Hydrogen content of thermally nitrided thin silicon dioxide films

Abstract

The hydrogen content of thermally nitrided silicon dioxide films (20–120 nm thick) was measured by means of the resonant nuclear reaction 1W(15N, αγ)12C. Although the hydrogen concentration in these films amounts to 1–3 at. %, no significant diffusion of hydrogen into the underlying silicon was observed. The hydrogen concentration is largest in the thinnest oxide films: nitridation at 1000 °C results in a higher hydrogen content than at 800 or 1160 °C. Although the exact shape of the in-depth hydrogen profile, especially in the surface and interface regions, could not be clearly resolved, the detected amount of incorporated hydrogen is such that only part of it can be bonded to nitrogen atoms. Hydrogen must also be incorporated as water, molecular hydrogen, Si–H or O–H groups, a fact which must play a role in the observed changes in electrical behaviour upon nitridation of thin silicon dioxide films.