Preparation of ultra-thin oxide films by low-temperature remote plasma-assisted process

Ultra-thin (1.0-3.0nm) gate dielectrics have been formed by remote plasma-assisted oxidation/nitridation of a crystalline Si(100) surface at low temperature (200-300 degrees C). Two different remotely plasma-excited gas mixtures (i)He/O-2 and (ii)He/N2O have been used for this process. On-line Auger electron spectroscopy (AES) was used to estimate the dielectric film thickness and to track the evolution of the film growth. AES results have established that the Si surface is O-atom terminated for the He/O-2 mixture, but N-atom terminated for the He/N2O mixture. And for the He/N2O mixture, the localization of N-atoms has been confirmed by non-linear optical second harmonic generation (SHG) spectroscopy studies of O- and N-atom terminated surfaces. Nitrogen atoms are incorporated not into the bulk of the dielectric film but the Si-SiO2 interface. However, if RF power from is increased from 30W to 60-100W, nitrogen atoms can be incorporated at the top surface of oxide as well.