JPH0969350A - Optical axis matching device of scanning electron microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an optical axis to be automatically matched by detecting the focus center of an image. SOLUTION: When an electron beam 1 scans the diameter of a hole on a diaphragm 4, the brightness is made to the maximum extent. A horizontal coordinate in which the vertical brightness in relation to the horizontal coordinate of an image memory 12 is maximized is found by a CPU 13, and the vertical coordinate in which the horizontal brightness in relation to the vertical coordinate is maximized is found. It is taken as the central coordinate of the diaphragm 4, and the deflection amount is found from the difference to the image center. Deflection signals are supplied to a horizontal deflection signal generating unit 5 and a vertical deflection signal generating unit 6, and the optical axis can be matched so that the electron beam 1 may pass the center part of the diaphragm 4. A means for specifying the center of the diaphragm 4 of the image is provided in stead of the central coordinate of the diaphragm 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical axis aligning device for a scanning electron microscope.

[0002]

2. Description of the Related Art A method of passing an electron beam through a diaphragm center is as follows.
The final confirmation is made by visual inspection, although the iris is directly moved or the axial alignment method by electric means is used.

[0003]

In the scanning electron microscope, the alignment of the electron beam is indispensable, and visual alignment makes the image result different depending on the operator, lowering the reliability, and further fully automating the operation. Interfere with

An object of the present invention is to detect the center of an image stop and automatically align the optical axis.

[0005]

In order to achieve the above-mentioned object, the present invention automatically detects the center of the aperture of the displayed image and makes the electron beam pass through the center of the aperture. A means for designating the center of the aperture is provided.

[0006]

The operability and reliability are improved by automatically detecting the aperture center of the displayed image and automatically allowing the electron beam to pass through the aperture center.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram of an apparatus embodying the present invention. The electron beam 1 is scanned on the diaphragm 4 in the X and Y directions by the scanning coils 3x and 3y. Scanning coils 3x, 3y
The scanning signals from the horizontal scanning signal generator 7 and the vertical scanning signal generator 8 are supplied to. CRT1 used for scanning image display
The scanning coils 9x and 9y of 0 have horizontal scanning signal generators 7,
A scanning signal is supplied from the vertical scanning signal generator 8. Further, the detection signal detected by the detector 11 is
2 and CRT10 are supplied as luminance signals, so CR
The scan image is displayed at T10. The CPU 13 analyzes the scan image captured in the image memory 12 to detect the center of the aperture,
By controlling the horizontal deflection signal generation unit 5 and the vertical deflection signal generation unit 6 and supplying the deflection signals to the deflection coils 2x and 2y, the electron beam 1 can be passed at the center position of the diaphragm 4.

FIG. 2 is an explanatory view showing an embodiment for automatically detecting the center of the diaphragm. Since the electron beam 1 scans the diaphragm 4, the CRT image is as shown in FIG. 3A, and the signal intensity of the image memory for the vertical coordinate yi is as shown in FIG. 3B. Since the brightness becomes maximum when the electron beam 1 scans the diameter of the hole on the diaphragm 4, the CUP 13 obtains the horizontal coordinate at which the brightness in the vertical direction with respect to the horizontal coordinate of the image memory 12 becomes maximum, and the horizontal coordinate with respect to the vertical coordinate is obtained. Find the vertical coordinate that maximizes the luminance in the direction. The calculated coordinates are used as the center coordinates of the diaphragm 4, the deflection amount is calculated from the difference from the center of the image, and the deflection signal is supplied to the horizontal deflection signal generation unit 5 and the vertical deflection signal generation unit 6, so that the electron beam 1 is moved to the diaphragm 4 The optical axis can be aligned so as to pass through the center of, and the CRT image is as shown in FIG.

Instead of the center coordinates of the diaphragm 4, FIG.
By specifying the coordinates with the mark 14 as shown in
Similarly to the above, the optical axis can be aligned so that the electron beam 1 passes through the center of the diaphragm 4, and the CRT image is shown in FIG.

[0011]

According to the present invention, in the scanning electron microscope and similar apparatus, the optical axis alignment can be automated so that the electron beam passes through the center of the diaphragm.

[Brief description of drawings]

1 is a block diagram of an apparatus for implementing the present invention.

FIG. 2 is an explanatory diagram of automatic optical axis alignment.

FIG. 3 is an explanatory diagram of a relationship between a CRT image and signal intensity.

FIG. 4 is an explanatory diagram of coordinate designated optical axis alignment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron beam, 2x, 2y ... Deflection coil, 3x, 3y ... Scanning coil, 4 ... Aperture, 5 ... Horizontal deflection signal generator, 6 ... Vertical deflection signal generator, 7 ... Horizontal scanning signal generator, 8 ... Vertical Scan signal generator, 9x, 9y ... CRT scan coil, 1
0 ... CRT, 11 ... Detector, 12 ... Image memory, 13 ...
CPU, 14 ... A mark that specifies coordinates.

Claims (3)

[Claims] 1. A means for scanning an electron beam on a diaphragm, a display means for displaying an image in synchronization with the scanning of the electron beam, an electron beam deflecting means orthogonal to each other, a deflection signal generating means, and the deflection signal generating. In the scanning electron microscope, which comprises means for changing and supplying the output of the means, and is configured to change the output of the deflection signal to deflect the electron beam, the center of the aperture of the displayed image is detected and the deflection is performed. An optical axis aligning device for a scanning electron microscope, which has a function of changing the output of a signal so that the electron beam passes through the center of the diaphragm. 2. An optical axis aligning device for a scanning electron microscope according to claim 1, further comprising means for detecting a change in a luminance signal of the image to detect a center of the diaphragm. 3. The optical axis aligning device for a scanning electron microscope according to claim 2, wherein the center of the diaphragm to be detected can be designated on an image.