JPS61151099A - Quality modification of gaas single crystal - Google Patents

Abstract

PURPOSE:A single crystal of GaAs is subjected to repeated heating and cooling under specific conditions in an inert gas and As vapor to produce the titled single crystal with resistance to cracking and warpage and reduced crystal defects. CONSTITUTION:An ingot of GaAs single crystal which is produced by the LEC method is placed on a support 11 and set in a quartz vessel 1 which is provided with infrared heaters which is divided into several blocks in the lengthwise direction. Then, the cover 3 is closed to seal the vessel 1 tightly. Then, the valve in the evacuation pipe 10 is opened and valves 7, 8 are opened to introduce an inert gas and a small amount of As steam through inlet 2. Then, the heater is operated to heat the main region in the vessel at the first-stage temperature (800 deg.C) and the temperature is kept for the first time (10-20min), then the ingot is cooled down from the seed-crystal side of the ingot 12 to the second temperature (550 deg.C) and kept for the second time (5min), then cooled down to the room temperature.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for refining a GaAs single crystal, and in particular, to a method for refining a GaAs single crystal.
c a raised using the EC method (liquid capsule method), etc.
A S q'i Removes residual strain and internal stress from the crystal ingot to create a G that has fewer crystal defects such as dislocations and is less likely to crack.
The present invention relates to a thermal refining method for obtaining an aAS wafer.

[Technical Background of the Invention] As is well known, the LEC method is the mainstream method for producing GaAs rti crystals. As is well known in the LEC method, in order to prevent the decomposition and evaporation of GaAs, GaAs melt (melting point 1
240℃) is covered with the melt of 8203 (E n
GaAs seed crystal while capsulating)
By pulling it up from m1Ht, a cylindrical G
AAS! l! Manufacture crystal ingots.

Problems with the L^Top technology] In the single crystal growth method using the L E C method, the single crystal growing on the GaAS seed crystal is
．． Due to the large temperature gradient during the process of passing through the melt layer and pulling it up into the space above the crucible, the G formed as it is pulled up
There is a problem in that residual strain due to thermal stress is generated inside the aAS single crystal ingot, and crystal defects such as dislocations are generated in multiple matrixes. Therefore, when a device formation process is applied to a wafer manufactured from the ingot, cracks or fractures often occur in the wafer, or the wafer is warped, and saw marks are created on the wafer surface during the process of slicing the ingot into wafers. I was worried about the undesirable results that are likely to occur.

Furthermore, since there are many crystal defects (dislocations) in the peripheral area of the wafer, it is easy to produce elements with poor characteristics or to have defective element formation.

For this reason, the manufacturing yield of GaAs semiconductor devices using GaAs single crystal substrates manufactured by the LEC method is extremely poor.
The manufacturing cost of GaAs semiconductor devices has become extremely high.

[Objective of the Invention 1 The object of the present invention is to develop a GaAs single crystal that is less likely to cause cracks or warp in a wafer in the manufacturing process of GaAs semiconductor devices, and that can obtain a GaAs single crystal with fewer crystal defects such as dislocations.
A method for refining As single crystals is provided.

[Summary of the Invention 1 The GaAs single crystal refining method according to the present invention consists of the structure described in the claims, that is, L
A GaAs single crystal ingot produced by the EC method is placed in a vessel filled with an inert gas and a small amount of arsenic vapor, and the ingot is heated to a predetermined first temperature ( For example, 800°C), the ingot is held at a second temperature (for example, 55°C) in order from the upper end side.
0°C), and from the time when the whole ingot reaches the second temperature, the ingot is held at the second temperature for a predetermined second time, and after the second time has elapsed, the ingot is Cool FJI to room temperature.

Residual strain and internal stress are removed from the GaAs single crystal ingots 1~ tempered by the method of the present invention, and
Dislocations are also significantly reduced, so this in-bore 1- to 1
The resulting GaAs wafer is less likely to develop cracks in the semiconductor device manufacturing process, and has less warpage than conventional wafers.

[Embodiments of the invention] FIG. 1 is a schematic diagram of an apparatus for carrying out the method of the invention.

In the figure, 1 is a quartz container, and one end of this quartz container 1 is provided with a gas inlet 2. Gas inlet 2
An inert gas supply pipe 5 and an arsine gas supply pipe 6 are connected to the inert gas supply pipe 5 and an arsine gas supply pipe 6, and valves 7 and 8 are provided in the inert gas supply pipe 5 and the arsine gas supply pipe 6, respectively. Also,
A lid 3 having an exhaust port 4 is provided at the other end of the quartz container 1, and an exhaust pipe 10 having a valve 9 is connected to the exhaust port 4. A stand 11 made of a material such as aluminum nitride or lead nitride is housed in the quartz container 1, and a GaAs single crystal ingot 12 manufactured by the LEC method is placed on the stand 11.
It is designed to be placed on top of the

A cylindrical infrared heater (not shown) is provided on the outside of the quartz container 1, and this infrared heater is composed of sections divided into several stages along the longitudinal direction of the quartz container 1. The heating range can be sequentially moved toward the other end.

When carrying out the method of the present invention, Ga produced by the LEC method is used.
First, as shown in FIG. 1, an As single crystal ingot 12 is placed on a stand 11 inside a quartz container 1, and then M3 is closed to seal the quartz container 1.

Next, after opening the valve 9, the valve 7 is opened and the inert gas air pipe 5 is opened.
An inert gas (Ar >) is introduced into the quartz container 1 to create an inert gas atmosphere inside the quartz container 1. After the inside of the quartz container 1 has become an inert gas atmosphere, the valve 7 is closed and the valve 8 is closed. Then, arsine gas (Ar-based gas containing 2 to 5% As) is introduced into the quartz container 1.

In this state, the heater is operated to raise the temperature inside the quartz container 1. When the temperature of the main area inside the quartz container 1 reaches 550°C, the valves 8 and 9 are closed, and air is supplied to and from the quartz container 1 while the quartz container 1 is filled with arsine gas. Stop exhaust.

In this state, the temperature of the main area inside the container 1 is raised to 800°C, and then the temperature rise is stopped when the inside of the container reaches 800°C, and this state is maintained for 10 to 20 minutes.

Figure 2 (a) is a diagram showing the temperature distribution inside the quartz container 1 at that time; in this figure, the vertical axis is the temperature ('C), and the horizontal axis is the temperature distribution with the left end of the quartz container 1 as the origin. 1. The horizontal length of the trapezoidal line segment A representing the temperature distribution corresponds to that in FIG.

Then, as shown in FIGS. 2(b) and 2(c), the temperature distribution inside the quartz container 1 increases by 55 mm from the left end (gas inlet side).
By controlling the heater so that the temperature is 0°C, the ingot 12 is heated to 550° C. from the upper end to the lower end.
Avoid lowering the temperature to ℃.

Then, when the temperature of the entire ingot 12 reaches 550℃,
After maintaining this state for 5 minutes, valves 8 and 9 are opened to allow arsine gas to flow into the quartz container 1 to lower the temperature inside the container 1 at a rate of 5°C per minute, and finally cool it to room temperature. let

After the inside of the container 1 and the ingot 12 reach room temperature, the valve 8
While closing the container 1, the valve 7 is opened to replace the arsine gas in the container 1 with Ar gas. Then, when the inside of the container 1 is completely replaced with inert gas, the valve 7 is closed, and then the valve 9 is closed.
After closing the lid 3, remove the ingot 1 from inside the container 1.
Take out 2.

The ingot 1-, which had been subjected to the above-mentioned rough refining treatment, that is, heat treatment, was subjected to a predetermined cleaning treatment, followed by outer periphery grinding and further slicing into wafers.

Semiconductor devices IN were manufactured using the wafers processed in the above steps, and cracks and warpage generated in the wafers during the process were measured and compared with conventional wafers.

As a result, as many as 60% of conventional wafers cracked and broke during the wafer process (wafer mirror polishing, element formation process, chip division process), but ingots processed using the method of the present invention In the wafers obtained from wafers, the percentage of cracks during the wafer process was less than 10%, and the wafer warpage was 20 μm or more for conventional wafers, but was 5 μm or less for wafers to which the method of the present invention was applied. On the other hand, wafers obtained from conventional LEG ingots have a thickness of 350 μm or more.
If there is no heat, cracks occur frequently, but by applying the method of the present invention, iF
It has become clear that mass production is possible (that is, there is no risk of frequent cracking) for wafers with a thickness of 250 μm or more.

Furthermore, when we compared the crystal structures of both wafers, we found that
It has also been revealed that wafers manufactured by applying the method of the present invention have significantly fewer crystal defects such as dislocations than conventional wafers.

[Effects of the Invention] As clarified in the above examples, according to the method of the present invention, a wafer that is less likely to break and has less warpage can be manufactured, and the wafer thickness can be reduced compared to the conventional method. It has become possible to significantly improve the manufacturing yield of GaAS semiconductor devices and to significantly reduce the manufacturing costs of the semiconductor devices.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of an apparatus for implementing the method of the present invention, and FIG. 2 is a temperature distribution diagram within the heating device to illustrate the heating process in the method of the present invention. 1...Quartz container, 2...Gas inlet, 3...
Lid, 4...Exhaust port, 5...Inert gas air pipe,
6...Arsine gas supply pipe, 7.8.9...Valve,
10...exhaust pipe, 11...unit, 12...ingot.

Claims (1)

[Claims] 1. A GaAs single crystal ingot manufactured by a pulling method such as the LEC method is placed in a container filled with an inert gas and a small amount of arsenic vapor, and the entire GaAs single crystal is placed in a predetermined position. After maintaining the GaAs single crystal ingot at a predetermined first temperature for a first time, the temperature of the GaAs single crystal ingot is lowered from the seed crystal side to a second temperature lower than the first temperature. It is characterized in that the GaAs single crystal ingot is maintained at the second temperature for a predetermined second time from the time when the whole reaches the second temperature, and after the second time has elapsed, the GaAs single crystal ingot is cooled to room temperature. Method for refining GaAs single crystal.