JPS5875748A - Image revolution corrector for scanning type analyzer - Google Patents

Abstract

PURPOSE:To simplify the modification of image magnification and facilitate the observation of an image by controlling a scanning signal supplied to a directional deflection coil and always making the scanning direction constant. CONSTITUTION:12 is a section which outputs the vertical position of a sample as a voltage signal. When the sample positional transducer section is a potentiometer, 12 is integrated. When the transducer section is a counter that counts a pulse motor supply pulse, 12 is a D/A converter, 13 is a function generator circuit and converts the voltage signal that indicates the sample position into an angle of revolution signal in accrdance with a predetermined function. 14 is a servoamplifier and 15 is a servomotor. The servomotor 15 is revolved only for the angle that corresponds to the angle signal obtained by 13. 16 is a two-way potentiometer with sintheta and costheta outputs, is driven by the servomotor 15, and obtains sintheta and costheta signals. These signals combine a signal X(t) supplied to an X directional deflection coil and a signal Y(t) supplied to a Y directional deflection coil in a circuit 7.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a device that uses an electromagnetic lens to correct image rotation in a device that scans a sample surface with a charged particle beam and displays the analysis output as an image, such as a scanning electron microscope. Regarding.

In the above-mentioned scanning electron microscope and the like, image rotation occurs when the position of multiple samples in the optical axis direction is changed by changing the strength of the electromagnetic lens. Since rotation of the image is inconvenient for visual observation of the image and video observation, normally in such cases, the scanning direction is adjusted manually by adjusting the sweep signals applied to the X-direction deflection coil and the Y-direction deflection coil. The image is rotated in the opposite direction by the rotation angle, and the scanning direction on the sample surface is set in a fixed direction specific to the analyzer, which makes operations such as changing the magnification of the image extremely troublesome.

Changing operations become very simple, and video observation becomes easier. The present invention will be explained below with reference to Examples.

FIG. 1 is a block diagram showing an entire embodiment of the present invention. 1 is an electron beam, and 2 and 3 are deflection coils that deflect the electron beam in directions perpendicular to each other.For convenience, 2 is called an X-direction deflection coil, and 3 is called a Y-direction deflection coil. The reason why I say "for convenience" is because the X-direction deflection coil controls the horizontal scanning of the sample surface, and the Y-direction lateral coil controls the vertical scanning. , 5°6 indicate the upper and lower positions of the sample, 5 is the high magnification position, and 6 is the low magnification position. 7 is a scanning image rotating device, and 8 is a scanning control section which generates an X sweep signal and a Y sweep signal. These signals are sawtooth waves whose periodic slopes are denoted by at and bt.

The scanning image rotation device receives the at and bt signals and rotates the
A signal X (t) given to the direction deflection coil 2 and a signal y 2 (t) given to the Y direction deflection coil 3 are configured. child\
X(t) = K a t + L b t・−・(1)
Y(t) = M a t -4-N b t ・-・
(2) In the above equation, M represents the direction of the scanning line, and L and N represent the interval between the scanning lines. In the standard state of the device, the X-direction deflection coil 2 controls only horizontal scanning, and the Y-direction deflection coil 3 controls only vertical scanning. In this case, the above formula % formula % is obtained, and L and M are O. In this state, if you want to rotate the image by multiple angles θ, refer to Figure 2 and turn it into = □co
θθ, M=Koθ1nθ ・43) L = N
□ sinθ, N = N (, cosθ
-(4) In FIG. 2, the lines represent scanning lines, and 1(, represents one period of horizontal scanning. The scanning image rotation device 7 is
The scanning signal is received, converted into X (t) and y (t) expressed by the above equations (1) and (2), and supplied to the coils 2 and 3. 9 is an excitation power source for the objective lens. Reference numeral 10 denotes a potentiometer which is a position detection unit that detects the position of the objective lens 9 of the sample in the optical axis direction, that is, in the vertical direction, and is slid on the sample stage. Alternatively, it may be a device that counts the driving pulses of a pulse motor for driving the sample stage up/down device. 11 is a control circuit that calculates the rotation angle of the image from the data on the vertical position of the sample obtained in 10 above, and rotates the image in the opposite direction by the same amount from the rotation angle as described in (3) above.
After performing the calculation in (4), the values of L, M, and N are determined and output to the scanning image rotation device 7.

The rotation of the image is related to the electromagnetic accelerating voltage and the magnetic flux density distribution of the electromagnetic objective lens 4, and can be calculated using a theoretical formula; however, it is not very practical to calculate the rotation angle by actually detecting the magnetic flux density distribution. The accelerating voltage and magnetic flux density are related to the focal length of the lens and the vertical position of the sample, so the rotation angle of the image is determined in advance as a function of the vertical position of the sample, and the vertical position of the sample is determined in advance. The rotation angle of the image is determined by detection, and the scanning signal supplied to the X-direction deflection coil and the Y-direction deflection coil is controlled to rotate the scanned image in the opposite direction, thereby canceling out the rotation of the image by the objective lens. The present invention is characterized in that the upper scanning direction is always constant.

FIG. 3 shows an example of the configuration of the scanning image rotation device 7 and control circuit 11 in FIG. 1. Reference numeral 12 denotes a part that outputs the vertical position of the sample as a voltage signal, and is integrated with 10 when the sample position detection section 10 is a potentiometer. 1
When 0 is a counter that counts the pulse motor supply pulses, 12 is a D/A converter. Numeral 3 is a function generating circuit which converts a voltage signal representing the sample position into a rotation angle signal according to a predetermined function. 14 is a servo amplifier; 15 is a servo motor; the servo motor 15 rotates by an angle corresponding to the angle signal obtained at 13; 16 is a double potentiometer with outputs of sin θ and co θθ, and is driven by 15 with a servo motor, +3) above.
Obtain signals of θ1nθ, c, and osθ used in equation (4). Using this signal, x(t) and y(t) in equations (1) and (2) above are synthesized in circuit 7.

Although the above-mentioned embodiment is an analog method, it is easy to obtain the output of the above fl) and +2) formulas using a microprocessor and without using any mechanical components such as a servo amplifier, sine output potentiometer, and cos output potentiometer. It is. The process is the same as above until the rotation angle θ signal is obtained, but depending on this angle signal, the X direction deflection coil 2 and Y
The direction deflection coil 3 may be mechanically turned by an angle θ. In addition, in order to correct the rotation angle of the image with higher precision, in addition to data on the sample position, the lens excitation current is detected instead of the accelerating voltage and magnetic flux density, and the image rotation angle is calculated as a function of these three quantities. All you have to do is ask for it.

According to the device of the present invention, regardless of the focal position of the objective lens,
The sample is scanned in a fixed scanning direction unique to the device, and there is no rotation of the image. Therefore, for example, when searching for the analysis position of the sample using a scanned image of the sample, it is necessary to locate the analysis point at low magnification and then examine that location at high magnification. The scanned image always matches the fine movement of the sample in the X and Y directions, making the operation much easier.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the entire apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between the rotation of a scanning line and each coefficient of a deflection signal, and FIG. 3 is a block diagram showing blocks 7 and 11 of FIG. 1. FIG. 2 is a detailed block diagram of the internal configuration of FIG. 1... Electron beam, 2... X direction deflection coil, 3...
...Y direction deflection coil, 4...Objective lens, 5, 6.
...2 positions of the sample, q...Scanning image rotation device, 8...
Scanning control section, 9... Excitation power supply, 10... Sample position detection section, 11... Rotation angle control section. Agent: Hiroshi Agata, Patent Attorney JP-A-58-75748 (3>

Claims (1)

[Claims] means for detecting the position of the sample in the optical axis direction of the analyzer; means for converting the output of the means into a signal corresponding to the rotation angle of the image;
An image rotation correction device for a scanning analyzer, comprising means for calculating a scanning signal to be applied to a direction deflection coil, the calculating means rotating the scanning direction by the same angle as the rotation angle of the image in the opposite direction.