JPH11121386A - Vapor phase growth system of gallium nitride based compound semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the crystallinity of a gallium nitride based compound semiconductor. SOLUTION: A raw gas and a carrier gas are led into a reaction chamber 11 in a reaction tube and the vapor phase of the gallium nitride based compound semiconductor is grown on a substrate mounted on a susceptor 22 in the reaction chamber. The system has a feeding inlet 125 feeding a first gas over the substrate, a leading inlet feeding a second gas to the substrate sideways, and a gas guiding member 12 continuous to the feeding inlet and flowing down the first gas over the substrate by guiding the gas spread out downward.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound semiconductor vapor phase growth apparatus.

[0002]

2. Description of the Related Art Conventionally, a gallium nitride-based compound semiconductor (Al _x Ga ₁ -xN; including x = 0) thin film is formed on a sapphire substrate by metalorganic compound vapor deposition (hereinafter referred to as “MOVPE”). There has been studied a light-emitting device in which a gallium nitride-based compound semiconductor thin film is used as a light-emitting layer. Since a single crystal wafer of a gallium nitride-based compound semiconductor cannot be easily obtained, a gallium nitride-based compound semiconductor is epitaxially grown on a sapphire substrate having a lattice constant close to that of the single crystal wafer. In a vapor phase growth apparatus using the MOVPE method used in conventional GaAs or the like, a reaction gas is uniformly flowed into a reaction chamber to grow a uniform crystal having no location dependence on a substrate. I have.

[0003]

However, when a gallium nitride-based compound semiconductor is grown on a sapphire substrate having a different lattice constant from a different substance, it is difficult to grow the crystal. This leads to lattice defects. In the case of vapor phase growth of a gallium nitride compound semiconductor, the growth temperature is high, so that the vapor pressure of the group V element is high, the balance of the stoichiometry is easily lost, and a uniform large-area crystal film is obtained. It is difficult. Therefore, it is necessary to increase the flow velocity without disrupting the laminar flow of the reaction gas.

However, in the conventional vapor phase growth apparatus, it is difficult to obtain a uniform gas flow, and the stoichiometric number balance is easily lost.
In the case of GaN or the like, it is difficult to obtain a uniform large-area crystal film, pits are easily generated in the crystal, and the surface morphology is poor. Further, in the conventional apparatus, in the crystal growth of the compound semiconductor, the crystal yield is as low as 20 to 30%, and the expensive reaction gas is often discarded as it is.

For example, in gallium nitride, a group III element G
Ammonia is used as a reaction gas of trimethylgallium and group V element N as a reaction gas of a. Since the N element tends to be insufficient in crystal growth, the supply ratio of the group III reaction gas to the group V reaction gas is 1/1000, and the ammonia gas is overwhelmingly larger. However, the proportion of GaN used for crystal growth is extremely small compared to the gas supply, and most of the ammonia gas is discarded as it is. As described above, the conventional apparatus has problems in crystallinity and economic efficiency of the formed thin film.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to make it possible to grow a large number of compound semiconductors having good crystallinity at one time, and to improve the economical efficiency of the production. It is to improve.

[0007]

According to an aspect of the present invention, a source gas and a carrier gas are introduced into a reaction chamber in a reaction tube, and gallium nitride is placed on a substrate mounted on a susceptor in the reaction chamber. In a vapor phase growth apparatus for vapor-phase growing a system compound semiconductor, a supply port for supplying a first gas from above a substrate, an introduction port for supplying a second gas from a side of the substrate, and a supply port continuous with the supply port. And a gas guide member for generating the first gas downward from above the substrate and guiding and supplying the first gas so that the flow spreads downward.

According to a second aspect of the present invention, the gas guide member includes a first roof portion for spreading the first gas blown from a supply port provided above the substrate downward, and a first roof portion.
And a second roof portion that covers the upper portion of the substrate by narrowing the gap between the first gas and the substrate downstream so as to contact the substrate from above with the first gas. It is characterized by comprising.

According to a third aspect of the present invention, there is provided a vapor phase growth apparatus for introducing an organometallic compound gas into a reaction chamber in a reaction tube and vapor-growing a compound semiconductor in the reaction chamber. Along the axial direction, a susceptor for mounting a substrate for crystal growth is disposed at a number of places, covers each susceptor from above, and supplies a first gas downward to each susceptor. A gas guide member is provided for each susceptor so as to guide the second gas from the upstream side to the downstream side along the tube axis direction.

According to a fourth aspect of the present invention, the gas guide member includes a first roof portion that spreads the first gas downward.
A second roof portion which is continuous with the first roof portion and guides the first gas to contact the substrate from above with respect to the substrate.

According to a fifth aspect of the present invention, in the portion where the substrate is mounted, the upper gap between the gas guide member and the substrate surface is narrowed uniformly and narrowly in the width direction of the substrate. A gas supply member for supplying at least one kind of reactant gas between the two substrates, the gas supply member having an inlet opening at an upstream side of the gas guide member for introducing the reactant gas; And a gas supply pipe for supplying the first gas from the supply port to the inside of the gas guide member.

[0012]

According to the first aspect of the present invention, a supply port for supplying the first gas from above the substrate, an introduction port for supplying the second gas from the side of the substrate, and a continuous supply port. A gas guide member for generating a first gas flow downward from above the substrate and guiding and supplying the first gas so that the flow spreads downward, so that the reaction gas layer on the substrate is provided. The flow is formed more efficiently. As a result, the crystals grown on the substrate are of good quality.

According to the second aspect of the present invention, the gas guide member is connected to the first roof portion that spreads the first gas downward and the first roof portion and transfers the first gas to the substrate. Since the first gas and the second gas on the substrate are further composed of a second roof portion that guides the substrate to contact the substrate from above,
A high-quality laminar flow can be obtained, and the quality of the crystal grown on the substrate can be further improved.

According to the third aspect of the present invention, in the reaction chamber, susceptors for mounting substrates for crystal growth are arranged at a number of places along the axial direction of the reaction tube, and each susceptor is covered from above. A gas guide that supplies a first gas downward to each susceptor and guides a second gas to each susceptor from the upstream side to the downstream side along the tube axis direction. Since the members are provided, a laminar flow in which the first gas and the second gas are mixed can be formed on the plurality of substrates, and high-quality crystal growth can be performed on many substrates.

According to the fourth aspect of the present invention, the first gas is connected to the first roof, which extends downward, and is connected to the first roof.
The laminar flow on the substrate is made denser by the action of the first gas and the second roof, which guides the first gas so as to contact the substrate from above, so that the crystallinity can be improved.

According to the fifth aspect of the present invention, since the upper gap between the gas guide member and the substrate surface is narrowed uniformly in the width direction of the substrate at the portion where the substrate is mounted, The density of the laminar flow of the reaction gas on the substrate can be further improved.

In the above-described crystal growth method and apparatus, for example, in the case of crystal growth of gallium nitride, trimethyl gallium gas and ammonia gas are supplied from an inlet tube. The supply ratio of trimethylgallium gas to ammonia gas is
At 1/1000, there is overwhelmingly more ammonia gas. Then, the two reaction gases are guided by the gas guide member and flow downstream.

On the susceptor holding member which is covered with the gas guide member and extends in the tube axis direction, susceptors are mounted at a number of positions along the tube axis, and the substrate is mounted on the susceptor. Both reaction gases are guided by the gas guide member and flow over the substrate in a laminar flow. At this time, the gap between the gas guide member and the substrate is narrowed uniformly and narrowly in the width direction of the substrate with respect to the substrate plane. As a result, the flow of both reaction gases in the gap on the substrate becomes a uniform laminar flow, Uniform and uniform crystal growth on the surface becomes possible.

On the other hand, a large amount of ammonia gas supplied from the gas introduction pipe is used for partial crystal growth, and the unused gas is further guided by the gas guide member and flows downstream. Further, only a trimethylgallium gas for supplying a group III element Ga is supplied from a gas supply pipe connected to a supply port of the gas guide member.

Thus, the deficient group III element Ga
Is supplied from the supply port on the upstream side of each substrate, and reacts with the excess ammonia gas to grow gallium nitride on the substrate on the downstream side. Thereafter, excess ammonia gas flows also to the substrate placed further downstream, and similar crystal growth is performed.

The gap above the substrate with respect to the gas guide member is
Since the thickness is narrowed down to a uniform thickness in the width direction of the substrate, the flow of the reaction gas in the gap becomes uniform and uniform in the width direction of the substrate. As a result, a high-quality crystal is obtained. In addition, the substrate is placed at many points along the gas flow, excess gas flows downstream, and only insufficient gas is supplied from the upstream side of each substrate, so that gas is used without waste, There is an effect that the efficiency of crystal growth is good. "

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on specific embodiments. In FIG. 1, a cylindrical quartz tube 10 is shown.
Is sealed at its left end by an O-ring
To the bolt 4 using the cushioning material 38 and the fixing tool 39.
6, 47 and nuts 48, 49, etc., are fixed to the flange 14 at several places. The right end of the quartz tube 10 is sealed by an O-ring 40 and the flange
1 and 42.

A susceptor holding member 20 extending in the tube axis (X-axis) direction is provided in the reaction chamber 11 surrounded by the quartz tube 10, and the reaction gas flows in the tube axis direction. The susceptor holding member 20 has an upper flat portion 201 and a lower semicircular leg 202 as shown in FIGS. The leg portion 202 is in contact with the bottom surface of the quartz tube 10, and the upstream end surface of the flat portion 201 is held by the holding member 17 fixed to the flange 14, so that the flat portion 201 is horizontal. ing. In many places along the tube axis of the flat portion 201, a concave susceptor holding portion 21a is formed.
-21d is formed. The susceptor holders 21a to 21d are provided with susceptors 22a to 22d which are inclined upward toward the downstream side.
Sapphire substrates 50a-50d grown on 22d
Are arranged.

On the other hand, a gas guide member 12 extending in the tube axis direction is provided so as to cover the flat portion 201 of the susceptor holding member 20 from above. The gas guide member 12 has an upper roof 121 and legs 122 and 123 projecting downward on both sides of the roof 121. The end surfaces of the legs 122 and 123 abut against the flat portion 201 of the susceptor holding member 20, and the side surfaces of the legs 122 and 123 abut against the projections 203 and 204 provided on the flat portion 201, and reactant gas Is prevented from leaking.

The upstream end of the roof 121 of the gas guide member 12 is held by a holding member 17.
Is held horizontally. The roof part 121 is a part 124 on which the sapphire substrates 50a to 50d are placed.
In a-124d, the gap between the sapphire substrates 50a-50d and the roof 121 is in the width direction of the sapphire substrate (Y axis).
Are uniformly narrowed. The gap is sapphire substrate 5
It is 12 mm at the upstream end of 0a-50d and 4 mm at the downstream end. Thus, in this embodiment, the gap above the sapphire substrate is narrowed along the downstream side. By doing so, a high-speed uniform laminar flow of the reaction gas can be obtained on the sapphire substrates 50a to 50d.

On the upstream side of the sapphire substrates 50b to 50d, supply ports 125b to 125d projecting upward are formed. In this state, open the flange 27,
The gas guide member 12 and the susceptor holding member 20 are connected to the reaction chamber 11.
And can be mounted inside the reaction chamber 11.

On the other hand, gas supply pipes 23b-23d penetrate the quartz tube 10 at positions corresponding to the supply ports 125b-125d.
Are arranged so as to be vertically movable while maintaining confidentiality. With the susceptor holding member 20 and the gas guide member 12 attached to the reaction chamber 11, the gas supply pipes 23b to 23d can be moved downward to be fitted into the supply ports 125b to 125d. On the upstream side of the gas guide member 12, a first gas pipe 28 and a second gas pipe 29 are open. The first gas pipe 28 is located inside the second gas pipe 29, and both pipes 28, 29 have a coaxial double pipe structure. Numerous holes 30 are formed in the periphery of the portion of the first gas pipe 28 not covered by the second gas pipe 29,
Many holes 30 are also formed in the gas pipe 29. Then, the reaction gas introduced by the first gas pipe 28 is blown out into a pipe constituted by the gas guide member 12 and the susceptor holding member 20, where the gas introduced by the second gas pipe 29 is removed. Mixed for the first time.

The first gas pipe 28 is connected to the first manifold 3
1 and the second gas pipe 29 is connected to the second manifold 32.
It is connected to the. The first manifold 31 has a carrier gas supply system I, a trimethylgallium (hereinafter, referred to as "TMG") supply system J, a trimethylaluminum (hereinafter, referred to as "TMA") supply system K, and a diethyl zinc (hereinafter, referred to as "TMA"). A supply system L (hereinafter referred to as “DEZ”) is connected to the second manifold 32, and an NH ₃ supply system H and a carrier gas supply system I are connected to the second manifold 32.

The gas supply pipes 23b-23d are connected to a third manifold 33. The third manifold 33 has a carrier gas supply system I, a TMG supply system J, a TMA supply system K, and a DEZ. The supply system L is connected. A cooling pipe 36 for circulating cooling water is formed on the outer periphery of the quartz tube 10, and a high-frequency coil 34 for applying a high-frequency electric field is provided on the outer periphery.

The tubular body composed of the gas guide member 12 and the susceptor holding member 20 is connected to an external pipe 35 via a flange 14, and a carrier gas is introduced from the external pipe 35. ing. With such an apparatus configuration, a mixed gas of TMG, TMA, DEZ, and H ₂ guided by the first gas pipe 28 and a mixed gas of NH ₃ and H ₂ guided by the second gas pipe 29 Near the outlet of the tube, and the mixed reaction gas is guided downstream by the gas guide member 12. Also, each gas supply pipe 23b-23d
The same kind of gas as that blown out of the first gas pipe 28 through the gas guide member 12 is introduced. As a result,
These reaction gases pass through the gap formed between the sapphire substrates 50a-50d and the upper tube walls 124a-124d of the gas guide member 12. At this time, the sapphire substrate 5
The flow of the reaction gas on Oa-50d is
The sapphire substrate is uniformly uniform in the width direction (Y direction) and the height direction (Z direction). As a result, a high-quality crystal with little place dependence on each of the sapphire substrates 50a to 50d grows.

When an N-type Al _x Ga ₁ -xN thin film is formed, DEZ is stopped and the first gas pipe 28 and the second gas
The mixed gas may be discharged from the gas pipe 29 and the gas supply pipes 23b to 23d. When an I-type Al _x Ga ₁ -xN thin film is formed, DEZ is supplied and the first gas pipe 28 is supplied. What is necessary is just to make each mixed gas flow out from the 2nd gas pipe 29 and the gas supply pipes 23b-23d. I-type Al _X Ga
_1-X when N thin film formation is, DEZ is sprayed thermally decomposing the sapphire substrate 50a-50d, the dopant element is doped in Al _X Ga _1-X N to grow,
I-type Al _x Ga ₁ -xN is obtained.

As described above, in the above apparatus, the Annimore gas is supplied only from the second gas 29 and flows from the upstream side to the downstream side. Further, TMG, TMA, and DEZ, which are insufficient downstream of the sapphire substrate 50a, are supplied to the gas supply pipe 23b.
-23d also reacts with the Annimore gas supplied from the upstream side, and a good crystal grows on the sapphire substrates 50b-50d on the downstream side.

Next, the sapphire substrate 50 is
A crystal was grown on a-50d as follows.
First, a single-crystal sapphire substrate 50a-50d having a (0001) plane as a main surface cleaned by organic cleaning and heat treatment is mounted on the susceptor 22a-22d, and the susceptor 22a-2
2d is the susceptor holder 21a- of the susceptor holder 20.
21d. Then, the gas guide member 12 was covered from above, and the integrated gas guide member 12 and the susceptor holding member 20 were set at predetermined positions in the reaction chamber 11.
Next, the gas supply pipes 23b to 23d were lowered and inserted into the supply ports 125b to 125d of the gas guide member 12.

Next, while flowing H ₂ at a rate of 3 liter / min through the first gas pipe 28, the second gas pipe 29 and the external pipe 35, the H ₂ flows into the pipe surrounded by the gas reaction member 12 and the susceptor holding member 20. Sapphire substrate 50a-50 at a temperature of 1100 ° C
d was vapor-phase etched. Next, the temperature was lowered to 400 ° C., and H ₂ was supplied from the first gas pipe 28 and the gas supply pipes 23b-23d at a rate of 10 liter / min, and H ₂ bubbled in TMA at 15 ° C. was supplied at a rate of 50 cc / min. . At the same time, H ₂ was supplied from the second gas pipe 29 at 40 liter / min and NH ₃ was supplied at liter / min for 2 minutes.

In this growth step, as shown in FIG.
An N buffer layer 51 was formed to a thickness of about 250 °. Next, the supply of TMA was stopped, the sample temperature was maintained at 1150 ° C., and H ₂ was bubbled through the first gas pipe 28 and the gas supply pipes 23b to 23d in TMG at −15 ° C. at 10 liter / min. the H ₂ was supplied at a rate of 100 cc / minute. At the same time, 40 liters / minute of H ₂ and 40 liters of NH ₃ are supplied from the second gas pipe.
N-type GaN with a thickness of about 7 μm supplied at ter / min for 60 minutes
Was grown. As a result of measuring the SEM image and the RHEED image of the N layer 52, it was found that a good crystal having no location dependency was obtained.

The thickness of the sapphire substrate 50 in the width direction (the direction perpendicular to the gas flow) and the length direction (the direction parallel to the gas flow) was measured, and a uniform film thickness was obtained.

In the above embodiment, the susceptors 22a-22d
Is inclined upward toward the downstream side.
As shown, the top surfaces of the sapphire substrates 50a-50d are flattened, and
Roof 124a-124 of gas guide member 12 on 50d
d may be formed in a downward slope along the downstream direction.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a vapor phase growth apparatus according to a specific embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a sectional view taken along the line III-III in FIG. 1;

FIG. 4 is a sectional view showing the structure of a thin film grown on a sapphire substrate.

FIG. 5 is a cross-sectional view showing a characteristic portion of an apparatus according to another embodiment.

[Explanation of symbols]

10 quartz tube 12 gas guide member 20 susceptor holding member 21a-21d susceptor holding portion 22a-22d susceptor 201 flat portion 121, 124a-124d roof portion 125a-125d supply port 23b-23d gas supply Pipe 28 ─ First gas pipe (introduction pipe) 29 ２ Second gas pipe (introduction pipe) 50 a-50 d ─ Sapphire substrate 51 ─ AlN buffer layer 52 ─ N layer H─ NH ₃ supply system I─ Carrier gas supply system J─TMG supply system K─TMA supply system L─DEZ supply system

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Katsuhide Shinbe 1 Ochiai Nagahata, Kasuga-mura, Nishi-Kasugai-gun, Aichi Prefecture Inside Toyoda Gosei Co., Ltd. No. 1 Toyoda Gosei Co., Ltd. (72) Inventor Norikatsu Koide Aichi Prefecture Nishikasugai-gun Kasugamura O-shape Ochiai character Nagahata 1 Address Toyoda Gosei Co., Ltd. No.Toyota Gosei Co., Ltd. (72) Inventor Isamu Isamachi, Chikusa-ku, Nagoya-shi, Aichi (No address)

Claims (5)

[Claims] 1. A vapor-phase growth apparatus for introducing a source gas and a carrier gas into a reaction chamber in a reaction tube and vapor-growing a gallium nitride-based compound semiconductor on a substrate mounted on a susceptor in the reaction chamber. A supply port for supplying a first gas from above, a supply port for supplying a second gas from the side of the substrate, and a supply port connected to the supply port. A gallium nitride-based compound semiconductor vapor phase growth apparatus, comprising: a gas guide member that generates a flow toward the flow and guides and supplies the flow to spread downward. 2. The gas guide member comprises: a first roof portion for spreading the first gas blown out from the supply port provided above the substrate downward; and the first roof portion. A second roof portion which is continuous with the first portion and which covers the upper portion of the substrate by narrowing a gap with the substrate downstream so that the first gas contacts the substrate from above with respect to the substrate. The gallium nitride-based compound semiconductor vapor phase growth apparatus according to claim 1, comprising: 3. A vapor-phase growth apparatus for introducing an organometallic compound gas into a reaction chamber in a reaction tube and vapor-growing a compound semiconductor in the reaction chamber, wherein the reaction chamber is formed along a tube axis direction of the reaction tube. ,
A susceptor on which a substrate for crystal growth is mounted is provided at a number of locations, the susceptor is covered from above, and a first gas is supplied downward to each of the susceptors. A gas guide member for guiding the second gas from the upstream side to the downstream side along the tube axis direction. 4. The gas guide member is connected to a first roof portion that spreads the first gas downward and the first roof portion, and communicates the first gas to the substrate. The gallium nitride-based compound semiconductor vapor phase growth apparatus according to claim 3, further comprising a second roof portion that guides the substrate from above in contact with the substrate. 5. The gas guide member according to claim 1, wherein an upper gap between the gas guide member and the substrate surface is narrowed uniformly and narrowly in a width direction of the substrate. Between the gas guide member and the gas guide member, the gas supply member has a supply port through which at least one gas of the reaction gas is supplied, and is opened on the upstream side of the gas guide member to guide the reaction gas. The gas supply pipe according to claim 4, further comprising a gas supply pipe connected to the supply port and configured to supply the first gas from the supply port to the inside of the gas guide member. Phase growth equipment.