Chemistry: electrical and wave energy – Apparatus – Coating – forming or etching by sputtering
Reexamination Certificate
1998-10-08
2001-06-12
Nguyen, Nam (Department: 1753)
Chemistry: electrical and wave energy
Apparatus
Coating, forming or etching by sputtering
C204S298110, C156S345420, C118S7230AN, C118S7230IR, C118S7230IR
Reexamination Certificate
active
06245202
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a plasma treatment device and a plasma processing method for use in the manufacture of substrates and the like which can be used in semiconductors and liquid crystal displays, and more particularly, it relates to a plasma treatment device and a plasma processing method suitable for treatments such as etching and film formation.
BACKGROUND ART
With the large scale integration of semiconductor devices, the enlargement of diameters of semiconductor wafers and the increase of areas of liquid crystal displays, the requirements of a treatment device for carrying out etching processing and film formation processing on the semiconductors become severe year by year. Also with regard to a plasma treatment device such as a plasma etching apparatus, a plasma CVD apparatus and a plasma ashing apparatus, the above situations are similar. That is to say, in order to improve a throughput, the increase of the density of plasma and the enlargement of the area of workpieces to be processed as well as the realization of cleaning have become important themes.
As plasma sources for use in the above-mentioned plasma treatment device, there are a radio-frequency capacitively coupled plasma source, a microwave ECR plasma source, a radio-frequency inductively coupled plasma source and the like, and they are used separately in treatment process to make the best use of the characteristics of each plasma source. Among these three plasma sources, plasma treatment devices provided with the radio-frequency inductively coupled plasma source have rapidly come into wide use in recent years.
One example of the inductively coupled plasma treatment device is disclosed in Japanese Patent Unexamined Publication No. 2-235332. In this inductively coupled plasma treatment device, a high-frequency electric power on the order of several hundred kHz to several hundred MHz is fed to a loop, coil, or spiral-shape antenna which is placed on the outside of the processing chamber via an insulator such as quartz forming part of the chamber, and an induced electric field formed by the antenna supplies energy to a process gas introduced into the processing chamber to generate and maintain a plasma.
There is a case of providing an antenna inside the chamber of the plasma treatment device of the radio-frequency inductively coupled plasma. For example, Japanese Patent Unexamined Publication No. 7-106095 describes a case where a spiral-shape antenna which is a RF induction coil is set up at a position facing semiconductor wafers which is a workpiece in the chamber. In these RF inductively coupled plasma treatment devices, an induction current is generated in the plasma and the plasma and the high-frequency antenna are inductively coupled in terms of electric circuit (a transformer circuit which treats the antenna as the primary coil and the current in the plasma as the secondary coil). Therefore, this is called the inductively coupled plasma treatment device.
The advantages of the plasma treatment device of the inductively coupled plasma are: (1) in a simple and low-cost construction of a simple antenna and a radio-frequency electric power source, a plasma of relatively high density of 10
11
to 10
12
(piece/cm
3
) can be generated under a low pressure of a few mTorr; (2) by arranging a coil in a planar manner facing the workpiece, a large-area plasma can be easily generated; and (3) because of the simple interior of the processing chamber, particles flying over the workpiece during processing can be reduced.
In such an inductively coupled plasma treatment device, a plasma of high density under low pressure is generated and the mean free path of ions becomes long. This makes it possible to true up the directions of ions incident upon the workpiece and a high processing rate and fine working can be obtained.
DISCLOSURE OF THE INVENTION
In the plasma treatment device described in the foregoing Japanese Patent Unexamined Publication No. 2-235332, a high-induction antenna is arranged on an atmosphere side via an insulator such as quartz with respect to a plasma in the processing chamber. As a result, the insulator must have sufficient strength to withstand atmospheric pressure, and in view of the current condition where a workpiece occupies a large area, it is necessary for the insulator to be made thick corresponding to the area of the workpiece.
It is also pointed out that the antenna and the plasma are capacitively coupled in addition to inductive coupling. And it frequently happens that the insulator is chipped by plasma. As a result, it is necessary to thicken the insulator in order to increase reliability sufficiently. When the insulator is made thick, as described in the paper by Keller et. al reported in Journal of Vacuum Science All (5), September/October 1993, p. 2487, the plasma generation efficiency greatly drops, giving adverse effects on plasmas ignitability and stability.
On the other hand, in the plasma treatment device disclosed in Japanese Patent Unexamined Publication No. 7-106095, the antenna is installed inside the chamber, so that the above-mentioned problem of generation efficiency can be solved to some extent. Nevertheless, new disadvantages as described hereinafter will occur.
Although the surface of the inductive antenna is protected by insulating materials, a strong plasma is normally generated around the antenna in case of the inductively coupled plasma apparatus. Therefore, damage to the protective film is extremely large in the apparatus such as a plasma etching apparatus using reactive gases. The antenna itself is made of metal, thus generating metallic ions when the protective film is broken and causing metallic contamination in the semiconductor wafers. Also, the antenna itself would need to be exchanged, necessitating a great deal of time and cost for maintenance. These are the disadvantages that would appear.
Further, there is another defect. Behind the antenna, there is installed a cooling plate which must be insulated against the antenna. In such construction, it is difficult for the cooling plate to be thermally put into close contact with the antenna. Under low pressure such as in vacuum or during plasma processing, heat transfer at the contact surface of structures is extremely poor, so that the cooling effect on the antenna by means of the cooling plate cannot be expected too much.
There is an additional disadvantage. Behind the antenna installed on the opposite side of the workpiece, there is also generated a plasma of as high density as that on the workpiece side. Since the plasma behind the antenna is not effectively used for plasma processing of the workpiece, the real plasma generation efficiency decreases and, at the same time, the chamber wall behind is subjected to the strong plasma.
The present invention is made to solve the abovementioned problems and disadvantages of conventional arts. Namely, it is the object of the present invention to provide a plasma treatment device which can generate a stable plasma with high efficiency under wider operating conditions by solving the problems of the plasma generation efficiency in case of the plasma treatment device where the induction antenna is installed on the atmosphere side, and the problems of surface protection and cooling of the induction antenna as well as the problem of a decrease in efficiency due to plasma generation behind the antenna in case of the plasma treatment device installed inside the processing chamber. It is another object of the present invention to provide a plasma treatment device which has high reliability with ease of maintenance.
A first embodiment of the present invention to accomplish the foregoing objects is that the foregoing problems can be solved by building the induction antenna as an integral part of the chamber inside the processing chamber. The antenna to which a high-frequency power is fed is insulated with an insulating material of proper thickness against the chamber, and to protect it from the plasma or reactive gases for processing plasma, the surface i
Edamura Manabu
Kanai Saburo
Nishio Ryoji
Yoshioka Ken
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Nguyen Nam
VerSteeg Steven H.
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