JPH02291111A - Vapor growth apparatus for compound semiconductor - Google Patents

Abstract

PURPOSE:To execute a crystal growth operation by which a growth speed and a quality of a crystal are little dependent on a place by a method wherein an introduction gas tube used to guide a reaction gas up to a substrate on which a compound semiconductor thin film is grown is installed and a blowoff port, facing the substrate, of the introduction gas tube is made long along a width direction of the substrate and is made short and flat in a height direction of the substrate. CONSTITUTION:An introduction gas tube 70 is installed so as to be extended up to a position A on the immediately left side of a sapphire substrate 50; reaction gases which have been blown off from a first gas tube 28 and a second gas tube 29 are guided to the sapphire substrate 50. A plane shape of the introduction gas tube 70 is made wide as it goes to the downstream side. A mixed gas of TMG (trimethylgallium), TMA(trimethylaluminum), DEZ(diethyl zincate) and H2, which bas been intruded by the first gas tube 28, and a mixed gas of NH3 and H2, which has been introduced by the second gas tube 29, are mixed near exits of these tubes; this mixed reaction gas is guided to a susceptor 20 by using the introduction gas tube 70; a gas stream on the sapphire substrate 50 becomes uniform; it is possible to obtain a crystal which is little dependent on a place.

Description

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

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

[Prior art]

Conventionally, organometallic compound vapor phase epitaxy (hereinafter [M○VPEJ
gallium nitride-based compound semiconductor (AA
Research is being carried out on vapor phase growth of a thin film (XGa, -XN; including X=0) on a sapphire substrate, and on light-emitting devices using the gallium nitride compound semiconductor thin film as a light-emitting layer. 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 that have a similar lattice constant to that of gallium nitride-based compound semiconductors. And MOVPE, which is used in conventional GaAs etc.
In a vapor phase growth apparatus using this method, a reaction gas is uniformly flowed into a reaction chamber to grow uniform crystals on a substrate without location dependence.

[Problem to be solved by the invention]

However, when crystals of a gallium nitride-based compound semiconductor are grown on a zaphire substrate that is a foreign material and has a different lattice constant, crystal growth is difficult, and 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 III 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. Therefore, as shown in FIG. 12, in order to improve the flow rate of the reactive gas, the present inventors guided the reactive gas to the side of the substrate 1 through a thin introduction tube 2 with a circular outlet, and By creating a high-speed flow of reactive gases, we were able to grow crystals of gallium nitride-based compound semiconductors even on sapphire substrates. However, when the purpose is to manufacture large-area, uniform gallium nitride compound semiconductor wafers with no location dependence,
With this method, it was found that the thickness of the elongate crystal and the quality of the crystal depend on the location. That is, as shown in Fig. 13, there are changes in the thickness of the crystal grown in the width direction (Y direction) of the substrate perpendicular to the gas flow in the upstream, middle, and downstream of the gas flow, and the thickness of the crystal grown is uniform. It wasn't thick. The present invention has been made to solve the above-mentioned problems, and its purpose is to solve the problems described above.
An object of the present invention is to provide an apparatus for growing a gallium nitride-based compound semiconductor on a zaphire substrate, with the growth rate and quality of the crystal less dependent on location.

[Failure to solve the problem]

The structure of the invention for solving the above problem is that an apparatus for vapor phase growth of a compound semiconductor thin film using an organometallic compound gas includes an introduction gas pipe for guiding a reaction gas to a substrate on which a compound semiconductor thin film is grown; The outlet of the introduction gas pipe facing the substrate is long in the width direction of the substrate and short in the height direction of the substrate, and is flat. In particular, this device uses a gallium nitride-based compound semiconductor (A It x Ga 1-XN;
-0)) is ideal for vapor phase growth.

[Action and effect]

An introduction gas pipe is provided to guide the reaction gas to the substrate on which the compound semiconductor thin film is grown, and the outlet facing the substrate of the introduction gas pipe is made long along the width direction of the substrate and short and flat in the height direction of the substrate. Therefore, the gas flow of the reaction gas blown out from the outlet is made uniform along the width direction of the substrate surface and the gas flow direction. That is, it is considered that the gas flow on the substrate is made uniform over the entire range. As a result, high-quality crystals with little location dependence were obtained.

【Example】

The present invention will be described below based on specific examples. FIG. 1 is a block diagram of a vapor phase growth apparatus according to a specific embodiment of the present invention. The quartz tube 10 is sealed with an O-IJ ring 15 at its left end and comes into contact with the flange 14, and is fixed to the flange 14 at several locations using a buffer material 38 and a fixture 39 with bolts 46, 47 and nuts 4849, etc. ing. Further, the right end of the quartz tube 10 is sealed with a circle ring 40 and fixed to the flange 27 with a screw fastener 4142. A reaction tube 12 is disposed in an inner chamber 11 surrounded by a quartz tube 10 . One end 13 of the reaction tube 12 has a flange 14
The other end 1 is held by a holding plate 17 fixed to the
The bottom part 18 of 6 is held on the quartz tube 10 by holding legs 19. On the downstream side of the reaction tube 12, a sample mounting chamber 21 having a rectangular cross section perpendicular to the X-axis in which the susceptor 20 is mounted is integrally connected. A susceptor 20 is placed on the bottom 22 of the sample placement chamber 21 . The susceptor 20 has a rectangular cross section perpendicular to the X-axis, but its upper surface 23 is gently inclined in the positive direction of the Z-axis with respect to the X-axis. The susceptor 20
A sample, that is, a rectangular sapphire substrate 50 is placed on the upper surface 23 of the
is placed. An operation rod 26 is connected to the susceptor 20, and by removing the flange 27 and using the operation rod 26, the susceptor 20 on which the zaphire substrate 50 is mounted can be installed in the sample mounting chamber 21, or when the crystal growth is finished. , TheSepta 20 can be taken out from the sample placement chamber 21. Furthermore, a first gas pipe 28 and a second gas pipe 29 are open on the upstream side of the reaction tube 12. The first gas pipe 28 is located inside the second gas pipe 29, and both the pipes 28 and 29 are coaxial and have a double pipe structure. A large number of holes 30 are opened around the second gas pipe 29, and the gas introduced through the second gas pipe 29 is passed through the holes 30.
Blows out from 0. A large number of holes 30 are also made in the peripheral part of the first gas pipe 28 that is not covered by the second gas pipe 29, and the reaction gas introduced through the first gas pipe 28 is passed through the second gas pipe 29. It is first mixed with the gas introduced through the gas pipe 29. The first gas pipe 28 is connected to the seventeenth second hold 31, and the second gas pipe 29 is connected to the second eyebrow hold 32. The 17th second hold 31 has a carrier gas supply system I and 1 to remethyl gallium (hereinafter referred to as rTMG).
A supply system J for trimethylaluminum (hereinafter referred to as I'TMAJ) is connected to a supply system K for trimethylaluminum (hereinafter referred to as I'TMAJ) and a supply system L for diethylzinc. A supply system H is connected. In addition, one end of the introduction gas pipe 70 is held by the holding plate 17, and the reaction gas blown out from the upstream side of the sample mounting chamber 21, that is, the position A immediately to the left of the sapphire substrate 50, is transferred to the sapphire substrate 50. leading up to. The cross section of the introduction gas pipe 70 perpendicular to the long axis (X-axis) of the quartz tube 10 varies depending on the position in the X-axis direction, as shown in FIGS. 2 to 4, and the planar shape of the introduction gas pipe 70 is As shown in FIG. 5, the width increases toward the downstream side. That is, the reaction gas flows in the X-axis direction, but the upstream side of the gas flow is circular as shown in Figure 2, and the downstream side (
As it advances in the positive X-axis direction, it becomes an ellipse with the Y-axis as its major axis, expanded in the major axis direction, and contracted in the minor axis direction, and at position A, which is slightly upstream where the susceptor 20 is placed,
That is, as shown in FIG.
It has an oblate elliptical shape that is thinner in the Z-axis direction and longer in the Y-axis direction. The length of the air outlet 71 (cross-sectional view in the IV-IV direction of FIG. 4) in the Y-axis direction is 7 cm, and the length in the Z-axis direction is 1.2 cm. A cooling pipe 33 for circulating cooling water is formed on the outer circumference of the quartz tube 10, and a high-frequency coil 34 for applying a high-frequency electric field is disposed on the outer circumference of the cooling pipe 33. Further, the reaction tube 12 is connected to an external tube 35 via a flange 14, and a carrier gas is introduced from the external tube 35. Further, an introduction pipe 36 extends from the outside into the sample holding chamber 21 by passing through the flange 14 from the side.
A thermocouple 43 and its conductive wire 44 are installed to measure the temperature of the sample.
45, and is configured so that the sample temperature 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 exit and guided to the septa 20 by the introduction gas pipe 70, so that the gas flow on the sapphire substrate 50 becomes uniform and a crystal with little location dependence is obtained. When forming an N-type AAxGa+-xN thin film, D
After stopping the supply of EZ, the first gas pipe 28 and the second gas pipe 2
It is sufficient to let the mixed gas flow out from 9, and the I type AAxGa
When forming an l-xN thin film, it is sufficient to supply DEZ and cause the mixed gas to flow out from the first gas pipe 28 and the second gas pipe 29. When forming a type AβxGa+-xN thin film, DEZ is sprayed onto the sapphire substrate 50 and thermally decomposed, and the dopant element becomes an elongated Ajl! xGa+
-xN doped, ■-type AAx Ga+
N 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 septa 20. Next, the zaphire substrate 50 was vapor-phase etched at a temperature of 1100° C. while flowing H2 at 3 l/min into the introduction gas pipe 70 through the first gas pipe 28, the second gas pipe 29, and the external pipe 35. Next, the temperature is lowered to 400°C, and H2 is supplied from the first gas pipe 28 to 10. 12/min, 50cc/min of H2 bubbled in TMA at 15°C.
10 l/min of H2 from the second gas pipe 29 and 1/min of NH3 from the second gas pipe 29.
．． 0! It was supplied for 2 minutes at 11 minutes. In this growth process, a buffer layer 51 of /W2N was formed to a thickness of about 250 mm, as shown in FIG. Next, stop the supply of TMA and raise the sample temperature to 1150°C.
H2 from the first gas pipe 28]0β/min, 15
H2 bubbled through TMG at 100 cc/min, H2 from the second gas pipe 29 at 10 l/min, and NH3 at 10 cc/min.
The supply was carried out at a rate of 1/min for 60 minutes to grow an N layer 52 made of N-type GaN with a film thickness of approximately 7 cm. The SEM layer and old IEIED image of this N layer 52 were measured. The results are shown in FIGS. 7 and 8. Furthermore, the relationship between the thickness and position of the N layer of N-type GaN was measured. The results are shown in FIGS. 9, 10, and 11. As can be seen from FIG. 9, the film thickness gradually decreases up to 20 mm from the upstream end of the Zaphire substrate 50, but after 20 mm
Further downstream, the film thickness became uniform. In the width direction, on the upstream side, as shown in Figure 10,
The film thickness is somewhat uneven, but downstream, the 11th
As shown in the figure, the film thickness became uniform. As explained above, by guiding the introduction gas pipe 70 to the immediate side of the sapphire substrate 50 and making its outlet 71 flat, the gas can be placed on the sapphire substrate 50 with less location dependence.
It was found that a crystalline film of aN could be 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, FIGS. 2, 3, and 4 are cross-sectional views of an inlet gas pipe of the apparatus, and FIG. Plan view of introduction gas pipe, No. 6
The figure is a cross-sectional view showing the structure of a thin film grown on a sapphire substrate, and Figures 7 and 8 are photographs showing the crystal structure of the grown N-type GaN thin film using a microscope (SEM), and old +1E
A photograph showing the crystal structure by ED, Figure 9 is N-type GaN
Figures 10 and 11 are characteristic diagrams showing the distribution of film thickness in the gas flow direction of the thin film, respectively, for an N-type GaN thin film.
Characteristic diagrams showing the distribution of film thickness in the width direction perpendicular to the gas flow direction in the upstream and downstream regions, Figure 12 is a schematic diagram of the vapor phase growth apparatus before improvement, and Figure 13 shows the film grown in the vapor phase growth apparatus. FIG. 2 is a characteristic diagram obtained by measuring the film thickness distribution in the width direction of an N-type GaN thin film. 10 Quartz tube 12 Reaction tube 20 Theceptor 21 Sample placement chamber 28 First gas tube 29 Second gas tube 50 Thefire substrate 5 1 -A A N buffer layer 5 2 -N layer 70 Introducing gas pipe 71 Air outlet H -N H 3 supply system ■ Carrier gas supply system J - T MG supply system K TMA supply system L
-D EZ supply system patent applicant Toyoda Gosei Co., Ltd. New Technology Development Corporation President of Nagoya University Figure 5 Figure 8 Figure 9 II Σ Position (mm)

Claims (1)

[Scope of Claims] An apparatus for vapor-phase growth of a compound semiconductor thin film using an organometallic compound gas, comprising an introduction gas pipe for guiding a reaction gas to a substrate on which the compound semiconductor thin film is grown; A vapor phase growth apparatus characterized in that an air outlet facing the substrate is long in the width direction of the substrate and short and flat in the height direction of the substrate.