JPH1196956A - Scanning electron microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To observe a cathode luminescence image and a reflected electron image simultaneously by making a reflected electron detector and an optical detector an identical detector. SOLUTION: An optical detector for detecting a cathode luminescence light 23 generated from a surface of a sample 7 by irradiating an electron beam 2 and a reflected electron detector 9 for detecting a reflected electron 22 are composed to be an identical detector. By using this, the luminescence light 23 is reflected by an aluminum vapor deposited mirror 13 formed on a surface of phosphor or a scintillator 17. The reflected electron 22 of the sample 7 penetrates the aluminum vapor deposited mirror 13, is irradiated to the scintillator 17, and is converted to a scintillator excitation light 24. As the luminescence light 23 cannot penetrate the aluminum vapor deposited mirror 13, the reflected electron detector 9 is not disturbed. As the scintillator excitation light 24 does not penetrate the aluminum vapor deposited mirror 13, the optical detector for detecting the cathode luminescence light 23 is not disturbed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for observing a cathodoluminescence image by irradiating a sample with an electron beam, and more particularly to a sample image observing apparatus suitable for use in a low vacuum atmosphere scanning electron microscope.

[0002]

By irradiation of the Related Art electron beam apparatus called cathode luminescence image system for image observation light as a signal generated from the sample is scanned conventionally electron microscope (S canning
E lectron M icroscope: hereinafter, mounted on abbreviated as SEM), dielectric, are used in ionic crystals, research on semiconductor. Light (cathodoluminescence) detectors are usually
It is arranged above the sample to be observed (below the objective lens).

When secondary electrons are detected in a state where a photodetector is arranged, a secondary electron collecting electric field generated from the secondary electron detector is shielded by the photodetector. Observation by secondary electron detection becomes difficult due to a decrease in the efficiency of trapping of electrons. In a low vacuum atmosphere scanning electron microscope, a backscattered electron detector is used as a detecting means. The backscattered electron detector is located below the same objective lens as the photodetector. For this reason, it becomes difficult to detect the reflected electrons simultaneously with the photodetector.

[0004]

In the prior art, when observing a cathodoluminescence image in a high vacuum scanning electron microscope, a photodetector is disposed below an objective lens to detect light. In this state, when the secondary electron image observation or the backscattered electron image observation is performed, there is a problem that the photodetector must be pulled out or moved from the lower surface position of the objective lens.

Similarly, when observing a cathodoluminescence image with a low vacuum atmosphere scanning electron microscope,
A light detector is arranged below the objective lens to perform light detection. In this state, when performing backscattered electron image observation, there is a problem that the photodetector must be pulled out or moved from the lower surface position of the objective lens.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned disadvantages of the prior art and to detect backscattered electrons in a high vacuum type scanning electron microscope and a low vacuum atmosphere type scanning electron microscope with the photodetector arranged below the objective lens. It is an object of the present invention to provide an apparatus capable of observing a cathodoluminescence image and a reflected electron image at the same time without separating the device from the lower surface of the objective lens.

[0007]

The above object can be attained by making the backscattered electron detector and the photodetector the same detector.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of the present invention. This is an embodiment in which the backscattered electron detector and the cathodoluminescence detector according to claim 1 or 2 of the present invention are the same detector in a low vacuum atmosphere scanning electron microscope.

In FIG. 1, an electron beam 2 extracted from an electron gun 1 is converged into a thin electron beam by a converging lens 3 and an objective lens 4, and is scanned on a sample 7 by a deflection coil 6 connected to a scanning power supply 5. Is done. Secondary electrons, reflected electrons, characteristic X
Signals such as lines and light are generated. Normally, a secondary electron is detected by the secondary electron detector 8 during observation in a high vacuum scanning electron microscope, but a secondary electron detector 8 is used in a low vacuum atmosphere scanning electron microscope to reduce the sample chamber pressure to 1 Pa to 540 Pa. Because the high voltage of the post-acceleration voltage used for the detector cannot be applied,
The signal that can be detected is reflected electrons.

A backscattered electron detector 9 is provided between the objective lens 4 and the sample 7 to detect the backscattered electron signal. With respect to the detected reflected electron signal, a signal from the signal amplifier 10 is input to the luminance modulation terminal of the CRT 12 through the video signal selection circuit 11, so that a scanning image based on the reflected electron signal can be observed.

On the other hand, a general cathodoluminescence detecting means comprises an aluminum-evaporated mirror 13, a light guide 20, an optical fiber 14, a spectrometer 15, and the like, and a video signal selection circuit 11 through a cathodoluminescence image signal amplifying circuit 16. Is connected to In addition, although not shown, there is a sample stage and a sample holder for holding the sample 7, and by cooling the sample and the sample 7 to a temperature close to the temperature of liquid nitrogen or liquid helium, the efficiency of cathodoluminescence from the sample 7 is increased. In order to obtain a structured spectrum, a cooling means for keeping the temperature extremely low is provided.

FIG. 1 is a schematic diagram showing an embodiment of the present invention. Combining a photodetector for detecting cathodoluminescence light 23 generated from the surface of the sample 7 by irradiation of the electron beam 2 and a backscattered electron detector 9 for detecting backscattered electrons 22 to form the same detector And The photodetector is composed of a phosphor or a scintillator 17, and its shape is elliptical with respect to the direction of the sample 7, as shown in FIG. It is a deposition mirror. One focus of the ellipse is on the sample 7 and the other focus is on the end face of the light guide 20 for light detection.

The cathodoluminescence light 23 generated from the sample 7 is transmitted from the aluminum vaporized mirror 13 through the optical fiber 14 and the spectrometer 15 to the signal from the cathodoluminescence image signal amplification circuit 16 through the video signal selection circuit 1.
1 and is input to the luminance modulation terminal of the CRT 12 so that a cathodoluminescence image can be observed. At this time, the cathodoluminescence light 23 emitted from the sample 7 cannot pass through the aluminum deposition mirror 13 and does not impair the backscattered electron detector for detecting the backscattered electrons 22.

In the same detector, the reflected electrons 22 generated from the sample 7 pass through the aluminum deposition mirror 13 and irradiate the phosphor or the scintillator 17 to be converted into scintillator excitation light 24. The optical information is transmitted to a photomultiplier (optical multiplier) 19 via the optical multiplier and converted into an electric signal.

At this time, the phosphor or scintillator 1
Since the scintillator excitation light 24 emitted in 7 cannot pass through the aluminum deposition mirror 13, it does not affect the photodetector for detecting the cathode luminescence light 23. The converted signal is input from the signal amplifying circuit 10 to the luminance modulation terminal of the CRT 12 through the video signal selecting circuit 11, so that a scanning image based on the reflected electron signal can be observed. By using this detector, the switching between the backscattered electron image and the cathode luminescence image can be performed by selecting the video signal selection circuit 11 without taking the detector in and out, so that both images can be observed simultaneously or alternately. it can.

In addition, since the detector becomes an effective detector even in a low vacuum atmosphere type scanning electron microscope, it is necessary to observe a cathodoluminescence image and a reflection electron image of a sample which cannot be subjected to pretreatment or an insulator or a sample containing moisture or oil. Observation becomes possible. Of course, by selecting the video signal selection circuit 11 without switching the cathodoluminescence image and the backscattered electron image without taking the detector in and out, both images can be observed simultaneously or alternately. .

Further, the same detector in which the photodetector for detecting the cathodoluminescence light 23 of the present invention and the backscattered electron detector for detecting the backscattered electrons 22 are pulled out below the objective lens, By adopting a moving system that allows insertion, the secondary electron can be observed during normal high-vacuum scanning electron microscopy by pulling it out.

[0019]

According to the present invention, the operability as a cathodoluminescence image observation apparatus can be improved in a low vacuum atmosphere type scanning electron microscope, and it can be observed as a detector of a normal high vacuum type scanning electron microscope. Become. Also,
Simultaneous or combined observation of the backscattered electron image and the cathodoluminescence image becomes possible, so that the backscattered electron image and the cathodoluminescence image can be easily superimposed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a scanning electron microscope according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron gun, 2 ... Electron beam, 3 ... Convergent lens, 4 ... Objective lens, 5 ... Scanning power supply, 6 ... Deflection coil, 7 ... Sample,
8 secondary electron detector, 9 backscattered electron detector, 10 signal amplifier, 11 video signal selection circuit, 12 CRT, 13
… Aluminum mirror, 14… optical fiber,
15: spectrometer, 16: signal amplification circuit for cathodoluminescence image, 17: phosphor or scintillator, 18:
Light guide for backscattered electron detector, 19: photomultiplier (light multiplier), 20: light guide for light detection, 2
1 ... shielding plate, 22 ... reflected electrons, 23 ... cathodoluminescence light, 24 ... scintillator excitation light.

Claims (4)

[Claims] In a scanning electron microscope for converging and irradiating an electron beam onto a surface of a sample, reflected electrons generated from the surface of the sample by irradiation of the electron beam and light generated from the surface of the sample by irradiation of the electron beam are generated. A scanning electron microscope having a detector capable of detecting at the same time. 2. The detector according to claim 1, wherein the backscattered electron detector and the photodetector are the same detector, so that the detector can be used in both a high vacuum type scanning electron microscope and a low vacuum atmosphere type scanning electron microscope without taking the detector in and out. The scanning electron microscope according to claim 1, wherein an electron image and a cathodoluminescence image can be observed simultaneously or simultaneously. 3. By using the detector, in a sample or the like containing an insulator or moisture and oil, reflected electrons generated from the sample surface by the irradiation of the electron beam and the sample surface by the irradiation of the electron beam. 2. The scanning electron microscope according to claim 1, wherein the scanning electron microscope is used in a low vacuum atmosphere type scanning electron microscope having an observation means for simultaneously detecting generated light. 4. The secondary detector according to claim 1, wherein said detector has a mechanism capable of being withdrawn and inserted and withdraws from the lower surface of the objective lens so that secondary electrons generated from the sample surface by irradiation of said electron beam during high vacuum observation are arranged elsewhere. 2. The scanning electron microscope according to claim 1, wherein the scanning electron microscope is configured to be detectable by an electron detector.