Stress in Amorphous SiO x :H Films Prepared by Plasma-Enhanced Chemical Vapor Deposition

Amorphous SiO x (a- SiO x ) films were deposited on single-crystal Si (c-Si) and fused quartz substrates by a plasma-enhanced chemical vapor deposition technique using SiH 4 –O 2 mixtures. For stoichiometric films (a- SiO 2 ) deposited on c-Si substrates, the observed stress is compressive, and its magnitude increases with increasing deposition rate or with decreasing deposition temperature T d . The elastic constant, deduced from the stress values for films on two different substrates, decreases with increasing T d between 100 and 300° C, and is constant independent of the deposition rate when T d is fixed at 300° C. It is found that there are close relationships among the stress, the Si–O stretching absorption, the buffered HF etch rate, the density of Si dangling bonds and the deposition rate. As a consequence, for stoichiometric films deposited at T d ≥300° C, it is concluded that the Si–O–Si bond angle decreases with increasing deposition rate, leading to a decrease in the peak frequency of the infrared absorption, and that films with higher deposition rates are more defective, showing relatively high compressive stress.