JPS60149121A - Method for depositing thin film - Google Patents

Abstract

PURPOSE:To obtain the amorphous Si solar cell of uniform quality and large area while accelerating the deposition speed by arranging a grid electrode between the electrodes of anode and cathode arranged in a vacuum tank and controlling the potential distribution arbitrarily when plasma discharge is generated between said electrodes so as to deposit the product generated by decomposition of a material gas. CONSTITUTION:A grid electrode 13 is arranged between an anode plate 11 in which a plurality of substrates 18 are embedded and a cathode lower electrode 12. At this time, the electrode 13 has the structure that an insulator 19 connects reticular metallic pieces 14, 15 and 16. Then the largest negative potential is applied to the piece 15 on the side of a peripheral part and the potential is reduced gradually toward the center to make it zero in the central piece 16. thus, when a gas is introduced to generate discharge, the kinetic energy of free electrons is restrained between the anode 11 and the cathode 12 and number of electrons which enter into the anode 11 and of negative ions are reduced thereby producing the good-quality thin film 17 with good productivity.

Description

[Detailed description of the invention] Industrial applications The present invention relates to thin film deposition methods.

It is a well-known fact that thin film technology is now an important technology that can play a central role in the future development of IT in all industries. Among them, PSG is related to electronic components, especially in the semiconductor field.

It has been in the spotlight as a material for padgelons such as NSG and SiN, and as a thin film functional element such as amorphous silicon solar cells. There are great expectations for the development of SaraK into new materials.

Structure of the conventional example and its problems Among the conventional methods for forming thin films, one effective method is the plasma CVD method. This plasma CVD
Various devices can be considered as devices for realizing the method, and many of them are actually used in mass production. The outline of the most common installation device among these is shown in FIG. 1, and the problems encountered when manufacturing an amorphous silicon solar cell using the above device will be briefly explained below.

The equipment used for mass production has a tray (anode) 1 and a fixed electrode as a lower electrode (cathode) 2, as shown in FIG. The first plate is placed on the substrate 4 of FIG.
As shown in FIG. A method is used to do so.

However, when an amorphous silicon film is deposited using the above method, if the average deposition rate over the entire surface of the tray 1 is about 18/sec, the film thickness distribution, dark room conductivity, and photoconductivity are all good for solar cells. A high-quality film that fully satisfies the required performance was created. However, in terms of mass production equipment, it is necessary to further increase productivity, and it is desirable to increase the deposition rate.

Therefore, in order to examine the essential performance of the above-mentioned apparatus, amorphous silicon was deposited on the substrate 4 while the tray 1 was fixed and the deposition rate was increased to about 38/sec. , dark room conductivity, photoconductivity, and the number of pinholes, as shown in FIGS. 2A, B, and C, the central part 7 and peripheral part 6 of the lower electrode 2 shown in FIG. , a completely heterogeneous membrane was created. In other words, the film in the peripheral part 6 of the lower electrode 2 is thicker than the central part 7, has a higher dark room conductivity, and has a lower photoconductivity, resulting in a film with many pinholes. . When a solar cell is made with this film, as shown in Fig. 3, the performance of the solar cell at the deposition rate of about 38/sec is higher than that when the solar cell is fabricated at the deposition rate of about 18/sec. The performance of the battery produced would be several orders of magnitude worse.

From the above results, it was not possible to manufacture high-performance amorphous silicon solar cells with good productivity using conventional methods.

OBJECTS OF THE INVENTION Therefore, it is an object of the present invention to provide a thin film deposition method that improves the drawbacks of the conventional methods described above and can produce films of high productivity and quality.

Structure of the Invention In order to achieve the above object, the present invention improves the film quality by suppressing the deposition rate in the peripheral area of the electrode where a film with a high deposition rate and poor film quality could not be obtained, and at the same time improves the film quality at the center of the electrode. This method is characterized by improvements that have been made to increase the deposition rate while maintaining the film quality in some areas.

Description of examples Examples of the present invention will be described in detail below.

As shown in FIG. 4, a grid electrode 13 is installed between the anode tray 11 and the cathode lower electrode 12. Note that the grid electrode 13 has a mesoche-like metal piece 14,
15 and 16 are connected with an insulator 19, etc., and a negative potential is appropriately distributed to each of the mesh-shaped metal pieces, and the largest negative potential is applied to the mesh-shaped metal piece 15 on the peripheral side. The mesh-like metal piece 1 on the center side
6, the negative potential is gradually decreased, and the metal piece 16 at the center is brought to zero potential.

When a predetermined gas is introduced into a device having such a structure and a discharge is performed, the large negative potential applied to the mesh-like metal piece 15 at the periphery creates a gap between the anode 11 and the cathode 12. The kinetic energy of electrons is suppressed, and the number of electrons and negative ions jumping into the anode 11 is reduced. Here, since the reaction in the plasma largely depends on the kinetic energy of electrons, the deposition rate of the film in the peripheral portion 16 is reduced, and furthermore, the loss of the film due to negative ions and the like is reduced. Further, due to the potential gradient between the peripheral part 16 and the central part 16 of the mesh-like metal 14, electrons are accelerated from the peripheral part 15 to the central part 16, and the deposition rate of the film in the central part 16 is accelerated.

In order to essentially evaluate the above method, an amorphous silicon film 17 was deposited on the substrate 18 at a deposition rate of 3 persons/second with the anode (tray) 11 completely fixed, and the film thickness, dark room conductivity, The distribution of photoconductivity and number of pinholes was investigated and is shown in Figure 5A.

As shown in B and C, a uniform, high-quality film was obtained over the entire surface of the substrate 18.

When a solar cell is manufactured using this method, as shown in Figure 6,
The one made with a deposition rate of 1 person/second and the one made with a deposition rate of 3 people/second.
We were able to produce a solar cell with performance comparable to that produced in seconds.

Effects of the Invention When an amorphous silicon solar cell is produced by the method of the present invention, it becomes possible to produce a high-quality solar cell that is uniform over a large area at a high deposition rate. It can also be applied to the deposition of thin films using the CVD method, and it is possible to create films with uniform physical properties without pinholes or cracks.

, 4. Brief explanation of the drawings Figure 1 shows a plasma CV that has been used in the past.
D is a schematic cross-sectional view of the device, A is a schematic diagram of the device, B is a diagram showing the installation state of the substrate, C is a diagram showing the deposition state of amorphous silicon on the substrate, and FIG. 2A is a diagram showing the lower electrode and thin film. Figure 2B is a diagram showing the relationship between the lower electrode and the dark room conductivity of the thin film. Figure 2C is a diagram showing the relationship between the lower electrode and the pinhole density of the thin film. Figure 3 is a diagram showing the characteristics of a conventional amorphous silicon solar cell, Figure 4 is a schematic cross-sectional view of a plasma CVD apparatus used in the uninvented manufacturing method,
Figure 5A is a diagram showing the relationship between the lower electrode and film thickness of the device;
Figure 6B is a diagram showing the relationship between the lower electrode and the dark conductivity of the thin film, Figure 6C is a diagram showing the relationship between the lower electrode and the pinhole density of the thin film, and Figure 6 is the manufacturing method of the present invention. FIG. 3 is a diagram showing the characteristics of an amorphous silicon solar cell obtained by the method.

11... Anode (tray), 12...
Cathode (lower electrode), 13...Grid electrode, 14...Metal part of grid electrode, 16...
... Peripheral part of grid electrode, 16... Central part of grid electrode, 17... Deposited thin film, 18.
...Substrate, 19...Insulator.

Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
Diagram A f3 c w, 3 (2) Bonsai pressure (A1 kō position)

Claims (1)

[Claims] When plasma discharge is performed between the anode and cathode electrodes installed in the vacuum chamber to decompose the source gas and deposit the product on the substrate, a grid electrode is provided between the two electrodes, and the potential within the grid electrode is A thin film deposition method characterized by depositing a thin film on a substrate placed on the anode electrode or the cathode electrode while controlling the distribution arbitrarily.