JPS594433A - Thin film forming device - Google Patents

Abstract

PURPOSE:To remarkably enhance uniformity of film thickness, by forming a recess having a depth similar to the thickness of a base on the surface of an electrode on which the base is to be placed, fitting the base to the recess, and leveling both surfaces of the base and the electrode to the same height. CONSTITUTION:The recess 7 is formed on the surface of a lower electrode 2, the base 5 is fitted to the recess 7, and both faces of the electrode, and the base are leveled equally. The use of such a device raises the uniformity of film thickness and film quality, and enhances film quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a thin film forming apparatus, and in particular, aims to improve the uniformity of the film thickness and film quality of amorphous thin film. The present invention relates to a thin film forming apparatus that makes it possible to improve solar cell characteristics.

[Technical background of the invention and its problems]

Techniques for forming thin films using plasma CVD have been put to practical use as a technology for forming insulating films and amorphous silicon films. The schematic structure of the conventional device is shown in FIG. A thin film is formed on a substrate 5 placed on an electrode 2 by glow discharge decomposition of the raw material gas supplied into the electrode 1 .

By the way, in the conventional device, when looking at the arrangement of the substrate 5 on the electrode 2, the substrate 5 is placed so as to protrude above the surface of the electrode 2, as shown in FIG. In order to reduce pinholes in the thin film being formed, the substrate 5 is sometimes placed on the surface of the upper electrode 3. In this case, for example, a holder 6 is used as shown in Fig. A protrusion is formed on the surface of the electrode 30.

In general, the presence of protrusions in the plasma prevents the flow of the raw material gas from changing from laminar to turbulent, and also causes a significant change in the potential distribution in the plasma. Problems arise in thin films, such as inconsistency in film thickness, non-uniformity in film quality, and deterioration.

[Purpose of the invention]

The present invention improves the above-mentioned drawbacks of the conventional apparatus, and can significantly improve the uniformity of the film thickness and film quality of thin films formed by plasma CVD, and can prevent deterioration of the film quality. The purpose of the present invention is to provide a thin film forming apparatus.

[Summary of the invention]

In the present invention, a concave portion having a depth comparable to the thickness of the substrate is provided on the surface of the electrode on which the substrate is placed, and the substrate is mounted in this concave portion so that the surface positions of the substrate surface and the electrode surface are aligned. It is characterized by

〔Effect of the invention〕

According to the present invention, since the substrate itself or the substrate holder does not form protrusions in the plasma, the flow of source gas can be made uniform over the entire surface of the substrate, and the potential distribution in the plasma can also be maintained as described above. Since it is not disturbed by the protrusions, the glazma potential over the entire surface of the substrate is also made uniform. When the raw material gas is decomposed by glow radiation, various types of ions are produced.

Radicals are generated and they cause a chemical chain reaction, depositing a thin film on the substrate surface. Due to the above-mentioned effect, the decomposition of the source gas proceeds uniformly over the entire substrate surface, so the thickness and quality of the N film are Uniformity is greatly improved. At the same time, it is also possible to prevent deterioration of film quality.

[Embodiments of the invention]

The substrate arrangement in the embodiment of the present invention is shown in Figure 3, corresponding to Figure 2.
As shown in the figure. FIG. 3(,) shows an example in which four parts 7 are provided on the surface of the lower electrode 2, a substrate 5 is mounted in this recess 7, and the electrode surface and the substrate surface are aligned.

Further, FIGS. 3(b) and 3(e) show an example in which a recess 7 is provided in the upper electrode 3 and a substrate 5 is attached to the four parts 7. In this case, in order to hold the substrate 5, a recess 7 is shown in FIG. 3(b).
A leaf spring 8 is provided inside, and in FIG. 3(e), a hole 9 for a vacuum chuck is provided in the electrode 3.

In the following, the effects of the present invention will be clarified using specific experimental data, taking the formation of an amorphous Si film as an example. The basic equipment configuration is the same as that shown in Figure 1, and a thin film is formed when a non-doped amorphous Si layer is formed on a 1OcrP substrate (any substrate such as glass, stainless steel, or organic film) by glow discharge decomposition of silane gas. The film thickness and photoconductivity distribution were measured.

FIG. 4 shows the conventional configuration in which the substrate protrudes above the electrode surface as shown in FIG. 2(b)), and FIG. 5 shows this embodiment with the substrate arrangement as shown in FIG. 3(b). This is the case. From the data in Figure 4, it can be seen that when a protrusion such as a substrate exists, gas turbulence occurs near the contact area between the substrate holder and the substrate, and the uniformity of the electric field is disturbed, resulting in a thicker film. It can be seen that the film quality (photoconductivity) deteriorates.

On the other hand, according to the data in FIG. 5, it was found that by using the configuration of this example, the uniformity of the film thickness and film quality was increased, and the film quality was improved. Note that the doping is performed by mixing zoderane and phosphine gas with silane gas and decomposing the mixture by glow discharge to form a p-type layer.

In the case of forming an n-type layer, the same tendency as in the case of the above-mentioned undog layer was obtained.

Using an amorphous S1 forming apparatus, a p-type layer, a non-doped layer (
(in layer) and n layer in a p-1-n structure to form an amorphous SI solar cell.

The p-layer has a thickness of 100 to 100X, the non-doped layer has a thickness of 05 to 2 μm, and the n-type layer has a thickness of Zoo to 100X.
.

The amount of Dogue is 0.1 to 3%. In the case of an amorphous heavy solar cell, the device characteristics largely depend on the thickness of each layer, especially the thickness of the amorphous Si@(p-type layer or n-type layer) on the light incident side. . Using the configuration of this example, amorphous S1
As a result of forming the solar cell, the optimal film thickness of each layer can be formed uniformly throughout the setting, and even in the case of large area solar cells (10 tyP or more), it is possible to prevent deterioration of device characteristics caused by uneven film thickness. Met. According to experiments, 10J
It has been found that the conversion efficiency of solar cells can be improved by about 10 to 20%.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram of a conventional thin film forming apparatus, and Figure 2 (-
) (b) is a layout diagram of the conventional electrode and substrate, Figure 3 (a)
(b) and (e) are diagrams showing the arrangement of the electrodes and the substrate in the embodiment of the present invention, and Figure 4 is the distribution of the film thickness and photoconductivity of the non-doped amorphous Si layer on the substrate using the conventional device. FIG. 5 is a diagram showing the distribution of the film thickness and photoconductivity of the non-doped amorphous Si layer on the substrate using the apparatus of the example. DESCRIPTION OF SYMBOLS 1... Vacuum container, 2, 3... Electrode, 4... High frequency power supply, 5... Substrate, 7... Recessed part. Applicant's representative Patent attorney Takehiko Suzue (Figure 1, Figure 2, Figure 3, Figure 4)

Claims (1)

[Claims] In an apparatus that supplies a raw material gas into a vacuum container and applies a high electric field between opposing electrodes to decompose the raw material gas by glow discharge to form a thin film on a substrate placed on one surface of the opposing electrode. 1. A thin film forming apparatus characterized in that a recess having a depth comparable to the thickness of a substrate is provided on the surface of an electrode on which a substrate is placed, and a substrate is mounted in the recess.