JPS63228676A - Manufacture of thin film semiconductor device - Google Patents

Abstract

PURPOSE:To form a film at a high speed by forming a grid electrode made of a porous plate parallel to discharge electrodes at the intermediate of a predetermined range on the substrate side of the opposed discharge electrodes over the whole substrate width or more, and reducing a plasma impact at the time of starting to form a semiconductor layer with the grid electrode to form the film. CONSTITUTION:Reaction chambers 1, 2, 3 of CVD plasma for forming p-type, i-type and n-type amorphous silicon layers, and an unwinding chamber 16 are connected by a buffer chamber 18 to a winding chamber 17, and the p-, i-and n-type layers are continuously formed while feeding a substrate 13 from an unwinding roll 14 to a winding roll 15 in a roll-to-roll system. In the chamber 2 for forming the i-type amorphous silicon layer, a grid electrode 11 is mounted at the intermediate between opposed discharge electrodes 6 and 7, a negative bias potential is applied to the electrode 11. When high frequency power applied to the electrodes 6, 7 is altered to grow an i-type amorphous silicon layer, an increase in the discharge power rises a depositing velocity. Thus, it can prevent a plasma to form a film at a high speed without influence of the grid electrode.

Description

[Detailed Description of the Invention] Technical Field> The present invention relates to a thin film semiconductor device in which a single layer or multiple thin film semiconductor layers are formed on a substrate that is transported in a plasma atmosphere by chemical vapor phase decomposition. The present invention relates to a manufacturing method, and particularly to a manufacturing method of a thin film semiconductor device suitable for manufacturing an amorphous silicon solar cell.

<Prior art> A method of manufacturing a semiconductor device by forming a single layer or multiple thin film semiconductor layers on a substrate in a plasma atmosphere by chemical vapor phase decomposition (hereinafter referred to as CVD) uses, for example, silane (S).
t H4) This is a well-known technique that is widely practiced as a method for manufacturing an amorphous silicon solar cell by discharging and decomposing gas. Among such manufacturing methods, a method of continuously transporting a substrate through a CvD plasma discharge atmosphere is known as one of the manufacturing methods suitable for efficiently forming a thin film semiconductor layer, that is, suitable for mass production.

This method can be roughly divided into the following two types.

One is to install a completely separate and independent single chamber for plasma discharge between the substrate loading chamber and the unloading chamber, and a reaction chamber consisting of multiple chambers as necessary, and a trolley for moving single substrates. This is a load-lock method in which film formation is performed while sequentially transporting the film from one chamber to another.

Another method is to make the board itself into a long roll, such as in JP-A-58-216475 and JP-A-59-34668, and there is a board passage between the unwinding chamber and the winding chamber. This is a roll-to-roll method in which a single reaction chamber or multiple reaction chambers are installed as needed, and films are formed on thin film substrates that are continuously transported.

When performing high-speed film formation in order to further increase production efficiency using such a manufacturing method, the conventional technique is to increase the concentration of active species in the plasma atmosphere by increasing the discharge power while supplying sufficient raw material gas. I've been exposed to it. However, in such a method, as the discharge power increases, the kinetic energy of the charged particles in the plasma atmosphere also increases, so that so-called plasma damage, in which the film formation surface is damaged by collisions of charged particles, becomes noticeable and the characteristics of the semiconductor iJl are affected. There was a drawback that the characteristics of the semiconductor device were adversely affected.

When a semiconductor layer is formed on a substrate and another type of semiconductor layer is formed on top of this, specifically, after forming a p layer or an n layer on the substrate in manufacturing an amorphous silicon solar cell. This effect was significant when an i-layer was formed thereon.

<Objective of the Invention> The first object of the present invention is to provide a method for manufacturing a thin-film semiconductor device that eliminates the drawbacks of the above-mentioned conventional techniques and allows high-speed film formation by increasing discharge power without adversely affecting the characteristics of the semiconductor device. The second object of the present invention is to provide a method for manufacturing a thin film semiconductor device particularly suitable for mass production of amorphous silicon solar cells.

<Structure of the invention> The above objects are achieved by the invention as follows.

That is, the present invention provides a method for manufacturing a thin film semiconductor device in which a predetermined semiconductor layer is formed on a substrate in a plasma atmosphere by chemical vapor phase decomposition while the substrate is being transferred. A thin film characterized in that a grid electrode made of a porous plate is provided between the discharge electrodes in parallel with the discharge electrode over at least the entire width of the substrate, and the film is formed by reducing plasma impact at the start of semiconductor layer formation by the grid electrode. This is a semiconductor device manufacturing method.

The above-mentioned present invention was made as follows.

That is, the present inventors disclosed the above-mentioned Japanese Patent Application Laid-Open No. 59-34668
Continuous Omukai production of amorphous silicon solar cells has been investigated using a continuous plasma C■0 apparatus similar to the one disclosed in the publication, but it has been found that increasing the discharge power to increase the deposition rate to improve productivity. A phenomenon in which the conversion efficiency decreased was observed. The cause of this is the intrinsic amorphous silicon layer (i
They found that this was due to the incorporation of impurities from the lower layer in the early stage of the formation of the i-layer, and that this was due to plasma bombardment of the lower layer in the early stage of film formation.
After various studies on this countermeasure, we found that by providing a grid electrode only on the substrate entry side between the discharge electrodes, the plasma energy can be effectively reduced only in the area where the grid electrode exists and its vicinity, and the plasma damage can be prevented. This discovery was made based on the discovery that high-speed film formation could be performed without being affected by the grid electrode in areas other than the lattice electrode.

As described above, although the present invention was made in the continuous production of amorphous silicon solar cells, it is clear from its purpose that it can be widely applied to similar methods of producing thin film semiconductor devices.

That is, as is clear from the above, the present invention is based on the fact that the adverse effect on the characteristics of a thin film semiconductor device that occurs when the discharge power is increased is mainly plasma damage to the interface between each semiconductor layer. Therefore, in the present invention, the characteristics of the thin film semiconductor device are adversely affected only when the interface between the substrate and the semiconductor thin film or the interface between semiconductor thin films of different conductivity types and constituent elements is exposed to plasma containing high-energy particles. Even if only the inside of the thin film away from the interface is exposed to high-energy plasma for the purpose of promoting decomposition of source gas, the characteristics of the semiconductor device will not be significantly adversely affected, and it can be widely applied to semiconductor devices.

Further, the grid electrode of the present invention is provided only on the substrate entry side of the discharge electrode. The area to be provided needs to be determined experimentally, depending on the semiconductor to be formed and the bias voltage applied to the grid electrode, but considering the film formation rate, it should be selected appropriately between the substrate entrance and half of the discharge electrode. is practical. As for the shape of the grid electrode, a perforated plate having a large number of holes over the entire surface, such as a net-like shape or an i-like shape, is used. The size of the pores is selected within a range that can confine the plasma without blocking the passage of active species as much as possible.Actually, it is determined experimentally, but in the case of a mesh, it should be selected to be no larger than No. 50 mesh. is practical.

Further, the present invention can be advantageously applied to the case where necessary semiconductor layers are continuously and sequentially formed on a long substrate. This method is especially effective when a semiconductor layer has already been formed on the substrate and a different type of semiconductor layer is to be formed thereon. It is particularly effective in forming an amorphous silicon semiconductor layer, especially in forming ili in the continuous production of amorphous silicon solar cells, which has a major problem as described above.

Hereinafter, the details of the present invention will be explained using continuous production of amorphous silicon solar cells as an example.

<Example> FIG. 1 is a block diagram of a continuous manufacturing apparatus for amorphous silicon solar cells according to the above example.

Its basic structure is disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 58-216475.

Same as that disclosed in Japanese Patent Application Laid-open No. 59-34668, p.
Type.

The reaction chambers 1, 2.3 of CVD plasma discharge forming each of the i-type and n-type amorphous silicon layers, the unwinding chamber 16, and the winding chamber 17 are connected by a buffer chamber 18 for gas isolation, The substrate 13 is transferred from the unwind roll 14 to the take-up roll 15 in a roll-to-roll manner, and three layers p, i, and n are successively formed. Note that 4 to 9 in the figure are discharge electrodes, and 10 in the figure is a high frequency power source that supplies high frequency power to each discharge electrode.

Such reaction chamber separated roll-to-roll type CVD
Using a plasma discharge device, a well-known predetermined raw material gas such as SiH4 gas is supplied to each reaction chamber 1.2.3, and p and i are applied onto a long substrate rolled up into a roll.

A solar cell was formed by sequentially stacking n-type amorphous silicon films. In this example, as described above, in the reaction chamber 2 in which the i-positive amorphous silicon layer which influences the characteristics of the solar cell is formed, the grid electrode 11 was installed between the opposing discharge electrodes 6 and 7. The grid electrode 11 is provided along the traveling direction of the flexible elongated substrate 13 so as to cover the first third of the discharge electrodes 6 and 7. A predetermined bias potential is applied to the grid electrode 11 from a power source 12. The material of the grid electrode 11 is a stainless steel wire mesh, and the roughness of the mesh is fine enough to trap the plasma, but coarse enough not to block the passage of active species. It was meshed.

As the substrate 13, in this example, 3000 aluminum metal and 50 stainless steel alloy were sequentially laminated on a polyethylene terephthalate film having a thickness of 100 μm, and the same procedure was used as in the above-mentioned Japanese Patent Application Laid-Open No. 59-34668.

I, N type amorphous silicon layers were continuously formed with constant consistency.

The thickness of p- and n-type amorphous silicon films is 200 to 30
The discharge power, substrate transfer speed, and reaction gas pressure were controlled so that the thickness of the i-positive amorphous silicon layer was approximately 5 mm. The electrode 11 is installed 25 m away from the substrate 13 (the distance between the discharge electrodes is 50 m), and the voltage is +200 to -200 cm.
The DC voltage is biased by a power supply 12 whose DC voltage can be set to an appropriate value between the two.

Figure 2 shows a negative bias potential (-20■) applied to the grid electrode 11.
A solid line A shows the relationship between the solar cell characteristics (conversion efficiency) and the discharge power when the i-positive amorphous silicon layer was formed by changing the high-frequency power applied to the discharge electrode 6.7. Naturally, an increase in discharge power increases the deposition rate as shown in FIG. 2, which corresponds to high-speed film formation. In the manufacturing method according to the present invention, as shown by the solid line A in FIG. 2, there is almost no deterioration in the characteristics of the solar cell even when the discharge power increases.

On the other hand, the characteristics of a solar cell formed in exactly the same manner using the above-mentioned apparatus except for the grid electrode 11 deteriorated as the discharge power increased, as shown by the broken line B in FIG.

In addition, when the grid electrode 11 is provided so as to cover not only the substrate entrance side but also the entire surface of the opposing discharge electrode 6.7, as shown by the dashed line C in FIG. 2, even if the discharge power is increased, The deposition rate did not increase, and high-speed film formation could not be achieved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of a continuous manufacturing apparatus for amorphous silicon solar cells according to an example of the present invention, and FIG. 2 is a graph showing the results of the example and comparative example. 1.2,3: CVD reaction'! 4.5.6, 7.8.9: Discharge electrode 11: Grid electrode 13: Substrate 18: Loose 'fJ
Patent applicant: Teijin Co., Ltd. Shinden Power Co., Ltd. (W) 21st offender

Claims (1)

[Claims] 1. In a method for manufacturing a thin film semiconductor device in which a predetermined semiconductor layer is formed on a substrate in a plasma atmosphere by chemical vapor decomposition while the substrate is being transferred, the substrate entrance side of the opposing discharge electrodes is provided. A lattice electrode made of a porous plate is provided in parallel with the discharge electrode in the middle of a predetermined range, and extends over at least the entire width of the substrate, and the lattice electrode reduces plasma impact at the start of semiconductor layer formation to form a film. A method for manufacturing a thin film semiconductor device. 2. The board is made of a long flexible board and can be rolled to
2. The method of manufacturing a thin film semiconductor device according to claim 1, wherein the thin film semiconductor device is continuously transported by rolls. 3. The method of manufacturing a thin film semiconductor device according to claim 1 or 2, wherein the substrate is a substrate on which a semiconductor layer different from that of the semiconductor to be formed has already been laminated. 4. The method for manufacturing a thin film semiconductor device according to any one of claims 1 to 3, wherein the semiconductor layer is an amorphous silicon semiconductor layer. 5. The thin film semiconductor device is an amorphous silicon solar cell,
5. The method of manufacturing a thin film semiconductor device according to claim 4, wherein the semiconductor layers to be laminated are intrinsic semiconductor layers of an amorphous silicon solar cell. 6. Amorphous silicon solar cells are manufactured by continuously transporting a long substrate in a roll-to-roll manner through gas-isolated reaction chambers that form the component semiconductor layers. A method for manufacturing a thin film semiconductor device according to claim 5.