JPH0629854B2 - Cathodoluminescence detector - Google Patents

Description

Detailed Description of the Invention a. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathodoluminescence detection device that scans a sample surface with an electron beam to disperse fluorescence emitted from the sample excited by an electron beam.

B. 2. Description of the Related Art A cathodoluminescence detector uses a scanning electron microscope to scan the sample surface with an electron beam, disperses the fluorescence emitted from the sample with a spectroscope, detects the dispersed light, and detects the fluorescence of a specific wavelength. The sample image is displayed on the CRT and the fluorescence spectrum is drawn. In this apparatus, the magnification of the sample image on the CRT becomes low when the scanning range of the sample surface by the electron beam is widened, and the magnification becomes high when the scanning range is narrowed. When viewed from the spectroscope, since the electron beam irradiation point on the sample surface is the light source, the moving range of the light source is wide when the magnification is low, and the moving range is small when the magnification is high. Therefore, if the slit width of the spectroscope is fixed, the range of movement of the light source image on the slit will exceed the slit width when the magnification is low, and on the contrary, when the magnification is high, the movement range of the light source image will be slit. There is a case where it fits within the width and there is still a surplus slit width. In such cases,
Since the fluorescence spectrum is a continuous spectrum distributed in a certain wavelength range, if the width of the exit slit is wide, light in the wavelength range determined by the slit width will be incident on the detector, and the wavelength resolution should be originally obtained. Is less than the resolution of. In addition, the sample surface is illuminated by the light of the filament of the electronic pig iron of the electron optical system, and its illuminance is weak,
Fluorescence itself is generally weak, so if the width of the entrance slit is wide, the light from this filament will enter the spectroscope in proportion to the slit width, thus strengthening the background to the fluorescence spectrum and increasing the fluorescence detection sensitivity. Will be lowered. Therefore, there is an optimum slit width in the spectroscope at each magnification according to the purpose of analysis, but in the past, since the slit magnification was adjusted independently of the magnification setting, analysis by cathode luminescence was performed. The operation of changing the magnification in various ways was quite troublesome.

C. It is an object of the present invention to automatically set the spectroscopic slit width which gives the highest wavelength resolution for each magnification in the cathodoluminescence detection device.

D. Configuration The cathode luminescence detection device of the present invention is configured such that the setting of the magnification and the drive of the slit width of the spectroscope are interlocked with each other, and the slit width is automatically set in accordance with a functional relationship preset according to the magnification. Have.

E. Embodiments The drawings show one embodiment of the present invention. In FIG. 1, the electron optical system is omitted because it is a known scanning electron microscope, and only the optical system is shown. S is a sample, E is an electron beam, and P is cathodoluminescence light. B is an objective lens of the electron optical system, and M is an objective concave mirror of the optical system. The cathodoluminescence light emitted from the sample S is reflected by the objective mirror M and the small mirrors m and m ¹ and guided to the outside of the body through the window W of the lens barrel of the electron optical system. After passing through the eyepiece lens 1 to enter the eye, the sample surface can be directly observed visually. A is a spectroscope, and in the spectroscope, 1 is a diffraction grating, 2 is an entrance slit, 2 ¹ is an exit slit, 3 is a collimator mirror and a camera mirror, and D is a photodetector. The light reflected by the semitransparent mirror H is condensed by the lens system L, and the light emission point on the sample S is incident on the incident slit 2 of the spectroscope A.
That is, an image of the electron beam irradiation point is formed. Further, on the exit slit 2 ¹ image of the incident slit 2 is formed.

Incident exit the slit 2, 2 ¹ s husband together in slit width continuously variable pulse motor PM spectrometers A, is by connexion driven PM ^1.

Figure 2 shows the control system of the slit 2, 2 ^1. As described above, the change of the magnification is to change the scanning range of the scanning of the sample surface by the electron beam, and the change of the scanning range is performed by changing the amplitude of the X and Y deflection signals given to the electron beam deflection coil. . In FIG. 2, G is an X, Y deflection signal generation circuit, the output of which is input to the X, Y deflection coils Cx, Cy via the X, Y deflection coil drive circuit PD of the electron optical system and also X for the CRT. , Y deflection signals are applied.
Q is a magnification setting device, which changes the gain of the drive circuit PD to change the amplitude of the X and Y deflection signals of the electron optical system. V is an amplitude detection circuit for detecting the amplitude of the X deflection signal, and the detected amplitude data is read into the control circuit CR. The control circuit CR calculates the counter count value corresponding to the predetermined slit width from the functional relationship between the preset amplitude (magnification) and the slit width of the slits 2 and 2 ¹ based on the read amplitude data. , Counters K and K ¹ are compared with the present count value to detect whether the difference between the two is positive or negative. Counters K and K ¹ are slit 2.
Pulse motor PM that drives a 2 ^1, is, the number of pulses supplied to the PM ^1. The control circuit CR supplies a pulse for forward rotation or a reverse rotation to the pulse motors PM and PM ^{1 according} to the positive or negative of the above difference, and the supplied pulse is supplied to the counters K and K.
^The value is incremented or decremented by ^{1 so} that the count values of the counters K and K ¹ match the calculated counter count value. The width of the entrance and exit slits of the spectroscope is automatically set for the magnification set in this way. Plural kinds of functional relationships between the magnification and the slit width, which are registered in the control circuit in advance, are prepared.
It is also possible to select one of the functional relationships depending on the purpose of analysis.

F. Effect According to the present invention, in the sample observation by cathodoluminescence, the width of the entrance and exit slits of the spectroscope is automatically set to the optimum according to the change of the magnification, so that the magnification can be easily adjusted to any desired value.
Cathode luminescence spectroscopy can be performed with the highest resolution according to the magnification, and the excess light entering the spectrometer can be reduced within the range possible for each magnification, and the background of the fluorescence spectrum can be kept low. , It is possible to bring fluorescence detection sensitivity to the maximum possible range, and to automate analysis. For example, to analyze one sample at various magnifications, or to analyze various samples at different magnifications. Can be automated.

[Brief description of drawings]

FIG. 1 is a block diagram of an optical meter according to an embodiment of the present invention, and FIG. 2 is a block diagram of a control system of the same. S ... sample, E ... electron beam, P ... cathodoluminescent Tsu sense of light, A ... spectroscope, D ... photodetector, 2,2 ¹ ... incident and exit slit, Cx, Cy ... electron beam deflection coil, PM,
PM ¹ ... Pulse motor, CR ... Control circuit.

Claims (1)

[Claims] 1. A means for changing the magnification of an electron optical system, and based on the changed magnification, a slit width of an input / output slit of a spectroscope corresponding to the magnification is calculated by a preset functional relationship, and the slit is calculated. A cathode luminescence detection device having a control circuit for controlling a drive mechanism.