JPH0677136A - Method and device for vapor growing compound semiconductor thin film crystal - Google Patents

Abstract

PURPOSE:To prevent thin film crystal deterioration and gas rectifier member blinding due to powder by supplying carrier gas in the vertical direction to a crystal substrate through the gas rectifier member and supplying material gas in the horizontal direction between the gas rectifier member and the crystal substrate. CONSTITUTION:A crystal substrate 11 is placed on the top plane of a disc- shaped rotating susceptor 10. A horizontal reacting tube 19 is used, a shower nozzle 12 is arranged above the crystal substrate 11 and two liner nozzles 13 and 14 are arranged on the side. The shower nozzle and the liner nozzles 13 and 14 are connected with gas supplying paths 16-18. After hydrogen purge, the rotating susceptor 10 is heated while introducing hydrogen gas and when the temperature of the crystal substrate 11 reaches 400 deg.C, ammonia is introduced into the reacting tube 19 through the bottom side liner nozzle 14. When the temperature of the crystal substrate 11 reaches 1000 deg.C, the disc-shaped rotating susceptor 10 is rotated and trimethyl gallium is introduced into the reacting tube 19 through the top side liner nozzle 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase growth method and a vapor phase growth apparatus suitable for application to the epitaxial growth of compound semiconductor thin film crystals on the surfaces of a large number of crystal substrates.

[0002]

2. Description of the Related Art Generally, in order to epitaxially grow a compound semiconductor thin film crystal on a crystal substrate surface, a carrier gas containing a plurality of raw material gases is fed to the crystal substrate in a heated state, and these raw material gases are deposited on the crystal substrate. The thermal decomposition reaction is usually performed, and typical vapor phase growth apparatuses therefor include a pancake type and a barrel type. The former vapor phase growth apparatus, a feed gas supply nozzle is arranged at the center of a disk-type rotary susceptor installed in a pancake-type reaction tube, and a carrier gas containing the feed gas is horizontally fed from the nozzle. By blowing out, the raw material gas is sent to a large number of crystal substrates placed on the rotary susceptor, while the latter vapor phase growth apparatus has a large number of crystal substrates around the barrel-type rotary susceptor. The material gas is sent to the crystal substrate by supplying it with a carrier gas containing the material gas from above, but in any vapor phase growth apparatus, unfavorable convection or eddy current tends to occur. Therefore, there is a problem in that a uniform thin film crystal cannot be grown on all of a large number of crystal substrates.

For this reason, one of the inventors of the present invention has previously proposed Japanese Patent Application No. 62-273445 (JP-A-1-117315).
Proposed the vapor phase growth method described in. In this method, as shown in FIG. 1, a gas rectifying member (for example, a partition plate 6 having a large number of small holes 7 functioning as gas outlets) is provided at a predetermined interval above the disc type rotary susceptor 5. The carrier gas containing the raw material gas is introduced from the upper supply port 3 of the reaction tube 2 and passes through the partition plate 6 to form a laminar flow in the shape of a shower, and then a plurality of crystal substrates is provided. 1 is sent to the surface. Therefore, by optimizing the area and shape of the small holes 7 of the partition plate 6 or the distribution of the hole diameters, it becomes possible to uniformly feed the raw material gas to all the crystal substrates 1, and the in-plane uniformity of the epitaxially grown crystal thin film can be obtained. Can be controlled within a desired range.

However, in this type of vapor phase growth method, the partition plate 6 is heated to a high temperature together with the crystal substrate 1 and the rotary susceptor 5, so that thermal decomposition occurs near the partition plate 6 and in the front chamber 8 of the reaction tube 2. It is not possible to prevent the reaction from occurring. When such a reaction occurs, undesired powder or solid matter is generated and floats, which hinders the growth of high-quality thin film crystals, and the generated powder or the like blocks the small holes 7 of the partition 6. Another troublesome problem occurs. Even if the partition plate 6 is cooled by some method, the crystal substrate 1
Since the radiant heat from (or the rotary susceptor 5) is strong, it is impossible to completely prevent the thermal decomposition reaction from occurring in the lower space of the partition plate 6.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, to deteriorate thin film crystals due to generation of powder or the like, and to gas rectifying member (shower nozzle, etc.).
An object of the present invention is to propose an improved crystal growth method and crystal growth apparatus capable of preventing the clogging of the crystal.

[0006]

Means for Solving the Problems Since the present invention is such that a plurality of raw material gases undergo a thermal decomposition reaction with each other, the present invention provides a high temperature partition plate (gas rectifying member) in a state where these raw material gases are mixed. Focusing on the problem of passing through itself, I came up with the idea of feeding carrier gas that does not contain raw material gas through a partition plate. Then, as a result of repeated experiments and consideration based on such an idea, even when the carrier gas alone was sent from the vertical direction through the partition plate, a desired plurality of raw material gases were provided in the space between the partition plate and the crystal substrate. It was confirmed that the thermal decomposition reaction necessary for crystal growth can be sufficiently caused by feeding another carrier gas containing the gas in a substantially horizontal direction.

Therefore, the object of the present invention is to feed a carrier gas alone (or in a state containing one source gas) toward a crystal substrate from a substantially vertical direction through a gas rectifying member, while a gas rectifying member and a crystal substrate. It can be effectively solved by adopting a vapor phase growth method characterized in that another carrier gas containing a plurality of raw material gases (or residual raw material gases) is fed from a substantially horizontal direction into a space between and. I can.

As long as the raw material gas is one of a plurality of raw material gases, it is also possible to supply the raw material gas by including it in a carrier gas which is vertically fed through a gas rectifying member. When one raw material gas is separated from the other raw material gas and supplied separately, it reacts with the other raw material gas even if the raw material gas comes into contact with the hot gas rectifying member and causes thermal decomposition. This is because it is impossible in principle to generate powder or the like.

In the above novel vapor phase growth method, a disk-type rotary susceptor for mounting a large number of crystal substrates and holding the crystal substrate in a heated state, and a predetermined space above the rotary susceptor. And a first gas supply means for feeding the carrier gas alone (or in a state containing one source gas) toward the crystal substrate from a substantially vertical direction through the rectifying member, and the rectifying member. A vapor phase growth apparatus provided with a second gas supply means for feeding another carrier gas containing a plurality of source gases (or residual source gases) from a substantially horizontal direction into a space between the crystal substrate and the substrate. It can be easily implemented.

The second gas supply means has a plurality of gas supply passages for separating the plurality of raw material gases from each other and then transporting the raw material gases into the space in order to prevent a thermal decomposition reaction of the raw material gas during transportation. It is desirable to have a function to feed a purge gas into the space in order to keep the inside of the reaction tube clean.

[0011]

[Function] First gas supply means for feeding a gas toward the crystal substrate from a substantially vertical direction through the gas rectifying member and another gas from a substantially horizontal direction into the space between the gas rectifying member and the crystal substrate. By using the crystal growth apparatus of the present invention which is provided with a second gas supply means for supplying the raw material gas, it is possible to arbitrarily control the supply conditions of the raw material gas so that the thermal decomposition reaction does not occur in the vicinity of the gas rectifying member. As a result, it is possible to simultaneously achieve two contradictory requirements (improvement of film thickness uniformity of thin film crystals and prevention of generation of undesired powder etc.) that could not be achieved by the above-mentioned conventional techniques. Become.

[0012]

EXAMPLES Below, MOVPE (metal-organic vapor de
position) method to epitaxially grow a compound semiconductor thin film crystal on the surface of a crystal substrate,
The present invention will be described in more detail with reference to examples.

Comparative Example 1 Using the general vertical growth furnace shown in FIG. 2, a thin film of gallium nitride (GaN) was formed on the surface of the sapphire crystal substrate 1 placed on the disc type rotary susceptor 5. The crystal was grown epitaxially. The source gas is
Trimethylgallium (TMG) and ammonia (N
H ₃ ) was used to mix these two raw material gases, dilute them with hydrogen gas (carrier gas), and simultaneously feed them from the gas feed port 3 above the reaction tube 2. The flow of mixed gas is
The direction is perpendicular to the surface of the crystal substrate 1. The crystal growth rate is calculated from the thickness of the generated gallium nitride thin film crystal,
As a result of calculating the utilization efficiency of the raw material gas from the values, trimethylgallium was about 10% and ammonia was about 0.01%. In addition, since a large amount of powder was generated, many projections that were considered to be caused by the generated powder were found on the surface of the thin film crystal.

<Comparative Example 2> A sapphire crystal substrate mounted on a disk-type rotary susceptor 5 using the vertical growth furnace of FIG. 1 equipped with a partition plate 6 (gas rectifying member) functioning as a shower nozzle. It was observed by epitaxially growing a thin film crystal of gallium nitride on the surface of 1. The mixed raw material gas consisting of trimethylgallium and ammonia was diluted with a carrier gas (hydrogen) as in the case of Comparative Example 1, and then simultaneously supplied from the gas supply port 3 above the reaction tube 2 and passed through the partition plate 6. Then, it was sent to the crystal substrate 1 as a shower-like laminar flow.
The utilization efficiency of the raw material gas was almost the same as that of Comparative Example 1, but the uniformity of the film thickness of the formed thin film crystal was ± 10% in comparison with that of Comparative Example 1. A significant improvement effect of 2% was confirmed. However, in the case of this comparative example, when a thin film crystal having a thickness of 1 μm was repeatedly grown 10 times, the small holes 7 of the partition plate 6 were completely clogged with the powder of the reaction product, and the subsequent epitaxial growth was performed. I couldn't continue.

Comparative Example 3 A gallium nitride thin film crystal is epitaxially grown on the surface of the sapphire crystal substrate 1 in the same manner as in Comparative Examples 1 and 2 using the well-known lateral growth furnace shown in FIG. I saw it. However, the mixed raw material gas composed of trimethylgallium and ammonia was sent by diluting it with a carrier gas (hydrogen) in parallel to the crystal substrate 1. The utilization efficiency of the raw material gas was even worse than in the cases of Comparative Example 1 and Comparative Example 2, with trimethylgallium remaining at about 5% and ammonia at about 0.005%.
However, when the face-down method in which the surface of the crystal substrate 1 is grown downward is adopted, the utilization efficiency of the raw material gas is about 10% for trimethylgallium and about 0.05% for ammonia, and the utilization efficiency of ammonia is Increased.

<Embodiment 1> FIG. 4 shows an embodiment of a vapor phase growth apparatus used in the crystal growth method according to the present invention.
In this device, a disc type rotary susceptor 10 having a diameter of 100 mm is used.
(Made of graphite), 50 mm x 50 on the top
A predetermined number of [0001] crystal substrates 11 made of sapphire having a size of mm were placed. As the reaction tube 19, as in the case of Comparative Example 3 (FIG. 2), a horizontal tube is used, and the crystal substrate 11 is used.
A shower nozzle 12 (a gas rectifying member for generating a laminar flow in the vertical direction) is arranged above the substrate at appropriate intervals, and two liner nozzles 1 are provided on the side of the substrate.
3, 14 (gas rectifying members for generating a laminar flow in the horizontal direction) were arranged. The shower nozzle 12 and the liner nozzles 13 and 14 were respectively connected to gas supply paths 16 to 18 for supplying a desired gas.

Prior to the growth of the thin film crystal, hydrogen purified through a palladium-type hydrogen purifier was introduced as a purge gas from the shower nozzle 12 and the liner nozzles 13 and 14 to clean the inside of the reaction tube 19. The purge gas flow rate is
It is set so as to be 10 cm / s or more on the surface of the crystal substrate 11, and the flow rate is at least 10 times or more.
The value was such that the gas in 9 was replaced. After the hydrogen purge, while continuously injecting hydrogen gas, the rotary susceptor 10 was heated by an appropriate high-frequency heating means (not shown) to raise the temperature of the crystal substrate 11 to a predetermined temperature.
The temperature of the crystal substrate 11 is finally 900 to 1050 ° C.
Is preferably in the range of 100, and in the case of this embodiment, 100
It was set to 0 ° C.

After the temperature of the crystal substrate 11 reached 400 ° C., ammonia diluted with hydrogen as a carrier gas was fed into the reaction tube 19 through the lower liner nozzle 14 from a substantially horizontal direction (see FIG. 5A). Partial pressure of ammonia gas in the reaction tube (partial pressure before growth) is 10 to 10 ² P
set to a. After the temperature of the crystal substrate 11 reached 1000 ° C., the temperature was kept as it was for several minutes, and the disk-type rotary susceptor 10 was rotated at a rate of 10 rotations / minute. Then, trimethylgallium diluted with hydrogen as a carrier gas is fed into the reaction tube 19 through the upper liner nozzle 13 from a substantially horizontal direction to cause a thermal decomposition reaction with ammonia in the reaction tube 19, and a gallium nitride thin film is formed on the surface of the crystal substrate 11. The crystal was vapor-grown to a thickness of about 1 μm. Reaction tube 1
The gas partial pressure of trimethylgallium in 9 was set to 1 Pa.

During the crystal growth, hydrogen gas (carrier gas) in a laminar flow state was fed through the shower nozzle 12 from a substantially vertical direction and uniformly sprayed on the entire crystal substrate 11. Regarding the in-plane uniformity, growth rate, quality, etc. of the thin film crystal, the amount of hydrogen gas supplied from each of the nozzles 12 to 14 should be adjusted so that the gas flow velocity and distribution in the upper space of the crystal substrate 10 have optimum values. Controlled by. In the case of the present embodiment, the amount of hydrogen supplied from the shower nozzle 12 is 4 liters / minute, the total amount of trimethylgallium and hydrogen supplied from the upper liner nozzle 13 is 1 liter / minute, and the lower liner nozzle is The total amount of ammonia and hydrogen supplied from 14 was set to 1 liter / min. The reaction gas in the reaction tube 19 was exhausted using a vacuum pump (not shown), and the pressure inside the furnace was adjusted to 10 ⁴ Pa in the upper space of the crystal substrate 11. The partial pressure of ammonia gas was maintained at 10 Pa during the crystal growth period.

As a result of performing the crystal growth under the above conditions, the utilization efficiency of the raw material gas obtained from the growth rate of the gallium nitride thin film crystal was 14% for trimethylgallium, but 1.4% for ammonia. I was able to make a big improvement. The number of protrusions on the surface of the thin film crystal caused by the generation of powder was extremely small, and the shower nozzle 12 was not clogged. This effect did not change particularly after performing the crystal growth operation 10 times or more. The uniformity of the film thickness was extremely good at ± 2% or less in the plane of 50 nm × 50 nm. Table 1 shows the results when the crystal growth was performed by changing the source gas supply conditions. The symbols A to E entered in the first column of the table correspond to the source gas supply systems shown in FIGS. 5A to 5E, respectively, and in each case, trimethylgallium, which is the source gas of the group III element, and It is common in that it is mixed with ammonia, which is a source gas of the group V element, in the form of being mixed with each other and does not pass through the shower nozzle 12.

Among the five source gas supply systems shown in FIG. 5, the gas supply systems shown in FIGS. 5A, 5D and 5E include the carrier gas (hydrogen) alone from the vertical direction in the reaction tube 1.
While supplying into the inside 9, shower nozzle 12 and crystal substrate 1
1 supplies all the source gas together with the carrier gas (hydrogen) into the reaction tube 19 from a substantially horizontal direction in the space between them. In addition, FIGS. 5B and 5C show that one source gas is the carrier gas. Reaction tube 1 with (hydrogen) from almost vertical direction
While supplying into the inside 9, shower nozzle 12 and crystal substrate 1
Carrier gas (hydrogen) with other source gas in the space between
In addition, the gas is supplied into the reaction tube 19 from a substantially horizontal direction. In the former case, as shown in FIG. 5D, for example, it is possible to mix all the raw material gases from the beginning and transport them in a carrier gas, but prevent an unexpected thermal decomposition reaction during transportation. In order to
As shown in A and FIG. 5E, it is desirable that the raw material gases are separately separated and transported using different gas supply paths 17 and 18 on the way to the reaction tube 19.

[0022]

[Table 1]

As is clear from Table 1, the effect of improving the film thickness uniformity and the raw material utilization efficiency was recognized in all gas supply systems. Among them, the gas supply methods B and C are particularly excellent in that the generation of powder in the shower nozzle 12 is suppressed and the productivity is improved. The reason is that the crystal substrate side of the shower nozzle 12 is always purged by the hydrogen gas supplied from the upper liner nozzle 13, and the generation of powder is effectively suppressed. The gas supply systems A and E had no particular problems in practical use. Although the gas supply method D was found to have some improvement effect as compared with the conventional method, it was not so remarkable.

Even when the crystal substrate side of the shower nozzle 12 was constantly purged, there was substantially no effect on crystal growth. The reason is that, as shown in FIGS. 5B and 5C, due to the horizontal gas flow, the two boundary layers cause the shower nozzle 1 to move.
As a result of being formed on the lower surface of 2 and the upper surface of the crystal substrate 11, one source gas supplied from the shower nozzle 12 diffuses through these boundary layers and reaches the surface of the crystal substrate 11, and is then discharged from the lower nozzle 14. This is because it reacts with other supplied source gases to grow an epitaxial crystal. However,
In order to make the diffusion of one source gas supplied from the shower nozzle 12 smoother, the distance l between the crystal substrate 11 and the shower nozzle 12 is set to the thickness of the upper boundary layer and the thickness of the lower boundary layer as shown in the figure. It is desirable to make it about the same as the sum of Sasano.

<Embodiment 2> Using the crystal growth furnace shown in FIG. 4, a gallium arsenide (GaAs) epitaxial thin film crystal is grown on a gallium arsenide (GaAs) crystal substrate in the same manner as in Embodiment 1. Let However, in this example, trimethylgallium (TMG) and arsine (AsH ₃ ) were used as source gases. The temperature of the substrate during crystal growth is 500 to 800 ° C., and the pressure in the furnace is 10 ³ to 10 ⁵ Pa.
In the furnace, the partial pressure of trimethylgallium in the furnace is 10 to ¹ to 1
Within the range of 0 Pa, the partial pressure of arsine in the furnace is 10 to ¹ to 10 ³ Pa.
Set to the range of. The obtained gallium arsenide thin film crystal was of extremely high purity and high uniformity as in the case of Example 1.

<Application> In the above, the case where the gallium nitride or gallium arsenide thin film crystal is vapor-phase-grown on the surface of the crystal substrate has been described. However, the present invention may be appropriately modified by a slight modification. By means of other compound semiconductor thin film crystals such as aluminum nitride (AlN),
III-V group compound semiconductors such as indium nitride (InN), indium phosphide (InP), indium arsenide (InAs), aluminum arsenide (AlAs) and aluminum phosphide (AlP), and thin film crystals composed of these mixed crystal semiconductors In addition, II-VI group compound semiconductors such as zinc selenide (ZnSe), zinc sulfide (ZnS), cadmium telluride (CdTe), and mercury telluride (HgTe), and thin film crystals of these mixed crystal semiconductors are grown by vapor phase growth. It is also possible to apply when making it.

Further, although the above-mentioned embodiment has explained the case where the thin film crystal is grown by using the lateral growth furnace, the present invention can be modified as shown in FIG. In addition to the vertical growth furnace shown, it can be applied to the case of growing a thin film crystal using various crystal growth furnaces.

[0028]

According to the crystal growth method or apparatus according to the present invention, the film thickness uniformity of the thin film crystal in each crystal substrate and the film thickness uniformity of the thin film crystal among a plurality of crystal substrates are significantly improved. In addition to being able to prevent the deterioration of the surface of the thin film crystal and the clogging of the gas rectifying member (shower nozzle, etc.) due to the generation of powder or solid matter, the raw material gas can be used to grow the thin film crystal. It is possible to widely control the supply conditions of.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a conventional vertical crystal growth apparatus equipped with a shower nozzle.

FIG. 2 is a vertical sectional view showing an example of a conventional general vertical crystal growth apparatus.

FIG. 3 is a vertical sectional view showing an example of a conventional general horizontal crystal growth apparatus.

FIG. 4 is a vertical sectional view showing an embodiment of a crystal growth apparatus according to the present invention.

5 is a vertical cross-sectional view showing some aspects of a source gas supply system that can be used in the crystal growth apparatus of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Crystal substrate, 2 ... Reaction tube, 3 ... Gas supply port, 4 ... Gas exhaust port, 5 ... Rotating susceptor, 6 ... Partition plate, 7 ... Small hole, 8
... front chamber part, 10 ... rotating susceptor, 11 ... crystal substrate, 1
2 ... Shower nozzle (gas straightening member), 13, 14 ... Liner nozzle, 15 ... Gas exhaust port, 16-18 ... Gas supply path, 19 ... Reaction tube.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoji Kuma 3550 Kidayomachi, Tsuchiura City, Ibaraki Prefecture Hitachi Cable Co., Ltd. Advanced Research Center

Claims (4)

[Claims] 1. A thin film of a compound semiconductor by feeding a plurality of raw material gases into a large number of crystal substrates placed on a disk-type rotary susceptor and heated to cause a thermal decomposition reaction of these raw material gases on the substrate surface. In a method of vapor phase growing a crystal, a gas rectifying member is arranged above a crystal substrate at a predetermined interval, and a carrier gas alone (or a state containing one source gas) is almost vertical through the rectifying member. While being fed from a direction toward the crystal substrate, another carrier gas containing a plurality of raw material gases (or residual raw material gas) is fed from a substantially horizontal direction into a space between the rectifying member and the crystal substrate. Vapor growth method. 2. A disk-type rotary susceptor for mounting a large number of crystal substrates and holding the crystal substrate in a heated state, a gas rectifying member disposed above the rotary susceptor at a predetermined interval, and the rectifying member. In the space between the rectifying member and the crystal substrate, there is provided a first gas supply means for feeding the carrier gas alone (or in a state containing one source gas) toward the crystal substrate from a substantially vertical direction through the member. A vapor phase growth apparatus for a compound semiconductor thin film crystal, comprising: a second gas supply means for feeding another carrier gas containing a plurality of source gases (or residual source gases) from a substantially horizontal direction. . 3. The second gas supply means is provided with a plurality of gas supply passages for separating and transporting a plurality of source gases from each other, and then feeding the plurality of source gases into the space. 2. The vapor phase growth apparatus according to 2. 4. The vapor phase growth apparatus according to claim 2 or 3, wherein the second gas supply means has a function of feeding a purge gas into the space.