JPH0727868B2 - Vapor phase growth equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a vapor phase growth apparatus for obtaining a film formation substrate by flowing a vapor phase growth gas in parallel with a substrate surface.

[Conventional technology]

The film-forming substrate is obtained by forming a growth film by thermochemically reacting the raw material gas in the vapor-phase growth gas and depositing a reaction product on the substrate surface. In this case, the vapor growth gas in the present invention means at least one source gas H ₂ (hydrogen), He.
(Helium), Ar (argon), N ₂ (nitrogen), and other gases diluted with a diluting gas. The source gas is an individual component gas that contributes to the vapor phase growth reaction, such as SiH ₄ (silane). , AsH ₃ (arsine), TMG (trimethylgallium) vapor, etc.

The source gases are used alone or as a mixture depending on the purpose. For example, when forming a GaAs film on a GaAs (gallium arsenide) substrate, both AsH ₃ and TMG vapor source gases are diluted with H ₂ for vapor phase growth. Use gas. An example of a conventional vapor phase growth apparatus will be described below with reference to the drawings.

FIG. 3 is a sectional view of a conventional vapor phase growth apparatus, and 1 is a cylindrical reaction tube. The reaction tube 1 has a vapor growth gas introduction tube 2 at one end.
Has a gas discharge pipe 3 at the other end, and a holding table (susceptor) 4 is provided inside, and the vapor growth gas introduction pipe 2 side of the holding table 4 smoothes the flow of the vapor growth gas. A flow channel 5 is provided. Incidentally, 6 is an RF coil provided on the outer circumference of the reaction tube 1.

In the conventional apparatus thus configured, the unprocessed substrate 7 is placed on the holding table 4, the holding table 4 is heated by the RF coil 6, and the substrate 7 is held at a predetermined high temperature through the holding table 4. At the same time, the vapor-phase growth gas is introduced laterally into the reaction tube 1 from the vapor-phase growth gas introduction tube 2 and flows over the surface of the substrate 7 placed on the holding table 4 provided in the reaction tube 1. By this operation, the vapor growth gas flows in the reaction tube 1 in parallel with the surface of the substrate 7 and is thermally decomposed in a high temperature portion near the substrate 7 to deposit a reaction product on the surface of the substrate 7 to form a growth film.

[Problems to be solved by the invention]

However, the conventional device has a drawback that the grown film does not have a uniform thickness and a good film formation substrate cannot be obtained. This is because the raw material gas in the vapor phase growth gas becomes a reaction product and the substrate 7
Even if the gas gradually grows on the surface, the supply of the source gas from the vapor-phase growth gas in the upper layer cannot be done in time, so that the source gas in the vapor-phase growth gas flowing on the surface of the substrate 7 decreases along the flow. This is because there is a concentration distribution, and as a result, the growth film on the surface of the substrate 7 is formed thicker on the upstream side and thinner on the downstream side. Further, since the vapor-phase growth gas is thermally decomposed and deposited in a high temperature portion near the substrate 7, a deposit 8 (hereinafter referred to as a harmful deposit 8) is also formed on the upstream side of the substrate 7.
That is, the surface of the harmful deposit 8 is peeled off and is accompanied by the vapor phase growth gas to adhere to the growth film on the surface of the substrate 7 to cause defects. And this increases as the amount of harmful deposits 8 increases. Therefore, normally, the defect rate of the grown film is checked while repeating the vapor phase growth process in batches, and when the defect rate exceeds a predetermined rate, the vapor phase growth process is interrupted and the inside of the reaction tube 1 is cleaned to remove the harmful deposition. Although the object 8 is removed, the conventional apparatus has a large amount of harmful deposits, and therefore frequent cleaning is indispensable, which is poor in productivity.

Therefore, a method of performing vapor phase growth in a state in which the substrate is inclined with respect to the flow direction of the vapor phase growth gas has been proposed against these disadvantages. According to this method, the thickness of the growth film formed on the substrate surface can be made uniform in the flow direction of the vapor growth gas, but since the vapor growth gas flows in a laminar state, the flow velocity at the center is high. In the direction perpendicular to the flow of the vapor deposition gas, the central portion is thick and the peripheral portion is thin, and the thickness is not uniform. In addition, if the substrate is tilted as described above, there is a new inconvenience that the substrate transfer mechanism for automatically transferring the substrate onto the holding table becomes complicated, and the harmful deposit is not reduced by this method. Productivity is not improved.

As still another method, a method of horizontally rotating the holding table 4 shown in FIG. 3 has been proposed. According to this method, the growth film can be made to have a uniform thickness, but it requires a separate rotation mechanism to complicate the apparatus configuration, and this method does not reduce the harmful deposits nor improve the productivity. .

[Means for solving problems]

The present invention has been made in view of the above-mentioned inconvenience, and provides a vapor phase growth apparatus capable of forming a uniform growth film and reducing the amount of the harmful deposit upstream of the substrate to improve the productivity. The feature is that the vapor phase growth gas flowing in the reaction tube in the lateral direction is flown onto the substrate surface placed on the holding table provided in the reaction tube to grow on the substrate surface. In a vapor phase growth apparatus for forming a film, a part in the reaction tube upstream of the substrate is divided into an upper channel and a lower substrate surface side channel by a partition plate arranged in parallel with the substrate surface to form a vertical parallel channel. That is, the vapor phase growth gas introduction pipe is formed in the upper flow path, and the intervening gas introduction pipe is connected in the lower substrate surface side flow path.

〔Example〕

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

FIG. 1 is a sectional view of a vapor phase growth apparatus according to this embodiment, and FIG. 2 is a sectional view taken along line II-II of FIG. 1, in which the same components as those in FIG. is there.

In the figure, 10 is a partition plate arranged in the reaction tube 1 upstream of the substrate 7 in parallel with the surface of the substrate 7. And a lower substrate surface side channel 9b to form an upper and lower parallel channel 9, and an upper growth channel 9a is provided with a vapor growth gas introducing pipe 11 and a lower substrate surface side channel 9b.
Intervening gas introducing pipes 12 are connected to 9b, respectively. Partition plate 10
Is a plate-like object having a length that does not reach the substrate 7, and its end on the substrate side
As shown in FIG. 2, the reference numeral 10a is formed in a shape that bulges out, for example, in a semicircular shape so that the central portion bulges out along the longitudinal direction.

The apparatus of the present embodiment configured as described above holds the substrate 7 at a predetermined temperature, introduces the intervening gas into the intervening gas introduction pipe 11 and introduces the vapor growth gas into the vapor growth gas introduction pipe 12, respectively. use. In this case, as the intervening gas, a diluting gas or a gas in which a small amount of a volatilization suppressing gas is added is used. The volatilization suppressing gas is a gas for suppressing volatilization of a component of the substrate 7 which is volatilized by heat. For example, in the case of a GaAs substrate, As is used to prevent volatilization of As.
A small amount of H ₃ is used as a suppressing gas.

As described above, the vapor-phase growth gas and the intervening gas separately flow in parallel in the upper channel 9a and the lower substrate surface side channel 9b of the upper and lower parallel channel 9, and the substrate side end portion 10a of the partition plate 10 is separated. After passing through, the interstitial gas flows toward the substrate 7 while diffusing with each other. Therefore, the intervening gas approaches the surface of the substrate 7 while gradually increasing the concentration of the raw material gas. The raw material gas in the vapor phase growth gas continuously enters the intervening gas, and the raw material gas in the intervening gas becomes a reaction product and is successively deposited on the surface of the substrate 7. Therefore, by appropriately adjusting the intervening gas, the flow velocity of the vapor growth gas, and the concentration of the raw material gas in the vapor growth gas, the amount of the raw material gas flowing from the vapor growth gas into the interposing gas and the interposition gas due to the deposition on the surface of the substrate 7 It is possible to balance the amount of the raw material gas disappeared per unit time per unit time, thereby forming a growth film having a uniform film thickness with a uniform concentration distribution of the raw material gas in the intervening gas when passing through the surface of the substrate 7 As a result, a good film formation substrate can be obtained.

Further, the intervening gas flows from the substrate-side end portion 10a onto the surface of the substrate 7 in a state where the source gas concentration thereof is lower than that of the vapor phase growth gas. The number of cleanings is reduced and the number of cleanings is also reduced, which improves productivity.

As described above, by providing the partition plate 10, the film thickness of the deposited film can be made uniform in the flow direction.
A more uniform film thickness can be obtained by forming a into a shape that bulges along the longitudinal direction of the partition plate 10 as in the semicircular shape in FIG. That is, since the intervening gas normally flows in a laminar flow in the reaction tube 1, the flow velocity distribution is fast in the central part and slow in the peripheral part,
For this reason, the growth film becomes thicker in the portion where the flow velocity is faster and thinner in the portion where the flow velocity is slower, but the semicircular shape of the end portion 10a is adjusted so that the start of the interdiffusion of the intervening gas and the vapor growth gas is delayed in the central portion than in the peripheral portion. As a result, the concentration distribution of the raw material gas in the intervening gas after passing through the substrate side end portion 10a is shown in FIG.
If b and 13c are used, the flow velocity distribution of the intervening gas becomes as shown by the broken line 14, so that the concentration of the source gas is thin in the part where the flow velocity of the intervening gas is fast on the surface of the substrate 7 and the part where the flow velocity of the intervening gas is slow. The concentration of the raw material gas can be made high, and the growth film can have a uniform thickness in the direction perpendicular to the flow direction of the intervening gas. Together with the uniformization of the flow direction, almost the entire surface can be made uniform. A good film formation substrate can be obtained. It should be noted that the above embodiment has been described in the case of an apparatus for processing one substrate, but it goes without saying that it can be applied to an apparatus for simultaneously processing a plurality of substrates.

〔The invention's effect〕

As described above, the apparatus of the present invention divides the upstream portion of the substrate in the reaction tube in which the vapor growth gas flows in the lateral direction into the upper channel and the lower substrate surface side channel by the partition plate parallel to the substrate surface. Since the upper and lower parallel flow paths are formed, the vapor phase growth gas introduction pipe is connected to the upper flow path, and the intervening gas introduction pipe is connected to the lower substrate surface side flow path, respectively. The vapor growth gas and the intervening gas that flow separately and in parallel with the lower substrate surface side flow path,
After passing through the end of the partition plate on the substrate side, they flow toward the substrate while diffusing each other, so that the intervening gas approaches the substrate surface while gradually increasing the concentration of the raw material gas, and the raw material in the intervening gas when passing through the substrate surface. Since gas becomes a reaction product and is deposited on the substrate surface one after another, compared with vapor phase growth using only vapor phase growth gas,
The thickness of the growth film formed on the surface of the substrate can be made uniform with respect to the flow direction of the vapor phase growth gas, and the vapor phase growth can be performed while the substrate is placed horizontally on the holding table. The substrate transfer mechanism is simpler than the conventional method of tilting, and the mechanism for rotating the holding table is not necessary compared to the conventional method of rotating the holding table, so that the apparatus configuration is simplified.

(2) Further, since the intervening gas flows on the substrate surface in a state where the source gas concentration thereof is thinner than that of the vapor phase growth gas, it is possible to reduce harmful deposits on the upstream side of the substrate during vapor phase growth as compared with the conventional case. Cleaning frequency is reduced, productivity is improved, and it is economical.

(3) Further, if the end portion of the partition plate on the substrate side is formed so that the central portion bulges along the longitudinal direction, the thickness of the growth film in the direction perpendicular to the flow of the vapor growth gas can be made uniform. In addition to the effects of (1) and (2) above, the thickness of the growth film can be made uniform over almost the entire surface. This is characterized by the fact that it can be realized without the need for a holder rotating mechanism, as compared with the conventional method in which the holder is rotated to obtain a uniform film thickness on the entire surface.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the vapor phase growth apparatus of the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is a sectional view of a conventional vapor phase growth apparatus. 1 ... Reaction tube, 3 ... Discharge tube, 4 ... Holding stand, 5 ... Flow channel, 5 ... FR coil, 7 ... Substrate, 8 ...
Hazardous sediments, 9 …… Upper and lower parallel flow paths, 9a …… Upper flow path, 9b
...... Lower substrate surface side flow path, 10 ...... Partition plate, 11 …… Gas phase growth gas introduction pipe, 12 …… Interposed gas introduction pipe

Claims (2)

[Claims] 1. A vapor phase growth apparatus for forming a growth film on a surface of a substrate placed on a holding table provided in the reaction tube by flowing a vapor growth gas flowing laterally in the reaction tube. In the above, the upstream portion of the reaction tube from the substrate is divided into an upper channel and a lower substrate surface side channel by a partition plate arranged parallel to the substrate surface to form an upper and lower parallel channel, and the upper channel is filled with air. A vapor phase growth apparatus comprising a phase growth gas introduction pipe and an intervening gas introduction pipe connected to a lower substrate surface side flow path. 2. The vapor phase growth apparatus according to claim 1, wherein the partition plate is formed in such a shape that the central portion bulges along the longitudinal direction at the substrate side end portion. .