JPS5834929B2 - Hand-painted Thai Hakumakuexousou Seichiyouhouhouhououoyobi Souchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for liquid phase growth of a group IV compound semiconductor and an apparatus for producing the same.

Gallium arsenide (hereinafter referred to as GaAs).

), gallium aluminum arsenide (hereinafter Ga 1-xA
It is written as 1xAs.

) can be grown epitaxially on thin films such as semiconductor lasers, superlattice negative resistance elements, GaAsF
Although it is necessary for manufacturing ETs, varactor diodes, etc., no sufficient growth technology has been established to date.

It is particularly difficult to grow a thin film with a thickness of 1.0 μm or less by liquid phase growth.

An overview of conventionally used liquid phase growth methods is described below.

FIG. 1 shows an example of the structure of a boat in a conventional liquid phase growth apparatus.

Here, 1 and 2 are graphite boats, 1 is a wafer holding boat, and 2 is a gallium solution reservoir.

3 is a GaAs single crystal substrate, 4 is a gallium solution, 5 is
is a GaAs source.

Growth is carried out in a hydrogen carrier gas in a reaction tube maintained at a constant temperature of 800° C. in this boat.

In detail, the temperature was 830°C and the GaAs source 5 (thus the saturated gallium arsenide solution 4 was heated to 800°C).
After lowering the temperature to 30 minutes or more, add gallium arsenide solution
is brought into contact with the crystal substrate 3, and the system is immediately cooled at a cooling rate of 2° C./min while the gallium arsenide solution 4 is stopped.

When the temperature reaches 780° C., the wafer holding boat 1 is slid to separate the gallium arsenide solution 4 and the crystal substrate 3, and the growth is stopped.

GaAs epitaxial films grown by this method not only have wavy irregularities on the surface, but also have poor controllability and reproducibility of the film thickness, impurities, and especially poor controllability for film thicknesses of 1 μm or less. There were problems such as having to allow for an error of ±100% or more of the set value.

The present invention solves these problems and uses a liquid phase growth method to
．． It is an object of the present invention to provide a method for growing a thin epitaxial film of 1μ or 0.1μ or less with good reproducibility, and an apparatus for manufacturing the same.

FIG. 2a shows the structure of a graphite boat for liquid phase growth according to the present invention.

Here, 1 is a wafer holding boat, 2 is a gallium solution reservoir, 3 is a crystal substrate, 4 is a gallium arsenide solution, and 6 is a gallium arsenide crystal for a source.

The most important feature of the present invention is that a thin epitaxial layer is formed on the crystal substrate 3 by continuously moving the gallium arsenide solution 4 without stopping it on the crystal substrate 3 as in the conventional method.

In the state shown in Figure 2a, hydrogen gas is poured onto the gallium solution in an electric furnace maintained at 800°C, and hydrogen gas is poured into the reaction tube.
A gallium arsenide solution 4 is prepared by placing an As source and melting it.

In this case, the amount of GaAs is 80
If the solubility at 0°C is 5~b, the amount does not need to be very accurate.

Next, the gallium solution reservoir 2 is slid to bring the gallium arsenide solution 4 into contact with the source gallium arsenide crystal 6 at 800°C (FIG. 2b).

Due to this contact, a small amount of gallium arsenide dissolves into the gallium arsenide solution 4, and the gallium arsenide solution 4 becomes a saturated solution at 800°C.

Next, the gallium solution reservoir 2 is moved again, and the gallium arsenide solution 4 is moved between the crystal substrate 3 and the source gallium arsenide crystal 6 as shown in FIG. 2C.

The temperature of this system was then cooled from To=800°C with a rapid cooling temperature of 6°C/min for a time t.

At the same time, the temperature T1 is set to 795°C, and this temperature is maintained for a certain period of time.

Through this operation, the gallium arsenide solution 4 becomes supercooled and becomes a supersaturated solution without precipitation of GaAs.

This process is carried out using a temperature program as shown in FIG.

At time T1, the gallium solution reservoir 2 is moved at a predetermined speed in the direction of the arrow shown in FIG. 2C by an external drive device.

The movement is carried out smoothly without vibration so as not to destroy the supercooled state of the gallium arsenide solution 4.

The moving speed is determined by the desired epitaxial film thickness, but is not necessarily constant.

As a result of this movement, the gallium arsenide solution 4
gradually comes into contact with the crystal substrate 3, and the growth stops when the gallium arsenide solution 4 passes over the crystal substrate 3 as shown in FIG. 2e.

At this time, if the length l of the gallium arsenide solution 4 and the driving speed V satisfy the relationship l/v<30 seconds, the epitaxial layer with good uniformity can be obtained. A membrane is obtained.

Therefore, the length of the gallium arsenide solution 4 does not necessarily need to be larger than the dimension of the crystal substrate 3 as in the conventional method, but rather the driving speed can be increased by making the length of the gallium arsenide solution 4 smaller. It is better because it is slower and the factors that disturb the supersaturation state such as vibrations are reduced.

The present invention enables the growth of epitaxial thin films with good surface conditions, and since the film thickness is controlled by the moving speed, thin films can be easily grown.
It has the advantage of being able to grow with good reproducibility.

The above is for the case of one crystal substrate 3 (although I have mentioned this in detail, it is also possible to process a plurality of crystal substrates continuously, in which case a graphite boat as shown in FIG. 4 is used).

Here 3-1, 3-2,...
3n is a crystal substrate.

According to this method, the number of substrates can be up to 20.

In this case, a sufficiently uniform epitaxial layer can be obtained even if the driving speed of the gallium solution reservoir 2 is constant, but in order to further improve the accuracy, the driving speed V should be set as a function of the distance X from the first wafer that comes into contact with v=Kx '(K is a constant).

In addition, as shown in Figure 5, a graphite boat with a structure in which the distance between the crystal substrates is larger than the width of the gallium arsenide solution 4 is used, and after growing shrimp on the first substrate, the gallium arsenide solution is placed in the region T between the crystal substrates. Continuous processing is possible by stopping step 4, holding it for 2 minutes, and growing again.

If a plurality of crystal substrates are to be processed continuously, this can be done by rotating the wafer holding boat 1 as shown in FIG.

FIG. 6a shows a plan view of the main part of the device, and FIG. 6a shows a sectional view thereof.

In FIGS. 6a and 6b, 1 is a wafer holding boat which has a function of rotating around an axis I-1'.

This wafer holding boat 1 has ten wafer holding recesses 8-1. ~8-10 are formed.

2 is a gallium solution reservoir, which rotates around axis n-n'.

This solution reservoir 2 is provided with four solution recesses 9-1 to 9-4.

The cross section of each of the solution recesses 9-1 to 9-4 is a hyperboloid of revolution as shown in FIG. 6a, and the uniformity of the film thickness and surface condition are better than that of a prism.

When the solution recess 9-1 is in contact with the wafer holding recess 8-2, the solution recess 9-3 comes into liquid contact with the source gallium arsenide crystal 6 to create a saturated solution.

Reference numeral 6' denotes a gallium arsenide crystal for a source for replacement, which is replaced by rotating the holding boat 1' around the l-111' axis.

The operating procedure of this device will be described in detail.

Wafer holding recesses 8-1 to 8 of wafer holding boat 1
-10, crystal substrates 3-1 to 3-10 are successively arranged.

The region A surrounded by the broken line in FIG.
Among 4-4, gallium arsenide solutions 4-1 and 4-3 are 8
00°C, 4-2.4-4 is kept at 795°C.

Further, the crystal substrates 3-1 to 3-10 accurately maintain uniform heating at 795°C.

The heating method may be either a hot-play method or an entire heating method.

By continuously rotating the wafer holding boat 1 around the rotation axis I-I' at a speed of 0.4 revolutions per minute, an epitaxial film of approximately 0.15 μm is continuously formed in the area in contact with the solution 4-1. grow to.

Here, since the area near the crystal substrate 3-7 is kept at room temperature through the air curtain, the grown crystal is immediately taken out and replaced with a new crystal.

Here, the gallium arsenide solution 4-2 is a solution that has already been used, and the amount of arsenic is less than the saturation amount, and the gallium arsenide solution 4-3 is in contact with the gallium arsenide crystal 6 for the source,
Forming a saturated solution at °C.

Further, the gallium arsenide solution 4-4 is a supersaturated solution and is used for the next growth.

When arsenic in the gallium arsenide solution becomes insufficient, the gallium solution reservoir 2
By rotating by 0 degrees, it is possible to perform epitaxial growth on the one hand and replenish the gallium arsenide solution on the other hand, thereby always obtaining an ideal supersaturated solution and facilitating mass production.

Next, one embodiment of the present invention will be described.

This example is based on the structure shown in FIG.

In other words, the crystal substrate 3 is 20 mm x 207 ft7 IL1
The surface was polished to a thickness of 250μ.

Using a chromium-added GaAs semi-insulating single crystal, the gallium arsenide crystal 6 for the source has a size of 20 mm x 20 mm1.
An additive-free single crystal with a thickness of 400 μm is used.

A gallium arsenide solution 4 is prepared by melting 2.2 g of gallium and 100 μm of GaAs polycrystal at 800°C, but in this case, the gallium arsenide solution 4 is thin and does not wet the crystal substrate 3 due to surface tension. Since there is a concern that the force S may deteriorate, a block of graphite or quartz is placed on the surface of the gallium arsenide solution 4 at this stage.

In the temperature program shown in FIG. 3, 800° C. was used as the temperature To, and 795° C. was used as the growth temperature T1.

The cooling rate was 5°C/min. 1.0 minutes, t1=
After 2.0 minutes, tl-io=l, and Q minutes, the gallium solution reservoir 2 was moved over the crystal substrate 3 at a driving speed of 20 mm/sec, and a GaAs epitaxial film with a thickness of 0.2 μm was grown.

This film has an ideal mirror surface with a height difference of 50
Less than 0 people.

The length of the gallium arsenide solution used at this time was 10 minutes.

When the driving speed was further increased to 40 mg/sec, the epitaxial film thickness was 0.1 μm and the surface condition was good.

However, when the driving speed was extremely reduced to G and the growth was performed at 10 mrn for 7 seconds or less, the surface of the grown crystal was likely to have irregularities.

The present invention is applicable not only to GaAs but also to compounds of Ga1-xAlxAs and Al, InGa, and P, As, and Sb.

As described above, the present invention provides a method and an apparatus for forming a thin epitaxial film by continuously moving supercooled gallium arsenide melt 4 over a crystal substrate 3, and the present invention provides a method and an apparatus for forming a thin epitaxial film by continuously moving supercooled gallium arsenide melt 4 over a crystal substrate 3. A good epitaxial film is
It has the advantage of being able to be formed with good controllability and reproducibility, as well as being excellent in mass production.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a boat of a conventional liquid-phase thin film growth apparatus, FIG. 2 a, b, c, d, and e are process diagrams sequentially showing the liquid-phase thin film growth method of the present invention, and FIG. 3 4 and 5 are cross-sectional views of the boat part of the liquid phase thin film growth apparatus according to the present invention, and FIGS. 6 a and 6 b are diagrams showing other liquid phase thin films according to the present invention, respectively. FIG. 2 is a plan view and a sectional view of the main parts of the growth apparatus. 1...Wafer holding board 1-12...
Gallium solution reservoir, 3,3-1 to 3-10...
Crystal substrate, 4...Gallium arsenide solution, 6,6'
...Gallium arsenide crystal for source, 9-1 to 9-
4... Concavity for solution.

Claims (1)

[Claims] 1. A step of contacting a compound semiconductor solution with a lower solubility with a compound semiconductor source to form a saturated solution, supercooling the saturated solution, and stopping the saturated solution on a crystal substrate. A semiconductor thin film liquid phase growth method consisting of a step of growing while moving the semiconductor thin film. 2. A holding boat having a recess for holding a crystal substrate and a compound semiconductor source, a solution reservoir for holding a compound semiconductor solution, means for moving said solution reservoir on said holding boat, and a means for moving said solution reservoir on said solution reservoir. means for cooling and maintaining the temperature of the compound semiconductor solution for a certain period of time after the compound semiconductor solution contacts the compound semiconductor source and before the compound semiconductor solution contacts the crystal substrate; and a means for controlling the speed of the solution in the solution reservoir over the crystal substrate and stopping the solution. A semiconductor thin film liquid phase growth apparatus comprising means for moving without moving the semiconductor thin film.