Large area radio frequency plasma for microelectronics processing

Radio-frequency ~rf! inductively coupled planar plasma ~ICP! provides a better way to generate spatially confined high density gas discharge plasmas for microelectronics processing. Commercial processing equipment using this technique is currently available, but is limited in size to 20 cm in diameter by problems with plasma uniformity and antenna dielectric window erosion. We have developed a new planar ICP antenna and dielectric window design that allows for larger dimensions ~up to 50 cm in diameter! with good uniformity. The current art ICP antenna requires a thick quartz ~or ceramic! plate vacuum window to separate the rf inductor and the plasma. The larger the antenna diameter the thicker the dielectric. The thick dielectric reduces inductive coupling efficiency. The large area coil and associated matching network can introduce plasma uniformity problems. Our device incorporates both the rf inductor and the dielectric window inside the vacuum chamber, allowing space for a thin layer of quartz or other dielectric material. Thus, the dielectric window design is only focused on materials for the given process chemistry to be placed between the coil and the excited plasma, rather than also including mechanical strength to hold a vacuum over a wide area. This thin dielectric layer with our newly designed planar coil coupler allows the plasma to be scaled to a 50 cm diameter while maintaining radial uniformity. In this article we report only plasma ashing results for a 20 cm planar ICP device that shows 2% nonuniformity across 15 cm wafers. The measured flux of atomic oxygen and atomic hydrogen generated by a larger planar ICP scale device is also presented. © 1995 American Vacuum Society.