JPS593021B2 - Electron beam deflection device for scanning electron microscopes, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam deflection device used in a scanning electron microscope or the like.

In devices such as scanning electron microscopes and X-ray microanalyzers, by scanning and deflecting an electron beam that irradiates a sample, and using a detection signal obtained from the sample as a brightness modulation signal of a cathode ray tube synchronized with the scanning, A brightness modulated scanned image is displayed on the cathode ray tube screen.

The magnification of the scanning image is the scanning of the electron beam irradiating the sample. It can be switched by controlling the deflection strength. In this case, it is assumed that the intensity of the excitation deflection current supplied to the deflection coil wound around a ferrite or other ferromagnetic core corresponds precisely to the image magnification, but in reality the magnetization of the ferromagnetic core Because there is hysteresis in the curve, the strength of the magnetization of the ferromagnetic core is not uniquely determined by the strength of the excitation current supplied to the coil, but is related to the previous magnetization state and is determined by the strength of the excitation current supplied to the coil. However, there may be a slight error in the actually obtained image magnification, and the development of a different observation field of view becomes particularly noticeable at high magnifications. 0 In order to avoid such development, if the ferromagnetic core of the deflection coil is removed, the output power of the scanning deflection power supply must be significantly increased, and the space occupied by the deflection coil installed near the electron beam path must be increased. This creates new problems such as increased heat generation and increased heat generation.

5. The object of the present invention is to eliminate the influence of hysteresis on high-magnification scanning images while using a deflection coil wound around a strong magnetic core.

FIG. 1 is a simplified diagram showing the main part of scanning according to an embodiment of the present invention. A current control system that supplies the deflection coil 3 and the X-direction deflection coil 4 is shown.

In normal operating conditions, an X-axis (horizontal) scanning power supply 5 and a Y-axis (vertical) scanning power supply 6 are synchronized with each other.
The sawtooth wave currents generated from the outputs of are supplied to the deflection coils 3 and 4 via interlocking variable amplifiers 7X and 7Y used as magnification adjustment means and switching circuits 8 and 9, respectively. The device of this embodiment is provided with a degaussing control circuit 10 which detects the variable magnification operation in the variable amplifier TY and operates based on the detection signal.

The control circuit 10lfC has a built-in timer for an extremely short period of time T after the magnification switching operation.
5, the control signal is applied to the degaussing power supply 11 and the switching circuits 8 and 9, and the degaussing power supply 1
The output of No. 1 is switched to be connected to coils 3 and 4, and a blanking signal is applied to the brightness modulation input of a cathode ray tube (not shown). FIG. 2 shows the waveform of the excitation current supplied to the coil 3 in the device shown in FIG.
1 and T2vc, the magnification switching operation is performed. ing. The sawtooth waves represented by W, , W2, and W3 in the figure represent the outputs of the variable amplifier circuit 7Y corresponding to the magnifications M1, M2, and M3 (M1, M2, and M3, respectively, and the time t1
AC waveform W shown at time T from the switching time of ~T2. represents the output of the degaussing power supply 11. The AC waveform W. is the initial amplitude H as shown in the figure. is about 1.5 times as large as the maximum amplitude of the sawtooth wave, and the amplitude is gradually attenuated. If such a device is used, the high magnification will always be set from a constant state regardless of the value of the viewing magnification before viewing the high magnification image 1, and the high magnification will be set from a constant state. No longer affected by hysteresis. As explained in detail above, according to the present invention, it is possible to eliminate the influence of hysteresis of the core of the deflection coil that occurs during high-magnification observation, and therefore, a great effect can be obtained in accurately observing samples using a scanning electron microscope. .

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the main parts of an apparatus according to an embodiment of the present invention, and FIG.
The figure is a schematic diagram showing the output waveforms of the apparatus of FIG. 1, 2...Ferromagnetic core, 3, 4...
Deflection coil, 5...X-axis scanning signal generation circuit, 6
...Y-axis scanning signal generation circuit, 7X, 7Y...
...Variable amplifier, 8,9... Switching circuit, 10... Demagnetization control circuit, 11...
Demagnetizing power supply.

Claims (1)

[Claims] 1. An electron beam deflection coil wound around a ferromagnetic core, a deflection power source for supplying a deflection current to the coil via a variable amplifier circuit and a switching circuit, and a deflection power supply for supplying a damped alternating current via the switching circuit. An electron beam deflection device for a scanning electron microscope or the like, comprising a degaussing power source and means for operating the switching circuit and the degaussing power source for a certain period of time in conjunction with a control operation of the variable amplifier circuit.