Relationship between the stress and bonding properties of amorphous SiNx:H films

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Abstract
Amorphous SiNx:H (a-SiNx:H) films were deposited at 300 °C on single-crystal Si and fused quartz substrates using SiH4-NH3 mixtures. The stress and vibrational absorption were investigated as a function of the N content x. Increased tensile stress subsequent to a reduction in the compressive stress with increasing x was observed. From the values of stress determined for films on two different substrates, values of Y/(1−ν) for a-SiNx:H films were estimated, where Y is Young’s modulus and ν the Poisson ratio. The values of Y/(1−ν) rapidly decreased with an increase in x, from 4.2×1012 dyn/cm2 for a-Si:H films to about 2.5×1011 dyn/cm2 for a-SiNx:H films having x above 1.0. It was found that the measured tensile stress in a-SiNx:H films for high x above 1.0 was caused by the intrinsic stress, and that incorporated NH bonds act to relax the intrinsic stress. These results were discussed in terms of the change in the bonding configuration as a function of x, based on a modified random bonding model.