JPS61181945A - Crystal evaluator - Google Patents

Abstract

PURPOSE:To enable the evaluation of a III-V family compound semiconductor crystal, by moving the relative position between a light source comprising a silica fiber induced Raman light generator and a bulk crystal to rate the quantitative spatial distribution of various defects in the bulk crystal. CONSTITUTION:When an emitted light 2 from a Nd:YAG laser 1 is made incident into a long-sized single mode silica fiber 3 about 1km long, a 1.06mum excited light converted in the wavelength serves as a fiber induced Raman light generator and provides an emitted light 4. Once turned to a fine-diameter beam by an appropriate means such as Selfoc lens 5, this emitted light 4 is made incident into a half-insulating GaAs crystal wafer 6 with the side and the end face thereof ground and the scattered light 7 obtained from the face thereof is taken with an infrared vidicon 9 through a wave-length selective interference filter 8. In this case, to measure the entire crystal, a moving mechanism 10 for the infrared vidicon is necessary which makes the relative position between the incident luminous flux and the crystal change.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a crystal evaluation device having a novel configuration.

(Prior art and its problems) As a result of the development of high-speed electronics technology in recent years, gallium arsenide (GaAs) has replaced silicon.
Integrated field transistor circuit using GaAs PE
TIC) K Interest is gathering. Such integrated circuits are usually manufactured by forming active regions and the like by ion implantation or other methods in a GaAs bulk crystal manufactured by a pulling method. In this case, one of the current biggest problems is that such GaAs crystals are not homogeneous, and there are non-uniformities in composition, dislocation density, precipitates, impurities, etc. not only between crystals but also within the same crystal. This results in non-uniformity in the characteristics of the nine FET ICs being fabricated. On the other hand, a FET IC directly on such a crystal
Manufacturing and evaluating the crystals requires a process involving many steps, so it is not realistic to carry out the process on a large number of crystals.

For this reason, there has been a long-awaited development of a method that can easily and non-destructively quantitatively evaluate m-vi compound semiconductor crystals such as bulk GaAs crystals.

(Object of the invention) The present invention has been made in view of these problems in the past,
The object of the present invention is to provide a crystal evaluation device that enables the evaluation of group 1-V compound semiconductor crystals, including GaAs bulk-pulled crystals, by a quantitative and non-destructive method.

(Structure of the Invention) The structure of the crystal evaluation apparatus of the present invention is that the crystal evaluation apparatus performs non-destructive evaluation by optical means of a ■-■ group compound semiconductor bulk crystal having an absorption edge in the near-infrared region.
A light source consisting of a silica fiber stimulated Raman light generator using a YAG laser as an excitation source; a means for moving the relative position of the light source and the bulk crystal; and a means for moving the relative position of the light source and the bulk crystal; and imageable photodetection means with wavelength selectable means for detecting and intercomparing the spatial distribution, for quantitatively evaluating the spatial distribution of various defects within the bulk crystal. Features.

(Principle of the Invention) In general, in m-v group compound semiconductor crystals, especially in semi-insulating GaAs crystals obtained by the pulling method, arsenic atoms exist in a stoichiometric excess in the crystal, and a considerable amount of Some parts form clusters of several atoms, creating deep levels that affect electrical properties, while other considerable parts form larger rasters and precipitate along dislocation lines or in the crystal. It is known that it has almost electrically neutral properties. On the other hand, regarding optical properties, a cluster of several atoms gives a unique absorption band around 1 μm.

Precipitates with a size comparable to the wavelength cause Rayleigh scattering and exhibit strong wavelength dependence, while even larger precipitates cause Mie scattering, which is almost unrelated to wavelength. For this reason, by detecting the presence of excess arsenic using various optical means, it is possible to obtain information such as the quality of the crystal or the degree of non-uniformity.

Until now, the spatial distribution of light absorption or light scattering in semi-insulating GaAs crystals has been measured individually, and GaAsFETIC
Although there are quite a number of examples in which comparisons have been made with the underlying characteristics of the conventional methods, the relationships between various measurement results have not been fully understood, and as a result, they have been insufficient as evaluation tools.

As a result of this research, absorption and scattering characteristics at multiple wavelengths can be measured separately by using a fiber-stimulated Raman light generator as a light source, which has many infrared emission lines and can obtain narrow beams. Now possible, GaAs
It has become possible to directly evaluate various defects in ■-■ group compound semiconductor crystals such as t-.

(Example) Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention.

In this embodiment, the emitted light 2 of the Nd:YAG laser 1 is
When input into a long single-mode silica fiber 3 with a length of about m, the 1.0.6 μm excitation light undergoes wavelength conversion and becomes a fiber-stimulated Raman light generator, 9,!
An emitted light 4 whose spectrum is shown in FIG. 2 is provided. This emitted light 4 is made into a narrow beam by a suitable means such as a Selfoc lens 5, and is made incident on a semi-insulating GaAs crystal wafer 6 whose side and end surfaces have been polished. The scattered light 7 is imaged by an infrared vidicon 9 via a wavelength-selective interference filter 8.

In this case, it is effective for analyzing scattered light to store images obtained by replacing a plurality of interference filters 8 in an appropriate storage device and directly compare them. Furthermore, in order to perform such measurements over the entire crystal area, an infrared vidicon moving mechanism 10 is required that can change the relative position of the incident light beam and the crystal.

FIG. 3 is a schematic diagram of a second embodiment of the invention.

In this embodiment, the emitted light 4 from the fiber stimulated Raman light generator (1 to 3) similar to that shown in FIG. 1 having the spectrum shown in FIG. The infrared vidicon 9 images the entire surface or part of the pattern of the crystal through the GaAs crystal 6 using the interference filter 8, and compares it with the spatial distribution of the scattered light to determine the absorption distribution within the crystal. You can also know.

This method has better parallelism compared to the commonly used method using tungsten lamps, so it has a good 1i
TI images can be obtained.

The evaluation method according to this example is based on the semi-insulating Ga
It can be applied not only to As crystals but also to other m-V group compound semiconductor crystals having absorption edges in the near-infrared region or mixed crystals thereof.

(Effects of the Invention) As explained above, according to the crystal evaluation apparatus of the present invention,
It becomes possible to effectively perform quantitative and non-destructive evaluation of ■-V group compound semiconductor crystals, including semi-insulating GaAs crystals for ICs such as ()aAsB'ET.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an embodiment of a crystal evaluation apparatus according to the present invention, and Fig. 2 Vi! FIG. 1 is a spectrum diagram of an example of light emission from a fiber-stimulated Raman light generator, and FIG. 3 is a schematic diagram of a second embodiment of the present invention. In the figure, 1...Nd: YAG laser, 2...
・Laser emission light, 3...Single mode silica
Fiber, 4... Fiber stimulated Raman light generator output light, 5 Mountain... Selfoc lens, 6...
...Semi-insulating GaAs crystal, 7...Scattered light, 8
......Interference filter, 9...Infrared vidicon, 10...Mobile device L 11...Heam expander, 12...1 It is a different kind of luminous flux. Agent: Patent Attorney Shinran Uchihara, -11

Claims (1)

[Claims] A silica fiber stimulated Raman light generator using a Nd:YAG laser as an excitation source is used in a crystal evaluation device that non-destructively evaluates III-V compound semiconductor bulk crystals having an absorption edge in the near-infrared region by optical means. a light source consisting of;
An image having means capable of moving the relative position of the light source and the bulk crystal, and wavelength selectable means for detecting and mutually comparing the wavelength and spatial distribution of transmitted light or scattered light from the bulk crystal. 1. A crystal evaluation device comprising a formable photodetection means.