Method of making group III-V compound semiconductor wafer

Details Method of making group III-V compound semiconductor wafer Method of making group III-V compound semiconductor wafer

2000-06-06

2001-09-25

Kunemund, Robert (Department: 1765)

Single-crystal, oriented-crystal, and epitaxy growth processes;

Forming from vapor or gaseous state

With decomposition of a precursor

C117S097000, C117S955000, C438S690000, C438S701000

Reexamination Certificate

active

06294019

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of making a group III-V compound semiconductor wafer, and more particularly, it relates to a method of making a group III-V compound semiconductor wafer having an epitaxial layer grown by vapor-phase epitaxy.
2. Description of the Prior Art
The recent development of optical communication has caused an increase in the production quantity of photodiodes and the like. For example, an InP photodiode (hereinafter referred to as a pin-PD) is prepared by growing an epitaxial layer on an indium-phosphorus (hereinafter referred to as (InP) substrate by chloride vapor-phase epitaxy.
In order to prepare a pin-PD, an InP substrate is formed by cutting an InP ingot into slices and chamfering and grinding and polishing each slice. Then, a group III-V compound layer is epitaxially grown on this substrate for preparing an InP wafer, and thereafter a Zn diffusion layer, a protective film and the like are formed on this InP wafer. While the InP wafer grown into a diameter of two inches is generally cut into a rectangular form and thereafter sub-jected to a device process of forming the Zn diffusion layer and the like, such a wafer has recently been subjected to the device process in the circular shape of 2 inches in diameter as such, in order to reduce the cost.
An end portion of the InP wafer, which is generally picked up and carried with tweezers or held by a conveying machine, may be chipped or cracked in the device process. In order to prevent this, the end portion of the substrate is generally chamfered. For example, Japanese Utility Model Laying-Open No. 58-103144 (1983) describes a technique of forming a prescribed chamfered part on an end portion of a GaAs substrate for preventing flaws in mirror grinding or chipping in step movement.
On the other hand, Japanese Patent Laying-Open No. 6-61201 (1994) discloses a technique of forming a prescribed chamfered part on an end portion of a silicon substrate for preventing occurrence of edge crowns.
When a wafer prepared by growing an epitaxial layer on an InP substrate provided with a chamfered portion is subjected to a device process, however, the wafer is disadvantageously cracked in a diffusion step for impurity introduction, a thermal CVD step for forming a protective film or an ultrasonic cleaning step for removing foreign matter.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been proposed for solving such a problem, and an object thereof is to provide a method of making a group III-V compound semiconductor wafer which is hardly cracked in a device process.
A group III-V compound semiconductor wafer prepared ac-cording to an aspect of the present invention comprises a semiconductor substrate consisting of a group III-V compound and a group III-V compound layer formed on this semiconductor substrate. An epitaxial abnormal grown part is removed from the outer peripheral edge portion of the group III-V compound semiconductor wafer. The epitaxial abnormal grown part is a part of the group III-V compound layer having a relatively large thickness.
A portion of the group III-V compound semiconductor wafer is removed up to a location separated from the original outer peripheral edge part by a distance L. The distance L is the length of the stock amount.
Further, the surface roughness Rmax of the outer peripheral edge of the group III-V compound semiconductor wafer formed by removing the abnormal grown part is preferably not more than 2/&mgr;m.
The group III-V compound layer is preferably formed to have a (100) plane as a plane substantially parallel to the major surface of the substrate. “Substantially parallel” means that the (100) plane forms an angle of not more than, 16 degrees with the major surface of the semiconductor substrate.
Before the epitaxial layer is formed, the semiconductor substrate consisting of a group III-V compound is chamfered in such a manner that an outer peripheral edge portion thereof has a sectional shape with an arcuate shape substantially having a radius R. The distance L satisfies an expression R≦L≦3R.
The semiconductor substrate is preferably exposed on a portion at a distance up to 0.1 mm from the outer peripheral edge of the group III-V compound semiconductor wafer.
The outer peripheral edge of the group III-V compound semiconductor wafer is preferably so chamfered when removing the abnormal grown part, so that its section has an arcuate shape substantially with a radius r, which is preferably at least 0.1 mm.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.


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