Optically High Transparent SiN Mask Membrane with Low Stress Deposited by Low Pressure Chemical Vapor Deposition

Abstract

Optically high transparent and low-stress silicon nitride film for X-ray mask membrane was successfully deposited by low pressure chemical vapor deposition (LPCVD). Deposition of silicon nitride films in a relatively higher temperature range of 900°C-1000°C was investigated as a function of deposition temperature and reactant gas flow (SiH₂Cl₂ and NH₃). Silicon nitride films of low tensile stress in the order of 3-5×10⁸ dyn/cm² with low refractive index of 2.05 were obtained at 1000°C. Silicon nitride membrane deposited at 1000°C showed optical transparency ∼95% (λ=633 nm). Use of such optically high transparent silicon nitride film will be helpful in reducing the alignment signal detection error, which is required for highly efficient mask wafer alignment.