JP2002184701A - Method of manufacturing gallium nitride layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the clogging of a barrier between a raw material and a substrate when a thick GaN film is formed on the substrate by sublimating the raw material. SOLUTION: The substrate 2 and raw material 4 are arranged in a reaction chamber 1 and the reaction between a source gas and the raw material 4 is adjusted by providing the barrier 5. Then a GaN crystal is grown on the substrate 2 by sublimating the raw material 4 with a heater. During the growth of the GaN crystal, a solid material formed in the barrier 5 is etched off by supplying an etching gas, such as a hydrogen gas, etc., instead of the source gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for growing a gallium nitride (GaN) layer on a substrate by sublimating a raw material.

[0002]

2. Description of the Related Art In recent years, GaN-based semiconductor devices have been widely used as light emitting devices. As a technique for forming a GaN crystal on a substrate, in addition to the MOCVD method, a source material containing Ga is sublimated in a source gas atmosphere such as ammonia, and the sublimated source material is reacted with the source gas on a heated substrate to obtain a Ga.
Methods for growing N are known.

FIG. 3 shows a method of manufacturing a GaN crystal (hereinafter referred to as DSM) disclosed in Japanese Patent Application Laid-Open No. 2000-233993.
(Referred to as Direct Synthesis Method). The substrate 2 and the raw material 4 are arranged opposite to each other in the reaction vessel 1, and the raw material gas is introduced, and the substrate 2 and the raw material (GaNxHy: x, y is a positive real number) are heated by the heater 7 to sublime the raw material. And a GaN crystal is grown on the substrate 2. The barrier 5 between the substrate 2 and the raw material 4 restricts the rate at which the raw material gas reaches the raw material 4, and the volatile crystal growth seeds (GaNxHy: x, y generated on the surface of the raw material 4 (Positive real number). The gas permeability of the barrier 5 is determined so that the generation rate of the crystal growth species and the evaporation rate are balanced, and the raw material 4 can always maintain the same state.

[0004]

However, in the above method, when the crystal growth seed (GaNxHy) passes through the barrier 5, it reacts with the raw material gas (ammonia) in the barrier 5 and GaN is introduced into the barrier 5. A solid containing
There is a problem that the gas permeability in the barrier 5 is changed by the solid. In general, the above-mentioned DSM has a growth rate of about 10 to 100 microns / hour, and it takes several hours to grow a GaN layer having a thickness of several hundred microns. Therefore, as described above, when the gas permeability changes (decreases), the growth rate decreases during the growth time, and as a result, it takes a long time to obtain a desired GaN layer, or a thick GaN film cannot be obtained. was there.

The present invention has been made in view of the above-mentioned problems of the related art, and has as its object to provide a method capable of forming a GaN thick film in a short time.

[0006]

According to the present invention, there is provided a method of growing a GaN layer on a heating substrate in the presence of a source gas by sublimating a source material. An etching gas is supplied. Supplying an etching gas during the growth of the GaN layer causes unnecessary solids formed in the reaction vessel, for example,
And the like can be removed, and even when an unnecessary solid is formed between the substrate and the raw material, this can be removed to promote the growth of the GaN layer. In one embodiment of the present invention, a barrier is provided between the substrate and the raw material, and unnecessary solids formed in the barrier can be removed with an etching gas.
Although the etching gas is supplied during the growth of the GaN layer, the etching gas can be supplied by interrupting the source gas, or the etching gas can be supplied together with the source gas.

The etching gas may be any gas that selectively etches solids other than GaN crystals, such as GaNH, GaNHC, etc., generated by the reaction between the raw material and the raw material gas, such as hydrogen gas, hydrogen chloride gas, Alternatively, it may be a gas containing nitrogen gas. Note that selective etching means that the etching rate of another solid is higher than that of a GaN crystal.

[0008]

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

In this embodiment, the above-described DSM is used as a basis. The configuration of the apparatus is the same as that shown in FIG.
GaNxHy (x and y are positive real numbers) are disposed as the solid raw material 4 in the closed container. G
aNxHy can be obtained by subjecting Ga metal to a heat treatment at a high temperature (1000 ° C. or higher) for about 1 hour under a flow of ammonia gas. GaNxHy, compared to Ga or GaN,
Hydrogen H can easily evaporate due to the bonding, and the growth rate can be increased.

On the other hand, a barrier 5 made of a metal such as porous carbon, porous quartz, molybdenum or the like is formed on one surface of the sealed container 6. Have been. Porous carbon and porous quartz are formed with a large number of vents having a diameter of about 1 to 50 microns, and a raw material gas such as ammonia flows into the closed container 6 through the vents.
GaNxHy sublimated from the raw material 4 reaches the substrate 2 through the air holes. Due to the presence of the barrier 5, the amount of source gas such as ammonia flowing into the source 4 is limited, and the amount of GaNxHy as the source 4 is also limited. The inflow amount of the raw material gas can be adjusted by controlling the diameter of the ventilation hole.

Further, a heater 7 is formed in the reaction vessel 1 so that the substrate 2 and the raw material 4 GaNxHy can be heated. The support 3 is used as a susceptor, and the heater 7 is
It is also possible to heat the substrate 2 and the raw material 4 by induction heating as an F coil.

In such a configuration, conventionally, the substrate 2 and the raw material 4 are heated to 950 ° to 1150 ° C., and a raw material gas such as ammonia is supplied, so that the Ga 2
Although the N layer was formed, GaNxHy sublimated in the barrier 5 and the ammonia gas reacted as described above,
A solid containing GaN is formed in the barrier 5 and blocks the air holes.

Therefore, in this embodiment, the solid in the barrier 5 is removed by interrupting the source gas during the growth of the GaN layer or by supplying the source gas with an etching gas.

FIG. 1 is a flowchart of the manufacturing method according to the present embodiment, and FIG. 2 is a schematic diagram.
First, a substrate 2 such as sapphire and a raw material such as GaNxHy are set at predetermined positions (S101).
Is heated to sublimate the raw material, and a raw material gas such as ammonia is supplied to grow the GaN layer (S102 and FIG. 2A). Next, it is determined whether or not a predetermined time has elapsed (S103). If the predetermined time has elapsed, the supply of the ammonia gas is interrupted, and the etching gas is supplied instead (S104 and FIG. 2B). The solid formed in the barrier 5 is a compound represented by the general formula GaNxHyCz, and a volatile crystal growth seed Ga formed on the surface of the raw material 4.
It is closer to GaN than NH and has a lower vapor pressure. Specifically, the vapor pressure increases in the order of GaNH (crystal growth seed)> GaNxHyCz (intermediate formed in barrier 5)> GaN crystal, and the reaction with other gases also increases in this order. Therefore, GaN, GaNxHy having a high vapor pressure is supplied by supplying the etching gas for a predetermined time.
Cz can be evaporated, and the solid formed in the barrier 5 can be removed. Although the GaN crystal is slightly etched by this process, it is negligibly small. As an etching gas, hydrogen gas or hydrogen chloride gas can be used. Since nitrogen gas also promotes evaporation, it can function as an etching gas.

It is desirable that the supply of the ammonia gas be interrupted and the supply of the etching gas be as short as possible. If you supply the etching gas for a long time,
This is because the original growth of the GaN layer may be hindered by the etching gas. More precisely, it is preferable to set the shortest time to obtain the effect of the etching. Of course, this time is determined according to the type of gas used for etching.

After the solid in the barrier 5 is removed by supplying the etching gas as described above, the source gas ammonia gas is supplied again to grow GaN (S105 and FIG. 2C). By repeating the above process a predetermined number of times (S
106), a GaN layer having a desired thickness can be obtained at a high growth rate.

In this embodiment, the supply of the ammonia gas as the source gas is interrupted to supply the etching gas into the reaction vessel 1. However, the supply of the source gas is not interrupted and the supply of the source gas is not interrupted. It is also possible to supply a raw material gas containing an etching gas.

[0018]

(1) GaN is grown for 1 hour by DSM, supply of ammonia gas is interrupted at the same temperature as growth, hydrogen gas is supplied for 5 minutes, and ammonia gas is supplied again to grow GaN again. Was. The flow rate of ammonia gas is 1
00 cc / min, flow rate of hydrogen gas is also 100 cc / mi
n. By repeating this process five times, a GaN layer having a thickness of about 200 microns could be obtained. When GaN was continuously grown for 5 hours without supplying hydrogen gas, the thickness of the GaN layer was about 70 microns. When the time for supplying hydrogen gas was changed between 30 seconds and 20 minutes, about 5 minutes was optimal. When the supply time was 10 minutes or more, the thickness of the grown layer was reduced, and roughness of the GaN surface was observed. On the other hand, when the supply time was 1 minute or less, no increase in the growth rate was observed. This is probably because a sufficient etching effect cannot be obtained.

(2) In the same process as in the above embodiment, 10 cc / hydrogen chloride gas diluted with 1% hydrogen was used instead of hydrogen gas.
The mixture was supplied at a flow rate of min for 1 minute, and was repeated 5 times in total. As a result, a GaN layer having a thickness of about 250 microns was obtained. No effect was observed when the hydrogen chloride gas was supplied for 10 seconds or less, and the layer thickness was significantly reduced for 5 minutes or more.

(3) During the growth of DSM, GaN was grown by supplying hydrogen chloride gas diluted with 1% hydrogen and mixed with 100 cc / min of ammonia gas at a flow rate of 10 cc / min. As a result of continuous growth for 5 hours without interrupting the growth, GaN with a thickness of 350 microns could be obtained.

(4) In the same process as in the embodiment of (1), 1 liter / min of nitrogen gas was supplied for 10 minutes instead of hydrogen gas. When this process was repeated 5 times,
00 micron GaN could be obtained. The optimal time for growth interruption was 10 minutes. When the time of the growth interruption was 30 minutes or more, the growth layer thickness decreased. No effect was observed below 5 minutes.

[0022]

As described above, according to the present invention,
The growth rate can be prevented from being saturated, and a thick GaN film can be reliably obtained.

[Brief description of the drawings]

FIG. 1 is a processing flowchart of an embodiment.

FIG. 2 is an explanatory diagram of a process according to the embodiment;

FIG. 3 is an apparatus configuration diagram.

[Explanation of symbols]

1 reaction vessel, 2 substrates, 3 supports, 4 raw materials, 5
Barriers, 6 closed vessels, 7 heaters.

Claims (4)

[Claims] 1. A method for producing a gallium nitride layer, comprising: growing a gallium nitride layer on a heated substrate in the presence of a source gas by sublimating a source material, wherein an etching gas is supplied during the growth. Method. 2. The method according to claim 1, wherein the etching gas includes a hydrogen gas. 3. The method according to claim 1, wherein the etching gas includes a hydrogen chloride gas. 4. The method according to claim 1, wherein the etching gas includes a nitrogen gas.