Intrinsic stress and hydrogen bonding in glow-discharge amorphous silicon films

Abstract

We have found a strong correlation between intrinsic stress and hydrogen bonding in glow-discharge amorphous silicon (a-Si:H) films. The stress of high-deposition-rate (HDR) films continuously changes from tensile to compressive with increasing rf power. In contrast, low-deposition-rate (LDR) films indicated compressive stress in all the rf power range which was varied. However, adding a small amount of Ar to SiH4 in the LDR film deposition changes its stress from compressive to tensile as in the HDR films. IR absorption spectroscopies showed that films with compressive stress always indicated a smaller ratio of absorptions at 2070 and 2000 cm−1 α(2070)/α(2000) than the value Rc(=0.9–1.2), whereas those with tensile stress showed a larger ratio. Consequently, zero or very weak stress is reached at the ratio approximately equal to Rc, regardless of varying deposition parameters. It is also shown that annealing alters the stress of all the HDR films to strong tensile, and that α(2070)/α(2000) decreases, differing from the correlation where the rf power and Ar mixing ratio are varied.