DEUTERIUM DIFFUSION INTO PLASMA-DEPOSITED SILICON OXYNITRIDE FILMS

Plasma-deposited silicon oxynitride films have been annealed in the temperature range 800-1000-degrees-C in a D2/N2 gas mixture in order to study the H-D exchange reaction in the surface region of these materials and the diffusion rate of hydrogen in these materials. The hydrogen and deuterium depth profiles and the H and D bonding configurations were examined using Elastic Recoil Detection and Fourier Transform Infrared Absorption Spectroscopy. In the as-deposited materials the diffusion of hydrogen appeared to be very fast. This allowed a separate study of the hydrogen-deuterium exchange reaction. We deduced the activation energy for the reaction of nitrogen-bonded hydrogen in the material with D2-bonded deuterium from the gas phase to be 1.5 eV. in the pre-annealed oxynitrides the diffusion rate appeared to be decreased down to values of 10(-12) to 10(-13) cm2/s in the range 900-1000-degrees-C. Both the exchange rate and the diffusion coefficient increase with the O/(O + N) concentration ratio for O/(O + N) > 0.3.