JPH11219994A - Mirror-surface evaluating method of gallium arsenide wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the surface of a gallium arsenide wafer to be quickly and accurately evaluated by a method wherein the mirror-surface of the gallium arsenide wafer is cleaned, dried out, and exposed to a nitric acid atmosphere after the gallium arsenide wafer is subjected to mirror-surface polishing, and then it is judged that the mirror-surface of the wafer is dried up well or not, observing whether stains are left on the mirror surface or not. SOLUTION: A gallium arsenide wafer specimen 1 whose surface is mirror- polished is cleaned and then dried up by the use of isopropyl alcohol vapor. Then, the gallium arsenide wafer specimen 1 is fixed above the liquid level of an acid-proof vessel 4 filled with nitric acid liquid 3 so as to set its mirror- surface 2 parallel with the liquid surface of nitric acid liquid 3 separating it from the liquid surface by a prescribed space, and the mirror-surface 2 is exposed to a nitric acid vapor atmosphere for a prescribed time. Then, it is visually checked in a condensed light by an inspector whether the mirror surface 2 of the gallium arsenide wafer specimen 1 is good or not. When a trace left by a flow of isopropyl alcohol is found as stains, it is judged that the mirror surface 2 is irregularly dried up.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for evaluating a mirror surface of a gallium arsenide wafer.

[0002]

2. Description of the Related Art Gallium arsenide, which is one of the compound semiconductor materials, has excellent properties different from silicon, such as semi-insulating properties.
Due to its light-emitting characteristics, etc., taking advantage of these features, a field-effect transistor (FET) or a laser diode (L
D), widely used as a basic material for devices such as light emitting diodes (LEDs).

In order to manufacture devices such as a field effect transistor (FET), a laser diode (LD), and a light emitting diode (LED), ions suitable for the operation function of the device are implanted into a gallium arsenide single crystal wafer surface. Or it is necessary to grow an epitaxial layer.

For this reason, the gallium arsenide wafer as a base material needs to be mirror-polished on its surface, washed with a cleaning agent and dried.

At this time, if cleaning and drying are insufficient (hereinafter referred to as cleaning and drying unevenness), normal functions cannot be exhibited even if ion implantation or crystal growth of an epitaxial layer is performed on the gallium arsenide wafer. That is, even if ion implantation is performed on a gallium arsenide wafer having cleaning and drying unevenness, a good device operation layer cannot be uniformly formed on the wafer surface, and when an epitaxial layer is crystal-grown,
Abnormal growth such as polycrystal growth or three-dimensional growth occurs, and a normal device operation layer cannot be formed.

As described above, the cleaning and drying steps after the mirror polishing of the gallium arsenide wafer are extremely important operations. Therefore, the surface evaluation of the mirror-polished, washed and dried gallium arsenide wafer is also an important operation.

[0007]

Conventionally, a method for evaluating the cleaning and drying of a mirror-polished gallium arsenide wafer has been to place the gallium arsenide wafer under a condensing light, and then an inspector visually judges the quality. . However, with this method, it was difficult to determine the level of altitude such as whether or not cleaning and drying were performed to the extent that ion implantation and epitaxial growth could be performed uniformly. That is, the visual inspection of the inspector was limited to screening for extremely severe washing and drying unevenness.

The cleaning and drying unevenness can be determined by forming a device layer on the surface of the gallium arsenide wafer and evaluating the characteristics of the device layer. At this point, surface defects due to the cleaning and drying unevenness were found. Then, the time and cost required for forming the device layer are wasted.

The present invention has been made in view of such a point, and an object of the present invention is to solve the above-mentioned disadvantages of the prior art, and to wash and dry a wafer surface before actually forming a device layer. An object of the present invention is to provide a method for evaluating a mirror surface of a gallium arsenide wafer, which can quickly and accurately determine a state.

[0010]

The gist of the present invention is to expose a mirror surface of a gallium arsenide wafer to a nitric acid atmosphere, observe the mirror surface, and judge the quality of drying based on the presence or absence of a stain. is there.

In the present invention, the gallium arsenide wafer is preferably exposed to a nitric acid atmosphere in a closed glass container that can be opened and closed, for example, a desiccator.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a method for evaluating a mirror surface of a gallium arsenide wafer of the present invention will be described with reference to the drawings.

(Preparation of gallium arsenide wafer sample)
100 gallium arsenide wafers whose surfaces were mirror-polished by an ordinary method were prepared.

Next, the prepared 100 gallium arsenide wafers were washed with a cleaning agent and dried with isopropyl alcohol vapor.

In the drying method using the isopropyl alcohol vapor, if there are places where the isopropyl alcohol vapor does not uniformly contact or there are places where condensed liquefied isopropyl alcohol flows, depending on the conditions of the vapor generation, etc. Means uneven drying.

Next, the prepared sample was subjected to the gallium arsenide wafer mirror surface evaluation method of the present invention (Example) and the conventional gallium arsenide wafer mirror surface evaluation method (Comparative Example).

Comparative Example Gallium arsenide wafer sample 100
With respect to the sheets, the inspectors visually judged the quality of the mirror surfaces under the light of a condenser.

As a result, no drying unevenness was found, and the pass rate was as high as 98%. (Example) First, an apparatus as shown in FIG. 1 was prepared. This may be a desiccator.

FIG. 1 is a partial sectional view showing an embodiment of a method for evaluating a mirror surface of a gallium arsenide wafer according to the present invention.

In FIG. 1, 1 is a gallium arsenide wafer sample, 2 is a mirror surface of the gallium arsenide wafer, 3 is a nitric acid solution,
4 is an acid-resistant container.

In carrying out the method for evaluating a mirror surface of a gallium arsenide wafer of the present invention, a nitric acid solution 3 is first placed in an acid-resistant container 4.

Next, the gallium arsenide wafer sample 1 used in the comparative example was placed above the liquid surface of the nitric acid solution 3 so that the mirror surface 2 was horizontal to the liquid surface of the nitric acid solution 3 and at a predetermined interval, for example, 2 cm. At a distance of.

Next, the mirror surface 2 of the gallium arsenide wafer sample 1 is exposed to a nitric acid vapor atmosphere for 30 seconds to 3 minutes in the above state.

Next, about 100 gallium arsenide wafer samples 1 exposed to a nitric acid vapor atmosphere, their mirror surfaces 2
The inspector visually judged the quality of the sample under the light of a light collector. As a result, a trace that appeared to have been caused by the flow of isopropyl alcohol condensed in the drying process was found as a new spot.

The pass rate of non-defective products by this method is 90.
%Met.

[0026]

According to the method for evaluating a mirror surface of a gallium arsenide wafer of the present invention, the quality of the mirror surface can be quickly and accurately determined, which is industrially useful.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing one embodiment of a method for evaluating a mirror surface of a gallium arsenide wafer of the present invention.

[Explanation of symbols]

 Reference Signs List 1 gallium arsenide wafer sample 2 mirror surface 3 nitric acid solution 4 acid-resistant container

Claims (2)

[Claims] 1. After mirror polishing, exposing the mirror surface of the washed and dried gallium arsenide wafer to a nitric acid atmosphere, observing the mirror surface, and judging the quality of the drying based on the presence or absence of stains. Method for evaluating mirror surface of gallium arsenide wafer. 2. The method for evaluating a mirror surface of a gallium arsenide wafer according to claim 1, wherein the mirror surface of the gallium arsenide is exposed to a nitric acid atmosphere in a closed glass container that can be opened and closed.