JPS63121732A - Cathode luminescence measuring instrument - Google Patents

Abstract

PURPOSE:To satisfactorily measure the change with lapse of time in the luminescence spectra of a sample which is deteriorated by electron ray projection by detecting the spectrally split luminescence by photodiode arrays and subjecting the same to computer processing, thereby measuring spectral elements at a high speed. CONSTITUTION:The sample 6 radiates the luminescence of the intensity corresponding to impurities and lattice defects according to the projection of the electron rays by an electron gun 3 in a high vacuum vessel. The luminescence thereof is outputted through a luminescence condenser system 7 and an optical window 8 and is spectrally split to spectra by a spectroscope 9. The spectrally split luminescences are detected by the plural photodiode arrays 10, 11 and are supplied through an A/D converter 13 to a computer 14. Two kinds of the radiated luminescences changing according to the crystal state changed by the electron ray projection are measured at a high speed via two units of detectors 10, 11 and the results of the successive measurements are stored in the memory built in the computer 14. The change with lapse of time of the luminescence spectra of the sample deteriorated by the electron ray radiation is thereby satisfactory measured.

Description

Detailed Description of the Invention (1) Description of the field to which the invention pertains The present invention involves irradiating a semiconductor crystal with an electron beam, measuring the spectrum and intensity of the light (luminescence) produced by the irradiation, and determining the cause of the spectrum. The present invention relates to a cathodoluminescence measuring device that analyzes the quality of semiconductor crystals by identifying certain impurities, lattice defects, and complexes thereof.

(2) Description of the Prior Art In general, the spectroscopic system of a cathodoluminescence device uses a combination of a wavelength dispersive spectrometer using a nine-diffraction grating and a detector placed immediately after the exit-side slit. FIG. 4 shows a typical spectrometer configuration using a diffraction grating. Only light of a specific wavelength is passed through a slit via a wavelength-dispersive spectral diffraction grating, and the wavelength is uniquely determined from the rotation angle of the diffraction grating, and the wavelength resolution is determined from the slit width. To obtain a spectrum with such a wavelength dispersive spectrometer, it is necessary to rotate the diffraction grating, and the time required to obtain the desired spectrum depends on the rotation speed of the diffraction grating. That is, if the rotation of the two diffraction gratings is made faster, the measurement time becomes shorter. However, there is a mechanical limit to the rotation speed of the two diffraction gratings, and generally it takes several minutes to several tens of minutes to measure a spectrum in the visible region.

If the slit width is narrowed in order to increase the wavelength resolution, there is a drawback that the measurement time becomes longer because it becomes necessary to compensate for the reduction in the amount of light. As described above, conventional cathodoluminescence devices have the disadvantage that it takes a long time to measure spectra with high precision.

In addition, cathodoluminescence measurement involves irradiating a sample with a rapidly accelerated electron beam in a vacuum and detecting the light produced by the irradiation.The highly accelerated electron beam changes the crystallinity of the sample. there is a possibility. When a sample is altered by electron beam irradiation, a conventional cathodoluminescence device has the disadvantage that it takes a long time to measure the spectrum, making it impossible to observe the true spectrum.

(3) Purpose of the Invention The present invention solves the problems of conventional cathodoluminescence devices, enables high-speed measurement of a wide range of luminescence spectral elements, and detects changes over time in the luminescence spectrum of samples that are altered by electron beam irradiation. The purpose of the present invention is to provide a cathodoluminescence measurement device for observation.

(4) Explanation of structure and operation of the invention FIG. 1 is a block diagram of one embodiment of the present invention, in which 1 is a vacuum vessel, 2 is an exhaust system, 3 is an electron gun, 4 is an electron beam optical system, and 5 is a block diagram of an embodiment of the present invention. Objective lens, 6 is the sample, 7 is the luminescence focusing system, 8
is an optical window, and 9 is a spectrometer.

10 is a photodiode array detector, 11 is a photodiode array detector, 12 is a signal processing system, 13 is an A/D converter, 14 is a computer, 15 is a memory, and 16 is a plotter.

To operate these, the inside of the vacuum vessel 1 is heated to a high vacuum (10-'To r r~10-9To
r r). In order to create a higher vacuum inside the vacuum container 1, the vacuum container 1 and its interior are designed to allow baking. An electron beam emitted from an electron gun 3 is focused by an electron beam optical system 4 and an objective lens 5, and is irradiated onto a sample 6.

Luminescence generated from the sample irradiated with the electron beam is led out into the atmosphere via the luminescence condensing system 7 and the optical window 8. Here, the luminescence focusing system 7 is composed of a spheroidal mirror or a combination of a spherical mirror and a plane mirror.

It has fine holes through which electron beams can pass.

Luminescence is incident on a spectroscope 9, and the luminescence that has been decomposed into spectra is directly input into a photodiode array detector 10.11 without going through a slit, and desired spectral elements of visible region luminescence and near-infrared region luminescence are collectively collected. Detect. Here, detector 1
0 and the detector 11 are both located at the focal position of the spectroscope 9 and can be independently moved above the focal position. The computer 14 measures the luminescence signal through a signal processing system 12 that amplifies the output of each detector and an A/D converter 13 that converts the luminescence intensity of each spectral element, which is an analog signal, into a digital signal. Performs calculation processing.

This data is stored in the memory 15, and the plotter 16 outputs the data.

FIG. 2 shows the detailed arrangement of the spectrometer with the exit slit removed and the two photodiode array detectors. In order to obtain a desired spectrum, the center position of the detector is adjusted to wavelength λ1 or wavelength λ3.

(5) Explanation of effects What are the specifications of a typical photodiode array detector?

For example, the detection area is 200 nm to 11100 nm, the number of photodiode elements is 1024 channels, the element size is 2Q mm, and the response speed is several μs.

When measuring cathodoluminescence, if a resolution of lnm is given to one photodiode element, the resolution is 200nm.
Luminescence of m to 1l100n can be measured at once. Also, Q for one photodiode element is
, lnm resolution, it is possible to measure luminescence in a region of about 1100 nm in a short time. The resolution for one photodiode element can be easily changed by exchanging the diffraction gratings of the two spectrometers. in particular.

For a spectrometer with a focal length of 25 cm and a diffraction grating of 600 lines/mm, the wavelength dispersion is 5.5 nm to 6.5 nm/m.
m, and luminescence in the range of 110 nm to 130 nm can be detected. By reducing the number of grooves in the diffraction grating, luminescence can be detected over a wider range.

As explained above, in the present invention, when measuring cathodoluminescence in the visible and near-infrared regions, a spectrometer equipped with a photodiode array detector is arranged. All spectral elements in the visible and near-infrared regions at once.

It also has the advantage of being able to be measured in a short time.

In addition, by arranging two photodiode array detectors, it has the advantage of being able to measure two arbitrary luminescence peaks at once with high resolution and in a short time on the order of several milliseconds. be.

If the sample changes in quality due to electron beam irradiation.

By using the apparatus according to the present invention, a true cathodoluminescence spectrum can be obtained for the first time, and there is an advantage that the deterioration process of a sample can be analyzed in real time on the order of milliseconds.

The specific effects will be explained using the schematic spectrum diagram shown in FIG. FIGS. 3(a) and 3(b) are true cathodoluminescence spectra at times T1 and T2 after electron beam irradiation, respectively. Wavelength A.

The peaks of luminescence intensity are shown in B and C, and each luminescence intensity decreases or increases over time. FIG. 3(C) is a spectrum obtained by measuring luminescence as described above by sweeping the wavelength from a low wavelength to a high wavelength using a conventional spectroscope with an exit slit.

Conventional methods require several minutes to several tens of minutes for measurement, making it impossible to obtain a true spectrum.

FIG. 3(d) shows two detectors according to the present invention arranged so as to be able to detect luminescence of wavelength A and wavelength C, respectively, at times T1 and T2 in FIG. 3(a) and (b). This is a spectrum obtained when measuring luminescence. By using the apparatus according to the present invention in which two photodiode array detectors are arranged, for example, it is possible to obtain two types of arbitrary luminescence peaks at once in a high resolution state and to obtain the true spectrum at each time. I can do it.

[Brief explanation of the drawing]

FIG. 1 shows the configuration of an embodiment of the present invention, FIG. 2 shows the configuration of essential parts of a spectrometer and a photodiode array detector, FIG. 3 shows a schematic diagram of a spectrum, and FIG. 4 shows a conventional configuration. 1: Vacuum container, 2: Exhaust system, 3: Electron gun, 4: Electron beam optical system, 5: Objective lens, 6: Sample, 7: Luminescence focusing system, 8: Optical window, 9: Spectrometer, 10 : Photodiode array detector, 11: Photodiode array detector, 12: Signal processing system. 13: A/D converter, 14: computer, 15:
Memory, 16: Pronota.

Claims (1)

[Scope of Claims] A sample is placed inside a high vacuum container, an electron gun that irradiates the surface of the sample with an electron beam, an electron beam optical system and an objective lens that converges the electron beam emitted from the electron gun. A cathodoluminescence device having a luminescence collection system that collects cathodoluminescence generated from a location irradiated with a photoelectron beam, a window that guides the collected luminescence to the outside of the vacuum container, and a spectrometer that decomposes the luminescence into spectra. , a movable detector consisting of a plurality of photodiode arrays that measure the spectral intensity, an analog signal processing system that electrically processes the spectral intensity signal, and a converter that converts the analog signal into a digital signal. A/D
A cathodoluminescence measuring device comprising a converter and a computer that stores and processes the digital signal.