JPH0481550B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a liquid phase epitaxial growth method and apparatus for forming a mixed crystal epitaxial layer.
In particular, it relates to a method and device for arbitrarily controlling the mixed crystal ratio in the thickness direction of crystals grown on a substrate.For example, if applied to the production of wafers having a mixed crystal epitaxial layer with a thickness of 50 μm or more, mass production is possible. Become superior in sex.

[Prior art] For example, when a mixed crystal epitaxial layer such as GaAlAs is grown thickly, the segregation coefficient of aluminum in gallium is too large, making it difficult to form an epitaxial layer with a uniform mixed crystal ratio in the thickness direction. very difficult to obtain. Therefore, when grown to a thickness of about 100 μm using a general horizontal furnace liquid phase growth method, if the aluminum alloy ratio is about 0.6 at the interface between the epitaxial crystal and the substrate. However, the surface of the epitaxial layer becomes almost zero.

Therefore, in order to prevent this from happening,
A special growth method was used that uses a temperature gradient to uniformly diffuse aluminum into the growth solution. In other words, in this method, since mixed aluminum tends to accumulate above the growth solution after the temperature is raised, the growth solution in the growth solution reservoir has a temperature gradient in the vertical direction, and cooling is reduced. By making the width larger at the top and smaller at the bottom, the aluminum mixed crystal ratio is made uniform in the thickness direction.On the equipment side, in order to create the temperature gradient mentioned above, a heater is installed vertically around the outer periphery of the growth solution reservoir. is provided to control the current flowing through this heater.

[Problems to be solved by the invention] However, the special growth method makes workability difficult, and since the substrates are brought into contact with the solution horizontally, the number of substrates that can be handled at one time is extremely small. However, it was difficult to increase the size of wafers, and mass productivity was poor.

Furthermore, it was difficult to form a desired temperature gradient by controlling the current of the heater.

[Object of the Invention] The object of the present invention is to solve the problems of the prior art described above, and to improve the mixing crystal ratio in the thickness direction in a mixed crystal epitaxial layer where segregation is a problem and the mixing crystal ratio is difficult to control. It can be controlled arbitrarily without
Moreover, it is an object of the present invention to provide a liquid phase epitaxial growth method and an apparatus therefor, which can easily increase the size of wafers and mass-produce them.

[Summary of the Invention] The liquid phase epitaxial growth method of the first invention which meets the above object is as shown in FIG. The liquid level of the growth solution 2 in the growth solution reservoir 3 is moved up and down with respect to the substrate 6 which is held upright in advance, and contact and non-contact between the substrate 6 and the solution 2 are repeated.

During this repetition, that is, when the liquid level is lowered and the substrate 6 and the solution are in a non-contact state, an arbitrary amount of the mixed crystal solution 7 is supplied from the mixed crystal solution reservoir 8 to the growth solution reservoir. Add to solution. Thereby, the mixed crystal ratio in the thickness direction of the crystal grown on the substrate 6 is controlled to an arbitrary value.

Further, the liquid phase epitaxial growth method of the second invention which meets the above object is an apparatus for carrying out the first invention method, which includes a hollow substrate holder part 5 that holds a plurality of substrates 6 upright therein; A growth solution reservoir 3 is attached to the lower part of the holder part so as to communicate with the inside of the holder part, and contains a growth solution. This growth solution reservoir 3 has a liquid level raising/lowering means 40.
is provided to raise and lower the liquid level of the growth solution 2 in the growth solution reservoir 3 so as to bring it into contact with the substrate 6 and break the contact therewith.

On the other hand, a mixed crystal solution reservoir 8 containing a mixed crystal solution 7 is provided above the growth solution reservoir 3, and a slider 10 is slidably provided at the bottom of this mixed crystal solution reservoir. And this slider 10
A transfer solution reservoir 11 is formed through the slider 10, and when the slider 10 is slid in one direction, it communicates with the mixed crystal solution reservoir 8 to accommodate a certain amount of the mixed crystal solution 7, and when the slider 10 is slid in the opposite direction. Then, a certain amount of the mixed crystal solution 7 stored in communication with the growth solution reservoir 3 is dropped into the growth solution reservoir 3.

By setting the substrates 6 in an upright position, a large number of substrates can be set, unlike the case where they are set horizontally. Furthermore, after raising the temperature of the reactor, if the liquid level of the growth solution 2 is allowed to rise and the substrate 6 is kept in contact with the growth solution 2 while being slowly cooled, epitaxial growth will occur on each substrate 6 at the same time. The layers grow.
Conversely, when the liquid level of the growth solution 2 is lowered, the substrate 6
The epitaxial layer growth is terminated by breaking the contact state with the epitaxial layer. By repeating the above steps after the growth is completed or at elevated temperatures, successively thicker epitaxial layers are obtained on the substrate. In this way, the epitaxial layer is grown by repeatedly raising and lowering the level of the growth solution, and as the amount of rise in the liquid level increases, a wider area of contact with the substrate is ensured. Then, the substrate on which epitaxial growth has been completed is replaced with a new substrate, but since the growth solution returns to the growth solution reservoir under its own weight, there is no need for replacement or transfer.

By the way, when the liquid level of the growth solution 2 is falling and returning to the growth solution reservoir 3, the slider 10
When the slider slides back and forth once, a certain amount of the mixed crystal solution is added to the growth solution. By repeating this, an arbitrary amount of the mixed crystal solution is replenished. By replenishing an arbitrary amount of the mixed crystal solution, the mixed crystal ratio in the thickness direction of the epitaxial layer grown on the substrate can be arbitrarily controlled.

The present invention is applicable to all types of growth of - group compound semiconductors such as GaAlAs, or mixed crystal epitaxial wafers of - group compound semiconductors.

[Example] An example of the present invention will be described below based on FIGS. 1 and 2.

FIG. 1 shows an embodiment of a liquid phase epitaxial apparatus for carrying out the method of the invention.

Reference numeral 1 denotes a solution storage part in which a growth solution reservoir 3 having an opening at the top is formed to contain a growth solution 2 .
This solution storage section 1 is provided with a piston 4 as a means for raising and lowering the liquid level. This piston 4 is inserted from one side of the solution storage part 1 into an insertion hole formed in the growth solution reservoir 3 in the horizontal direction, and the tip of the piston 4 is inserted into and out of the growth solution reservoir 3 so that the growth solution 2 can be removed. It is designed to move up and down.

At the front of the upper part of the solution storage part 1 in which such a piston 4 is provided so as to be freely retractable (on the extrusion direction side of the piston 4), there is a hollow substrate holder part whose upper and lower sides are open and whose lower part communicates with the growth solution reservoir 2. 5 is attached, and a plurality of substrates 6 are mounted in the substrate holder section 5.
can be held upright, for example, in an arrangement facing each other. Therefore, when the piston 4 is pushed out, the pushed-up growth solution 2 enters the substrate holder part 5 and comes into contact with the substrate 6, and when the piston 4 is pushed back, the liquid level of the growth solution 2 falls. Thus, contact with the substrate 6 is cut off.

In addition, a mixed crystal solution 7 is provided at the rear of the upper part of the solution storage section 1.
A mixed crystal solution reservoir 8 containing the mixed crystal is attached.
The bottom of this mixed crystal solution reservoir 8 is open, and an insertion hole 9 formed laterally along this open bottom is provided, and the mixed crystal solution reservoir 8 is connected to the mixed crystal solution reservoir 8 through this insertion hole. It communicates with the growth solution reservoir 3. A slider 10 that closes the opening bottom of the mixed crystal solution reservoir 8 and the insertion hole is inserted into the insertion hole 9 so as to be slidable in the same direction as the piston 4.

A transfer solution reservoir 11 of a fixed volume is formed in the middle of the slider 10 and passes through the slider 10 in the vertical direction. When the slider 11 is slid in the pulling direction, it communicates with the mixed crystal solution reservoir 8 and the mixed crystal solution 7 When the slider 10 is slid in the extrusion direction, a certain amount of the mixed crystal solution 7 is communicated with the growth solution reservoir 3 and dropped into the growth solution reservoir 3.

In this embodiment, the insertion hole 9 for the slider and the solution reservoir 8 for the mixed crystal are integrally formed in the thick part on one side of the substrate holder part 5, but they may be formed separately or The holder portion 5 may be attached integrally to the solution storage portion 1 or may be detachably attached.

Then, the operation order of the above-mentioned growth apparatus was changed to GaAlAs.
A specific example of application to the epitaxial growth method will be described.

In advance, set 30 2-inch wafers facing each other in the substrate holder part 5, and place them in the growth solution reservoir 3.
1,500g of Ga and 60g of GaAs are set in the mixed crystal solution reservoir 8, and 50g of Ga and 5g of Al are set in the mixed crystal solution reservoir 8.The growth apparatus thus set is inserted into a horizontal reaction tube (not shown) and the inside is opened. Replace with H ₂ s.

After replacing with H ₂ gas, first raise the temperature of the reactor to the growth starting temperature of 800°C, and after raising the temperature, move the slider 10 back and forth 10 times to drop the Ga solution containing dissolved Al into the growth solution reservoir 3. . In this example, one round trip is required.
A solution of 120 mg of Al and 1.2 g of Ga falls. fell down
The Ga solution containing dissolved Al diffuses into the growth solution.
After falling, the piston 4 is pushed out to push up the GaAs growth solution and bring it into contact with the substrate 6. After contact 5
After a minute, slow cooling is started and crystal growth is performed. After 30 minutes of contact, when the piston 4 is immersed, the pushed-up growth solution descends into the growth solution reservoir 3.
It returns under its own weight and growth stops.

Next, the temperature of the furnace is raised to 800°C again. At this time, the slider 10 is reciprocated again to replenish the growth solution with the insufficient amount of the Ga solution in which Al has been dissolved so as to have the same amount as described above. Immediately after 20 minutes after the temperature rise, the piston 4 is pushed out to bring the growth solution into contact with the substrate 6. At this time, since the furnace is not yet stable, the surface of the substrate tends to melt back to some extent. Five minutes after contact, slow cooling is started and growth is performed again.

By repeating the above steps, thick film
GaAlAs epitaxial wafers can be obtained. In this example, by repeating the temperature raising step 20 times, it was possible to grow a GaAlAs mixed crystal epitaxial layer with a thickness of 150 μm, a surface mixed crystal ratio of 0.25, and extremely good uniformity in the thickness direction.

As described above, according to this embodiment, it is possible to grow mixed crystal epitaxially on about 30 2-inch wafers with a thickness of 50 μm or more at a time, and it is possible to achieve larger size and mass production of such wafers. This is possible because the thickness of the epitaxial layer is increased by raising and lowering the growth solution while setting the substrate upright, and also by increasing the thickness of the epitaxial layer. The reason why the ratio can be made uniform is that when the growth solution is returned to the solution reservoir, the mixed crystal ratio is adjusted by replenishing the missing amount of the mixed crystal solution.

In the above examples, the case of an epitaxial wafer in which the mixed crystal ratio is uniform in the thickness direction was described, but depending on the amount of the mixed crystal solution added, the mixed crystal ratio can be changed as shown in Fig. 2. increases in the thickness direction,
It is possible to grow epitaxial layers with various types of profiles, such as reduced or even two-step profiles. Furthermore, if the thickness is as small as several μm, it is possible to grow an epitaxial layer in which the mixed crystal ratio increases rapidly.

Furthermore, even if a dopant other than Al with a large segregation coefficient is added, a thick epitaxial layer with a uniform carrier concentration in the thickness direction can be grown.

[Effects of the Invention] In summary, the present invention exhibits the following excellent effects.

(1) There is no need to create a temperature gradient in the growth solution, and by repeatedly raising and lowering the growth solution level and replenishing the mixed crystal solution, epitaxial growth of any thickness and any mixed crystal ratio can be achieved. A layer can be grown on the substrate. In addition, by standing up the substrates, any number of substrates can be handled at one time, and many substrates can be set at the same time.Moreover, since the raw material solution returns to the bottom of the substrate, just by replacing the substrate, the raw material solution can be removed. Because it does not require replacement or transfer and can be used as is, it is easier to work with than conventional methods, and allows for larger wafers, making it suitable for mass production.

(2) To drop a certain amount of mixed crystal solution into the growth solution reservoir, push a piston into the mixed crystal solution reservoir, and use the overflow from the top of the mixed crystal solution reservoir due to this extrusion. However, if the device of the present invention described above is used and the slider with the transfer solution reservoir is moved back and forth, a predetermined amount of mixed crystal solution can be replenished without adjusting the stroke. , the work is easier and the accuracy of weighing the amount of falling supply can be improved. Furthermore, there is no need for a heater for temperature gradients, there is no need to control its current, and the device has only a simple mechanical configuration, so it has better durability and operability than conventional devices.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing an embodiment of a liquid phase epitaxial growth apparatus according to the present invention, and FIG. 2 is a line showing a profile of the possible mixed crystal ratio in the thickness direction when the present invention is implemented. It is a diagram. In the figure, 2 is a growth solution, 3 is a growth solution reservoir,
4 is a piston, 5 is a substrate holder part, 6 is a substrate, 7
8 is a mixed crystal solution, 8 is a mixed crystal solution reservoir, 10 is a slider, 11 is a solution reservoir for transportation, and 40 is a liquid level raising/lowering means.

Claims (1)

[Claims] 1. With respect to a substrate that is held upright above a growth solution reservoir in a non-contact state with the growth solution, the liquid level of the growth solution is moved up and down to make contact and non-contact with the substrate. By repeatedly supplying an arbitrary amount of mixed crystal solution from the mixed crystal solution reservoir to the growth solution reservoir during this repetition, the mixed crystal ratio in the thickness direction of the crystal grown on the substrate can be arbitrarily controlled. A liquid phase epitaxial growth method characterized by: 2. A hollow substrate holder part that holds a plurality of substrates upright therein, a growth solution reservoir attached to the lower part of the holder part so as to communicate with the inside of the holder part and containing a growth solution, and a growth solution reservoir in the growth solution reservoir. a liquid level raising/lowering means provided for raising and lowering the liquid level of the growth solution; a mixed crystal solution reservoir provided above the growth solution reservoir for accommodating a mixed crystal solution; and a slide at the bottom of the mixed crystal solution reservoir. A freely provided slider is formed through the slider, and when the slider is slid in one direction, it communicates with the mixed crystal solution reservoir to accommodate a certain amount of mixed crystal solution, and when it is slid in the opposite direction, it is connected to the mixed crystal solution reservoir, and when it is slid in the opposite direction, it is used for growth. 1. A liquid phase epitaxial growth apparatus comprising a transfer solution reservoir that communicates with the solution reservoir and drops a fixed amount of mixed crystal solution contained therein into the growth solution reservoir.