JPH0474791A - Epitaxial growth in liquid phase and apparatus therefor - Google Patents

Abstract

PURPOSE:To enable formation of a thick epitaxial layer of excellent crystallinity with hardly any dispersion in layer thickness or composition by changing the thickness of a solution placed in a solution reservoir and varying the growth rate during epitaxial growth in the liquid phase. CONSTITUTION:A pulling rod 6 for a substrate holder 4 is initially operated to slide the substrate holder 4 to bring a GaAs substrate 5 into contact with the solution 2 for growing the first layer and directly allowed to stand for about 2.5 hr. Thereby, the epitaxial layer of the first layer is formed. In the process, the thickness of the solution for growing the first layer is about 6mm. A pulling rod 8 for a partition member is then moved in the direction of an arrow while keeping the GaAs substrate 5 in a contact state with the solution 2 for growing the second layer to move the partition member 7. The solution 2 for growing the first layer is divided into the upper and lower parts to change the thickness of the solution 9 in contact with the substrate 5 on the side of the lower part to about 3mm. After completing the growth of the first layer, the substrate holder 4 is further slid to bring the GaAs substrate 5 into contact with a solution 3 for growing the second layer to form the second layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid phase epitaxial growth method using a slide board method and an apparatus therefor.

[Prior Art] Semiconductor devices, particularly compound semiconductor devices, are generally manufactured using the liquid phase epitaxial growth method, and optical semiconductor devices such as light emitting diodes and semiconductor lasers are mainly manufactured using the slide board method.

FIG. 6 shows a schematic diagram of a slide board used for manufacturing light emitting diodes. A required solution, in the illustrated example, a first N growth solution 2. Add the second layer growth solution 3, slide the slidable substrate holder 4 on which the GaAs substrate 5 is placed in the direction of the arrow by the pull rod 6, and add the first and second layer growth solutions 2 and 3. Ga
The epitaxial layer is grown layer by layer while being successively brought into contact with the As substrate 5. High purity H2 gas is used as the growth atmosphere, and a uniform temperature distribution in the length direction of the slide board is required. FIG. 7 shows an example of a growth temperature program required for manufacturing a light emitting diode when a slow cooling method is adopted for temperature distribution.

[Problems to be Solved by the Invention] Incidentally, when manufacturing a light emitting diode, it is said that an epitaxial layer thickness of 20 μm or more is required to prevent the influence of propagation of crystal defects from the substrate. Maybe,
The epitaxial layer having this thickness of N is required to be of high quality.

One of the important factors determining the quality of the epitaxial layer is the growth rate of the epitaxial layer. In the conventional slow cooling method shown in Figure 7, the growth rate of the epitaxial layer is determined by the thickness of the solution and the slow cooling temperature gradient, and the thickness of the solution during growth is kept constant in the range of 3 to 10 mm. There is.

Since the temperature gradient is usually fixed by the program, determining the thickness of the growth solution is an easy way to obtain a high-quality, thick bitaxial layer.

However, if the growth solution is thin, an epitaxial layer with uniform growth thickness and composition can be obtained, but a thick epitaxial layer cannot be obtained.

Conversely, if the solution is thick, a thick epitaxial layer can be obtained, but the epitaxial layer thickness and composition will vary within the wafer surface. For example, when a thick solution of 5 mm or more is used, in-plane compositional variations occur, resulting in in-plane emission wavelength variations. In addition, because the growth rate is fast, the crystallinity is poor and the luminous output is low, making it difficult to obtain.

An object of the present invention is to provide a liquid phase epitaxial growth method and an apparatus therefor, which eliminates the drawbacks of the prior art described above and can form a thick epitaxial layer with good crystallinity and no variation in layer thickness or composition. It's about doing.

[Means for Solving the Problems] The liquid phase epitaxial growth method of the present invention involves placing a required solution in a solution holder lined with solution reservoirs under a uniform temperature distribution formed in the length direction of a slide board, It is applied to the liquid phase epitaxial growth method, in which the bitaxial layer is grown layer by layer while successively contacting the substrate.

During growth by such liquid phase epitaxial growth method,
In order to advantageously control the thickness of growth 2 and growth homology,
The growth rate is changed by changing the thickness of the solution placed in the solution reservoir.

In addition, the liquid phase epitaxial growth apparatus of the present invention moves the substrate holder holding the substrate relative to the solution holder in which solution reservoirs containing the required solution are arranged, thereby sequentially bringing the required solution into contact with the substrate. It is applied to liquid phase epitaxial growth equipment that grows epitaxial layers one by one.

In such a liquid phase epitaxial growth apparatus, in order to change the growth rate by changing the thickness of the solution in the solution reservoir, the solution in the solution reservoir is doubled vertically to increase the thickness of the solution in contact with the substrate. It is provided with a slidable partition means for changing the area.

[Function] As mentioned above, in the slow cooling method, one of the factors that determines the growth rate of the epitaxial layer is the thickness of the solution. When manufacturing light emitting diodes, if the solution is thick, the growth rate is fast, so only those with poor crystallinity and low light emitting output can be obtained. A thick epitaxial layer can be obtained.

By the way, even if the thickness of the solution is thick, the composition of the grown layer is initially controlled with high precision and an epitaxial layer with a uniform composition can be obtained, but as growth progresses, the composition of the grown layer begins to collapse. This is because the composition of the solution changes between the upper and lower parts of the solution, and the transport of substances in the solution, which determines the growth rate, becomes difficult.

Therefore, if the thickness of the solution remains thick, the composition of the grown layer will begin to collapse during the growth.

Therefore, if the thickness of the solution is reduced during the growth, convection will be almost ignored out of the combination of diffusion or diffusion and convection that determines the mass transport in the solution, so mass transport will be successful, and the thin solution The benefits of this can be obtained even during the growth stage.

[Example 7] Examples of the liquid phase epitaxial growth method and apparatus thereof according to the present invention will be described below with reference to FIGS. 1 to 5.

Figure 1 shows the liquid phase epitaxial growth method of the present invention in red G.
a An example of a slide board required for application to AI As light emitting diodes is shown.

A plurality of solution reservoirs 12.13 are arranged in the solution holder 1, and a first layer growth solution 2.1 for forming a first growth layer is placed in these solution reservoirs 12.13. A second N growth solution 3 for forming a second growth layer is respectively placed.

The substrate holder 4 passes through the solution holder 1 and is slidably provided in the length direction of the slide board, and has a substrate holder pull rod 6 attached to the end of the substrate holder 4.
This allows the GaAs substrate 5 placed on the substrate holder 4 to be brought into contact with each of the growth solutions 2 and 3 of the solution holder 1.

Then, the solution holder 1 doubles the first layer growth solution 2 in the solution reservoir 12 vertically on the solution reservoir 12 side into which the first N growth solution 2 is placed, so that the thickness of the solution in contact with the GaAs substrate 5 is It is equipped with partition means 10 for changing the height.

This partitioning means 10 is composed of a partitioning member 7 and a partitioning member tension rod 8 for slidingly operating the second partitioning member 7. The partition member 7 is a plate-shaped member that penetrates the solution reservoir 12 and is slidably provided in the same five directions as the substrate holder 4, and has an opening approximately the same diameter as the solution reservoir 12 in the middle. Before sliding, the opening is aligned with the solution reservoir 12, and the opening position is moved by sliding to divide the solution reservoir 12 into upper and lower parts.

Next, a case will be described in which a red GaAIS light emitting diode is grown using the liquid phase epitaxial growth apparatus having the above configuration. FIGS. 2 and 3 show the arrangement of the partition member 7 during actual operation, and FIG. 4 shows the growth temperature program and timing of the operation.

First, operate the board holder pull rod 6 to hold the board holder 4.
Slide the GaA, s substrate 5 into the first layer growth solution 2.
The first epitaxial layer was grown by contacting with the substrate and leaving it as it was for 2 hours and 30 minutes (FIG. 2). The thickness of the first N growth solution at this time was 6 mm.

Next, while keeping the GaAs substrate 5 in contact with the second layer growth solution 2, the partition member tension rod 8 is moved in the direction of the arrow (FIG. 1) to move the partition member 7, and the first layer is grown. The growth solution 2 is divided into upper and lower parts, and the thickness of the lower part of the solution 9 in contact with the substrate 5 is changed to 3 mm, and the first layer growth is continued (FIG. 3).

After the first layer growth was completed, the substrate holder 4 was further slid to bring the GaAs substrate 5 into contact with the second layer growth solution 3 to grow the second layer.

When the 1Nth film thickness of the epitaxial wafer on which two epitaxial layers were grown in this manner was examined, the 1Nth layer had grown by about 40 μm, and the desired film thickness was obtained. Furthermore, this epitaxial wafer has red GaAl.
When an As light emitting diode was formed and its luminous intensity was compared with that of a light emitting diode manufactured by a conventional method, the results were as shown in FIG. Luminous intensity is 30%
The variation in the emission wavelength within the wafer surface was also reduced to 1/2 that of the conventional method.

As described above, according to this embodiment, the growth rate is changed by changing the thickness of the solution during the epitaxial growth process. Therefore, even when a thick solution of 5 mm or more is used, the in-plane There is no variation in the composition, and there is no in-plane variation in the emission wavelength. In addition, it has good crystallinity and can provide high light emitting output, making it possible to significantly improve the light emitting characteristics of the light emitting diode.

In addition, in the above example, a case was explained in which the growth rate was changed by changing the thickness of the solution only for the − layer, but the present invention is not limited to this, and can also be applied to multilayers. It is.

Furthermore, the present invention is not limited to compound semiconductors or optical semiconductors,
The method can be widely applied to semiconductor devices requiring an epitaxial layer, and the growth temperature is not limited to the slow cooling method.

Moreover, although the case where the growth solution is doubled as a partitioning means has been described, a structure may be adopted in which the growth solution is doubled and the upper part is excluded.

Furthermore, in the partitioning operation, it is possible to first partition the solution using a partitioning means, and then release the partition during the growth, thereby changing to a thick solution midway through the growth.

This also makes it possible to control the mixed crystal ratio.

[Effects of the Invention] As described above, the present invention provides the following effects.

(1) According to the liquid phase epitaxial growth method according to claim 1, even if a solution of a certain thickness is initially used, the thickness of the solution is changed during the epitaxial growth process to change the growth rate. , a thick epitaxial layer with excellent crystallinity without variations in layer thickness or composition can be obtained.

(2) According to the liquid phase epitaxial growth apparatus according to the second aspect, a thick epitaxial layer with excellent crystallinity can be obtained with a simple configuration of providing a partitioning means.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a liquid phase epitaxial growth apparatus using a slide board method according to an embodiment of the present invention, and FIGS.
The figure is a partially enlarged sectional view of the liquid phase epitaxial growth apparatus during the growth process according to this embodiment, FIG. 4 is a temperature characteristic diagram explaining the growth temperature program according to this embodiment, and FIG. FIG. 6 is a schematic diagram of a conventional slide board method, and FIG. 7 is a temperature characteristic diagram illustrating a growth temperature program using a slow cooling method during growth of a conventional light emitting diode. 1 is a solution holder, 2 is a first N growth solution, 3 is a second layer growth solution, 4 is a substrate holder, 5 is a GaAs substrate, 6 is a tension rod for the substrate holder, 7 is a partition member, and 8 is a tension rod for the partition member. , 9 is the lower solution when the solution thickness is changed, and 10 is a partition means.

Claims (1)

[Claims] 1. Under a uniform temperature distribution formed in the length direction of the slide board, the required solution is poured into a solution holder lined with solution reservoirs, and the pitaxial layer is sequentially brought into contact with the substrate. A liquid phase epitaxial growth method in which growth is performed layer by layer, and the growth rate is varied by changing the thickness of a solution added to a solution reservoir during growth. 2. Solution reservoir containing the required solution. By moving the substrate holder holding the substrate relative to the lined up solution holders, the epitaxial layer is grown layer by layer while the required solution is successively brought into contact with the substrate. In a phase epitaxial growth apparatus, the solution in the solution reservoir is divided into upper and lower halves,
A liquid phase epitaxial growth apparatus characterized in that a partition means is slidably provided to change the thickness of a solution in contact with a substrate.