Thermal stresses and cracking resistance of dielectric films (SiN, Si3N4, and SiO2) on Si substrates

In device-manufacturing technology, it is important to understand why dielectric films crack. With this objective in mind, we have constructed an apparatus for measurement of thermal stresses in thin films (25–500 °C), obtained results on various reactively plasma deposited (RPD) Si-N and CVD SiO2 films, and developed a model which quantifies the cracking resistance of different types of RPD Si-N films. Measurements were made of the coefficient of thermal expansion α (T), which increases on going from SiO2→Si3N4→SiN→Si and the intrinsic stress, which is compressive for RPD Si3N4, nearly zero for thermal SiO2 and tensile for RPD SiN and CVD SiO2. The cracking resistance of Si-N film at a given temperature is functionally related to its density, intrinsic stress, thermal mismatch with Si, and the deposition temperature.