JPS6281022A - Apparatus for manufacturing amorphous semiconductor film - Google Patents

Abstract

PURPOSE:To improve the quality of an amorphous semiconductor film by increasing the quantities of H atoms and H ions existing in reaction gas in case of manufacturing an amorphous semiconductor film which mainly contains amorphous silicon by a plasma CVD method or a photo-CVD method to reduce a dangling bond in the obtained film. CONSTITUTION:When a voltage is applied across an upper electrode 2 and an electrode 8 made of metal mesh and silicon compound gas fed into a reaction tank 1 is SiH4, glow discharge decomposition product to be accumulated on a substrate 5 passing through the electrode 8 is mixed with H atoms, H ions and H radicals produced by the decomposition of H2 gas. In this case, if the discharging power for producing the glow discharge of the H2 gas is increased, the quantities of the H atoms and H ions increase. Thus, the quantity to be associated in the film to be formed increases. Therefore, dangling bond in the film can be sufficiently compensated.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to an apparatus for manufacturing an amorphous semiconductor film mainly made of amorphous silicon, which decomposes silane gas or the like using a plasma CVD method or a photoCVD method.

[Prior art and its problems]

Amorphous silicon thin films produced by plasma CVD or photoCVD have attracted attention as solar cell materials for large-scale power generation for the past 17 years, and research and development are underway. Figure 2 shows a typical example of an amorphous semiconductor film manufacturing apparatus using the plasma CVD method. Raw material gas introduced into the reaction tank 1 from the gas inlet 6 through the gas circuit system is high-frequency The amorphous film is decomposed by the glow discharge generated between the lower electrode 2 and the lower electrode 3 due to the amount all or the direct current ff1iff12, and an amorphous film is deposited on the substrate 5 mounted on the lower electrode 3. Note that unreacted gas is exhausted through the gas exhaust lower. Currently, the amorphous silicon film widely used as a solar cell material is an a-5r:H film formed using a mixed gas of StH and H2 or a mixed gas of 5ix) I& and H2 as a raw material gas. , and 5jHa. a − using a mixed gas of 5iFn and H2 as a raw material gas
Research is also progressing on a 5i:F:H film and an aSi:Ge:)l film using a mixed gas of SiL, GeH4, and H2 as a raw material gas. In such an amorphous semiconductor film, if dangling bonds exist in the film, these become electrical defects and cause deterioration of the film quality, so the dangling bonds must be compensated as much as possible. However, for example, when a mixed gas of SiH4 and 11 is used as the raw material gas, 5iHaO is more easily decomposed because SiH bonds are more easily dissociated than H-H bonds. By the way, in the process of depositing the a-5i:H film by the decomposition of St,... and H2, S i II a becomes S i If t + S
While H2 is incorporated into the film in the form of i Hz or these complex bonding states, H2 is incorporated in the form of l (atoms or H ions. Therefore, what is incorporated into the film by the decomposition of SiHm On the other hand, H atoms or H ions resulting from the decomposition of H2 are incorporated into the film in a way that compensates for the dangling bonds existing in the Si and H network.As mentioned above, when S+H4 When a mixed gas of H3 is glow-discharged, 1(yo) is more difficult to decompose, so it becomes impossible to sufficiently compensate for the dangling bonds that occur in the network of silicon and hydrogen, and the photoelectric properties of a -3i+H# Therefore, a method can be considered to increase the proportion of IIt in the mixed gas to increase the number of H atoms and H ions in the glow discharge plasma, thereby reducing the dangling bonds generated in the film. However, in this case, since the SiHm content in the source gas is small, the film formation rate is significantly reduced.
In the case of a mixed gas of i2 as well, 5izHb is more easily decomposed and more likely to form dangling bonds in the film, resulting in electrical defects and deterioration of film quality. As described above, a -3i:tl is obtained by plasma CVD method.
When forming a film, the II quality of the obtained film is degraded because there are few H atoms and H ions in the plasma. In addition, in the case of the a-3i:F:H film and the a-5i:Ge:H film, the film quality of the obtained film deteriorates because there are few H atoms and H ions in the plasma due to the glow discharge of the mixed gas. The same applies when using the photo-CVD method.

[Purpose of the invention] In the present invention, when manufacturing an amorphous semiconductor film mainly made of amorphous silicon by a plasma CVD method or a photo CVD method, by increasing the amount of H atoms and H ions present in a reaction gas, It is an object of the present invention to provide a manufacturing apparatus that can reduce dangling bonds in the obtained film and improve the film quality. [Key points of the invention]

The present invention produces an amorphous material mainly made of amorphous silicon on a substrate placed in a reaction tank by generating glow discharge or irradiating light in a reaction gas containing a solicon compound in a reaction tank. The device for forming a semiconductor film is equipped with a hydrogen gas introduction tube whose tip/end reaches near the substrate. By being connected to a power supply, the introduced hydrogen becomes H atoms, H ions, and H radicals and is sent onto 71E+a, which replenishes the H atoms or H ions that are deficient during the decomposition of compound gases. The above objective is achieved by compensating for dangling bonds in the membrane.

[Embodiments of the Invention] Some embodiments of the present invention will be described below with reference to the drawings. In each figure, parts common to those in FIG. 2 are given the same reference numerals. In the embodiment shown in FIG. 1, a voltage is applied between the upper electrode 2 and the electrode 8 made of a metal mesh, and the inlet 6
The silicon compound gas sent into the reaction tank 1 is decomposed by glow discharge, and a film is deposited on the saw plate 5 mounted on the support base 4 through the menonyu electric scraper 8. On the other hand, H! The gas is made to flow onto the substrate 5 through the introduction pipe 21, and at this time, the metal tip 22 of the introduction pipe 21
A voltage is applied between this and a metal fi pole rod 23 installed in parallel thereto by a simple frequency electric field a24. This voltage causes a glow discharge to occur inside the entrance of the tip 22. As a result, the H2 gas passing through the tip 22 decomposes into H atoms. The H ions and H radicals flow onto the base 1 and 5 and mix with the decomposed silicon compound gas from the inlet 6 to form an amorphous silicon thin film on the substrate 5. When this silicon compound gas is filled with Sin, the glow discharge decomposition products deposited on the substrate through the mesh electrode are mixed with H atoms, H ions, and H radicals produced by the decomposition of H2 gas. At this time, if the discharge power for causing glow discharge of H2 gas is increased, the amount of H atoms and H ions will increase, and therefore the amount incorporated into the formed film will also increase. Therefore, the dangling bonds in the film can be sufficiently filled and the film quality can be improved. H2
It is also effective to superimpose a DC voltage using voltage #25 as the voltage for gas glow discharge. FIG. 3 shows a second embodiment of the present invention, in which H! A plurality of gas introduction tubes are formed, and a voltage is applied between the tip of each introduction tube 21 and the metal support base 4 on which the substrate 5 is mounted by a high frequency power source 24 or a DC t# 25. Furthermore, by rotating the support table 4 using a motor controlled by the circuit 26, the amounts of H atoms, H ions, and H radicals flowing onto the substrate are made uniform. Therefore, the film quality and uniformity of the obtained film can be improved. Incidentally, as the silicon compound gas, 5jJi, SiF4
and SiH. The quality of the obtained film can be similarly improved when using a mixed gas of GeHa and Sill4 or a mixed gas of GeHa and Sill4. FIG. 4 shows a case where a photo-CVD method is applied as a third embodiment of the present invention. 5izHb is introduced into the reaction tank 1 from the inlet 6 as a raw material gas, and ultraviolet light is irradiated from the mercury lamp 27 through the lens 28 to decompose the 5izHb. On the other hand, H2 gas passes through the introduction pipe 21 to the substrate 5.
At this time, if a high frequency or DC voltage is applied between the metal tip 22 of the introduction tube 21 and the metal support base 4 on which the substrate 5 is mounted, water flows into the tip 22. A glow discharge occurs. As a result, the decomposition products of 5itHa due to ultraviolet light irradiation are removed from the tip 2 of the introduction tube 21.
A film is formed on the substrate 5 by mixing with H atoms, H ions, and H radicals flowing out from the substrate 5 . In this case as well, that H
Dangling bonds generated in the film due to atoms and H ions are reduced, resulting in improved film quality. Effects of the Invention According to the present invention, in an amorphous semiconductor film manufacturing apparatus using a plasma CVD method or a photo CVD method, hydrogen gas is supplied to a substrate to be formed into a film through a gas inlet pipe, separately from a raw material gas such as a silicon compound gas. The H
Atoms, H ions, and other plasma species are supplied into the reaction atmosphere of the source gas. Dangling bonds in the film thus generated are compensated, defects in the film are reduced, and film quality is improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of one embodiment of the present invention, FIG. 2 is a cross-sectional view of an amorphous semiconductor film manufacturing apparatus using a conventional plasma CVD method, and FIGS. 3 and 4 are different embodiments of the present invention. FIG. 1: Reaction tank, 2: Upper electrode, 4: Support stand, 5: Substrate, 6
: Gas inlet, 7: Gas outlet, 8: Metosh electrode, 2
1: o, gas introduction pipe, 22: introduction pipe tip Fig. 2

Claims (1)

[Claims] 1) An amorphous semiconductor film mainly made of amorphous silicon is formed on a substrate placed in a reaction tank by generating glow discharge or irradiating light in a reaction gas containing a silicon compound in the reaction tank. The hydrogen gas inlet tube has a hydrogen gas introduction tube whose tip reaches near the substrate, and at least the tip of the introduction tube is made of metal, and is connected to a power source that applies a voltage that generates a glow discharge near the tip. An amorphous semiconductor film manufacturing device characterized by: