JPS6128372B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a low pressure vapor phase growth apparatus widely used for manufacturing semiconductor devices.

Chemical vapor deposition (CVD) is a process in which a gaseous substance is supplied onto a semiconductor substrate, etc., and chemical reactions such as thermal decomposition, hydrolysis, and oxidation that occur between the gaseous substance itself or between it and the substrate are used. This is a method in which polycrystals, insulating films, etc. are deposited on a substrate, and the low pressure vapor phase growth apparatus used to implement this method has become indispensable in the manufacturing process of semiconductor devices.

FIG. 1 is a partial sectional view showing an example of a conventional low pressure vapor phase growth apparatus commonly used. In the figure, a reaction tube 1 is made of a heat-resistant material such as quartz and has a cylindrical shape, and has an exhaust pipe 1a at one end and a load door 2 at the other end. Further, a heater 4 surrounds the outer periphery, and an electric furnace is constructed as a whole. The load door 2 serves as a lid that seals the furnace, and is made of a heat-resistant material such as quartz or stainless steel. A gas introduction pipe 3 is provided passing through the load door 2, and is connected to a pipe 6 via a valve 5. This pipe 6 is connected to a gas cylinder (not shown) as a gas supply source. A support boat 7 made of graphite is housed inside the reaction tube 1 with a silicon wafer 8 as a semiconductor substrate placed thereon.

Chemical reactions in a reduced pressure vapor phase growth apparatus with such a configuration are usually carried out at high temperatures of 600 to 900°C and temperatures of 0.1 to
The test is carried out under reduced pressure of 1.0 Torr. For example, when growing a silicon nitride film on a silicon wafer 8, the inside of the reaction tube 1 is heated by the heater 4 and exhausted from the exhaust pipe 1a to 750° C. and 0.5 Torr.
dichlorosilane and ammonia are introduced from the gas introduction pipe 3 together with a carrier gas. The introduced gas causes a chemical reaction in the thermal reaction section where the wafer 8 is placed, forming a silicon nitride film on the wafer.

As described above, in the conventional reduced pressure vapor phase growth apparatus, the reaction depends only on the heat applied from the outside to the thermal reaction part of the reaction tube 1 by the heater 4, so it takes a long time and the temperature is extremely high. There was also a high possibility that the semiconductor substrate would be thermally damaged. Furthermore, since the gas flows unreacted to the wafer placement area (thermal reaction area) where the desired vapor phase growth is actually performed, there is also a problem in uniformity. Furthermore, due to the structure of these reduced pressure vapor phase growth devices,
The generated substances adhere not only to the wafer but also to all parts of the reaction tube, such as the inner walls of the reaction tube, and over time, they accumulate and obstruct gas flow, or flake off in small pieces, causing dust. or Therefore, there was a drawback that the reaction tube had to be replaced periodically.

An object of the present invention is to provide a reduced pressure vapor phase growth apparatus that can efficiently produce a uniform film.

Another object of the present invention is to provide a reduced pressure vapor phase growth apparatus in which the reaction tube can be easily cleaned.

In order to achieve such an object, the reduced pressure vapor phase growth apparatus according to the present invention is provided with a plasma generating device on the gas introduction side of the thermal reaction section on which the wafer is placed.
The gas introduced into the reaction tube is turned into plasma in advance to increase its activity, facilitating the subsequent vapor phase growth reaction, and etching gas is introduced to plasma-etch unnecessary products attached to the inner walls of the reaction tube, etc. It has been made possible. Hereinafter, the reduced pressure vapor phase growth apparatus according to the present invention will be explained in detail using the drawings.

FIG. 2 is a partial sectional view showing an embodiment of the reduced pressure vapor phase growth apparatus according to the present invention, and the same parts as in FIG. 1 are designated by the same symbols and detailed explanations are omitted.
In this embodiment, the load door 2 is made of an electrically insulating quartz plate, and as shown in FIG. 3, one end of a support member 9 is fixed to the plate surface and a power supply connector 10 is implanted therein. . A plasma generation electrode 11 is held at the other end of the support member 9 . The support member is made of a conductor, and together with the power supply connector 10 and the conductive wire 12 constitutes an electrical connection member. High frequency power is supplied from an external power source to the plasma generation electrode 11 through these electrical connection members. Hereinafter, the operation of the reduced pressure vapor phase growth apparatus having the above configuration will be explained in detail.

First, the inside of the reaction tube 1 is heated by the heater 4 and exhausted from the exhaust pipe 1a to maintain a high temperature and reduced pressure state. Further, high frequency power is supplied to the plasma generation electrode 11 from an external power supply through the power supply connector 10, the conductive wire 12, and the support member 9. Here, for example, monosilane and nitrogen as a carrier gas are introduced from the gas introduction pipe 3. The gas introduced into the reaction tube 1 generates a discharge between the electrodes 11 and becomes a plasma before reaching the thermal reaction section where the wafer 8 is placed. The plasma-turned gas then causes a thermal reaction in a thermal reaction section at a high temperature, and a polycrystalline silicon film is grown on the silicon wafer 8. Because the activity of the gas is increased by plasma formation, the reaction is easier and more efficient than when the gas supplied from the gas source is reacted from the beginning only with heat applied from outside. A desired film can be grown. In addition, since the gas introduced into the reaction tube from the outside is turned into plasma before it reaches the thermal reaction zone where the desired vapor phase growth occurs, it is more uniform than when it directly flows into the thermal reaction zone. It is possible to grow a uniform film even if there are a large number of semiconductor substrates. The operation for growing a desired film on a semiconductor substrate has been described above.

Next, the operation when cleaning the reaction tube will be explained. Polycrystalline silicon produced in the above-described vapor phase growth process adheres not only to the desired silicon wafer but also everywhere within the reaction tube. Therefore, as the vapor phase growth process is repeated, the film deposited on the inner walls of the reaction tube gradually increases in thickness, and if left untreated, it can obstruct the flow of gas or flake off into small pieces, causing dust. It becomes necessary to periodically clean the reaction tube. For this purpose, for example, once every several dozen vapor phase growth steps, CF4 is added to the reaction tube from which the semiconductor substrate has been removed.
A fluorocarbon-based etching gas such as fluorocarbon etching gas is introduced from the gas introduction pipe. The introduced etching gas passes through the plasma generation electrode 11 to which a high frequency voltage is applied.
A discharge occurs between the two, creating an active plasma state.
The unnecessary polycrystalline silicon film deposited on the inner wall of the reaction tube is plasma etched. Therefore, the inside of the reaction tube can be easily cleaned without requiring troublesome work such as removing the reaction tube from the apparatus.

As mentioned above, since the plasma generation electrode 11 is supported by the support member 9 not by the main body of the reaction tube 1 but by the removable load door 2, it is easy to assemble and handle for subsequent maintenance. be. In addition, the following configuration is also possible.

FIG. 4 is a partial cross-sectional view showing another embodiment of the reduced pressure vapor phase growth apparatus according to the present invention, and FIG. 5 is a perspective view showing the plasma generator section thereof, showing the same parts as FIGS. The same symbols are used and detailed explanation thereof is omitted. In the figure, the load door 2 is composed of conductor parts 2a, 2b and an insulator part 2c. The conductor portions 2a, 2b and the support member 9 that fixes the plasma generation electrode 11 also serve as a part of the electrical connection member for supplying high frequency power to the electrode 11, and these load door conductors The body parts 2a, 2b, the support member 9, and the plasma generation electrode 11 are integrally constructed. The load door itself has a composite structure of a conductor and an insulator, but there is no need to separately provide a power supply connector or conductor, making the structure simpler and more robust. By converting the gas entering the reaction tube into an active plasma state on the gas supply side before it reaches the thermal reaction section, vapor phase growth is facilitated, and by introducing etching gas and turning it into plasma, the vapor phase growth is facilitated. The effect of removing unnecessary films deposited inside the reaction tube during the growth process can be obtained in exactly the same manner as in the embodiments shown in FIGS. 2 and 3.

In all of the above embodiments, the plasma generation electrode was attached to the load door, but if it is on the gas introduction side of the thermal reaction section where the semiconductor substrate is placed and the desired vapor phase growth is performed, it can be attached to the inside of the reaction tube. It may also be supported at other locations, such as on the inner wall of the reaction tube.
Furthermore, it goes without saying that the location for attaching the power supply connector is not limited to the load door, but may be, for example, the inner wall of the reaction tube. Furthermore, the plasma generator may be located outside the reaction tube. For example, a portion of the gas introduction pipe protruding from the outside of the load door can be expanded and placed inside the door. When provided outside the reaction tube in this manner, unlike when provided inside the reaction tube, the reaction tube is not exposed to a high temperature atmosphere, so there is an advantage that thermal damage can be reduced.

As explained above, according to the reduced pressure vapor phase growth apparatus according to the present invention, plasma is generated in the reaction tube between the thermal reaction section where the wafer is placed and desired vapor phase growth is performed, and the gas inlet. By providing a plasma generator equipped with a plasma electrode, the gas supplied from the gas supply source can be turned into plasma before reaching the thermal reaction part of the reaction tube, increasing its activity. Vapor phase growth can be performed more efficiently than when relying only on heat, and compared to when completely unreacted gas just supplied from the gas supply source is directly introduced into the thermal reaction zone. The uniformity of the produced film can be improved. Furthermore, since it is possible to introduce an etching gas and turn it into plasma, and to plasma-etch the reaction products deposited on the inner wall of the reaction tube, etc., it has various excellent effects such as extremely easy cleaning of the inside of the reaction tube.

Furthermore, since the plasma generation electrode is supported by the load door, it has the advantage of being easy to assemble and handle thereafter.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view showing a conventional low-pressure vapor phase growth apparatus, and FIGS. 2 and 3 are partial cross-sectional views showing an embodiment of the low-pressure vapor phase growth apparatus according to the present invention, and its plasma generator section. FIGS. 4 and 5 are a partial cross-sectional view showing other embodiments of the reduced pressure vapor phase growth apparatus according to the present invention, and a perspective view showing the plasma generator section thereof. DESCRIPTION OF SYMBOLS 1...Reaction tube, 2...Load door, 4...Heater, 9...Support member, 10...Power supply connector, 1
1... Electrode for plasma generation, 12... Conductive wire.

Claims (1)

[Claims] 1. A gas supply source, a reaction tube into which gas is introduced from the gas supply source, a heater provided on the outer periphery of the reaction tube, and a load door that closes one end of the reaction tube. A reduced pressure vapor phase growth apparatus comprising: a plasma generation electrode located between the thermal reaction part and the gas inlet in the reaction tube; a support member for supporting this electrode on a load door; and a support member for supplying power to the electrode. 1. A reduced pressure vapor phase growth apparatus comprising a plasma generating apparatus having an electrical connection member. 2. The reduced pressure vapor phase growth apparatus according to claim 1, wherein the electrical connection member includes a support member and a part of the load door.