Massive stress changes in plasma-enhanced chemical vapor deposited silicon nitride films on thermal cycling

Massive irreversible increases in tensile stress (up to 2 GPa) on thermal cycling are demonstrated for plasma-enhanced chemical vapor deposited (PECVD) silicon nitride films. Results give further evidence for the claim that this phenomenon is generic to PECVD films and is attributable to the removal of bonded hydrogen: the magnitude of stress increase is independent of the film stress and can be accounted for with a calculation involving the amount of evolved hydrogen. The massive stress changes cause film fracture in most of the films discussed here, with a large diversity of fracture behavior exhibited. The effects of deposition conditions (temperature, plasma frequency, substrate) on film modulus, hardness and coefficient of thermal expansion, as well as stress and stress hysteresis are also examined.