JPS592374B2 - Plasma vapor phase growth equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plasma vapor phase growth apparatus that generates plasma between two electrodes having a parallel plate structure, causes a chemical reaction of a reactive gas in the presence of this plasma, and During the vapor phase growth of a specified film on the electrode, the disturbance in the plasma distribution that occurs at the peripheral edge of the electrode prevents unreacted gas and reaction byproducts from adhering to unnecessary parts such as the inner wall of the chamber. The purpose of the present invention is to provide a plasma vapor phase growth apparatus.

A plasma vapor phase growth apparatus having a parallel plate structure is generally arranged vertically facing each other in a reduced pressure chamber.

An upper high-frequency electrode in the form of a hollow flat plate connected to a reaction gas supply pipe and having numerous pores on the lower surface, and a lower high-frequency electrode on which a substrate is heated and placed are placed vertically in a chamber under reduced pressure, facing each other. In this device, by applying a high frequency voltage between the upper and lower electrodes, plasma is generated between the two electrodes, and in the presence of this plasma, a chemical reaction of the reactant gas is caused. A vapor phase growth film is thereby formed on the substrate. FIG. 1 shows, for example, silane SiH
4. Silicon nitride film Si3 using ammonia NH3
It is a diagram showing a conventional vapor phase plasma growth apparatus for forming N4.
- inside the chamber 3 installed via the ring 2;
A planar upper high frequency electrode 5 connected to the reaction gas supply pipe 4 and hollow and having a large number of pores 5b in the bottom 5a is disposed, and the lower part of the upper high frequency electrode 5 is electrically connected to the chamber base 1, A heater block 6 for heating the substrate, which also serves as a lower high-frequency electrode, is arranged to face the substrate.

Note that T is a semiconductor substrate on which a silicon nitride film is formed, and is placed on a susceptor 8 placed on the heater block 6. Further, the heater block 6 is fixed to the chamber base by a conductive column 11 and is electrically at the same potential as the chamber base, and its temperature is controlled by the tube heater 1 based on the detection signal of the thermocouple 9.
This is done by controlling the input voltage of zero. Further, 12 is an exhaust port, 13 is a vacuum gauge for measuring the reaction pressure inside the chamber, and 14 is a door for taking out a sample (vapor-phase grown substrate). In such an apparatus, a silicon nitride film is grown in a vapor phase as follows.
In other words, between the upper high frequency electrode and the heater block,
When a mixed gas of SiH4, NH3 as a reaction gas and nitrogen N2 or argon Ar as a carrier is introduced while applying a high frequency voltage (13.56 MH2), the gas uniformly mixed in the upper high frequency electrode 5 flows through the pores 5b. erupts from. By the way, plasma is generated between the upper and lower high-frequency electrodes by applying the above-mentioned high-frequency voltage, and in the presence of this plasma, a chemical reaction occurs between the reactant gases as shown in the following reaction formula, and nitriding occurs on the semiconductor substrate. A silicon Si3N4 film is formed. 3SiH4+4NH3→Si3N4+12
Note that the plasma distribution is relatively uniform in most of the area surrounded by the upper high-frequency electrode 5 and the heater plotter 6, which is the lower high-frequency electrode, so that most of the reaction gas is converted to Si3N4 by the above chemical reaction. The by-products are deposited on the semiconductor substrate and are exhausted from the exhaust hole 12, but in the region around the electrode, the above-mentioned reaction does not proceed smoothly due to disturbances in the plasma distribution, and unreacted gas remains. , reaction by-products are also difficult to reach the exhaust port, and these unreacted gases and reaction by-products are transported to low-temperature areas within the chamber, such as the back side of the upper high-frequency electrode 5, the inner wall of the chamber, the inner wall of the chamber base 1, or the inner wall of the exhaust port. It adheres as a residue to the surface.

Some of these deposits are hydrolyzed by the moisture in the air that flows into the chamber when the door 14 is opened to take out the sample on the susceptor, and turn into white oxides.

This oxide has strong hygroscopicity, which makes it difficult to evacuate the chamber during intermittent vapor phase growth, lowering the ultimate vacuum, and promoting abnormal decomposition of NH3, making it difficult to control the reaction pressure. Otherwise, it not only causes inconveniences such as adhesion to the surface of the semiconductor substrate and causes pinholes, but also
During the cleaning of the upper high frequency electrode and susceptor by plasma etching of Freon CF4, which is normally performed before the vapor phase growth process, the oil in the vacuum pump is significantly removed due to the action of moisture adsorbed by the fluorine F and oxides in Freon. It can also cause severe deterioration. Therefore, in order to maintain the film quality of the Si3N4 film over a number of vapor phase growths, the above-mentioned deposits must be removed frequently, and this removal operation must be simple and complete. However, cleaning the back side of the upper high-frequency electrode and the top surface of the chamber 1 facing it is extremely difficult because it is not easy to remove the chamber 1 and the structure of the upper high-frequency electrode 5 is complicated, and there is no simple removal method. In some cases, it has been almost impossible to completely remove the deposits adhering to these parts. Therefore, in the conventional plasma vapor deposition apparatus, the above-mentioned disadvantages caused by deposits still remain even after cleaning operations. The present invention has been made in view of the above problems, and by bringing the back surface of the upper high frequency electrode and the top surface of the first chamber into close contact with each other, the back surface of the upper high frequency electrode and the top surface of the first chamber opposite thereto can be The aim is to eliminate the adhesion of reaction by-products and unreacted gases, simplify the cleaning inside the chamber, complete the removal of adhering substances, and form a high-quality vapor-phase grown film. Next, the plasma vapor phase growth apparatus of the present invention will be explained with reference to FIG.

The basic structure of the plasma vapor deposition apparatus of the present invention is the same as that of the conventional apparatus, but as shown in the figure, when the chamber is set in a sealed state, an upper high-frequency electrode 5 is placed on the top surface 3a of the chamber. In addition, quartz isolation walls 15a to 15d are installed around the upper high-frequency electrode 5 in a removable relationship, and these isolation walls 15a to 15d This structure differs from the conventional structure in that consideration has been taken in the structure of integrally surrounding both the upper and lower high-frequency electrodes and the plasma generation region sandwiched between them. In the plasma vapor deposition apparatus of the present invention having such a structure, the back surface of the upper high-frequency electrode 5 and the top surface 3a of the chamber 1 are in close contact with each other, so that reaction by-products etc. do not adhere to both parts. The cleaning of the apparatus after the vapor phase growth process is simple and complete.

Note that isolation walls 15a to 15 surrounding the high frequency electrodes
d functions to specify the exhaust path for reaction by-products, etc., to prevent them from adhering to the inner wall of the side of the chamber, and to guide them to the exhaust hole. Residues such as reaction by-products are also prevented from adhering to the inner wall, and most of the residues adhere to the isolation wall.

Therefore, when cleaning the equipment when an isolation wall is installed, it is only necessary to remove the isolation wall and perform chemical treatment to remove the deposits attached to it, which is much easier than when there is no isolation wall. Simplified〇As is clear from the above explanation, in the plasma vapor phase growth apparatus of the present invention,
The adhesion of reaction by-products to the back side of the upper high-frequency electrode and the top inner wall of the chamber, which are difficult to clean, is almost completely eliminated, and the inconvenience caused by adhesion remaining on these parts even after cleaning is eliminated. This has many effects, such as improving the durability of the device itself, simplifying maintenance work such as cleaning, and improving the quality of the vapor-grown film formed.

Although the present invention has been described using plasma vapor phase growth of a silicon nitride film on a semiconductor substrate as an example, the application of the plasma vapor phase growth apparatus of the present invention is not limited to the above-mentioned films; Similar effects can be obtained when used as an apparatus for forming a film or a coating such as a polycrystalline silicon film.

Further, in the embodiment, an isolation wall is provided around the periphery, but the isolation wall is not necessarily necessary, and it is still more effective if it is attached only when necessary.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a conventional plasma vapor phase growth apparatus, and FIG. 2 is a schematic structural diagram of a plasma vapor phase growth apparatus according to an embodiment of the present invention. 1...Chamber base, 2...0-
Ring, 3... Chamber one, 3a...
Top surface, 4... Reaction gas supply pipe, 5...
Upper electrode, 6... Heating heater block, 7...
...Semiconductor substrate, 8...Susceptor, 9...
...Thermocouple, 10 ...Tube heater, 1
1... Prop, 12... Exhaust port, 13.
...Vacuum gauge, 14...Door, 15a~1
5d... Bulkhead.

Claims (1)

[Claims] 1. In a chamber, a hollow upper high-frequency electrode that is connected to a reaction gas supply pipe and has a number of pores on the lower surface and a substrate heating table that also serves as a lower high-frequency electrode are arranged vertically facing each other, and the upper high-frequency electrode A plasma vapor deposition apparatus characterized in that the entire back surface of the chamber is in close contact with the top surface of the chamber.