JPS627696A - Method and apparatus for liquid-phase epitaxial growth - Google Patents

Abstract

PURPOSE:To efficiently grow a crystal having an optional mixed crystal ratio by moving the liq. level of a soln. for growth up and down, repeating contact and noncontact of the level with a substrate vertically held above the level and supplying a soln. for a mixed crystal to a soln. reservoir. CONSTITUTION:In a liq. phase epitaxial growth device, a soln. 2 is repeatedly brought into contact and noncontact with a substrate 6 vertically held above the reservoir 3 of a soln. for growth by reciprocating a piston 4 to move the level of the soln. 2 for growth up and down. Meanwhile, a slider 10 provided with a soln. reservoir 11 for transfer is arranged to the rear above a soln.-contg. part 1 and the slider is reciprocated requisite times to add the required amt. of a soln. 7 for growth in a reservoir 8 of a soln. for a mixed crystal into the soln. 2 for growth through the soln. reservoir 11. When contact and noncontact of the soln. 2 with the substrate 6 are repeated, an optional amt. of the soln. 7 for a mixed crystal is supplied and a mixed crystal epitaxial layer having a mixed crystal ratio in the optional direction is grown in the liq. phase.

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, and in particular to a method for forming a mixed crystal epitaxial layer, and particularly to a method for controlling the mixed crystal ratio in the thickness direction of crystals grown on a substrate. This invention relates to a method and an apparatus for arbitrarily controlling the above-mentioned conditions, and if applied to the production of wafers having a mixed crystal epitaxial layer with a thickness of 50 μm or more, for example, it would be extremely serious.

[Prior Art] For example, when a mixed crystal epitaxial layer such as GaAfAs 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. It's very difficult. Therefore, when grown to a thickness of about 100 μm using a general horizontal furnace liquid phase growth method, even if the aluminum alloy ratio is about 0.6 at the interface between the epitaxial crystal and the substrate, the epitaxial The surface of the cell layer becomes almost zero.

Therefore, in order to avoid this problem, a special growth method has been adopted in which a temperature gradient is used to uniformly diffuse aluminum into a 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. The width is thicker at the top and smaller at the bottom to make the aluminum mixed crystal ratio uniform in the thickness direction.In order to create the above-mentioned temperature gradient, there is a A heater is provided and the current flowing through the heater is controlled.

[Problems to be solved by the invention] However, since the growth method is special, workability is poor, and since the substrates are kept horizontal to avoid contact with the solution, the number of substrates that can be handled at one time is extremely small. However, it was difficult to increase the size of the wafer, 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,
In a mixed crystal epitaxial layer where segregation is a problem and the mixed crystal ratio is difficult to control, it is possible to control the mixed crystal ratio in the thickness direction not only at the same level but also at any desired level, and in addition, it is easy to increase the size of wafers and mass production. An object of the present invention is to provide an epitaxy cell growth method and apparatus.

[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 the substrate 6 and the solution 2 are moved up and down.
Repeated contact and non-contact.

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, a liquid phase epitaxial growth apparatus according to a second invention in accordance with the above object is an apparatus for carrying out the method of the first invention, and includes a hollow substrate holder part 5 that holds a plurality of substrates 6 upright therein, and a holder. A growth solution reservoir 3 is installed at the lower part of the holder so as to communicate with the inside of the holder and accommodates a growth solution. This growth solution reservoir 3 is provided with a liquid level raising/lowering means 40, which raises and lowers 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 or break the contact. let

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.

This slider 1° is provided with a transfer solution reservoir 11 formed through it, and when the slider 10 is slid in one direction, it communicates with the mixed crystal solution reservoir 8 and the mixed crystal solution 7 is transferred.
A certain amount of mixed crystal solution 7 is accommodated therein, and when it slides in the opposite direction, it communicates with the growth solution reservoir 3 and drops a certain amount of the accommodated mixed crystal solution 7 into the growth solution reservoir 3 .

By setting the board 6 in an upright position, a large number of boards can be set, unlike the case where the board 6 is set horizontally. Furthermore, after raising the temperature of the reactor, the liquid level of the growth solution 2 is raised and the growth solution 2 is slowly cooled while maintaining the contact state between the substrate 6 and the growth solution 2, thereby forming an epitaxial layer on each substrate 6 at the same time. grow up.

Conversely, when the liquid level of the growth solution 2 is lowered, the contact with the substrate 6 is broken and epitaxial layer growth is completed. By raising the temperature again after growth and repeating the above steps,
Successively thicker epitaxial layers are obtained on the substrate. In this way, the epitaxial layer is grown by repeatedly raising and lowering the liquid 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 slider 10 is slid back and forth once while the liquid level of the growth solution 2 is falling and returning to the growth solution reservoir 3, 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 mixed crystal epitaxial wafers of III-V group compound semiconductors such as GaAlAs or ■-■ 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 has a piston 4 as a means for raising and lowering the liquid level.
is provided. 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.

A solution storage part 1 in which such a piston 4 is provided so as to be freely retractable
A hollow substrate holder part 5 which is open at the top and bottom and whose lower part communicates with the growth solution reservoir 2 is attached to the front of the upper part (on the extrusion direction side of the piston 4).
Inside, a plurality of substrates 6 can be held upright, for example, 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. Board 6
Contact with the government has been cut off.

Further, a mixed crystal solution reservoir 8 for containing a mixed crystal solution 7 is attached to the upper rear part of the solution storage section 1 .

The bottom of this mixed crystal solution reservoir 8 is open, and an insertion hole 9 formed laterally along the opening is provided at the bottom of the opening. 8 and the growth solution reservoir 3 are in communication.

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.

In the middle of this slider 10, a solution reservoir 11 for transfer having a constant volume is formed that passes through the slider 10 in the vertical direction.
When the slider 10 is slid in the pulling 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 extrusion direction, it communicates with the growth solution reservoir 3 to accommodate a fixed amount of the mixed crystal solution 7. The mixed crystal solution 7 is 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.

A specific example will be described in which the above-described operating order of the growth apparatus is applied to the QaΔ2As epitaxial growth method.

In advance, 30 2-inch wafers were set in the substrate holder part 5 in a facing arrangement, and the growth solution reservoir 3 was filled with Qal,
500g and 60g of GaAs, and Q in the mixed crystal solution reservoir 8.
a50g and AI! 5a, and put the growth apparatus set in this way into a horizontal reaction tube (not shown).
and replace the inside with H2 gas.

] After replacing the gas with 12 gases, first heat 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 Aρ into the growth solution reservoir 3. . In this embodiment, AI! is completed in one round trip. 120m
The solution of g and Ga1,2a falls. The fallen Aβ-dissolved Ga solution diffuses into the growth solution. Drop erosion, push out the piston 4 to push up the GaAS growth solution,
It is brought into contact with the substrate 6.

Five minutes after contact, 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 and returns to the growth solution reservoir 3 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 A (dissolved Ga solution) so as to have the same amount as described above. Immediately after 20 minutes after raising the temperature, the piston 4 is The growth solution is extruded and brought 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. 5 minutes after contact, slow cooling is started and growth is performed again. .

By repeating the above steps, the GaAffi
An As epitaxial selvedge web can be obtained. In this example, by repeating the temperature raising process 20 times, the thickness was 15 mm.
It was possible to grow a GaAβAs mixed crystal epitaxial layer with extremely good uniformity in the thickness direction at a surface mixed crystal ratio of 0 μm and 0.25.

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 increase the size and mass production of such wafers. By setting the substrate upright and repeatedly raising and lowering the level of the growth solution,
This is because the thickness of the epitaxial layer is increased, and the mixed crystal ratio in the thickness direction can be made uniform when the growth solution is returned to the solution reservoir.
This is because the mixed crystal ratio is adjusted by replenishing the insufficient amount of the mixed crystal solution.

In the above example, the epitaxial wafer has a uniform mixed crystal ratio in the thickness direction, but depending on the amount of the mixed crystal solution added, the mixed crystal ratio varies depending on the thickness as shown in increase or decrease in the direction, or even 2
It is possible to grow epitaxial layers with various types of profiles, such as stepwise. Furthermore, if the thickness is as small as several micrometers, it is possible to grow an epitaxial layer in which the mixed crystal ratio increases rapidly.

Furthermore, even if a dopant having a large analytical coefficient other than A″ββ is added, it is possible to grow a Jl film epitaxial layer with a uniform carrier concentration in the thickness direction.

[Effects of the Invention 1 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 liquid level at the growth stage and replenishing the mixed crystal solution, an epitaxial layer can be formed with any thickness and any mixed crystal ratio. can be grown on the substrate. In addition, by standing up the board, the number of boards that can be handled at one time is arbitrary.
It is possible to set a large number of substrates at the same time, and since the raw material solution returns to the bottom of the substrate, just by replacing the substrate, the raw NWJ solution can be used as many times as it is without the need for replacement or transfer. Compared to other methods, this method has better workability 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 the piston into the mixed crystal solution reservoir,
The overflowing liquid from the upper part of the mixed crystal solution reservoir due to this extrusion may be used, but if the device of the present invention described above is used and the slider with the transfer solution reservoir is made to spin once and for all, it is possible to Since it is now possible to replenish a predetermined amount of mixed crystal solution without adjusting the amount, the work becomes easier and the scale mgi of the supply dropper can be increased. Also, m 1
There is no need for a heater for the 11 gradient, there is no need to control the current, and since it consists only of an inexpensive mechanical structure, it has better durability and operability than conventional devices.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of a liquid phase epitaxial growth apparatus according to the present invention, and FIG. 2 is a diagram showing a possible profile of the mixed crystal ratio in the thickness direction when the present invention is implemented. . 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 is a mixed crystal solution,
8 is a mixed crystal solution reservoir, 10 is a slider, 11 is a solution reservoir for transfer, and 40 is a liquid level raising/lowering means. Patent Applicant Hitachi Cable Co., Ltd. Representative Patent Attorney Nobuo Kinutani Figure 1) 1? , f f mountain (b) "a figure

Claims (2)

[Claims] (1) The substrate is held upright above the growth solution reservoir in a non-contact state with the growth solution, and the liquid level of the growth solution is moved up and down to repeatedly make contact and non-contact with the substrate, and this process is repeated. At this time, by supplying an arbitrary amount of mixed crystal solution from the mixed crystal solution reservoir to the growth solution reservoir, the mixed crystal ratio in the thickness direction of the crystal grown on the substrate can be arbitrarily controlled. Liquid phase epitaxial growth method. (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 the growth solution a liquid level raising/lowering means provided in the reservoir 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 bottom portion of the mixed crystal solution reservoir. A slider that can be slid freely on the
It was formed through the slider, and when the slider was slid in one direction, it communicated with the mixed crystal solution reservoir and contained a certain amount of the mixed crystal solution, and when the slider was slid in the opposite direction, it communicated with and accommodated the growth solution reservoir. A liquid phase epitaxial growth apparatus comprising a transfer solution reservoir for dropping a fixed amount of a mixed crystal solution into a growth solution reservoir.