JPH0476491B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a liquid phase epitaxial growth method,
In particular, the present invention relates to a method for forming multilayer epitaxial crystal layers by liquid phase epitaxial growth using a plurality of semiconductor solution baths.

Recently, liquid phase epitaxial growth method has been put into practical use as an epitaxial growth method for semiconductor devices. A high-purity semiconductor material on a semiconductor crystal and a high concentration of n-type and p-type
It is necessary to epitaxially grow multiple crystal layers of the mold, and there is a need for a liquid phase epitaxial growth method that can achieve this.

[Conventional technology]

FIG. 2 is a perspective view of essential parts of a conventional liquid phase epitaxial growth apparatus.

In the figure, 1 is a carbon boat stand, and a groove 2 provided in the carbon boat stand 1 has a groove for epitaxial growth slightly lower than the depth of the groove 2.
A GaAs single crystal substrate 3 and a source crystal plate 4 made of GaAs polycrystal are successively arranged adjacent thereto.

Further, on the carbon boat stand 1, a semiconductor solution tank group 5 in which a plurality of semiconductor solution tanks 6 are formed is placed so as to slide and move. 8 is GaAs
Formed from polycrystalline carbon boat stand 1
The bottom surface portion that slides is open and in contact with the source crystal plate 4 on the carbon boat stand 1.

Each of these semiconductor solution tanks 6 is filled with a semiconductor solution 7 made of GaAs, and the entire device is housed inside a quartz tube (not shown) and heated to a temperature of about 800 to 900°C from the outside. By heating, the GaAs polycrystals from the side wall surface 8 and the bottom are heated to a high temperature and dissolved into the semiconductor solution 7, so that the GaAs polycrystal is always in a supersaturated solution state of GaAs.
Furthermore, a dopant according to the components corresponding to the semiconductor layer to be grown is appropriately mixed to form a predetermined n-type or p-type semiconductor solution.

FIG. 3 is a cross-sectional view of a main part of a gallium-aluminum-arsenide compound (GaAlAs) semiconductor crystal layer formed in multiple layers by liquid phase epitaxial growth, as an example, and shows a GaAs single crystal layer with a thickness of 300 to 400 μm. An n-GaAlAs layer 12 with a thickness of 40 to 55 μm is sequentially formed on the surface of the substrate 3 by liquid layer epitaxial growth.
and a first p-GaAlAs layer 1 with a thickness of 0.8 to 2.0 μm.
3, a second p-GaAlAs layer 14 with a thickness of 0.8 to 2.0 μm, and a third p-GaAlAs layer 14 with a thickness of 0.8 to 2.0 μm.
The layers 15 are formed in a laminated manner.

FIGS. 4a to 4c are cross-sectional views of essential parts sequentially showing the steps of forming the multilayer structure of the GaAlAs semiconductor crystal layer of FIG. 3 by a conventional liquid phase epitaxial growth method.

As shown in FIG. 4a, a GaAs single crystal substrate 3 for epitaxial growth is placed in a groove 2 provided at a predetermined position on the surface of the carbon boat stand 1, and a GaAs single crystal substrate 3 for epitaxial growth is placed adjacent to the groove 2.
Multiple source crystal plates 4 made of GaAs polycrystal
a, 4b, 4c, 4d, and 4e are consecutively arranged.

At the top, there are multiple semiconductor solution tanks 6.
A carbon slider 10 equipped with a semiconductor solution bath group 5 consisting of a, 6b, 6c, 6d, and 6e covers the surface of the GaAs single crystal substrate 3 with a part of the carbon slider 10 as shown in the figure. The semiconductor solution tanks 6a, 6b, 6c, 6d, and 6e are placed in contact with the source crystal plates 4a, 4b, 4c, 4d, and 4e so as to form a bottom portion.

Further, the leading semiconductor solution tank 6a of the semiconductor solution tank group 5 is filled with an n-GaAlAs solution 7a, and each adjacent semiconductor solution tank 6b, 6 is filled in the following order.
The first p-
GaAlAs solution 7b, second p-GaAlAs solution 7c,
Third p-GaAlAs solution 7d, fourth p-
It is filled with GaAlAs solution 7e.

Then, the carbon boat stand 1 on which the carbon slider 10 having the semiconductor solution tank group 5 is mounted is housed in a quartz tube (not shown) and heated to approximately 900°C.
The carbon slider 10 is heated to a temperature of
is slid in the direction of the arrow by the length of one tank of the semiconductor solution tank to bring the n-GaAlAs solution 7a in the semiconductor solution tank 6a into contact with the surface of the GaAs single crystal substrate 3.

At that point, the substrate temperature is lowered to a predetermined value and set to the growth temperature, thereby forming an n-GaAlAs layer 12 (FIG. 3) with a thickness of 40 to 55 μm on the surface of the GaAs single crystal substrate 3. n-GaAlAs layer 1 with this thickness
Approximately 250 minutes of growth time is required to form 2.

Next, as shown in Fig. 4c, the carbon slider 1
0 further in the direction of the arrow by the length of one tank of the semiconductor solution tank, and the first layer in the semiconductor solution tank 6b is placed on the surface of the n-GaAlAs tank 12 on the GaAs single crystal substrate 3. By contacting the p-GaAlAs solution 7b, a first p-GaAlAs layer 13 (FIG. 3) having a thickness of 0.8 to 2.0 μm is formed.

Hereinafter, in the same manner, the first p-GaAlAs layer 13
(Fig. 3) On top, there are second and third layers with a thickness of 0.8 to 2.0 μm.
By sequentially stacking p-GaAlAs layers 14 and 15 (FIG. 3), an epitaxial GaAlAs semiconductor crystal layer having a multilayer structure having a p-n junction is obtained.

Note that each of these first to third p-GaAlAs layers 1
In short, the growth time for forming Nos. 3, 14, and 15 is about 2 to 15 minutes.

[Problem that the invention seeks to solve]

By the way, in the conventional liquid phase epitaxial growth method as described above, the groove 2 on the carbon boat stand 1
The plurality of source crystal plates 4a, 4b, 4c, 4d, and 4e made of GaAs polycrystals arranged in The n-GaAlAs solution 7a is in contact with the source crystal plate 4a, and when the semiconductor solution tank group 5 is moved and the semiconductor solution tank 6b is positioned above the source crystal plate 4a, the source crystal plate 4a is The n-GaAlAs solution 7a slightly left in the
p-GaAlAs solution 7b.

Moreover, due to the contact with this n-GaAlAs solution 7a, the n-GaAlAs layer 1 is formed on the surface of the GaAs single crystal substrate 3.
2 is grown for a long time, and the heating temperature at that time is nearly 900°C, the degree of mixing becomes large, and as a result, the first p-
There is a problem in that the purity (p conductivity) of the GaAlAs solution 7b deteriorates.

And such a first p-GaAlAs solution 7b
A first p- layer is formed on the n-GaAlAs layer 12 by
In the semiconductor crystal in which the GaAlAs layer 13 is stacked, p
There was a drawback that the -n junction became non-uniform and the barrier voltage between the p-type layer and the type layer became low.

[Means for solving problems]

The present invention provides a liquid phase epitaxial growth method that solves the above-mentioned problems. For epitaxial growth, a semiconductor solution layer group in which at least two or more p(n) type semiconductor solution layers containing an (sometimes n) type semiconductor solution are arranged in series is sequentially arranged on a carbon boat stand. While moving in one direction over the crystal substrate and the source crystal plate corresponding to the material in each solution tank,
In the liquid phase epitaxial growth method for growing an n(p) type semiconductor layer and a p(n) type semiconductor layer on the crystal substrate, the first n(p) type semiconductor solution tank of the semiconductor station tank group and The semiconductor solution tank located at the boundary with the p(n) type semiconductor solution tank of the next tank is set to an empty state, and the empty tank is placed at the position where the semiconductor solution was located before the growth during the epitaxial growth of the first tank. This is achieved by a method in which epitaxial growth is performed using a p(n) type semiconductor solution in the next bath.

[Effect]

In the present invention, the semiconductor solution tank located at the boundary between the first n(p) type semiconductor solution tank and the next p(n) type semiconductor solution tank in the semiconductor solution tank group is left in an empty state. Therefore, for example, when an n-type semiconductor crystal layer is epitaxially grown on a crystal substrate for epitaxial growth using an n-type semiconductor solution in the first n-type semiconductor solution tank, the n-type semiconductor solution is The empty tank comes to be located at the position of the source crystal plate that was in contact with the source crystal plate before contacting the source crystal plate.

Therefore, the p-type semiconductor solution in the p-type semiconductor solution tank of the next tank does not come into contact for a long time on the source crystal plate that was in contact with the n-type semiconductor solution before it came into contact with the crystal substrate. This prevents the problem that a small amount of n-type semiconductor solution left on the source crystal plate mixes into the p-type semiconductor solution.

Therefore, it is possible to epitaxially grow a p-type semiconductor crystal layer on the n-type semiconductor crystal layer without being affected by the deteriorated conductivity caused by the mixing of the n-type semiconductor solution.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIGS. 1a to 1c are sectional views of essential parts for sequentially explaining an embodiment of the liquid phase epitaxial growth method according to the present invention.

First, as shown in Figure 1a, the carbon boat stand 1
In the groove 2 provided at a predetermined position on the top, a GaAs single crystal substrate 3 for epitaxial growth is placed, as in the conventional example.
Multiple source crystal plates 4 made of GaAs polycrystal
a, 4b, 4c, 4d, and 4e are consecutively arranged.

Further, on the top thereof, there are a plurality of semiconductor solution tanks 6a,
A carbon slider 10 equipped with a semiconductor solution bath group 5 consisting of semiconductor solution baths 6b, 6c, 6d, and 6e covers the surface of the GaAs single crystal substrate 3 with a part of the carbon slider 10 as shown in the figure. The respective semiconductor solution tanks 6a, 6b, 6c, 6d, and 6e are placed in contact with the source crystal plates 4a, 4b, 4c, 4d, and 4e so as to form a bottom portion.

Further, the leading semiconductor solution tank 6a of the semiconductor solution tank group 5 is filled with the n-GaAlAs solution 21, and the semiconductor solution tank 6b next to it is an empty tank (hereinafter referred to as empty tank 6b). The first p-
GaAlAs solution 22, second p-CaAlAs solution 23,
A third p-GaAlAs solution 24 is filled.

Then, as described above, the carbon boat stand 1 with the carbon slider 10 mounted thereon was housed in a quartz tube and heated to a temperature of about 900°C. As shown in b, slide the carbon slider 10 in the direction of the arrow by the length of one tank of the semiconductor solution tank,
A semiconductor solution bath 6 is provided on the surface of the CaAs single crystal substrate 3.
Contact the n-GaAlAs solution 21 in a.

At that point, the substrate temperature is lowered to a predetermined value and set to the growth temperature, and the surface of the GaAs single crystal substrate 3 is
A 50 μm thick n-GaAlAs layer 12 (FIG. 3) is formed.

On the other hand, during this epitaxial growth, the n-
Since the next empty tank 6b is located on the source crystal plate 4a that the GaAlAs solution 21 was in contact with before it came into contact with the GaAs single crystal substrate 3, the second empty tank 6b is located in the semiconductor solution layer 6c of the next tank as in the conventional case. 1 p-GaAlAs solution 2
2 no longer comes into contact with the source crystal plate 4a on which a small amount of n-GaAlAs solution 21 remains, or comes into contact for a long time, and the n-GaAlAs solution 21 is mixed into the first p-GaAlAs solution 22. This will be prevented.

Next, as shown in FIG. 1c, the carbon slider 10 is moved in the direction of the arrow by the length of two of the semiconductor solution baths to form an n-GaAlAs layer on the GaAs single crystal substrate 3. By bringing the first p-GaAlAs solution 22 in the semiconductor solution tank 6c into contact with the surface of the semiconductor solution tank 6c, the first p-GaAlAs solution 22 with a thickness of 0.8 to 2.0 μm and having good purity and no contamination with the n-GaAlAs solution 21 is brought into contact with the surface of the semiconductor solution tank 6c.
A GaAlAs layer 13 (FIG. 3) can be formed.

Hereinafter, in the same manner, the first p-GaAlAs layer 13
(Fig. 3) On top, there are second and third layers with a thickness of 0.8 to 2.0 μm.
By sequentially stacking the p-GaAlAs layers 14 and 15 (FIG. 3), a uniform p-n junction is formed, and the n-
It becomes possible to obtain a GaAlAs epitaxial semiconductor crystal layer with a multilayer structure in which the voltage applied to the GaAlAs layer 12 is increased.

〔Effect of the invention〕

As is clear from the above description, according to the liquid phase epitaxial growth method according to the present invention, one tank of n(p) type semiconductor solution layer and at least two or more p(n) type semiconductor solution layers arranged in series can be used. By using a carbon slider with an empty tank between it and the semiconductor solution tank and moving it in one direction to perform epitaxial growth, n is added to the p(n) type semiconductor solution in the p(n) type semiconductor solution tank. This prevents the possibility of contamination with (p) type semiconductor solution, resulting in uniform p-n
It becomes possible to obtain a high-quality GaAlAs epitaxial crystal layer with a multilayer structure having junctions.

Therefore, a semiconductor device using such a multilayered GaAlAs epitaxial crystal layer has a great practical effect in that it can provide high performance functions.

[Brief explanation of the drawing]

Figures 1a to 1c are cross-sectional views of essential parts for sequentially explaining an embodiment of the liquid phase epitaxial growth method according to the present invention, and Figure 2 shows a conventional liquid phase epitaxial growth apparatus. A perspective view of the main part, Figure 3 is a multilayer structure formed by liquid phase epitaxial growth.
4a to 4c, cross-sectional views of main parts showing a GaAlAs semiconductor crystal layer, are sequential steps of forming the multilayer structure of the GaAlAs semiconductor crystal layer shown in FIG. 3 by a conventional liquid phase epitaxial growth method. In the partial sectional views, Figures 1a to 1c and 3, 1 is a carbon boat stand, 2 is a groove, 3 is a GaAs single crystal substrate, 4a to 4e are source crystal plates, and 5 is a group of semiconductor solution baths. , 6a to 6e are semiconductor solution tanks, 10 ₈
Carbon slider, 12 is n-GaAlAs layer, 13
14 is the first p-GaAlAs layer, and 14 is the second p-GaAlAs layer.
GaAlAs layer, 15 is the third p-GaAlAs layer, 21
is n-GaAlAs solution, 22 is first p-GaAlAs
23 represents the second p-GaAlAs solution, and 24 represents the third p-GaAlAs solution.

Claims (1)

[Claims] 1. One n(p) type semiconductor solution tank 6a containing an n(or p) type semiconductor solution 21 and p(or n)
at least two containing type semiconductor solutions 22-24.
A semiconductor solution tank group 5 in which more than one p(n) type semiconductor solution tanks 6c to 6e are arranged in series includes a crystal substrate 3 for epitaxial growth sequentially arranged on a carbon board stand 1 and each solution tank. A liquid phase that grows an n(p) type semiconductor layer 12 and p(n) type semiconductor layers 13 to 15 on the crystal substrate 3 while moving in one direction over the source crystal plates 4a to 4e corresponding to the inner material. In the epitaxial growth method, a semiconductor solution tank 6b located at the boundary between the first n(p) type semiconductor solution tank 6a and the next p(n) type semiconductor solution tank 6c of the semiconductor solution tank group 5 is The empty tank 6b is placed in the position where the semiconductor solution 21 was located before the growth during epitaxial growth in the first tank, and then the p (or n) type semiconductor solution in the next tank is placed in the empty tank state. A liquid phase epitaxial growth method characterized by performing epitaxial growth according to No. 22.