JPS59154731A - Charged beam deflection system - Google Patents

Abstract

PURPOSE:To extract a signal such as a video signal by deflecting at a high speed the charged beam through the process that a sine wave is used as a deflection signal, it is detected that the charged beam has shifted for the constant position by such signal and sampling is carried out in such a timing. CONSTITUTION:A sine wave deflection signal generated by a deflection signal generator 1 is supplied to a deflection coil 6 through a deflection amplifier 5. simultaneously, the deflection sine wave signal is also supplied to a sampling pulse generator 2. when the charged beam shifts for the specified interval, this generator 2 detects it and generates the sampling pulse at thimemory 4. A detected signal such as a video signal detected by the detector 7 is supplied to a converter 3 through an amplifier 8. At this timing, the detected signal is sapled by the pulse supplied from the pulse generator 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a charged beam deflection method, and more particularly to a charged beam deflection method suitable for deflecting a consonant beam or the like in a scanning electron microscope, an electron beam lithography apparatus, or the like.

[Prior art]

Conventional methods for deflecting electron beams, etc. in scanning seiko microscopes, etc., require a deflection signal to move the electron beam at a constant speed for reasons such as keeping the irradiation time of the electron beam constant at each sampling point on the sample surface. A sawtooth wave or a triangular wave is used. In this case, since the moving speed of the electron beam is constant, in order to sample the value of each point at constant position intervals of the electron beam, it is sufficient to sample the deflection signal at constant time intervals.

However, in such conventional deflection methods, since the deflection means such as a deflection coil that directly deflects the electron beam etc. does not consist of pure resistance components, discontinuities in the deflection signal wave, i.e. local maxima such as sawtooth waves, triangular waves, etc. - All vibrations are generated near the minimum point due to the actance component of the deflection means.

This vibration of the deflection signal wave results in vibration of the irradiation position of the electron beam or the like. This vibration did not pose a particular problem when the scanning period was long, that is, when the deflection was performed at a low speed, but when the deflection was performed at a high speed, the Kld,
The ratio of the vibration part due to the actance component to the straight part of the deflection signal wave becomes large, and a normal image cannot be obtained. For this reason, the scanning period had to be long, and there were drawbacks such as the inability to increase the deflection speed.

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art and to provide a charged beam orientation system capable of deflecting an electron beam or the like at high speed. Vibration due to the actance component of the deflection means such as a coil is caused by the phase of each frequency component included in the sawtooth wave or triangular wave with discontinuities used in the conventional deflection No. 100 being shifted by the actance component of the deflection means. Focusing on this, we used a sine wave as a deflection signal to eliminate vibrations due to this reactance component, and because using this sine wave, the moving speed of the charged beam would no longer be constant, we decided to use conventional sampling at fixed time intervals. Since it is not possible to sample the value at fixed position intervals of the charged beam, it is detected from the sine wave deflection signal that the charged beam has moved by a fixed position interval, and at that timing, the sampling pulse generator stage This is a charged beam deflection method that is characterized by being able to sample at positional intervals.

[Embodiments of the invention]

Hereinafter, as an embodiment of the present invention, a case where the present invention is applied to a scanning electronic forehead microscope using a deflection coil as the deflection means will be described.

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the charged beam deflection method according to the present invention, in which numeral 1 indicates a deflection signal generator (sine wave generator) that generates a sine wave signal; 2 is a sampling pulse generator that generates a sampling pulse by detecting that a charged beam (electron beam) has moved by a certain distance from a deflection signal, 6 is A, / 1) converter, 4 is a memory, 5 is a deflection 6 is a deflection coil which is a deflection means for deflecting a charged beam; 7 is a detector for capturing video signals of a sample etc. obtained by irradiation with the deflected charged beam; and 8 detection signal amplifiers. Figure 2 shows each part i++! for explaining the operation of Figure 1. + This is a waveform diagram.

With this configuration, the sine wave deflection signal (voltage) 2 generated by the deflection signal generator 1 is supplied to the deflection coil 6 which is the deflection means through the deflection amplifier 5 which is a constant current amplifier for driving. Deflect the charged beam. At the same time, the sinusoidal output 1d of the deflection signal generator 1 is also supplied to the sampling pulse generator 2 - this causes the sampling pulse generator 2 to receive a deflection signal V of a constant 1 - pressure distribution width as shown in FIG. When the charged beam changes, that is, when the charged beam position 4Qx moves by a certain distance in proportion to this, this is detected and a sampling pulse is generated at that timing 1-2, and this sampling pulse is sent to the A/D converter. 6 and memory 4. As a result, when a detection signal such as a video signal of a sample (not shown) captured by the detector 7 is applied to the A/D converter through the detection signal amplifier 8 (-), this detection signal is transferred to the sampling The video signal etc. at each point of the moving position (irradiation position) of the charged beam at that timing is sampled by the sampling pulse supplied from the pulse generator 2, and is converted to A'/I) by the A/D converter 3. The memory 4 can store and record the values of video signals and the like at certain fixed position intervals of the charged beam.

Next, FIG. 3 is a circuit diagram illustrating the circuit configuration of the sampling pulse generator 2 shown in FIG. is a monostable multivibrator7,
FIG. 4 is an operation waveform diagram of each part for explaining the operation of FIG.

With this configuration, the deflection signal (voltage) input to the sampling pulse generator 2 of this circuit is
The hold value VH of the deflection signal at a certain time held by the subtracter 10 and the absolute value circuit 11
The absolute value of the difference (IV-VHl) can be found.

Then, the absolute value of this difference is constantly determined by the comparator 12.
It is compared with a set threshold value VTR. When the absolute value of this difference (iv-vHl) exceeds the set threshold value VTHf, the output of the comparator 12 changes and the monostable multivibrator 13-i) IJ is activated.At this time, the output from the monostable multivibrator 1 Using this pulse, the deflection signal V at that time is held in the sample/hold 9, and this is set as a new hold value VH. From then on,
By repeating this process, the hold value VH of the sample/hold 9 of each waveform corresponding to the sine wave deflection signal (voltage) ■ as illustrated in FIG. 4 + the absolute value of the difference (1V V
H1) + Monostable multi-by-break 1 sampling pulse signal is obtained.

In this way, the pulse output from the monostable multivibrator 16 becomes the sampling pulse, which is the output of the sampling pulse generator 2 of this circuit, and becomes the deflection coil 6 of FIG.
Sampling of the video signal etc. from the detector 7 is performed at each timing when the deflection signal V to changes by the set threshold value VTH, that is, sampling is performed at constant position intervals corresponding to the electron beam. Therefore, the constant position interval of this sampling is determined by the comparator 12
This can be easily changed by making the set threshold VTR'c variable.

In the above embodiment, the video signal etc. from the detector 7 is stored in the memory through A/D converter 7, but it may also be displayed on a cathode ray tube or the like which is scanned synchronously. Furthermore, although an electromagnetic deflection coil is used as the deflection means, other electrostatic deflection plates or the like may be used. Furthermore, although the above embodiment has been described with reference to a case where it is applied to a scanning electron microscope using a deflection coil, other devices such as an electron beam lithography device, etc., which utilize a charged beam such as a deflected electron beam or an ion beam, etc. The present invention can be similarly applied to devices that display or record video signals obtained by charged beams.

As described above, according to this embodiment, in a scanning electron microscope or the like, a charged beam can be deflected at high speed and sampled at constant position intervals without causing vibrations due to actance components such as deflection coils. can be easily and easily obtained. 1. According to this embodiment, a single sine wave is used for the deflection wave of the charged beam, so there is no high-order harmonic component included in the conventionally used sawtooth wave or triangular wave. 0 [Effects of the Invention] As is clear from the above explanation, the load 5 beam deflection method of the present invention has the advantage that the band of the deflection amplifier that drives the deflection coil etc. that is the deflection means is low. According to the invention, it is possible to deflect the charged beam J- at high speed and extract signals such as video signals without causing vibrations due to actance components of deflection means such as conventional deflection coils, and it is widely used as a deflection method for charged beam devices. is available.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the charged beam deflection system according to the present invention, FIG. 2 is an example of operation waveforms of each part of FIG. 1, and FIG. 3 is a diagram of the sampling pulse generator of FIG. 1. FIG. 4 is a circuit diagram illustrating the circuit configuration, and FIG. 4 is an example diagram of operation waveforms of each part in FIG. 3. 1.Deflection signal generator (sine wave generator) 2..Sampling pulse generator 3..A/D converter 4..Memory 6..Deflection means (deflection coil) 7.Detector 1st 12 Kuchi Isamu 3I ¥] Shima 4 times

Claims (1)

[Claims] a deflection signal generator that generates a sinusoidal deflection signal; a deflection means that deflects a charged beam using the deflection signal from the deflection signal generator; A charged beam deflection method consisting of a means for sampling and extracting a charged beam at fixed position intervals.