JPH0568440B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a slide boat type liquid phase growth apparatus.

[Conventional technology] Improvements in crystal growth technology have made it possible to obtain large substrates for compound semiconductors.
There is a demand for larger epitaxial wafers.

Among liquid phase growth methods, the slide board method is generally widely used, and FIG. 5 is an explanatory diagram of a conventional liquid phase growth apparatus.

1 is a substrate such as GaAs, 2 is a substrate holder that supports the substrate 1, and 5 is a solution holder in which a raw material solution 3 is accommodated in a raw material solution reservoir 4;
The solution holder 5 can be slid horizontally.

[Problems to be Solved by the Invention] FIGS. 6 to 8 are explanatory diagrams showing problems of the conventional liquid phase growth apparatus, and the same parts as in FIG. omitted.

In other words, in FIG. 6, when the substrate 1 becomes larger, the raw material solution 3 used also needs to be increased, but the raw material solution 3 is increased in proportion to the larger area.
If the growth temperature is increased, the raw material solution 3 will become round due to surface tension and will not be able to cover the entire surface of the substrate 1.

Therefore, in order to cover the entire surface of the substrate 1 with the raw material solution 3, as shown in FIG. 7, the amount of the raw material solution 3 must be larger than the area ratio, or as shown in FIG. It is necessary to make the raw material solution 3 a constant thickness.

However, in Fig. 7, the raw material cost increases, and in Fig. 8, the presence of the lid 6 prevents the raw material solution 3 from coming into contact with the _H2 gas flowing around the device, resulting in insufficient purification. There was a problem.

[Object of the Invention] In view of the problems of the prior art described above, the object of the present invention is to provide a liquid phase growth apparatus that can uniformly grow on a substrate surface with a small amount of raw material solution and that can also improve the purity of the raw material solution. It is about providing.

[Means for Solving the Problems] The gist of the present invention is that a member for reducing the internal volume of the raw material solution reservoir is provided in the raw material solution reservoir.

[Function] That is, FIGS. 1 and 3 are explanatory diagrams showing an embodiment of the present invention, and as shown in FIG. 1, a perforated plate 7 with a plurality of holes is provided in the raw material solution reservoir 4. Alternatively, by providing a grating 8 as shown in FIG. 3, the internal volume of the raw material solution reservoir 4 is reduced, and even if the raw material solution 3 is poured into the raw material solution reservoir 4, the raw material solution does not flow as shown in FIG. 3 does not become rounded and can cover the entire surface of the substrate 1.
Note that the raw material solution 3 needs to be in an amount such that the perforated plate 7 and the grates 8 are completely buried in the raw material solution 3, and since the raw material solution surface is exposed, there is no possibility of interaction with the H ₂ gas flowing around the device. FIG. 4, which has a large contact area and requires a short time for high purification, is an explanatory view of the A-A' cross section in FIG. 3.

The holes in the perforated plate 7 are circular 9 as shown in FIG.
It may be a triangle 10, a quadrangle 11, or any other polygon as long as it has a size that allows the raw material solution 3 to flow downward.

Further, it is desirable that the distance between the substrate 1 and the perforated plate 7 and the grating 8 be approximately 3 to 10 mm, but the distance may be appropriately set to 3 mm or more depending on the size of the substrate 1.

The substrate holder 2 and the solution holder 5 are generally made of graphite, and have a perforated plate 7 and a slatted plate 8.
It is also desirable that the material is graphite.

[Example] Example 1 A 3-inch board holder made of graphite
Set the CaAs substrate. The raw material solution reservoir of the graphite solution holder has a thickness of 3 mm and a diameter of 5 mm.
A graphite board with holes 7 mm apart on its entire surface was installed so that the distance between it and the GaAs substrate was 3 mm.

Ga120g was added to this raw material solution reservoir so that the above-mentioned perforated graphite plate was completely buried in the raw material solution.
Add 10 g of As, set in the reaction tube, and after replacing hydrogen gas, raise the temperature to the growth temperature of 800°C. After the temperature stabilized, the temperature started to decrease at a cooling rate of 1℃/min, and
When the temperature drops, the GaAs substrate and the raw material solution are brought into contact, and after the growth is completed, the substrate holder is slid.
Separate the GaAs substrate and raw material solution.

When the characteristics of the epitaxial wafer grown by the above method were measured, the carrier concentration was 2.5×10 ¹⁴ cm ⁻³ in an undoped state. As for the thickness, 3μ
When grown to a thickness of 3 μm or more, there was a slight influence of the graphite plate, but when grown to a thickness of 3 μm or less, an epitaxial wafer with a uniform thickness of ±10% or less could be obtained.

Example 2 A grating made of graphite was installed in the raw material solution reservoir and liquid phase growth was performed under the same conditions as in Example 1. The carrier concentration was undoped.
2.0×10 ¹⁴ cm ⁻³ , and the thickness uniformity was approximately ±10% or less, as in Example 1.

Comparative example: A 3-inch GaAs substrate is set on a substrate holder, and Ga300 is placed in a raw material solution reservoir with nothing inside.
After putting 25 g of GaAs and setting it in the reaction tube, replacing the tube with H ₂ gas for about twice as long as in Examples 1 and 2,
Raise the temperature to a growth temperature of 800℃.

After the temperature stabilized, the temperature started to decrease at a cooling rate of 1°C/min, and when the temperature dropped by 4°C, the GaAs substrate was brought into contact with the raw material solution, and after growing to a thickness of 3 μm, the substrate holder was slid to separate the GaAs substrate and the raw material solution. To separate.

This epitaxial wafer was undoped and had a carrier concentration of 1.5×10 ¹⁴ cm ⁻³ , but the thickness uniformity was ±20%.

The reason for the poor thickness uniformity is that the raw material solution is more than twice as large as in Examples 1 and 2, so it takes time to replace the H ₂ gas for high purity. This is because the surface of the GaAs substrate becomes uneven due to thermal deterioration (volatilization of As).

In this example, a 3-inch substrate was used, but even in the case of a 2-inch substrate, the amount of raw material solution is about half of the conventional amount, and since the amount is small, it is possible to achieve even higher purity by replacing H gas in the same time. becomes. Moreover, the present invention
In addition to GaAs, InP, GaAlAs, GaAlP, etc.
It goes without saying that this method can also be applied to the growth of group compounds and -group compounds.

[Effects of the Invention] As explained above, the liquid phase growth apparatus of the present invention provides the following remarkable effects.

(1) Since the amount of raw material solution is half or less than that of the conventional method, inexpensive epitaxial wafers can be obtained.

(2) Since the amount of raw material solution is small, higher purity can be achieved by H ₂ gas replacement.

(3) Since the time required for H ₂ gas replacement is short, thermal deterioration of the substrate can be avoided as much as possible.

[Brief explanation of drawings]

FIGS. 1 to 4 are explanatory diagrams showing an embodiment of the present invention, and FIGS. 5 to 8 are explanatory diagrams showing a conventional example. 1: Substrate, 2: Substrate holder, 3: Raw material solution,
4: Raw material solution reservoir, 5: Solution holder, 6: Lid,
7: Perforated board, 8: Slatted board.

Claims (1)

[Scope of Claims] A liquid phase growth apparatus comprising a substrate holder for supporting a substrate and a solution holder provided with a raw material solution reservoir for storing a raw material solution, in which the solution holder is completely submerged in the raw material solution within the raw material solution reservoir, and A liquid phase growth apparatus characterized in that a member is provided for reducing the internal volume of the raw material solution reservoir, which is arranged at a distance of 3 mm or more from the substrate. 2. The liquid phase growth apparatus according to claim 1, wherein the member is a plate with a plurality of holes. 3. The liquid phase growth apparatus according to claim 1, wherein the member is a drainboard. 4. The liquid phase growth apparatus according to claims 1 to 3, wherein the member is made of the same material as the substrate holder.