Molecular models and activation energies for bonding rearrangement in plasma-deposited alpha-SiNx : H dielectric thin films treated by rapid thermal annealing - art. no. 245320

Hydrogen and nitrogen release processes in amorphous silicon nitride dielec trics have been studied by MeV ion scattering spectrometry in combination w ith infrared spectroscopy. The outdiffusion of those light constituents was activated by the thermal energy supplied to the samples by rapid thermal a nnealing treatments. Molecular models of how these reactions proceed have b een proposed based on the information obtained from the infrared spectra, a nd the validity of the models has been tested by an analysis of the activat ion energy of the desorption processes. For this purpose, the evolution of the hydrogen concentration versus the annealing temperature was fitted to a n Arrhenius-type law obtained from a second-order kinetics formulation of t he reactions that are described by the proposed structural models. It was f ound that the low values of the activation, energies can be consistently ex plained by the formation of hydrogen bonding interactions between Si-H or N -H groups and nearby doubly occupied nitrogen orbitals. This electrostatic interaction debilitates the Si-H or N-H bond and favors the release of hydr ogen. The detailed mechanism of this process and the temperature range in w hich it takes place depend on the amount and the proportion of hydrogen in SI-H and N-H bonds. Samples with higher nitrogen content, in which all bond ed hydrogen is in the form of N-H bonds, are more stable upon annealing tha n samples in which both Si-H and N-H bonds are detected. in those nitrogen- rich films only a loss of hydrogen is detected at the highest annealing tem peratures.