Atomic-layer selective deposition of silicon nitride on hydrogen-terminated Si surfaces

Abstract

Atomic layer selective deposition of silicon nitride films on the hydrogen-terminated Si surface has been investigated. The film is deposited by alternate supply of SiH 2Cl 2, and NH 3 dissociated by thermal catalytic reaction on a tungsten filament. Thin (<4 nm) silicon nitride films can be selectively grown on a hydrogen-terminated Si surface. However, no film growth takes place on thermal chemically-vapor-deposited (CVD) silicon nitride in the initial ∼30 deposition cycles. The mechanism of the selective deposition is studied by means of Fourier transform infrared attenuated total reflection (FT-IR-ATR) spectroscopy. It is shown that the film growth takes place only on the surface with Si–H x ( x=1∼3) bonds, because the first nitridation by NH 3 exposure occurs only at the surface with Si–H x bonds. Once the surface N–H y ( y=1 or 2) bonds are formed, the SiH 2Cl 2 molecules react with the N–H y bonds and the film growth starts to take place. On the other hand, no film growth takes place on the thermal CVD silicon nitride since there are no Si–H x and N–H y bonds on the surface. By using the thermal catalytic method, the film quality is improved in comparison with films deposited by using NH 3 plasma.