Ultrahigh-Vacuum Electron Cyclotron Resonance-Plasma Chemical-Vapor-Deposited SiNx Films for X-Ray Lithography Mask Membrane: As-Deposited Properties and Radiation Stability

Abstract

In this paper, a new approach to improve the radiation stability of silicon nitride film is presented using an ultrahigh-vacuum electron cyclotron resonance plasma chemical vapor deposition system. A membrane with a high optical transmittance (∼99% at 633 nm) can be obtained with a lower SiH4/NH3 flow ratio. The X-ray radiation immunity, however, can be improved with a higher SiH4/NH3 flow ratio at the sacrifice of optical transmittance. Shrinkage of the band gap and the generation of energy states in the band gap with increasing Si/N ratio of the film are speculated to be primary parameters for improving the radiation stability of silicon nitride film. Hydrogen content in the low 1021 atom/cm3 range, however, does not seem to have a critical effect on the radiation immunity, even though the Si-H bonds may act as the source for the radiation-induced damage.