Stress development kinetics in plasma-enhanced chemical-vapor-deposited silicon nitride films

Abstract

The kinetics of post-deposition irreversible tensile stress development on annealing in plasma-enhanced chemical-vapor-deposited silicon nitride films are described. Films were deposited at 150, 250, and 300 °C, and in situ stress measurements were performed during thermal cycling and annealing at various temperatures up to 500 °C and for annealing times up to 36 h. A constitutive relationship between stress development and hydrogen concentration change based on a modified first-order rate law that assumes a spread in activation energies for hydrogen reaction and exsolution is proposed and found to adequately describe stress development kinetics. The long-standing belief that stress development is generated by the evolution of bonded hydrogen is validated on comparison of film stress and hydrogen concentration, as measured by forward recoil spectrometry and infrared spectroscopy. Stress development is found to be proportional to the reduction in hydrogen concentration throughout annealing with a proportionality constant that depends on deposition temperature.