High Speed Ashing of Ion Implanted Photoresist by Microwave Excited Water Vapor Plasma with Powered Substrate

This study examined a substrate bias voltage introduced into a microwave excited water vapor plasma to enable fast ashing of photoresist implanted with high-dose ions without occurring popping. The ashing rate at the center of the ashing distribution for the photoresist implanted with boron with an implantation dose of 1×1016 atoms/cm2 was estimated as 1.0 μm/min. Results of plasma emission diagnostics suggest that rf bias application effects generated a plasma rich in excited hydrogen and oxygen atom near the substrate surface. This plasma is presumed to assist the removal of the hardened layer of ion implanted photoresist and to affect hydrogen gas addition. A self-bias voltage during bias application was sufficiently low, approximately -30 V, at a peak-to-peak voltage of 1 kV at 1 MHz.