JPH0310600B2 - - Google Patents

Description

[Detailed Description of the Invention] [Background and Objectives of the Invention] The present invention relates to a method for producing a low dislocation single crystal, and particularly relates to a method for producing a low dislocation single crystal suitable for effectively reducing dislocation. be.

Methods for producing GaAs single crystals can be roughly divided into horizontal boat methods and pulling methods. The horizontal boat method can obtain low-dislocation single crystals compared to the pulling method, but crystals with a dislocation density (EPD) ≦500/cm ² used for semiconductor lasers can only be obtained stochastically in Si-doped crystals. It is still in the process of being sold, and the yield is poor. In addition, with regard to the pulling method, various companies are developing and manufacturing undoped semi-insulating crystals for FETs and ICs using the direct synthesis pulling method, but in terms of dislocation density, it is possible to manufacture crystals with EPD≦100,000 cells/ ^cm2 . However, it seems difficult to manufacture those with EPD≦50,000 cells/cm ² .

There ^is an urgent need to reduce dislocations in semi-insulating crystals using the pulling method.
It is said that unless something with a density of ≦1000 cells/cm ² can be produced, there will be no hope for the development of ICs and LSIs.

As an attempt to reduce dislocations, it has been considered to lower the temperature gradient at the crystal growth interface to prevent the generation of dislocations due to _{thermal strain} . Increased thickness and crystallization within capsules are beginning to be used.

Another attempt is to increase the strength of the crystal itself to prevent dislocations from being incorporated. So-called impurity hardening
This is a method called "hardening" and is a method of adding elements of groups other than Ga and As that do not affect the electrical characteristics. Regarding this, In (indium), Sb (antimony), B
There are reports of adding single elements such as (boron). In particular, the effect of In addition seems to be the greatest, and the outer diameter
There are reports that dislocation-free crystals of approximately 20 mm and length of 40 mm have been obtained. However, practical crystals with a diameter of 50 mm or more with EPD≦10,000 crystals/cm ² have hardly been obtained.

In addition, attempts have been made to add In using the boat method, but adding more than 1 mol% has no effect;
It has been revealed that defects that are thought to be caused by precipitation occur. In addition, due to segregation, In is pushed out to the rear end of the crystal, making it difficult to enter the crystal, and "wetting" between the pushed out In and the quartz boat.
It has also been revealed that there are some drawbacks, such as problems.

The present invention has been made in view of the above, and its purpose is to effectively cure the
An object of the present invention is to provide a method for manufacturing a low dislocation single crystal that can reduce the dislocation of a GaAs single crystal.

[Summary of the Invention] The feature of the present invention is that in a method for manufacturing GaAs single crystals by a horizontal boat method or a pulling method, 0.02% of each of In and Sb, which do not affect the electrical characteristics, are added to the raw materials of the GaAs single crystal. mole% or more,
The point is that crystal growth is performed by adding less than 1.0 mol%.

[Example] An example of the manufacturing method of the present invention will be described in detail below with reference to FIGS. 1 and 2.

Example 1 When using the horizontal boat method A seed crystal and a raw material were placed at one end of a quartz glass reaction tube.
A quartz boat containing 800 g of Ga, 2.5 g of In (0.1 mol%), and 2.7 g of Sb (0.1 mol%) was placed, and 890 g of As was placed at one end of the other side and welded.
Evacuate at 10 ^-6 Torr or less for more than 1 hour, then seal.

This reaction tube was installed in a double electric furnace, with the boat side (high temperature furnace) heated to over 1200℃ and the As side (low temperature furnace) heated.
Raise the temperature to 610℃. After the GaAs synthesis reaction is completed, the temperature of the high-temperature furnace is further increased while keeping the temperature of the low-temperature furnace constant, and the seeded portion is heated to the melting point of GaAs.
Adjust the temperature gradient to 1.0deg/cm so that the temperature on the boat body side is higher than that of 1238℃. After partially melting the inserted seed crystal in this way, the temperature is lowered at a rate of about 1.0 deg/hr while keeping the temperature gradient constant. After confirming that the entire crystal has solidified, it is cooled to room temperature at a rate of 100 deg/hr, and the crystal is taken out.

A GaAs single crystal weighing approximately 1600 g was obtained by the above method. The obtained crystal was of n-type, had a carrier concentration of n=1×10 ¹⁸ to 3.5×10 ¹⁸ cm ⁻³ , and had no particular problems in terms of electrical properties. Furthermore, when we measured the dislocation density by etching with molten KOH, we found that
The entire crystal had a low dislocation density of EPP≦500/cm ² except for a portion approximately 5 mm inward from the portion in contact with the boat wall. Figure 1 shows the internal dislocation density distribution of the obtained crystal wafer, and the numbers shown in each frame indicate the dislocation density (unit: x 100 cells/cm ² ).
It is.

In addition, the experiment was repeated more than 30 times, and In,
When compared with the case without adding Sb, it was found that crystals with an EPD≦500/cm ² could be obtained with a yield that was more than twice as high.

Example 2 In Example 1, In0.50g (0.02 mol%),
Similar single crystal growth was performed with the addition of 0.52 g (0.02 mol%) of Sb. As a result, it was found that single crystals with EPD≦500/cm ² were obtained, and the yield was 20 to 30% better than when nothing was added.

Example 3 Using the pulling method 1000 g of Ga, 1100 g of As, 3.3 g of In (0.1 mol%) in a PBN (Pyrolitic Boron Nitride) crucible,
After adding 3.5 g (0.1 mol%) of Sb and 500 g of B ₂ O ₃ (boron oxide) capsules and placing it in a pulling device, the GaAs synthesis reaction was carried out at 700°C and 70 atm. , the pressure was lowered to 20 atm and GaAs single crystal was pulled. As a result, outer diameter 65-75
Approximately 1500 g of single crystals of cm were obtained. After slicing the obtained single crystal along {100} planes and etching it with molten KOH, the central portion with a diameter of approximately 50 mm was
It was a semi-insulating crystal with a low dislocation density of EPD≦10,000/cm ² . FIG. 2 is a diagram showing the dislocation density distribution within the wafer plane of the obtained crystal, and the numerical values shown in each frame are numerical values indicating the dislocation density (unit: ×100 cells/cm ² ).
Next, a comparative example will be explained.

Comparative example In Example 1, In25g (1 mol%), Sb27
Similar single crystal growth was performed by adding g (1 mol %). As a result, although the dislocation density becomes smaller,
It was found that it has the following drawbacks.

(1) Defects that appear to be caused by In precipitation occur in the latter half of crystal growth.

(2) In exceeds the solid solubility limit and precipitates around the crystal, causing "wetting" with the boat and causing slip dislocations.

(3) Twinning is likely to occur in conjunction with "wetting." Furthermore, when In and Sb are added individually, less than 1 mol% has little effect on reducing dislocation density, and when more than 1 mol% is added, In×Ga(1-X)As or GaAs( 1-
X) It becomes an Sbx mixed crystal, and the lattice constant and other properties may change. Furthermore, in reality, if 1 mol % or more of In is added, defects likely to be caused by In precipitation tend to occur in the latter half of crystal growth, making it unusable as a GaAs single crystal.

By the way, as in the manufacturing method of the present invention, In and
When Sb is added at the same time, adding only 0.1 mol % of each has a remarkable effect on lowering dislocations, and adding 0.02 mol % of each is the boundary region between whether or not it is effective. In addition, In and Sb were each 1 mol%
If In is added, defects likely to be caused by In precipitation will occur in the latter half of crystal growth, as in the case of In alone, so it is necessary to avoid adding such a large amount.

As mentioned above, according to the embodiment of the method of the present invention, when applying the impurity curing method, In and Sb
Since these are added at the same time, the synergistic effect produces the following effects.

(1) Compared to the case where only a single element is added, a smaller amount is required, so the characteristics of the GaAs crystal are less likely to change.

(2) Precipitation of impurities added at the same time or occurrence of "wetting" when using the horizontal boat method can be suppressed.

(3) Due to the synergistic effect, the effect is significantly greater than when the same amount of a single element is added.

[Effect of the invention] As explained above, according to the present invention, In and
By adding Sb to GaAs in an amount of 0.02 mol % or more and less than 1.0 mol %, respectively, it is possible to effectively reduce dislocations in the GaAs single crystal by an impurity hardening method.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the in-plane dislocation density distribution of a crystal wafer obtained by the present invention using the horizontal boat method;
FIG. 2 is a diagram showing the in-plane dislocation density distribution of a crystal obtained according to the present invention using a pulling method.

Claims (1)

[Claims] 1 By horizontal boat method or hoisting method
In the method of manufacturing a GaAs single crystal, the GaAs
0.02 mol% each of In and Sb in the single crystal raw material
A method for producing a low dislocation single crystal, characterized in that crystal growth is performed with addition of less than 1.0 mol%.