Low-Temperature Conformal Atomic Layer Deposition of SiNx Films Using Si2Cl6 and NH3 Plasma

A plasma-enhanced atomic layer deposition (ALD) process was developed for the growth of SiNx thin films using Si2Cl6 and NH3 plasma. At substrate temperatures <= 400 degrees C, we show that this ALD process leads to films with >95% conformality over high aspect ratio nanostructures with a growth per cycle of similar to 1.2 angstrom. The film growth mechanism was studied using in situ attenuated total reflection Fourier transform infrared spectroscopy. Our data show that on the SiNx growth surface, Si2Cl6 reacts with surface -NH2 groups to form surface -NH species, which are incorporated into the growing film. In the subsequent half cycle, radicals generated in the NH3 plasma abstract surface Cl atoms, and restore an NHx (x = 1,2)-terminated surface. Surface Si-N-Si bonds are also primarily formed during the NH3 plasma half-cycle. The infrared data and Rutherford backscattering combined with hydrogen forward scattering shows that the films contain similar to 23% H atoms primarily incorporated as -NH groups.