Film strain and compositional changes in thermally nitrided silicon dioxide thin films

The nature of the Si-O bonds, composition, and film strain changes in thermally nitrided silicon dioxides in NH3 at 1000 °C and 1 atm is investigated with Fourier transform infrared spectroscopy and spectroscopic ellipsometry. Shifts of the transverse optical and longitudinal optical phonons of O in Si-O-Si bridging bonds are the results of both compositional and strain within the silicon dioxide matrix. Red shifts during the initial nitridation period are followed by blue shifts at longer nitridation times. Red shifts can be explained by nitrogen incorporation and strain accumulation, while bulk film strain relaxation in nitrided oxides is most likely responsible for the blue shifts.