JPH03112128A - Vapor growth device for compound semiconductor - Google Patents

Abstract

PURPOSE:To mix the reactive gas introduced into a liner tube in the upstream part of the liner tube, and also to throttle the gas flow above a substrate so as to obtain a uniform laminar flow by constituting a susceptor out of a liner tube in the shape of an inner tube when placing the substrate for crystal growth on the susceptor, and providing a minute gap at the side where the substrate is placed. CONSTITUTION:A conical liner tube 12, which is expanding in the direction of gas downstream, is provided in an inner chamber 11 surrounded by a quartz tube 10. That is, the cross section vertical to the axis of the liner tube 12 is constituted in a circle that the radius is large along the direction of an X axis being the gas flow direction. Moreover, on the side of the downstream of the liner tube 12, a conical susceptor 20 of barrel type is provided to cover it from upstream side. Moreover, the side of the susceptor 20 on which to place many sapphire substrates 50 is covered with the liner tube 12 small intervals apart. This way, the gap to the upper tube wall 24 of the liner tube 12 is 12mm at the upstream part of the substrate 50, and 4mm at the downstream part, and the reactive gas is made into a high speed and uniform laminar flow above the substrate 50.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a compound semiconductor vapor phase growth apparatus.

[Prior art]

Conventionally, a thin film of a gallium nitride compound semiconductor (A I phase growth,
Light-emitting devices using the gallium nitride-based compound semiconductor thin film as a light-emitting layer are being researched. Since single-crystal wafers of gallium nitride-based compound semiconductors are not easily obtained, gallium nitride-based compound semiconductors are epitaxially grown on sapphire substrates having a lattice constant similar to that of gallium nitride-based compound semiconductors. In GaAs, a conical barrel-shaped MOVP
Using a vapor phase growth apparatus based on the E method, a large number of wafers are vapor phase grown at a time.

[Problem to be solved by the invention]

However, when crystals of gallium nitride-based compound semiconductors are grown on a sapphire substrate that is a foreign material and has a different lattice constant, the crystal growth is circular, so subtle disturbances in the reaction gas immediately lead to lattice defects. In addition, in the case of vapor phase growth of gallium nitride-based compound semiconductors, the high growth temperature increases the vapor pressure of group V elements, which tends to upset the stoichiometric balance, making it difficult to obtain a homogeneous crystal film with a large area. It is difficult to do so. Therefore, it is necessary to increase the flow rate without disrupting the laminar flow of the reaction gas. However, with conventional barrel-type vapor phase growth equipment, it is difficult to obtain a uniform gas flow, and the stoichiometric balance is easily lost.
With aN and the like, there are problems in that it is difficult to obtain a homogeneous crystal film with a large area, bits are likely to occur in the crystal, and the surface morphology is poor. The present invention has been made to solve the above problems, and its purpose is to grow a compound semiconductor, particularly a gallium nitride compound semiconductor, on a sapphire substrate in a barrel-type vapor phase growth apparatus. An object of the present invention is to provide an apparatus for growing a large amount of crystals in which the growth rate and crystal quality are less dependent on location.

[Means to solve the problem]

The structure of the invention for solving the above problem is that, in an apparatus for vapor phase growth of a compound semiconductor thin film using an organometallic compound gas, the compound semiconductor thin film is grown in a conical shape that is sharply pointed toward the upstream side of the reaction gas flow. a barrel-shaped susceptor on which a large number of substrates to be grown are disposed on its side; and a liner that covers the upper part of the side surface of the susceptor on which the substrates are disposed with a minute gap and also covers the susceptor from the upstream side of the reaction gas. A tube, and a plurality of introduction tubes for separating and guiding the reaction gas into the inside of the liner tube.

[Effect]

A substrate for crystal growth is placed on a barrel-shaped susceptor with a conical shape. The susceptor is covered with a conical liner tube with a minute gap left at the side surface on which the substrate is placed. Therefore, the reaction gas introduced into the liner tube through the introduction tube is mixed at the upstream portion of the liner tube, and at the top of the substrate, the gas flow is constricted to create a high-speed laminar flow that is uniform in the circumferential and radial directions. can get. [Effects of the Invention] As a result, uniform crystal growth is possible regardless of the position of the side surface of the conical susceptor, and a large number of crystal-grown wafers can be obtained at one time.

【Example】

The present invention will be described below based on specific examples. In FIG. 1, the quartz tube 10 has an O-ring 15 at its upper end.
46.47 and nut 48.49 using the cushioning material 38 and fixture 39.
It is fixed to the flange 14 at several locations by, for example, The lower end of the quartz tube 10 is sealed with an O-ring 40 and fixed to the flange 27 with screw fixing devices 41 and 42. An inner chamber 11 surrounded by a quartz tube 10 is provided with a liner tube 12 for guiding a reaction gas. The liner pipe 12 has a conical shape that widens in the downstream direction of the gas. Therefore, the cross section perpendicular to the axis of the liner tube 12 has a circular shape whose radius increases along the X-axis direction, which is the direction of gas flow, as shown in FIGS. 2 to 5. Further, on the downstream side, the liner pipe 12 covers a conical barrel-shaped susceptor 20 from the upstream side. At the side surface of the susceptor 20 on which a large number of sapphire substrates 50 are placed, the liner tube 12 is connected to the susceptor 20.
covered with a tiny gap. That is, the gap between the sapphire substrate 50 and the upper tube wall 24 of the liner tube 12 facing it is 12 mm at the upstream portion of the sapphire substrate 50 and 4ffII6 at the downstream portion. In this way, in this embodiment, the minute gap 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 substrate 50. An operating rod 26 is connected to the susceptor 20, and by removing the flange 27 and using the operating rod 26, the susceptor 20 on which the sapphire substrate 50 is mounted can be installed inside the liner tube 12, or when crystal growth is finished. , the susceptor 20 can be taken out from the liner pipe 12. Further, on the upstream side of the liner pipe 12, a first gas pipe 28 and a second gas pipe 29 are arranged. The first gas pipe 28 is located inside the second gas pipe 29, and both pipes 28 and 29 are coaxial and have a double pipe structure. The second of the first gas pipe 28
A large number of holes 3o are made in the periphery of the part not covered by the gas pipe 29, and a large number of holes 3o are made in the second gas pipe 29 as well.
o is opened. Then, the reaction gas introduced through the first gas pipe 28 is blown into the liner pipe 12, where it is first mixed with the gas introduced through the second gas pipe 29. The first gas pipe 28 is connected to a first manifold 31 and the second gas pipe 29 is connected to a second manifold 32. The 17th second hold 31 includes a carrier gas supply system I, a trimethyl gallium (hereinafter referred to as "rTMG") supply system J, and a trimethyl aluminum (hereinafter referred to as "rTMG") supply system I.
diethylzinc (hereinafter referred to as r) in the supply system of
The 27th second hold 32 is connected to an NHs supply system H and a carrier gas supply system I. A cooling pipe 33 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 disposed on the outer periphery of the cooling pipe 33. Further, the liner pipe 12 is connected to the outer pipe 35 via the flange 14.
The carrier gas is introduced into the external pipe 35. Further, a thermocouple 43 for measuring the temperature of the sample is arranged on the sample mounting surface 20a on the side surface of the susceptor 20, and a conductive wire 44°45 connected to the thermocouple 43 runs along the operating rod 26. and extends to the outside, so that the temperature of the sample can be measured from the outside. With this device configuration, the mixed gas of TMG, TMA, DEZ, and H2 led through the first gas pipe 28 and the mixed gas of NH3 and H2 led through the second gas pipe 29 are The mixed reaction gases are mixed near the outlet and are guided to the susceptor 20 side by the liner tube 12 and pass through the gap formed between the sapphire substrate 50 and the upper tube wall 24 of the liner tube 12. At this time, the flow of the reaction gas on the sapphire substrate 50 becomes a uniform laminar flow in the circumferential direction and height direction of the cone due to the minute gaps. As a result, high-quality crystals with less location dependence on the substrate grow. In addition, when forming an N-type (DA I When forming an AJII Gat-x N thin film,
DEZ is supplied to the first gas pipe 28 and the second gas pipe 29I!
: All you have to do is let the respective mixed gases flow out. When forming a type A I
By doping with N, type Aj2xGa+-xN is obtained. Next, using this apparatus, crystal growth was performed on the sapphire substrate 50 in the following manner. First, it was cleaned by organic cleaning and heat treatment (0001)
A single-crystal sapphire substrate 50 having a main surface is attached to the susceptor 20. Next, the sapphire substrate 50 was vapor-phase etched at a temperature of 1100° C. while flowing H2 into the liner tube 12 through the m1 gas pipe 28, the second gas pipe 29, and the external pipe 35 at a rate of 31/min. Next, the temperature is lowered to 400°C, and H3 is supplied from the first gas pipe 28 at 101/min.
50 cc/min of H3 bubbled in TMA at 5°C;
H2 from the second gas pipe 29 for 1017 minutes, NH, for 101 minutes
/min for 2 minutes. In this growth step, the AIN buffer layer 51 was formed to a thickness of about 250 Å, as shown in FIG. Next, stop the supply of TMA and raise the sample temperature to 1150°C.
Hl is supplied from the first gas pipe 28 at 101/min, -1
100 cc/H2 bubbled in TMG at 5°C
min, H3 from the second gas pipe 101/min, NH, 101/min
/min for 60 minutes to grow eight layers 52 made of N-type GaN with a film thickness of about 7 mm. As a result of measuring the S8M image and the RHBBD image of this eight layer 52, it was found that good crystals were obtained. Further, the film thickness of the sapphire substrate 500 in the width direction (direction perpendicular to the gas flow) and length direction (direction parallel to the gas flow) was measured, and a uniform film thickness was obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a vapor phase growth apparatus according to a specific embodiment of the present invention, and FIGS. 2, 3, 4, and 5 show a liner tube perpendicular to the Cross-sectional view, FIG. 6 is a cross-sectional view showing the structure of a thin film grown on a sapphire substrate. 10...-Quartz tube 12°...Liner tube 20...Susceptor 28...First gas pipe 29...-Second gas pipe 50...
Sapphire substrate 51...AIN buffer layer 52...N layer H...-NH, supply system ■...Carrier gas supply system J-...-TMG supply system K...TMA supply system L...DEZ supply system

Claims (1)

[Claims] In an apparatus for vapor phase growth of a compound semiconductor thin film using an organometallic compound gas, a large number of substrates having a conical shape with a sharp point toward the upstream side of a reaction gas flow and on which a compound semiconductor thin film is grown are formed. a barrel-shaped susceptor disposed on a side surface; a liner tube that covers the upper part of the side surface portion of the susceptor on which the substrate is disposed with a minute gap and also covers the susceptor from the upstream side of the reaction gas; and the liner tube. A compound semiconductor vapor phase growth apparatus comprising: a plurality of introduction pipes for separating and guiding a reaction gas into the interior of the apparatus;