Plasma ashing using microwaves via slot antenna for 300-mm wafers

Abstract

We developed a downflow asher which incorporates a large-sized microwave excited plasma source with a slot antennas, for 300 mm wafers. An ashing rate of 4.5 micrometer/min and uniformity of plus or minus 5.1% were obtained at a wafer temperature of 250 degrees Celsius. The ashing rate was approximately fourfold and the uniformity level was similar to those obtained with conventional downflow asher. The newly developed asher incorporates: (1) a high-density plasma source with slot antennas, (2) a processing chamber the shape of which is optimized by gas flow simulations and (3) a compact, high- speed wafer transportation system with an originally developed vacuum robot which is primarily responsible for the high ashing rate. The maximum overall throughput, including that of the transportation system, is 160 wafers/h. Application of this system to the ashing of 300 mm wafers is expected.