M. Nagatsu, I. Ghanashev, S. Morita, N. Toyoda* and H. Sugai

Graduate School of Engineering, Nagoya University
Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
nagatsu@nuee.nagoya-u.ac.jp

*Nissin Inc., 10-7, Kamei-cho, Takarazuka, 665, Japan

We have been studying the production of large planar surface wave plasmas excited by a 2.45 GHz microwave via a pair of inclined slot antennas through a large quartz window (with a diameter of 22 cm). High density (>3x1011 cm-3), planar plasmas have been produced in a cylindrical chamber at Ar pressures between 10 mTorr and 1 Torr. To realize a large diameter plasma source with a diameter of >60 cm, however, it will be generally required to use a larger and thicker dielectric window. From a point of view of developing an economical and impurity-less etching plasma source, it is advisable to reduce the area of the dielectric-covered part of the chamber lid, containing the slot antennas, as much as possible. In this study, we present the experimental results of non-magnetized overdense Ar plasma produced under a metal-plasma boundary.

We used an aluminum discharge chamber consisting of two sections; the upper part was a cylindrical section with a diameter of 22 cm and a length of 9 cm and the lower part was a cubic plasma reactor section . Two small quartz disks with a diameter of 70 mm were fitted in the stainless steel circular plate (24 cm-diameter) attaching a thin metal plate with a pair of slots. The 2.45 GHz microwave with a power of 0.2~3.0 kW was fed into the discharge chamber filled with Ar through a pair of slot antennas below the small quartz disks. Measurements of the plasma parameters and electric field intensity were carried out using a f 0.7 mm tungsten wire probe, movable in the z-direction.

Experimental results show that overdense, homogeneous plasmas can be successfully produced at a pressure of ~15 mTorr. The present experimental results suggest that the proposed microwave plasma source using the new type of locally vacuum sealed slot antennas is attractive and promising for the next-generation large-area processing plasma devices.