Effect of thermal annealing on mechanical stress in PECVD silicon oxides

Plasma Enhanced Chemical Vapour Deposition (PECVD) has been used to obtain silicon oxide films on silicon substrates from SiH4 and N2O as reactant gas es. The deposited layers contain moisture and other impurities. which are d esorbed during thermal cycles thus affecting the physical properties. The e volution of the mechanical stress during thermal cycles up to 350 degrees C is analysed. A significant stress hysteresis, which depend on the gas flow ratio R = [N2O]/[SiH4] and deposition temperature, is found.