JPS5927214B2 - Vapor phase growth equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generates a plasma state by glow discharge,
For example, the present invention relates to a vapor phase growth apparatus for producing amorphous silicon films used in solar cells.

Amorphous silicon has excellent optical and electrical properties as a material for solar cells, and its light absorption coefficient in the visible light region is
The deviation of crystalline silicon is also much better.

Such an amorphous silicon film is formed by turning monosilane SiH4 into a plasma state by glow discharge and growing ions of decomposed silicon atoms on a substrate, and can be obtained extremely economically even over a large area. .

To generate glow discharge, a direct current voltage or high frequency voltage is applied between opposing electrodes inside the reaction vessel, or a high frequency current is passed through a coil provided outside the reaction vessel.

The present invention generates a plasma state by glow discharge,
The purpose of this invention is to further improve characteristics such as uniformity of film quality in an apparatus for depositing ions on a substrate to obtain a vapor-phase grown film.

The purpose of this is to arrange two electrodes facing each other with a grid electrode in the middle that allows ions to pass through, apply a voltage that causes glow discharge between one electrode and the grid electrode, and connect the grid electrode to the other electrode. This is achieved by applying a DC voltage between.

In the present invention, ions in a plasma state are not necessarily uniform, and include atoms with different valences and even neutral atoms, and when these are mixed and deposited on a substrate, a uniform film with excellent properties is obtained. It is based on the recognition that it cannot be obtained.

That is, the aim is to make the properties of the ions deposited on the substrate as uniform as possible, thereby improving the film quality.

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

In the figure, reference numeral 1 indicates a vacuum container, which is maintained at a vacuum of 10 Torr or less, for example, 1 to 5 Torr, by evacuating from the exhaust port 2 with a vacuum pump and introducing SiH4 gas from the gas introduction port 3.

A grid electrode 6 is arranged between the electrodes 4 and 5 in the vacuum vessel.

Among them, the electrode 4 and the grid electrode 6 are used as plasma generation electrodes, and for example, the electrode 4 has a voltage of +500V.
7D, and the electrode 6/i is brought to the ground potential, and a glow discharge is generated between the two electrodes.

A voltage of -100 V is applied to the electrode 5, and the grid electrode generates an electric field that accelerates ions formed by decomposing SiH4 due to glow discharge toward a substrate (not shown) placed on or near the electrode 5. Formed between 6 and 6.

The electrode 6 is meshed to allow the flow of ions from the glow discharge region to the acceleration region.

If the substrate were placed on or near the electrode 6, most of the ions or atoms existing between the electrodes 4 and 6 would be deposited on the substrate, making it impossible to obtain the desired film quality. Can not.

However, according to this device, the electric field between the electrodes 6 and 5 causes only the ions to be suppressed, and the ions above the electrode 5 -! ! Since it is deposited on a substrate placed near the bamboo shoots, it is possible to achieve uniform film quality.

Furthermore, by changing the distance between the electrodes 6 and 50 and the voltage, it is possible to limit the properties of ions that reach the substrate, and it is also possible to make the quality of the grown film more uniform.

A similar effect can also be obtained when a high frequency voltage is applied between the electrode 4 and the grid electrode 6 to cause a glow discharge and ionize silicon atoms.

Note that a glow discharge is caused between the electrode 5 and the grid electrode 6,
Ions are transferred to the electrode 4 by the electric field between the grid electrode 6 and the electrode 40.
It is also possible to grow the particles on the lower surface of the substrate placed under the electrode, in which case it is possible to prevent particles attached to the upper electrode from falling onto the substrate and damaging the film quality.

As mentioned above, the vapor phase growth apparatus based on the present invention easily improves the film quality of vapor phase growth films by separating the electric field for plasma generation and the electric field for ion flow control, and is suitable for use in solar cells. It can be applied not only to the growth of amorphous silicon films, but also to general vapor phase growth equipment using gas in a plasma state.

[Brief explanation of the drawing]

The figure is a sectional view schematically showing the structure of an embodiment of the present invention. 1... Vacuum container, 2... Gas inlet,
4, 5...electrode, 6...grid electrode.

Claims (1)

[Claims] 1 In a device in which a compound gas is introduced into a vacuum container and ions generated in a plasma state by glow discharge are deposited on a substrate, two electrodes are arranged facing each other with a grid electrode that allows ions to pass between them, and one A vapor phase growth apparatus characterized in that a voltage for causing glow discharge is applied between one electrode and the other grid electrode, and a DC voltage is applied between the grid electrode and the other electrode.