RTCVD POLYSILICON GRAIN DIMENSION CONTROL

摘要

Rapid thermal chemical vapor deposition (RTCVD) process conditions were developed to duplicate low-pressure chemical vapor deposition (LPCVD) polysilicon grain structure, surface roughness and amorphous content. The original RTCVD polysilicon process designed for high throughput produced random grain structures that did not distribute conducting dopants with the same characteristics as the columnar structure of LPCVD polysilicon. The need for ambient control of thin gate dielectric studies in RTCVD cluster systems initiated the effort to match LPCVD polysilicon, since it was the CMOS device reference. Models and results from other referenced works were used to determine surface diffusion length and nucleation driving forces as important mechanisms. Silane partial pressure was modified in the RTCVD process to achieve columnar grain structure. A design of experiment methodology was used to further match the RTCVD polysilicon surface roughness and amorphous content to LPCVD film properties. After process definition, film thickness uniformity and repeatability was monitored for production applications.