The removal of hardened photoresist layers by plasma ashing is an important process tool frequently used in the lithographic processing of microelectronic and optoelectronic devices. The existing techniques for plasma resist ashing have undesired ion damage to underlying device layers resulting in degraded device performance. While UV photo ashing avoids radiation damage from plasma ions, these systems are limited by very low throughput. Researchers are investigating a newly developed dual source of atomic oxygen and VUV photons to ash photoresists at high rates, at low substrate temperatures, and over wide areas with minimum ion damage and residual contamination. A spatially confined active oxygen plasma of disc shape will be used to ash hardened photoresist films with the goal of plus/minus five percent variation in uniformity over entire 15 cm diameter wafers. Wafers are located in a field free downstream plasma region, in the near afterglow, where the resist surface is exposed primarily to both a reactive atomic oxygen flux as well as a flux of 130.6 nm oxygen resonance radiation. Researchers are measuring various polymer ashing activation energies, evaluating radiation damage effects, and measuring residual surface contamination for comparison ofthe ashing approach to traditional methods.The potential commercial application as described by the awardee: Research will result in the provision of a high throughput, low temperature near afterglow plasma asher which avoids radiation damage from energetic plasma ions and minimizes residual contamination for use in the microelectronics and optoelectronics industries.
