Plasma sources and process equipment for 300-mm fabrication

The first of the two types of high-density plasma sources developed by Tadahiro Ohmi, Ph.D., of Japan`s New Industry Creation Hatchery Center and his team taps the potential of plasma excited by uniform microwave radiation from a radial line slot antenna (RLSA). In an experimental setup, researchers mounted an RLSA over a quartz plate on a cylindrical vacuum chamber. Microwaves radiated from the antenna were directed into the vacuum chamber through a quartz plate. High-density plasma was maintained with the electrons accelerated by an intense microwave electric field. Results suggest that plasma is excited near the quartz plate surface and diffuses toward the electrode. Researchers also found that extremely low ion energy is realized even when the electron density exceeds 1x1012cm-3, suggesting that various kinds of damage-free high-quality films can be formed using this plasma source. Findings from other parts of their work suggest that high-grade silicon nitride film can be formed by using high-density plasma with RLSA and this film is suitable for gate insulator applications.

The researchers also described a balanced electron drift magnetron source that realizes damage-free uniform high-rate processing on the large wafer. The process window is wide enough, according to the team, that it can deal with various etching and sputtering materials.

Researchers also proposed equipment that realizes a uniform process on large-diameter wafers. Such equipment consists of a transfer chamber containing a robot beneath the process chamber. It partitions between the process chamber and the transfer chamber at the bottom part of the process chamber and no gate valve is used at the side wall of the process chamber. Therefore, this plasma chamber can be axis-symmetrical. Consequently, the uniform plasma can be obtained above the wafer surface and the uniform wafer process can be realized, without using a large process chamber.