to the present invention, even when there is no astigmatism, the in-focus position can be obtained by the same processing as when there is astigmatism. Therefore, regardless of the presence or absence of astigmatism and the distribution state of each edge in the sample, the in-focus position can always be obtained, and the in-focus position can always be obtained by the same process.

[Brief description of the drawings]

FIG. 1 is a diagram showing an apparatus configuration for realizing an automatic focusing method in a scanning electron microscope according to one embodiment of the present invention.

FIG. 2 is a diagram for explaining a method of calculating a y-direction integral information signal.

FIG. 3 is a diagram for explaining a method of calculating an x-direction integration information signal.

FIG. 4 is a graph showing each detected value in the x direction and each detected value in the y direction with respect to each objective lens current value in a state where there is no astigmatism.

FIG. 5 is a graph showing an example of each detected value in the x direction and each detected value in the y direction with respect to each objective lens current value in a state where there is astigmatism.

FIG. 6 is a graph showing another example of each detected value in the x direction and each detected value in the y direction with respect to each objective lens current value in a state where astigmatism is present.

FIG. 7 is a diagram showing a positional relationship between uv coordinates and xy coordinates.

FIG. 8 is a flowchart illustrating a processing procedure of an automatic focusing method according to the embodiment.

FIG. 9 is a diagram showing the configuration of a conventional apparatus for realizing an automatic focusing method in a scanning electron microscope.

FIG. 10 is a diagram showing a two-dimensional information signal group.

FIGS. 11A and 11B are diagrams showing a focusing state of the electron probe in a state without astigmatism and in a state with astigmatism. FIGS.

FIG. 12 is a graph of a conventional detection value.

FIG. 13 is a diagram for explaining a problem of the related art.

[Explanation of symbols]

2: electron gun 3: converging lens 5: scanning coil 6: objective lens 7: electron probe 8: sample h (x, y): information signal Ry (x): y-direction integration information signal Rx (y): x-direction integration Information signal Sx (I): Detected value in x direction Sy (I): Detected value in y direction I: Objective lens current value Ix: Objective lens current value corresponding to the maximum value of detected value in x direction Iy: Maximum detected value in y direction Object current value corresponding to value If: Object lens current value corresponding to focus position

Claims (1)

[Claims] An electron beam emitted from an electron gun is converged and two-dimensionally scanned and irradiated on a sample surface, and a two-dimensional information signal group obtained from the sample based on the electron beam irradiation. In the automatic focusing method in the scanning electron microscope for detecting the focus position by detecting the two-dimensional information signal group, the x-direction along the direction (x-direction) on one side of the two-dimensional information signal group A detected value is calculated using a predetermined arithmetic expression with a y-direction integrated information signal obtained by integrating information signals along a direction (y direction) orthogonal to the x direction as a unit information value, and the y direction is calculated. The y-direction detection value along is calculated as a unit information value using the x-direction integration information signal obtained by integrating the information signal along the x direction using a predetermined arithmetic expression, while changing the objective lens current value. ,
The x-direction detection value and the y value for each objective lens current value
A direction detection value is obtained, a maximum value of the x-direction detection value and a maximum value of the y-direction detection value are detected, and a sum is calculated based on the maximum value of the x-direction detection value and the maximum value of the y-direction detection value. An automatic focusing method in a scanning electron microscope, wherein a focusing position is determined and focusing is performed.