JPS6016703B2 - Scanning method in scanning electron microscope, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a scanning method that can efficiently scan an electron beam on a sample or on the screen of an observation display tube at any speed between slow speed for photography and high speed for television with high Z accuracy. This paper relates to a scanning method in a type electron microscope, etc.

With scanning electron microscopes, etc., when observing the sample to be analyzed, consider the use of a television monitor or VTR, and use a television speed to transmit the Shigeko line onto the sample or the screen of the observation display tube. When photographing a sample to be analyzed, it is scanned at a slow speed for photographing.

That is, as shown in FIG. 1, an electron beam E emitted from an electron gun 1 and focused onto a sample 3 by a focusing lens 2 is scanned by a deflector 4 over the sample. The deflector receives a horizontal scanning signal from a scanning signal generator 5 as shown in FIG.
The horizontal scanning signal is also supplied via a resistor R
, , R2, R3, a power amplifier Ap, and a deflection circuit 8 of the observation cathode ray tube 7, which is comprised of a power amplifier Ap and a deflection coil C, is also supplied with V. A secondary electron beam signal generated from the sample 3 is detected by a detector 9 and supplied to a brightness modulation grid of the observation cathode ray tube 7 and an amplifier 10. The grid and amplifier 10 are also supplied with a horizontal planking signal as a synchronization signal from the scanning signal generator 5 as shown in FIG. 2b. The output of the amplifier 10 has a waveform as shown in FIG. 2e and is supplied to a VTR or television monitor 11. When taking a photograph, the scanning signal generator 5 generates a low frequency scanning signal. When observing, a scanning signal having a high frequency similar to that of a VTR or television monitor 11 is generated from the scanning signal generator 5, and the scanning signal is transmitted to the observation cathode ray tube 7, VTR or television monitor 1.
1 shows the sample image. By the way, observation cathode ray tube 7
A deflection current i as shown in Fig. 2C flows through the deflection coil C of , but if you try to scan the electron beam on the cathode ray tube screen at a television speed during observation,
Since the deflection angle of the electron beam on the screen of the cathode ray tube is large, it is necessary to generate a significantly large voltage e as shown in FIG. 2d at both ends of the deflection coil C during the retrace period.

However, it is difficult to realize a power amplifier that can generate such a large voltage, and therefore an amplifier with insufficient power must be used, which deteriorates the linearity of the scanning signal. Furthermore, even if an amplifier with high power is realized by force, the cost will be extremely high, and when considering the power efficiency during scanning, the waste of power will be too large. The present invention has been made in view of these points, and provides a novel scanning method.

FIG. 3 is a schematic diagram of a scanning electron microscope showing an embodiment of the present invention, in which the same numbers used in FIG. 1 indicate the same transverse elements.

In the figure, reference numeral 12 denotes a timing signal generation circuit consisting of, for example, a bistable multipipulator, which changes its state in binary every time a horizontal line signal as shown in FIG. 5b sent from the scanning signal generator 5 arrives. An inverted timing signal (synchronizing pulse signal) as shown in FIG. 5c is generated.

The timing signal is supplied to the grid of the observation cathode ray tube 7 as a retrace synchronization signal, and is also supplied to the waveform conversion circuit 13. The waveform conversion circuit converts the horizontal scanning signal as shown in FIG. 5a sent from the scanning signal generator 5 into the horizontal scanning signal shown in FIG. As shown in FIG. Convert to horizontal scanning signal. To be more specific, the waveform conversion circuit, as shown in FIG. resistor r,,[2
, a terminal t4 connected to the positive terminal of the amplifier ○p, a switch S2 connected to the terminal t4, and a non-terminal t6. In this circuit, a timing signal generation circuit 12
The /・i part of the timing signal from switch S,,S
When the signal is sent to terminal t2, switch S, switches to the terminal t2 side, and switches S2 to terminal t2.
is connected to the t6 side, so the horizontal scanning signal from the scanning signal generator 5 is inverted, and when the low part of the timing signal is sent, the switch S, is connected to the terminals side, and S2 is connected to the t3 side, so the horizontal scanning signal is inverted. The scanning signal is output as is.
In such an apparatus, when observing a scanned image of the test sample 3, the scanning signal generator 5 generates a speed equal to the scanning speed of the VTR or television monitor 11.
The deflector 4 and the waveform conversion circuit 13 are supplied with a horizontal scanning signal (FIG. 5a) having a waveform.

Further, the horizontal female line signal from the scanning signal generating circuit 5 is sent to the amplifier 1.
0 and is supplied to the timing signal generation circuit 12. As mentioned above, the waveform conversion circuit 13 is connected to the timing signal generation circuit 1.
FIG. 5d according to the timing signal from FIG. 2 (FIG. 5c).
A horizontal scanning signal whose waveform has been converted as shown in FIG. 1 is generated and supplied to the deflection circuit 8 of the observation cathode ray tube 7. Therefore, as shown in FIG. 5e, the deflection coil C of the deflection circuit has one horizontal scanning period and blanking period of the horizontal scanning signal (FIG. 5a) from the scanning signal generating circuit 5, as shown in FIG. 5e. Then, the horizontal scanning current is such that the next horizontal scanning period and blanking period become one horizontal line period. flows at both ends of the deflection coil, where the inductance of the deflection coil is L and the female portion is r (L charge ri).
) 1, and only a significantly lower voltage occurs during retrace as shown in FIG. 5f. At this time,
The timing signal from the timing signal generation circuit 12 is supplied to the brightness modulation grid of the observation cathode ray tube 7 as a retrace synchronization signal. The signal generated from the sample 3 is also supplied from the detector 9 to the grid and to the amplifier 10. Therefore, cathode ray tube 7, VTR or television monitor 1
1 displays an image of the specimen. Incidentally, a signal having a waveform as shown in FIG. 5g is a signal supplied to a VTR or television monitor 11. Note that the output signal waveform of the waveform conversion circuit has sharp parts i and ii as shown by the broken line in FIG. 5d.
, iii, . Solid line portions i, U, iii in Figure 5 d...
As shown in , since only slight irregularities occur, the horizontal scanning signal to the observation cathode ray tube 7 is hardly adversely affected.

Further, when the unevenness occurs, the timing signal generation circuit 12
Since a timing signal is input as a retrace signal to the luminance modulation grid of the cathode ray tube, no effect of the unevenness signal appears on the screen of the cathode ray tube. In the present invention, during high-speed scanning for television, on the screen of the observation display tube, one horizontal scan and blanking period on the sample is one horizontal scanning period, and the next horizontal scanning and blanking period is one horizontal scanning period. Since the electron beam is scanned to match the period of time, the number of scanning lines on the viewing display tube screen will be 1/2 that of the conventional one, but a small voltage will be applied to both ends of the deflection coil of the viewing display tube during retrace. The electron beam can be scanned with good linearity simply by applying . Therefore, even when a normal power amplifier is used in the deflection circuit of the observation display tube, a sample image without distortion can be observed.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a scanning Atsuko microscope implementing the scanning method of the present invention, FIG. 2 is a signal waveform diagram, and FIG. 3 is a schematic diagram of a scanning electron microscope implementing the scanning method of the present invention. FIG. 4 is a partially detailed diagram thereof, and FIG. 5 is a signal waveform diagram. 3: Test sample, 4: Deflector, 5: Scanning signal generation circuit, 7
: Observation cathode ray tube, 8: Deflection circuit, 12: Timing signal generation circuit, 13: Waveform conversion circuit. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. In a scanning method in which an electron beam is scanned over a sample or the screen of an observation display tube at any speed between slow speed for photography and high speed for television,
During high-speed scanning for television, one horizontal scan and blanking period on the sample is observed in one horizontal scanning period on the screen of the observation display tube, and one horizontal scanning and blanking period on the next sample is observed. 1. A scanning method for a scanning electron microscope, etc., characterized in that an electron beam is scanned for each horizontal scanning period on the screen of a display tube.