JPH0531263B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an apparatus for visualizing and displaying measurement signals over time, such as a scanning electron microscope or an electron beam microanalyzer.

(b) Prior art When observing the analysis results of the sample surface as a CRT image of the sample surface using the above-mentioned apparatus, depending on the detector, background drift may be large;
There were cases in which the brightness of the background changed significantly during one CRT screen scan, making it difficult to observe the image. For example, when a Ge detector is used to detect the infrared fluorescence emitted from the sample when it is irradiated with an electron beam and display the image, the background drift is expressed in terms of the brightness value of the CRT screen.
100/min 90 minutes after the detector has cooled down, and drops to about 20/min 100 minutes later. On the other hand, since the brightness range of a CRT is about 28, the time required to scan one screen is reduced to 1 when taking a photograph of a CRT image.
Even if you wait 100 minutes after the detector has cooled before starting scanning, the background alone will occupy 70% of the screen contrast range at the bottom of the screen, making it extremely difficult to observe the sample image.

(C) Purpose The purpose of the present invention is to provide a countermeasure against the case where the measurement system drift of a scanning analyzer is large and it becomes difficult to observe a sample using a CRT image.

(D) Structure When scanning a sample surface with a beam of valence particles such as electrons, the present invention performs blanking of the scanning beam during the retrace period of the scanning line every time an appropriate number of scanning lines are swept. The output of the measurement system during the blanking period is held as a correction value until the next blanking operation, and the correction value held during that period is calculated from the output of the measurement system between one blanking operation and the next blanking operation. This is subtracted to obtain the CRT luminance signal.

(E) Embodiment FIG. 1 shows an embodiment of the present invention. A detector D detects appropriate radiation emitted from the sample S excited by the electron beam E. The output of the detector D is input as a luminance signal to the CRT via a buffer amplifier A1, an amplifier A2, and a differential amplifier A3.
H is a sample and hold circuit to which the output of the buffer amplifier A1 is input through the sampling switch Sw. A blank signal is input from the scan control circuit C to the buffer circuit B, and the output of the buffer circuit B is input to the beam deflection coil K via the driver circuit Dr. While a blank signal is input to the coil K, the electron beam is deviated sideways and does not enter the sample S, so no radiation from the sample enters the detector D, and the detector output during this period is back. Indicates ground level. The blank signal output from the buffer circuit B is included in the blank signal period by the waveform shaping circuit F, and is converted into a narrower pulse signal than the same signal. While this signal is present, the sampling switch Sw is turned on and the blank signal period ends. The output of the buffer amplifier A1, that is, the background signal of the detector D is sampled and input to the sample hold circuit H. The sampling switch is off during periods other than the period in which the pulse signal is output from the waveform shaping circuit F, and during this period the sample and hold circuit H holds the previously sampled background signal. A background signal is applied to the inverting terminal of differential amplifier A3. Therefore, while the electron beam is sweeping the sample surface, the differential amplifier A
3, the background level of the detector D at the beginning of the period is applied to the inverting terminal, and the output of the differential amplifier A3 is the net detection signal of the detector D.

FIG. 2 is a time chart illustrating the operation of the above-mentioned apparatus. In the same figure, X is the X-direction scanning signal output from the scan control circuit C in FIG. 1, which is input to the deflection coil K, and BL is the signal output from the control circuit C corresponding to the retrace period of the X-direction scanning signal. This is a blank signal. Sl is the output signal of the waveform shaping circuit F and is included in the blank signal period, and is a sampling signal for closing the switch Sw and sampling the background signal of the detector D. D is detector D
At the output of , BC is the changing background level, and the true sample signal is denoted by S. V is a luminance signal that is the output of the differential amplifier A3, and the background level is pulled back to 0 at each starting point of the X direction scan.

In the above embodiment, the background correction is performed every time one X-direction scan is performed, but it goes without saying that the background correction may be performed once every several X-direction scanning lines depending on the degree of drift. Nor.

(c) Effect Since the charged particle beam scanning analyzer of the present invention has the above-described configuration, it is possible to obtain images with a uniform background level even when using a detector with a large drift. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an apparatus according to an embodiment of the present invention, and FIG. 2 is a time chart illustrating the operation of the apparatus. E...electron beam, S...sample, K...electron beam deflection coil, D...detector, Sw...sampling switch, H...sample hold circuit,
C...Scanning control circuit.

Claims (1)

[Claims] 1 Every time an appropriate number of X-direction scanning lines of the charged particle beam scan the sample surface, blanking of the scanning beam is performed during the retrace period of the scanning line, and the measurement system during this blanking period is The output is sampled as a correction value signal and held until the next blanking, and the previously sampled and held correction value signal is used to perform background correction on the measurement system output during that period. A charged particle beam scanning analyzer characterized by performing the following steps and supplying the signal to a CRT as a video signal.