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same bonding configurations. The picture that rises from IR and DMR indicates that for aSi:N:H,D films, grown from source gas mixtures of R > 2, one has a significant population of N-

"Hbonds that are nearest neighbor to Si-H and N-H bonds. The close proximity of the H in the N"Hbond with another NH is measured by the IR NH resonance frequency peak at 3330 cm-I;

within this work, we measure this NH stretch vibration for films grown with R > 4 before the thermal treatment. Also, the DMR doublets, correspondent to the Si-D and N-D bonds, are shifted about 2 kHz with respect to one another. This indicates of a nearest-neighbor coupling between the deuterium of a Si-D and the more electronegative SiN-D group. This proximity produces, as far as the IR vibrational modes are concerned, a repulsive interaction that shifts the SiH stretch frequency up to 2190 cm-1 , which is beyond the chemical induction limit of 2150 cm-1 derived from an Si-H in a-Si 3N4 stoichiometric or near-stoichiometric nitrides [3]. The higher Si-H frequency is caused by an increase in the effective force constant of the Si-H bond, due to the proximity of an SiN-H group. Thus, the IR bond-stretching frequencies of the SiH and NH vibrations are determined from the particular host matrix were the bond resides, and also by the effects of nearest-neighbor N-H and Si-H bonds.[3-5] This paper shows that indeed, the films for which R > 2 do have SiH and NH bonds in nearest-neighbor arrangements. We do measure hydrogen gas evolution due to thermal annealing that is accompanied by Si-N re-bonding. Also, the SiN-H vibration peak moves to higher wave numbers with the annealing sequence and the hydrogen evolution. The remaining N-H groups, at a higher RTA temperature, are evermore distant from other SiN-H groups. Thus, the nearest neighbor frequency coupling effect between the H in one N-H group and another SiN-H group is reduced by the H2 evolution and Si-N re-bonding. The low activation energies measured for the

Si-H and N-H bond dissociations, and also a very low Si-N re-bonding activation energy are indicative of the complex collective bond breaking, H2 gas evolution, and Si-N bond formation present during the thermal annealing treatment of the nitride films. 345 Mat. Res. Soc. Symp. Proc. Vol. 398 01996 Materials Research Society

2. EXPERIMENTAL We have deposited a-Si:N:H,D films with thicknesses that ranged from 3000-5000 A. Even though an 800 A thick sample is sufficient for a regular FTIR measurement, as the sample undergoes the RTA sequence, a thicker sample provides the IR signal to account for the bonded hydrogen decrease. The IR measurements were done by a Nicolet, Magna-IR-750, Fourier Transform Infra Red spectrometer running under OMINC 1.20 software. Stretch mode area integration's, line width measurements, peak wave numbers, normalization of the data, and plotting were done in the spectrometer and at an auxiliary PC station. The ex-situ RTA experiment samples were grown on N-type (100) infrared wafer substrata in an ultrahigh vacuum multi-ch