JP2852619B2 - Liquid phase growth method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid phase growth method, and more particularly, to a method in which a difference in carrier concentration between batches is small, a carrier concentration corresponding to a charged amount of impurities is obtained, and a carrier concentration in an epitaxial layer is obtained. To a liquid phase growth method capable of making the uniformity.

[0002]

2. Description of the Related Art Crystal growth in liquid phase epitaxy occurs in a state closest to thermal equilibrium among various crystal growth methods. Therefore, the crystals obtained by liquid phase epitaxy are:
In general, it has high integrity with few structural defects. In addition, since liquid phase epitaxy is performed at a temperature considerably lower than the melting point of the semiconductor, the crystal obtained by epitaxy, that is, the structure of the epitaxial layer has high integrity. Therefore, the liquid phase epitaxial growth method is used for growing various epitaxial layers.

In the above-mentioned liquid phase epitaxial growth method, for example, when an AlGaAs semiconductor is grown, for example, a melt of Ga is kept in a high-temperature hydrogen atmosphere for several hours to reduce oxygen in Ga. Then this G
a using a melt as a solvent and GaAs as an As source
s, Al as an Al supply source and Zn or GaTe as an impurity (dopant) are dissolved to prepare a crystal growth solution (hereinafter, also referred to as a melt), and then temperature is controlled by a slow cooling method or a temperature difference method. An epitaxial layer (hereinafter also referred to as an epi film) is grown on a substrate.

[0004]

However, in the above method, since the impurities are dissolved in the Ga melt immediately before the growth of the epitaxial film, the diffusion of the impurities in the melt is insufficient. Further, a part of impurities such as Te may react with some oxide components of solute Al to form an oxide. From these facts, it is said that the amount of impurities taken into the epitaxial film differs between batches, that it is difficult to obtain a carrier concentration corresponding to the charged amount of impurities, and that the carrier concentration in the epitaxial layer after growth tends to vary. There was a problem.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, to reduce the difference in carrier concentration between batches, to obtain a carrier concentration corresponding to the charged amount of impurities, and to make the carrier concentration in the epitaxial layer uniform. It is an object of the present invention to provide a liquid phase growth method.

[0006]

Means for Solving the Problems The inventors of the present invention have repeatedly studied paying attention to the method of adding impurities to a solvent, and have found that the above-mentioned object is achieved by the present invention described below.
That is, in the liquid phase growth method of the present invention, an impurity is added to one melt of a semiconductor raw material, and after reducing this melt, another semiconductor raw material is added to the melt to prepare a solution for crystal growth. Is prepared.

[0007]

According to the liquid phase growth method of the present invention, in the preparation of a melt, a reduction treatment is carried out by adding impurities to one of the melts of the semiconductor material in advance. As a result, the impurities are sufficiently diffused into the melt by the time of epitaxy growth, and the impurities are reacted with the oxide component of the semiconductor material to form an oxide because the reduction treatment of the melt is performed after the addition of the impurities. Is suppressed.

Hereinafter, the liquid phase growth method of the present invention will be described with reference to AlGaAs.
The process will be specifically described by taking the growth of an s crystal as an example.

(1) First, impurities are added to the Ga melt.

The above impurities are appropriately selected according to the type of crystal (semiconductor) to be grown. When growing AlGaAs, impurities such as Zn, Te, Si, and S
Those containing e, Mg, P and the like are exemplified. In the present invention, in order to prevent an oxide component of Al, which is one of the semiconductor raw materials, from reacting with impurities such as Te and Zn to form an oxide, before adding Al to the melt, The reduction treatment is performed by adding impurities to the melt. Where Te and A
Since l tends to form an oxide particularly, the present invention is particularly useful when this Te-containing substance is used as an impurity.

(2) Next, a reduction treatment is applied to the melt.

The above-mentioned reduction treatment includes, for example, a method of maintaining the solution at a high temperature in a reducing gas atmosphere for a predetermined time (hereinafter, referred to as baking).

In the above baking, AlGaAs
750 ° C. or less, preferably 720 ° C.
Hereinafter, more preferably at 600 to 400 ° C., H ₂ , H
6 to 12 hours, preferably 8 to 10 hours in a reducing gas atmosphere such as a mixed gas of N ₂ and an inert gas (N ₂ , Ar ₂ etc.) (particularly preferably in an H ₂ atmosphere). Is desirable. By setting the baking temperature and time within the above ranges, it is possible to suppress, for example, desorption of As in the GaAs substrate installed in the slide boat and deterioration of the crystallinity of the substrate.

(3) Thereafter, a semiconductor material other than Ga is added to the melt to prepare a melt, and a crystal is grown.

The above crystal growth can be performed by a method known per se, such as a tilt method and a slide boat method. Also,
A known method such as a slow cooling method or a temperature difference method may be used as a temperature control method, and the cooling rate may be appropriately set according to the type of crystal (semiconductor) to be grown.

The liquid phase growth method of the present invention can be generally applied to any crystal (semiconductor) that can be grown by the liquid phase growth method. However, in particular, AlGaAs
In the case of s, it was particularly difficult to stably obtain a desired carrier concentration by the conventional method due to the above-described problem of the reactivity between Al and Te.
It is particularly useful when growing lGaAs semiconductors.

[0017]

The present invention will now be described more specifically with reference to examples. Note that the present invention is not limited to these examples.

Example 1 1 mg of GaTe was added to 50 g of Ga (0.02 m / g of Ga).
g) was added and melted at 600 ° C., which was kept in an H ₂ atmosphere for 10 hours, and then 1.5 g of GaAs was added to the melt.
And 0.3 g of Al were dissolved to prepare a melt. Thereafter, an AlGaAs film having a thickness of about 30 μm was grown on the GaAs substrate by the slow cooling method using the above-mentioned melt.

Comparative Example 1 In Example 1, GaTe was not added before baking, and 1.9 mg (G) was added to 50 g of Ga after baking.
A melt was prepared and crystal growth was carried out in the same manner except that 0.0375 mg per ag was added.

(Measurement of Carrier Concentration) In Example 1, melt preparation and crystal growth were carried out under the same conditions to obtain a total of three epi films (E1, E2, and E3). Also in Comparative Example 1, melt preparation and crystal growth were performed under the same conditions, and a total of three epi films (C
1, C2 and C3). The above E1 to C3 and C
When the carrier concentration of each of the epitaxial films 1 to 3 was measured, the results shown in FIG. 1 were obtained. It should be noted that, in the figure, the length of each graph indicates the actually measured value width in the depth direction of the epi film. Also,
In Example 1 described above, the amount of GaTe charged was varied as shown in FIG.
When the carrier concentration of each of the obtained epi films was measured, G
The relationship between the charged amount of aTe and the carrier concentration was as shown in FIG. Similarly, in Comparative Example 1, the relationship between the charged amount of GaTe and the carrier concentration was examined.
As shown in FIG.

In FIG. 1, there is no large difference in the carrier concentration between the E1 to E3 epi films, and the measured values in the depth direction of each epi film are relatively uniform.
In the epi-films C1 to C3, the difference in carrier concentration is large, and the variation in the measured value in the depth direction of each epi-film is large. In FIG. 2, the carrier concentration substantially reflects the amount of GaTe charged as compared to FIG.

[0022]

As described in detail above, according to the present invention,
In the preparation of the melt, impurities are added in advance to one of the melts of the semiconductor raw material and the reduction treatment is performed. Therefore, the impurities are sufficiently diffused into the melt by the time of epitaxial film growth, and the reduction treatment of the melt is performed. Since this is performed after the addition of the impurity, the impurity is prevented from reacting with the oxide component of the semiconductor raw material to form an oxide. Therefore, the difference in carrier concentration between batches can be reduced, a carrier concentration corresponding to the charged amount of impurities can be obtained, and the carrier concentration in the epitaxial layer can be made uniform.

[Brief description of the drawings]

FIG. 1 is a graph showing the carrier concentration of each epitaxial layer obtained in Examples and Comparative Examples.

FIG. 2 is a graph showing the relationship between the charged amount of GaTe and the carrier concentration in the method of the embodiment.

FIG. 3 is a graph showing a relationship between a charged amount of GaTe and a carrier concentration in a method of a comparative example.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-91490 (JP, A) JP-A-63-31628 (JP, A) JP-A-2-138732 (JP, A) JP-A-7-107 115065 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C30B 19/00-19/12 C30B 28/00-35/00 H01L 21/208

Claims (3)

(57) [Claims] An impurity is added to one melt of a semiconductor raw material, the melt is reduced, and then another semiconductor raw material is added to the melt to prepare a crystal growth solution. A liquid phase growth method characterized by the above-mentioned. 2. An AlGaAs crystal growth solution is prepared by using Ga as a melt, a substance containing Zn or Te as an impurity, and a substance containing As and a substance containing Al as semiconductor materials other than Ga. 2. The liquid phase growth method according to claim 1, further comprising the step of: 3. The reduction treatment is performed by reducing the melt to H ₂ at 750 ° C. or lower.
The liquid phase growth method according to claim 1, wherein the liquid phase growth method is carried out by holding in an atmosphere for 6 to 12 hours.