JPH09259807A - Scanning electron microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the selection of field of view by providing field-of-view moving and electron beam deflecting means so as to switchingly display an observed image and an image having the position and magnification corresponding to a square frame displayed on the observed image. SOLUTION: An electron beam 1 passed through an electron beam passage is deflected by a polarizing coil 2, shifted by an electromagnetic field-of-view moving coil 3, and scanned on a sample 6 through an objective lens 4. The electron according to the form of the sample 6 is generated, detected by a detector 8, and digitally converted and stored by an image memory 9, and an image of low magnification is then displayed on a display device 13. The observing field-of-view range is displayed within the screen by a moving mechanism 7, a square frame is superposed on an intended observing field-of-view range and displayed, and the current of the deflecting coil 2 is then changed to vary the extending magnification.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method for selecting an observation field of view in a scanning electron microscope.

[0002]

2. Description of the Related Art To select a field of view in a scanning electron microscope, first, observe a wide field of view at a low magnification, search for a target site, move the sample so that the target site is at the center of magnification, and increase the magnification. It was done manually one by one.

[0003]

These operations are generally performed by repeating the movement of the position and the operation of increasing the magnification, which is a complicated operation. An object of the present invention is to perform sample movement and determination of magnification in one operation.

[0004]

The apparatus of the present invention makes it possible to automatically perform sample movement control and magnification control by indicating a portion to be magnified and observed with a rectangular frame on a low-magnification observation image, thereby facilitating field selection. It is characterized by

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram of an embodiment of the present invention. In the figure, 1 is an electron beam, and 2 is a deflection electromagnetic coil for scanning the surface of the sample with the electron beam, which is provided with coils in the X and Y directions. 3 is an electromagnetic field moving coil for electromagnetically moving the visual field, 4 is an objective lens for focusing an electron beam on the sample, 5 is a sample chamber kept in a high vacuum state, 6 is a sample, 7 is a moving mechanism of the sample, 8 is a detector of secondary electrons generated from the sample, 9 is an image memory for digitizing the detection signal from the detector and storing it as image data, 13 is an image display device, Reference numeral 12 is a control circuit using a deflection electromagnetic coil, an objective lens, a microcomputer for controlling a sample moving mechanism, and the like. Here, 10 is a rectangular frame display memory for displaying a rectangular frame by overlaying it on the observed image, and 11 is an image superimposing circuit for overlaying the observed image and the rectangular frame.

The electron beam 1 passes through an electron beam path kept in a high vacuum state, is deflected by the magnetic field of the deflection coil 2, is shifted by the electromagnetic field moving coil 3, and is focused on the sample 6 by the objective lens 4. And scan over the sample. When the sample is irradiated with an electron beam, secondary electrons, reflected electrons, and the like that accompany the shape of the sample are generated, detected by the detector 8, digitally converted and stored in the image memory 9, and then displayed on the display device 13. Is displayed. Here, the position of the sample is set by the moving mechanism 7.
It can be moved to a desired observation position, and the magnifying power can be changed by changing the current of the deflection coil 2. These are usually controlled by the control circuit 12 in response to an instruction from the operator to move the sample or change the magnification.

As a method of using the above-described apparatus, a low-magnification image is first displayed on the display device 13, and the sample is moved so that the desired observation visual field range is displayed on the screen. Next, a rectangular frame is superimposed and displayed on the target observation visual field range. The rectangular frame may be represented as long as a rectangular area can be designated, and a box cursor, a square cross mark display, or the like can be considered. FIG. 2 shows a diagram in which the rectangular frame 14 is displayed on the low-magnification image on the left and an enlarged image on the right. As a method of inputting the rectangular frame 14, the position and size of the frame are determined by pointing the target observation site with an input device such as a mouse. The position and magnification of the enlarged image are calculated by the control circuit 12 such as a microcomputer from the X and Y pixel information on the image memory for the frame, and the moving mechanism 7 and the deflection coil 2 are controlled.

FIG. 3 shows a procedure for calculating the position and magnification of the enlarged image from the X and Y pixel information of the rectangular frame. Here, the sample position (center coordinate) before enlargement is (x1, y1), the sample position (center coordinate) of the enlarged image is (x2, y2), and the square frame 14
Let xd2, yd2 be the distance from the center of the display image, s1 be the width of the image before enlargement, and s2 be the width of the image after enlargement.

S1, s2 and xd2, yd2 are usually expressed by the number of display pixels. First, the sample position (center coordinates) (x2, y2) of the enlarged image is obtained from xd2 and yd2 as follows. (X2, y2) = (x1 + xd2 * lmag1, y1 + yd
2 * lmag1) Here, lmag1 is the distance per pixel in the observation magnification mag1 before enlargement, and is uniquely determined from the magnification of the observed image and the number of display pixels.

Next, the magnifying power mag2 is obtained as follows.

Mag2 = mag1 * (s1 / s2) In this way, the control circuit 12 uses (x2, y
2), mag2 is obtained, the sample is moved so that the coordinates become (x2, y2), and the deflection coil 2 is controlled so as to obtain the observation magnification of mag2.

In the above-mentioned embodiment, the moving mechanism of the sample is used as the moving means of the observed image, but the moving precision is improved by using the electromagnetic field movement during the observation at high magnification. Generally, since the movable range of the electromagnetic visual field is limited, the electromagnetic visual field movement may be used when the moving distance to the screen center of the designated area is within the movable range.

[0014]

According to the present invention, the observation field of view, which is one of the troublesome operations in a scanning electron microscope or the like, can be easily selected, and the operability is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a scanning electron microscope.

FIG. 2 is a diagram showing selection of a visual field by a rectangular frame on an image.

FIG. 3 is a diagram showing a procedure for enlarging a rectangular frame.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron beam, 2 ... Electromagnetic coil for deflection, 3 ... Electromagnetic field moving coil, 4 ... Objective lens, 5 ... Sample chamber, 6 ... Sample, 7 ... Sample moving mechanism, 8 ... Detector, 9 ... Image memory,
10 ... Square frame display memory, 11 ... Image overlay circuit, 12
... Control circuit, 13 ... Display device, 14 ... Square frame.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichiro Tomizawa 1040 Ichige, Ichima, Hitachinaka City, Ibaraki Prefecture Hitachi Science Systems, Inc. Within Hitachi Science Systems

Claims (3)

[Claims] 1. A scanning electron microscope equipped with a deflector for scanning a focused electron beam on a sample according to a magnification, a moving mechanism for moving the sample, and a control device therefor. A means for controlling the sample movement and the deflection of the electron beam is provided so as to superimpose and display a square frame of an arbitrary position and size, and then switch and display the image of the position and the magnification corresponding to the square frame, A scanning electron microscope characterized by facilitating field selection. 2. The scanning electron microscope according to claim 1, wherein the sample moving mechanism is controlled so that the center position of the rectangular frame is at the center of the observation image to be switched and displayed. 3. The magnification of the observation image after switching and selecting is determined from the ratio of the size of the square frame to the size of the entire observation image and the observation magnification in the state in which the square frame is displayed. A device characterized by.