JPS60146132A - Method and apparatus for evaluating semiconductor crystal - Google Patents

Abstract

PURPOSE:To measure a semiconductor without destruction quickly, by transmitting a light beam through a cylinder shape semiconductor sample, converting the light, which is transmitted, refracted and outputted, into an electric quantity, and obtaining the space distribution of a deep level in a crystal. CONSTITUTION:A semiconductor crystal is machined into a circular cylinder shape and mounted on a rotary sample table 2 as a sample 1. Light 11 having a wavelength, which can transmit through the sample 1, is projected from a light source 3 in a beam shape. The light 11 is transmitted through the sample 1 and becomes refracted light 11'. The light 11' is converted into an electric quantity by a light detector 5, on which a plurality of light receiving devices 6 are arranged, and displayed. For example, when the semiconductor is a GaAs single crystal or an InP single crystal, wavelengths of 1.0-1.5mum and 1.3mum are used for the light source 3. The light source 3 is moved in the direction of the Z axis with a Y-Z plane (the axis of the cylinder is made to be Z) being moved. The light beam is projected with the sample table rotated, and the measurement is performed. By obtaining the distribution of the absorption coefficient due to the deep level in the semiconductor crystal, the semiconductor crystal can be accurately evaluated without destruction quickly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor crystal evaluation apparatus and evaluation method, and more particularly to a semiconductor crystal evaluation apparatus and evaluation method that can non-destructively determine the spatial distribution of deep levels in a semiconductor crystal. .

In recent years, as a result of the increasing need for high-speed and highly functional electronic circuits, compound semiconductors with higher mobility have replaced the conventionally used 8i integrated circuits (hereinafter referred to as ICs). There is growing interest in ICs using .

The crystals currently used for the substrates of such ICs have a high resistance of G.
In recent years, undoped crystals to which impurities are not intentionally added are generally being used in place of the conventionally used Cr doped crystals. GaA from such crystals
The current problems in forming s-IC are:
The various properties of the crystal are not necessarily uniform, and when an lli'ET circuit, which is a typical IC, is formed, the pinch-off voltage becomes non-uniform, which causes a practical problem.

Recent research has revealed that such nonuniformity is related to dislocations in the crystal or the distribution of deep levels. For these reasons, there is currently a great deal of interest in determining the spatial distribution of crystal dislocations or deep levels, preferably by a non-destructive method. Typical methods include exposing etch bits corresponding to dislocations by etching and calculating the dislocation density, or forming KFETs directly on the wafer to obtain a two-dimensional characteristic distribution. There were methods such as measuring and evaluating the situation. However, all of these methods are destructive, requiring large man-hours and low yields. Furthermore, the methods of measuring photoluminescence and cathodoluminescence are inherently unreliable, and cannot be used as an accurate means of evaluating the quality of crystals. 9 who was also recently
It has been shown that direct knowledge of deep levels can be obtained by spatially measuring the distribution of light absorption between 1.0 and 1.3 μm. However, the absorption coefficient of crystals in this wavelength range is as low as 1 cm' or less, and in order to measure and obtain an accurate distribution, K requires a crystal with a thickness of 5 dragons or more and optically polished on both sides, which is far from common. It was not possible to provide a usable evaluation tool.

As described above, conventional methods have the disadvantage that either they are destructive and require a large number of steps and have low yields, or that non-destructive methods are impractical.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor crystal evaluation device and evaluation method that can eliminate the above drawbacks and quantitatively evaluate deep levels in a crystal non-destructively, quickly and accurately.

The semiconductor crystal evaluation apparatus of the present invention includes a rotary sample stage having a mechanism for placing a sample to be measured made by processing a semiconductor crystal into a cylindrical shape and rotating the sample about the axis of the column; a light source that emits a beam of light at the desired wavelength;
When the axis of the cylinder of the sample is the Z axis, the light source is Y-Z
A light-receiving device comprising: an I-Z moving mechanism that moves the sample in two dimensions; and a plurality of photodetectors that receive transmitted light emitted from the light source and transmitted through and refracted through the sample, and convert it into an electrical quantity. and a computer for processing data information from the light receiving device.

The semiconductor crystal evaluation method of the present invention includes a first process in which a semiconductor crystal to be measured is processed into a cylindrical shape and the surface is polished to a smooth surface.
a second process of placing the sample on a rotating sample stand with the rotational axis of the rotating sample stand aligned with the cylindrical axis of the sample; and a second process of placing a light beam of a wavelength that can pass through the sample on the sample. a third process in which the transmitted light is incident perpendicularly to the side surface of the cylinder and is transmitted and refracted through the sample, and the transmitted light is received by a light receiving device equipped with a photoelectric conversion mechanism, and the information from the light receiving device is input into a computer and stored; a fourth process in which the sample is moved a short distance in the Y-axis direction when the axis of the cylinder of the sample is the Z-axis, and then the third process is repeated until the sample has been moved a predetermined distance in the Y-axis direction; a fifth process in which the sample is rotated by a small angle around the Z-axis and then the third process and the fourth process are repeated until the sample rotates once; and a fifth process in which the sample is rotated in the Z-axis direction. a sixth process of repeating the third process, the fourth process and the fifth process after moving a small distance until the movement is completed a predetermined distance in the Z-axis direction; The present invention is characterized in that it includes a seventh process of reconstructing and displaying the distribution of absorption coefficients due to a specific deep level in the crystal of the sample through calculation processing.

First, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the semiconductor crystal evaluation apparatus of the present invention.

This embodiment includes a rotary sample stage 2 having a mechanism for placing a sample 1 to be measured made of semiconductor crystal processed into a cylindrical shape and rotating it around the axis of the cylinder, and a light beam of a wavelength that can pass through the sample 1. 11 in a beam shape, light #3, and sample 10.
When the axis of the cylinder is ZJII+, there is an X-Y moving mechanism 4 that moves the light source in two dimensions of Y-Z, and an electric light source that receives the transmitted light 11' that is emitted from the light source 3, passes through the sample 1, is refracted, and comes out. It is configured to include a light receiving device 6 which is formed by arranging a plurality of photodetectors 5 that convert the data into quantities, and a computer 7 which processes data information from the light receiving device 6.

When the sample is a GaAs single crystal, the light source is a laser (with a wavelength in the range of 1.0 to 1.5 μm).
For example, Nd:YAG laser (f-) with a wavelength of 1.06 μya is suitable, and in the case of InP single crystal, the wavelength is 1.3 μya.
It is preferable to use a semiconductor laser of m. The light source is not limited to lasers, and ordinary infrared rays can also be used. Further, although a COD is suitable for the photodetector 5, other light receiving elements can also be used.

Next, a method for evaluating a semiconductor crystal according to the present invention will be explained.

FIG. 2 is an optical path diagram for explaining one embodiment of the semiconductor crystal evaluation method of the present invention.

In this example, GaAs, which is a typical fast conductor of the ■-v group compound, is selected as the sample to be measured, but the present invention is also applicable to other compound semiconductor crystals of the
■-■ group compound semiconductor crystals such as dS, SI + G
It can also be applied to single-element semiconductor crystals such as e.

First, sample 1 is prepared by processing a semiconductor crystal to be measured into a cylindrical shape and polishing the side surface to make it smooth. This is placed on the rotating sample stage 2.

A Nd:YAG laser is used as the light source 3, and the wavelength is 1.0.
A laser beam 11 of 6 μm is made incident on the cylindrical side surface of the sample 1 in a direction perpendicular to the axis of the cylinder (this is defined as the Z axis).

The laser beam is refracted at the interface with the sample 1, passes through the sample 1, is refracted at the interface, and comes out as transmitted light 11'. The transmitted light 11' is received by the photodetector 5, converted into an amount of electricity, and transmitted to the computer 7 as data information to be stored in the computer.

The multi-light source 3 is moved by a small distance in the Y-axis direction as shown by the arrow 12 by the Y-Z moving mechanism, and the light 11 is again incident on the sample 1 to receive the transmitted light, and the data is sent to the computer 7. to be memorized. The process of moving a small distance in the Y-axis direction, receiving transmitted light, and storing data is repeated until a predetermined distance in the Y-axis direction has been moved. When moving in the Y-axis direction, if the movement is too large, the reflection at the crystal interface will increase and the result will be easily influenced by surface non-uniformity, so it is appropriate that the incident angle θ is 20 degrees or less. .

Next, the sample is rotated by a small angle around the Z-axis, and the incident of the light beam 11, reception of transmitted light, and data storage are repeated while moving the light source 3 a short distance in the Y-axis direction. After the light source has moved a predetermined distance in the Y-axis direction, the sample is again rotated by a small angle around the two axes, and the same operation as described above is repeated. This operation is repeated until the sample rotates.

Next, once the sample has completed one rotation, move the sample a short distance in the Z-axis direction, move the light source 3 in the Y-axis direction, and rotate the sample by a small angle around the Z-axis. Repeat this operation until the sample rotates once.

When the sample completes one rotation, the sample is moved again by a small distance in the Z-axis direction, and the same operation is repeated until the sample has been moved a predetermined distance in the two-axis directions.

After the movement and measurement in the Z-axis direction are completed, the data stored in the computer 7 is entered into the simultaneous equations used in known tomography, and the computer calculates and solves it to calculate the absorption caused by deep levels in the crystal. Reconstruct the distribution of coefficients. From this, we can determine the spatial distribution of deep levels in the crystal.

As described above in detail, the present invention provides a semiconductor crystal planning device and evaluation method that can quantitatively evaluate deep levels in a crystal nondestructively, quickly, and accurately.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the evaluation bag number of semiconductor crystals of the present invention, and FIG. 2 is an optical path diagram for explaining an embodiment of the semiconductor crystal evaluation method of the present invention. 1...Sample, 2...Rotating sample stage, 3.
...Kourin, 4...Y-Z movement mechanism, 5.
...Photodetector, 6...Photodetector, 7...
...Computer, 11...--Light beam, 11'
...Transmitted light, 12...Y-axis direction.

Claims (2)

[Claims] (1) A rotating sample stage with a mechanism for processing a semiconductor crystal into a cylindrical shape and placing a sample for growth halide measurement on it and rotating it around the axis of the cylinder, and a beam of light with a wavelength that can pass through the sample. A light source that emits light in the direction of Y-Z and a Y-
a Z-movement 1 mechanism, a light receiving device comprising a plurality of photodetectors arranged to receive transmitted light emitted from the light source and transmitted through and refracted through the sample, and convert it into an electrical quantity; 1. A semiconductor crystal evaluation device comprising: a computer for processing data information. (2) The semiconductor crystal to be measured is processed into a cylindrical shape and the surface iMi
a first process in which the sample is smoothly polished to obtain a sample; a second process in which the sample is placed on a rotating sample stand with the rotational axis of the rotating sample stand aligned with the cylindrical axis of the sample; A light beam of a wavelength that can be transmitted is made perpendicular to the cylindrical side surface of the sample, and the transmitted light that is transmitted and refracted through the sample is received by a light receiving device equipped with a photoelectric conversion mechanism, and the information from the light receiving device is converted into a computer. A third process in which the cylinder of the sample is manually memorized, and when the axis of the cylinder of the sample is taken as the Z axis, the sample is moved a small distance in the Y-axis direction and then the third process is performed by moving it by a predetermined distance in the Y-axis direction. a fourth process that is repeated until the
After rotating the sample by a small angle around the Z-axis, the third
A fifth process in which the sample is repeated with a spindle in which the sample rotates once, and a fourth process in which the sample is rotated twice.
a sixth process of repeating performing the third process, the fourth process and the fifth process after moving a small distance in the axial direction until the movement is completed a predetermined distance in the Z-axis direction; A method for evaluating a semiconductor crystal, comprising a seventh process of processing information to reconstruct and display a distribution of absorption coefficients caused by a specific deep level in a crystal of a sample.