Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With radio frequency antenna or inductive coil gas...
Reexamination Certificate
2001-05-02
2004-04-13
Hassanzadeh, Parviz (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With radio frequency antenna or inductive coil gas...
C118S7230IR, C118S7230AN, C315S111510
Reexamination Certificate
active
06719876
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an internal electrode type plasma processing apparatus and plasma processing method, more particularly, relates to a plasma processing apparatus and plasma processing method provided with an inductive coupling type electrode suited for deposition of an amorphous silicon thin film used for solar cells or thin film transistors and the like on a large-area substrate.
BACKGROUND ART
The electrodes of internal electrode type plasma CVD apparatuses have conventionally been of the parallel-plate type or the inductive coupling type.
If using the parallel-plate type electrode, when trying to raise frequency of a high frequency power in order to increase a film deposition rate and improve film characteristics, the problem arises that the electric discharge becomes non-uniform. This is caused by the occurrence of a standing wave on the electrode plate resulting on non-uniform distribution of plasma density and by the production of plasma at undesirable locations due to the voltage created by the feedback current to the ground. Further, as the substrate holder is made to function as a ground electrode, the backing plate for the substrate becomes required and there is the difficulty of maintaining the clearance between the backing plate and substrate uniform when the size of the electrode plate is increased so as to form a film on a large-area substrate. Also, handling of the backing plate becomes difficult generally. Therefore, a parallel-plate type electrode is not well suited to the deposition of a film on a large-area substrate.
As opposed to the above parallel-plate type electrode, an inductive coupling type electrode is free from the above problems. Accordingly, the inductive coupling type electrode is well suited to the deposition of a film on a large-area substrate when used in an internal electrode type plasma CVD apparatus, for example.
As an internal electrode type plasma CVD apparatus using an inductive coupling type electrode, for depositing an amorphous silicon thin film on a large-area substrate to form a solar cell etc, there is the apparatus disclosed in Japanese Unexamined Patent Publication (Kokai) No. 4-236781, for example. In this plasma CVD apparatus, the electrode for discharge is formed by a flat coil having a ladder-like structure which is arranged parallel to the substrate. The ladder-like flat coil is formed by a conductive wire. The source gas is introduced from a reaction gas introduction pipe provided at a single location of the reactor, while the inside of the reactor is evacuated through an evacuation pipe provided at a single location of the reactor. This flat coil increases the intensity of the electromagnetic field and improves the uniformity of the field. Further, as a similar conventional plasma CVD apparatus, there may be the apparatus disclosed in Japanese Patent No. 2785442. In this plasma CVD apparatus, as the electrode arranged facing the substrate, a flat coil electrode formed by a single conductive wire bent multiple times to form a zigzag configuration is used. A high frequency power is supplied from a high frequency generator to the two ends of this electrode.
Concerning the above inductive coupling type electrode, the ladder-shaped flat coil electrode according to Japanese Unexamined Patent Publication (Kokai) No. 4-236781 does not have a uniform current flowing at each rung of the ladder configuration and therefore does not give a uniform distribution of the electromagnetic field, so has the problem of the inability to deposit a uniform film on the large-area substrate.
The ladder-shaped flat coil electrode is a distributed constant circuit in view of an electric circuit. A current flowing at each section in the distributed constant circuit can not be calculated simply from resistance and path length of the circuit. In the ladder type electrode, an impedance of each ladder rung relative to other ladder rungs and a geometrical relation between each ladder rung and a feeding point is related to the magnitude of Poynting vector at each ladder rung. Experimentally, the phenomenon that most of the current flows at the ladder rung near the feeding point is observed.
Further, since the zigzag flat coil electrode according to Japanese Patent No. 2785442 is produced by bending a single long conductive wire and the high frequency power is supplied from one end, the power cannot be fed efficiently. Further, while effort is made in the design to prevent the generation of a standing wave as much as possible, it is impossible to prevent the generation of a standing wave at undesirable locations due to the configuration of the electrode. Therefore, the film deposition is disturbed. That is, an unintentional standing wave is produced at the electrode, and this standing wave disturbs the distribution of plasma and results in poor uniformity of film deposition.
Then, in the plasma CVD apparatus and the like of the internal electrode type and inductive coupling type, it is desired to generate the plasma around the electrode by positively producing and utilizing the standing wave along the electrode arranged in the processing chamber. The plasma generated around the electrode receives energy for plasma generation from the antinode portion of the standing wave. Accordingly, it is preferred to control the standing wave generated along the electrode and the number or the positions of the antinodes to be formed in a desirable situation. Thereby, the standing wave can be actively used in a controllable state so that the antinodes are produced at desirable positions along the electrode, and therefore it is possible to skillfully control a distribution of plasma and to deposit a film on a large-area substrate with a good situation.
Further, as a general discussion, when proposing an electrode configuration in the internal electrode type plasma processing apparatus, concerning the standing wave positively produced on the electrode, the relationship between the frequency of the high frequency power supplied to the electrode and plasma produced around the electrode in the reactor due to the high frequency power sometimes cannot be ignored. Further, the plasma exited around the electrode due to the standing wave formed on the electrode, specifically the plasma parameters, have a major effect on the standing wave and sometimes make it necessary to reevaluate the design parameters of the electrode configuration. In this case, it is required that sufficient consideration be given to the plasma parameters when designing the electrode.
The objective of the present invention is to solve the above problems, positively utilize a standing wave in a controllable state to achieve a good uniformity of the plasma density, realize a configuration of the electrode considering the plasma parameters around the electrode, and to provide an internal electrode type plasma processing apparatus and plasma processing method which is suitable for deposition of a film on a large-area substrate for a solar cell etc.
DISCLOSURE OF INVENTION
The internal electrode type plasma processing apparatus and method according to the present invention are configured so as to achieve the above objects.
The plasma processing apparatus of the present invention is the apparatus of the internal electrode type provided with an inductive coupling type electrode arranged in a vacuum processing chamber. The above electrode is formed so that the total length thereof is substantially equal to an excitation wavelength, and one end of the electrode is grounded and another end is connected to a high frequency power source. A standing wave of one wavelength is produced along the electrode when the high frequency power source supplies a high frequency power to the electrode. When producing the standing wave on the electrode, a node of the standing wave along the electrode is formed at a central portion of the electrode, and antinodes of the standing wave are formed at half portions of said electrode, which exists at both sides of a center point.
Each part of the standing wave,
Takagi Tomoko
Ueda Masashi
Hassanzadeh Parviz
Ishikawajima-Harima Heavy Industries Co. Ltd.
Oliff & Berridg,e PLC
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