The kinetics of irreversible tensile stress development during annealing of dielectric films fabricated by plasma-enhanced chemical vapor deposition (PECVD) were studied, and the hypothesis of a rate-limiting H diffusion process was tested. Extra-long anneals (~36 h) with in situ stress measurements were made: experimental observations on a silicon nitride film do not display the characteristics expected of stress development limited by diffusion. Nor do these data imply a limiting first-order reaction process. Infrared spectroscopy results indicated that the amount of bonded H decreased in proportion with the stress increase, strongly implying stress development was a result of the reduction of bonded H alone. These findings demonstrated that diffusion in PECVD films does not limit stress development; instead, it was likely governed by non-straightforward kinetics of H bond breaking, which was followed by the rapid diffusion of product molecules.

Hydrogen Diffusion as the Rate-Limiting Mechanism of Stress Development in Dielectric Films. M.P.Hughey, R.F.Cook: Applied Physics Letters, 2004, 85[3], 404-6