Atomic Layer Deposition of Silicon Nitride from Bis(tertiary-butyl-amino)silane and N-2 Plasma Studied by in Situ Gas Phase and Surface Infrared Spectroscopy

摘要

The atomic layer deposition process (ALD) of silicon nitride (SiNx), employing bis(tertiary-butyl-amino)silane (SiH2((NHBu)-Bu-t)(2), BTBAS) and N-2 plasma, was investigated by means of Fourier transform infrared (FT-IR) spectroscopy. In situ gas phase, film, and surface infrared measurements have been performed during different stages of the ALD process. From gas phase IR measurements it can be concluded that tert-butylamine is the main reaction product released during precursor exposure. Infrared measurements performed on the deposited SiNx films revealed the incorporation of C in the form of CN and SiC, where more fragments C is incorporated at a deposition temperature of 85 degrees C compared to 155 or 275 degrees C. Surface IR measurements, employing a four-axes sample manipulator, showed the formation of SiHand NH-groups on the surface and revealed that most of the H is incorporated during the precursor exposure step. Furthermore, after the N-2 plasma step a vibrational mode around 2090 cm(-1) was observed. This mode could be attributed to the formation of Si-NCH complexes and are likely to be formed by the so-called redeposition effect. For higher deposition temperatures, these Si-NCH complexes are removed again during the following precursor exposure step. At 85 degrees C, some of the complexes remain at the surface. Overall, from the gained knowledge about the surface chemistry, a reaction mechanism of the SiNx ALD process has been proposed.