JPH06101506B2 - Method for measuring EL2 distribution of gallium arsenide semiconductor wafer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is intended to measure the EL2 distribution of a gallium arsenide semiconductor wafer used for measuring the EL2 distribution of a semiconductor wafer made of gallium arsenide, particularly in the manufacturing process of LS1 and the like. Regarding the method.

[Prior art and its problems]

Among various compound semiconductor wafers, in particular, in semiconductor wafers made of gallium arsenide, a portion having a unique energy level, which is commonly called EL2, is partially formed during the manufacturing process. There are various theories about the cause of this EL2, and although it has not been theoretically elucidated at the moment, its characteristic is that it exists at a position farther from the normal donor level such as deep donor. It has been clarified through experiments and the like that

That is, in such a gallium arsenide wafer, in actual use, a phenomenon in which the electrical characteristics of the wafer in which the EL2 is present largely changes occurs. Therefore, in the above gallium arsenide wafer,
It is extremely important in designing a semiconductor wafer to know the existence and distribution of EL2 in advance.

Conventionally, as a method for measuring the EL2 distribution of such a gallium arsenide semiconductor wafer, a contact-type measuring method such as a DLTS method in which a plurality of measuring elements are brought into contact with each other on the wafer has been exclusively used.

However, any of the conventional contact-type measurement methods described above is a so-called destructive inspection method in which a tracing stylus comes into contact with the wafer surface at the time of measurement and causes scratches and metal contamination, and thus can be applied to measurement on a sample. However, it has a fundamental drawback that it cannot be used for measuring what is considered to be a product.

[Object of the Invention]

The present invention has been made in view of the above circumstances, and its EL2 distribution can be measured in a non-contact state with respect to a semiconductor wafer made of gallium arsenide, and thus can be applied to measurement of a product. Method for measuring gallium arsenide semiconductor wafer EL2 distribution.

[History of invention]

The inventor of the present invention, as a result of intensive research on measurement of the non-contact EL2 distribution of the semiconductor wafer made of gallium arsenide, a wavelength of 90 g
When irradiating electromagnetic waves such as microwaves and laser light while irradiating 4 nm laser light and measuring the amount of reflection and transmission thereof, only EL2-level free carriers excited by the laser light interact with the electromagnetic waves. It is found that a peculiar value occurs in the measurement value such as the reflection amount and the transmission amount caused by the occurrence of the wafer, and further, the distribution of the measurement value obtained by the above method is similar to that of the wafer obtained by the conventional contact type measurement method for the same wafer. EL2
We came to the knowledge that it is very similar to the distribution.

[Structure of Invention]

The gallium arsenide semiconductor wafer EL2 distribution measuring method of the present invention is based on the above-mentioned findings, and irradiates a part of the semiconductor wafer with electromagnetic waves while irradiating the semiconductor wafer made of gallium arsenide with laser light having a wavelength of 904 nm. The amount of transmission or reflection of the electromagnetic wave is measured on the entire surface of the semiconductor wafer by repeating the measurement while changing the measurement position along the semiconductor wafer. The distribution is obtained, and the EL2 distribution position of the gallium arsenide semiconductor wafer is specified from the distribution of the measured values.

〔Example〕

1 and 2 are schematic views of an apparatus used in an example of the measuring method of the present invention.

In FIG. 1, on one side of a wafer 1 made of gallium arsenide, a laser diode 2 for irradiating the wafer 1 with laser light is provided. On the other hand, on the other surface side of the wafer 1, a waveguide 6 for irradiating the wafer 1 with the microwave 5a from the microwave oscillator 3 through the circulator 4 is provided. Further, a wave detector 7 and an amplifier 8 for detecting the microwave 5b reflected without being absorbed in the wafer 1 are further connected to the waveguide 6 via the circulator 4. Here, as the waveguide 6, a focusing type waveguide having an H-shaped end face 9 as shown in FIG. 2 is used.

Then, in order to measure the EL2 distribution of the gallium arsenide wafer 2, first, the laser diode 2 irradiates the wafer 1 with laser light having a wavelength of 904 nm, and at the same time, a microwave having a constant frequency is used to measure the EL2 distribution. The output voltage at each position on the wafer 1 in each direction indicated by the XY arrow is measured via the wave detector 7 and the amplifier 8 to obtain the distribution of the change. At this time, it is possible to measure the output voltage within a narrow range of the wafer 1 by using the above-mentioned focusing type waveguide as the waveguide 6, but it is necessary to obtain a distribution for finer points. In this case, it is possible to easily adapt by increasing the frequency of the microwave or using laser light to converge the irradiation beam. Then, the distribution of the amount of reflection of the microwave at each position of the wafer 1 measured in this way, the distribution of the amount of reflection obtained by the measurement method previously investigated for the same type of wafer, and the conventional contact-type measurement method The EL2 distribution on the wafer 2 is obtained by comparing the correlation with the EL2 distribution obtained by the above with each other.

Then, such EL of gallium arsenide semiconductor wafer
According to the 2 distribution measurement method, the EL2 distribution of the wafer 1 can be measured without contacting the gallium arsenide wafer 1. Therefore, the EL2 distribution of the product gallium arsenide semiconductor wafer can be appropriately measured during the manufacturing process, so that the quality of the semiconductor wafer can be improved.

[Experimental example]

FIGS. 3 to 5 show that different kinds of semiconductor wafers made of gallium arsenide are irradiated with a laser beam of λ = 904 nm by a laser diode and the frequency is 10 G.
It shows the experimental results when a microwave of Hz is incident, and shows the distribution of the measured value (mV) of the reflection amount, respectively. Here, FIG. 3 shows the results performed on the gallium arsenide semiconductor wafer to which chromium was added, and FIGS. 4 and 5 show the results performed on the gallium arsenide semiconductor wafer to which chromium was not added, respectively. It is a thing. In FIGS. 3 to 5, EL2 distributions are measured within the range indicated by the chain line in the drawings.

〔The invention's effect〕

As described above, the gallium arsenide semiconductor wafer EL2 distribution measuring method of the present invention is a method of irradiating a semiconductor wafer made of gallium arsenide with a laser beam having a wavelength of 904 nm while irradiating an electromagnetic wave to a part of the semiconductor wafer and transmitting the electromagnetic wave. Amount or the magnitude of the amount of reflection, this measurement is repeated while changing the measurement position along the semiconductor wafer to obtain the distribution of the measured values of the amount of transmission and reflection of the electromagnetic waves on the entire surface of the semiconductor wafer. Since the EL2 distribution position of the gallium arsenide semiconductor wafer is specified from the distribution of the measured values, the EL2 distribution position can be easily and quickly determined without touching the wafer.

As a result, it is possible to measure the EL2 distribution in the semiconductor wafer of gallium arsenide as a product, so that the quality of this type of semiconductor wafer can be improved.

[Brief description of drawings]

1 and 2 are schematic views of an apparatus used for an embodiment of the measuring method of the present invention, and FIGS. 3 to 5 show experimental examples using the measuring method of the present invention. FIG. 6 is a distribution diagram showing the value of the amount of reflection of microwaves. 1 ... Gallium arsenide semiconductor wafer, 2 ... Laser diode, 3 ... Microwave oscillator, 6 ... Waveguide, 7 ...
… Detector, 8 …… Amplifier.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-76136 (JP, A) JP-A-61-115453 (JP, A)

Claims (1)

[Claims] 1. A semiconductor wafer made of gallium arsenide is irradiated with a laser beam having a wavelength of 904 nm and a part of the semiconductor wafer is irradiated with electromagnetic waves to measure the amount of transmission or reflection thereof. Obtaining the distribution of the measured values of the amount of transmission or reflection of the electromagnetic waves on the entire surface of the semiconductor wafer repeatedly while changing the measurement position along the semiconductor wafer, and from this distribution, the distribution position of EL2 of the gallium arsenide semiconductor wafer. A method for measuring an EL2 distribution of a gallium arsenide semiconductor wafer characterized by specifying.