JPH03108322A - Vapor growth equipment - Google Patents

Abstract

PURPOSE:To prevent the damage of vacuum exhaust system caused by etching gas by a method wherein, in order to chemically eliminate a silicon oxide film, a means which introduces and discharges etching gas is installed independently of the vacuum exhaust equipment of a vessel. CONSTITUTION:A wafer 7 is inserted into a reaction pipe 8; the inside of a pressure vessel 2 is vacuumized with a vacuum exhaust equipment 5; inert gas is fed from a material gas introducing pipe 4; when the pressure returns to about 1atm, gas like hydrofluoric acid gas is fed from an etching gas introducing pipe 21, and a silicon oxide film on the wafer surface is eliminated. At this time, a vacuum exhaust valve 16 is kept shut and an etching exhaust valve 23 is opend; thus the etching gas is discharged and corrosion of the equipment 5 is prevented. After that, the etching gas is stopped and pushed out by inert gas; a valve 23 is closed and material gas is fed fom an introducing pipe 4; thereby a film can be formed on the wafer 6 surface, in the same way as the case of a usual low pressure vapor growth equipment.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a reduced pressure vapor phase epitaxy apparatus used for manufacturing semiconductor wafers, and particularly relates to the reduction of natural oxide films formed on the wafer surface during the manufacturing process. .

[Conventional technology]

FIG. 2 is a side sectional view showing a conventional reduced pressure vapor phase growth apparatus. In the figure, 7 is a semiconductor wafer, which is placed on a boat 6 usually made of quartz glass or silicon carbide, and a reaction tube made of the same material. 8, and further the reaction tube 8
is placed in a pressure vessel 2 made of the same material.

A front flange 3 is provided at the front and rear of the pressure vessel 2, respectively. There is a rear flange 13, one or more raw material gas supply pipes 4 are connected to one side of the rear flange 13, and a vacuum exhaust device 5 is connected to the other side of the rear flange 13.
are connected via an exhaust pipe 15.

16 is an exhaust valve provided in the middle of the exhaust pipe 15. A heater 1 is arranged outside the pressure vessel 2 to heat the inside of the reaction tube 8. Hereinafter, this shaped device will be referred to as a horizontal reduced pressure vapor phase growth device, and the boat 6 is moved in and out of the reaction tube 8 using a boat holder (not shown).

Next, the operation will be explained.

The wafer 7 is inserted into the furnace through the front or rear flange 3.13. The wafer 7 inserted into the furnace is kept in a reduced pressure state while flowing an inert gas such as nitrogen gas until its temperature stabilizes, and then the raw material gas is transferred to the raw material provided on the front or rear flanges 3 and 13. The gas is introduced into the pressure vessel through the gas introduction pipe 4. The introduced raw material gas forms a film such as a polycrystalline silicon film or a silicon nitride film on the wafer 7 depending on the type of gas.

By the way, in some manufacturing processes of semiconductor devices, a natural oxide film formed on the surface of a silicon wafer or polycrystalline silicon film in the air may have an adverse effect on the product. For example, in the semiconductor device shown in FIG. In the manufacturing process, the surface of a silicon substrate 101 is covered with a silicon oxide film 102, and a second polycrystalline silicon film 104 is formed over the opening 103.
By forming using a vapor phase growth apparatus as shown in the figure,
Silicon substrate 101 and polycrystalline silicon film 104 are electrically connected. If a natural oxide film is formed on the silicon substrate in this opening 1.degree. 3, electrical connection between the silicon substrate 101 and the polycrystalline silicon film 104 may not be established. Therefore, before such a step, an etching step is performed to remove the natural oxide film on the wafer surface using an aqueous hydrofluoric acid solution or the like.

However, the opening 103 is formed between the etching process of the natural oxide film and the insertion of the silicon wafer into the furnace.
5. The silicon substrate is oxidized in the air, and a native oxide film as thin as 1 nm is formed. In addition, in the case of a vapor phase growth apparatus as shown in Fig. 2, since the semiconductor wafer is heated in the air when it is inserted into the furnace, an additional
A 3 nm native oxide film is formed on the silicon substrate. Hereinafter, this oxide film will be referred to as a rolled oxide film.

Regarding this entrainment oxidation, by using a vertical vapor phase growth apparatus in which reaction tubes are arranged vertically as shown in FIG. 4, the thickness of the oxide film could be reduced to about 1 nm.

That is, in the vertical vapor phase growth apparatus, the wafer 7 is set in a boat 6 placed on a heat-insulating tube 9, and this heat-insulating tube 9 is raised and lowered by a boat loader 10. This is because at this time, convection between the inside of the reaction tube 8 and the outside air is difficult to occur, so that the generation of an entrained oxide film is suppressed.

However, as semiconductor devices become more highly integrated, the area of the opening 103 becomes narrower, for example in the example shown in FIG. This has come to impede the electrical connection of the polycrystalline silicon film 104. This was a problem that could not be solved using conventional devices, including the device shown in FIG.

In order to solve these problems, conventional epitaxial growth equipment has been used to grow silicon substrates by keeping the wafer at a high temperature of 900'C or higher and flowing hydrogen gas into the furnace after inserting the wafer into the equipment. The natural oxide film on the surface was chemically removed.

[Problem to be solved by the invention]

Conventional low-pressure vapor phase growth equipment was configured as described above, but in recent years, with the increasing integration of semiconductor devices, the heat treatment temperature to which semiconductor devices are subjected has tended to decrease in order to avoid thermal diffusion of impurities. 900°C for high temperature products
The above heat treatment is not allowed, so the method described above cannot be applied to a general vapor phase growth apparatus.

For example, it is well known that silicon oxide films can be removed even at low temperatures by using hydrofluoric acid gas, but normally such gases are extremely corrosive, and as shown in Figures 2 and 4. There is a problem in that when this type of gas is allowed to flow through the vapor phase growth apparatus, it corrodes the vacuum evacuation apparatus 5, shortening its lifespan.

This invention was made to solve the above problems. After a silicon wafer is inserted into a vapor phase growth apparatus, it is isolated from the outside air and the natural oxide film and entrained oxide film on the wafer surface are chemically removed. The purpose of this invention is to reduce the defective rate of semiconductor devices by removing them quickly and at low temperatures, and to obtain more highly integrated semiconductor devices.

[Means to solve the problem]

The vapor phase growth apparatus according to the present invention includes a pipe for introducing a gas for chemically removing a silicon oxide film, an exhaust device for exhausting this gas, and a source gas for film formation. It is provided separately from the exhaust device.

[Effect]

In this invention, a pipe for introducing gas for chemically removing a silicon oxide film and an exhaust device for exhausting this gas are used as a device for exhausting raw material gas for film formation. After the wafer is inserted into the furnace, an etching gas that can chemically remove the silicon oxide film is introduced into the furnace. After removing the oxide film, the introduced gas is exhausted from a dedicated exhaust path.

〔Example〕

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

FIG. 1 is a side sectional view of a reduced pressure vapor phase growth apparatus according to an embodiment of the present invention. In the figure, the same reference numerals as in FIG. 2 indicate the same parts, 21 is an oxide film etching gas introduction pipe, 22
is an etching gas exhaust pipe, and is made of a material such as synthetic resin that is not easily corroded by etching gas. 23 is an etching gas exhaust valve.

Next, the operation will be explained.

After the wafer 7 is inserted into the reaction tube 8, in order to remove the outside air that has entered the reaction tube 8, the inside of the pressure vessel 2 is first evacuated using the evacuation device 5, and then the raw material gas introduction tube 4 is An inert gas is introduced into the pressure vessel.

When the pressure inside the pressure vessel returns to approximately 1 atmosphere, a gas such as hydrofluoric acid diluted to 10% or less by volume with an inert gas such as nitrogen is introduced into the reaction tube through the etching gas introduction pipe 21. 8 to remove the silicon oxide film on the wafer surface. At this time, the temperature of the wafer does not need to be the same as the temperature when forming the film.
Further, the concentration of the etching gas and the etching time can be changed depending on the thickness of the oxide film to be removed and the temperature of the wafer.

Since these gases are usually extremely corrosive, if a vacuum exhaust device 5 is used to exhaust the raw material gas, the life of this exhaust device will be significantly shortened. Therefore, while this etching gas is flowing, the vacuum exhaust valve 16 is kept closed, the etching gas exhaust pulp 23 is opened, and the etching gas is exhausted from the etching gas exhaust pipe 22.

Thereafter, the etching gas is stopped and an inert gas such as nitrogen is supplied instead to push out the etching gas in the reaction tube 8 and the etching gas exhaust pipe 22. When the etching gas is pushed out from the reaction tube 8, the etching gas exhaust pulp 23 is closed.

The subsequent processing is carried out in the same manner as in a normal reduced pressure vapor phase growth apparatus, by flowing an inert gas into the furnace through the gas introduction pipe 4 while maintaining the inside of the furnace in a reduced pressure state, and waiting for the temperature of the wafer 6 to stabilize. Further, if the temperature at which the oxide film is etched is different from the temperature at which the film is formed, the temperature of the heater 1 is adjusted at this point so that the temperature of the wafer 6 becomes a temperature suitable for film formation. When the temperature of the wafer 6 becomes stable, the raw material gas is introduced into the gas introduction pipe 4.
The wafer 6 is then poured into a furnace to form a film on the surface of the wafer 6.

After the film is formed, the source gas is stopped, the inside of the reaction tube is purged by flowing an inert gas, and then the wafer 6 is taken out.

In addition, although the above-mentioned embodiment showed an example in which the present invention was applied to a horizontal type reduced pressure vapor phase growth apparatus, the present invention may be applied to a vertical type reduced pressure vapor phase growth apparatus. Furthermore, gases other than hydrofluoric acid may be used as the etching gas.

〔Effect of the invention〕

As described above, according to the reduced pressure vapor phase growth apparatus according to the present invention, the piping for introducing the gas for chemically removing the silicon oxide film and the exhaust device for exhausting this gas can be connected to the film. The device is installed separately from the device that exhausts the raw material gas for formation, and the natural oxide film on the wafer surface is completely removed within the low-pressure vapor phase growth device, reducing the defective rate of semiconductor devices and allowing for higher integration. It becomes possible to manufacture standardized semiconductor devices. Further, since a dedicated exhaust path is provided for the etching gas for removing the natural oxide film, damage to the vacuum exhaust system of the reduced pressure vapor phase growth apparatus can be prevented.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of a conventional horizontal reduced pressure vapor phase growth apparatus, FIG. 3 is a diagram showing a part of a semiconductor device, and FIG. 4 is a vertical diagram. 1 is a diagram showing an example of a type reduced pressure vapor phase growth apparatus. l... Heater, 2... Pressure vessel, 3... Flange, 4... Raw material gas supply pipe, 5... Vacuum exhaust device, 6
...Boat, 7.Wafer, 8.Reaction tube, 9.
...Heat insulation tube, 10...Boat loader-113...Rear flange. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In order to place the silicon wafer in a reduced pressure state, a container for storing the silicon wafer, a vacuum evacuation device connected to the container, a means for heating the wafer placed in the container, and a device for heating the wafer placed in the container; In a vapor phase growth apparatus for forming a thin film on the surface of a silicon wafer, the apparatus is equipped with piping for supplying raw material gas, and a means for introducing a gas for chemically removing a silicon oxide film, and a means for exhausting the gas. A vapor phase growth apparatus characterized in that the following are provided separately from the vacuum evacuation apparatus.