Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – Having glow discharge electrode gas energizing means
Reexamination Certificate
2000-03-07
2002-09-17
Mills, Gregory (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
Having glow discharge electrode gas energizing means
C118S7230ER, C118S7230AN
Reexamination Certificate
active
06451160
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to Japanese Patent Application No. Hei 11(1999)-039578 filed on Feb. 18, 1999, whose priority is claimed under 35 USC §119, the disclosure of which is incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma generation apparatus and method for manufacture of a functional thin film of a semiconductor or the like by plasma-enhanced chemical vapor deposition. In particular, the invention relates to apparatuses for performing plasma-enhanced chemical evaporation of or plasma etching on a semiconductor thin film such as a hydrogenated amorphous silicon thin film or an insulating film with high-frequency plasma enhancement.
2. Description of the Related Art
The plasma-enhanced chemical vapor deposition (CVD) that forms a semiconductor film by using plasma is widely employed in manufacturing electronic devices such as integrated circuits, liquid crystal displays, and solar panels. A general method of plasma-enhanced CVD will be described with reference to FIG.
8
.
Electrically insulated conductive plates
102
and
103
are provided in a vacuum container
101
as electrodes that are opposed to each other. High-frequency power having a frequency of 13.56 MHz, for example, is supplied from a plasma generation power source
104
via an adjustment circuit
105
. When a high-frequency voltage is applied to the electrode
102
, glow discharge occurs between the electrode
102
and the ground-potential electrode
103
, whereby plasma is generated between the electrodes
102
and
103
. A material gas G that is caused to flow between the electrodes
102
and
103
is dissociated. With the presence of the dissociated material gas G, a semiconductor film is formed on a substrate S that is mounted on the electrode
103
.
In recent years, to increase the film forming rate by increasing the plasma density and to form a high-quality film by reducing the degree of ion damage of films by decreasing the ion sheath voltage, apparatuses have been developed that use a power source of higher frequency bands, in particular, an RF band (13.56 MHz), a VHF band (tens of megahertz), and a UHF band (hundreds of megahertz). In particular, it has already been reported that satisfactory film formation can be attained by a method in which plasma CVD is performed by using small-area electrodes and applying high-frequency power of a VHF band.
Further, in recent years, functional thin films measuring about 1 meter have come to be desired for electronic devices such as liquid crystal displays and amorphous solar panels and attempts to develop a large-area film forming technique using the above manufacturing method have been made. One of the important subjects in attaining the large-area film formation is to develop a technique for forming a film that is uniform in thickness and film quality. An example of such a technique is such that the surface shapes of electrodes are modified so that the electric field strength between the electrodes becomes uniform in the same plane. One factor that relates to a phenomenon that the uniformity of the film thickness and (or) the film quality becomes lower as the film area is increased is a power feeding method for the glow discharge electrode.
In the conventional feeding method for the glow discharge electrode, the skin effect causes supplied high-frequency waves to travel through the surface of the outer wall of a metal reaction container and hence the high-frequency waves are applied to the cathode electrode, for example, from a peripheral portion of the outer wall of the reaction container. This feeding method has problems that the feeding position with respect to the electrode cannot be changed even if the feeding point (power source connecting portion) is changed and that the impedance to the electrode as viewed from the feeding point is large.
A method in which a plurality of contact bodies are interposed between the power source connecting portion and the electrode surface (Japanese Unexamined Patent Publication No. Sho 64(1989)-89316) is known as a method for decreasing the impedance from the power source to the electrode.
Although plasma CVD apparatuses using high-frequency power of a VHF band or a UHF band provide the advantage of improved film quality as mentioned above, they have a problem that the film forming rate and the film quality become non-uniform when those apparatuses are applied to formation of a large-area film. For example, if high-frequency power of VHF or the like is used in a large-area film forming apparatus, the film forming rate at an electrode peripheral portion is much smaller than at an electrode central portion.
Non-uniformity in film forming rate in the electrode plane and resulting non-uniformity in film quality lead to reduction in the characteristics of an amorphous silicon solar panel, for example, and hence they are serious problems in film forming apparatuses for solar panels. It is generally known that the non-uniformity in film forming rate is due to a non-uniform in-plane profile of the electric field strength between the electrodes and that the electric field strength profile in the electrode plane becomes less uniform as the wavelength of high-frequency waves applied approaches the electrode length. As the electric field strength profile becomes less uniform, a variation occurs in the plasma density profile and the radical density profile and hence in the film forming rate profile. In plasma etching apparatuses, a variation similarly occurs in the profile of the electric field strength between the electrodes, which causes a problem that the etching rate varies.
On the other hand, the method of the above-mentioned publication No. Sho 64(1989)-89316 has been proposed to make the in-plane profile of the high-frequency electric field strength uniform. However, this method cannot decrease the impedance to a large extent because of the skin effect. In particular, when high-frequency power of a VHF band or a UHF band is used, the impedance becomes large and the profile of the electric field strength between the electrodes becomes non-uniform.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems in the art, and an object of the invention is therefore to provide a plasma generation apparatus and method capable of making the film forming rate and the film quality uniform by preventing the impedance from becoming unduly large and thereby making the profile of the high-frequency electric field strength in the electrode plane uniform even in a case where in a semiconductor film forming apparatus or the like the frequency of power supplied to an electrode is increased to improve the film quality to such an extent that the electrode length is no longer negligible with respect to the wavelength of high-frequency waves.
According to the present invention, there is provided a plasma generation apparatus comprising: a high-frequency power source section; a reaction container to which a material gas is to be supplied; a pair of electrodes that are provided in the reaction container so as to be opposed to each other to generate plasma in between when supplied with high-frequency power by the high-frequency power source section; a conductive connection member that is part of an outer wall of the reaction container and that has, on one side, at least one power source connecting point that is connected to the high-frequency power source section and has, on the other side, at least one electrode connecting point that is connected to the one of the pair of electrodes; and high-frequency current transmitting means provided in the conductive connection member in the vicinity of the at least one power source connecting point, for adjusting impedance between the at least one power source connecting point and the at least one electrode connecting point.
That is, the high-frequency power source section is connected to one of the electrodes (e.g., a cathode electrode) via the conducti
Nakano Takanori
Taniguchi Hiroshi
Crowell A. Michelle
Mills Gregory
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
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