A viscous nitride model for nitride/oxide isolation structures

The authors evaluate the properties of thin film LPCVD (low-pressure chemical-vapor-deposited) Si/sub 3/N/sub 4/ layers which are often used in local oxidation and shallow trench isolation structures. Experiments to distinguish between elastic nitride behavior and viscous nitride behavior were performed. The results favor a viscous model of nitride deformation over an elastic model, and provide the first experimental estimates of thin-film, Si/sub 3/N/sub 4/ viscosity as a function of temperature. The viscosity of thin nitride films depends on the stoichiometry of the deposited films and is well modeled by an Arrhenius dependence over typical processing temperatures. Based on these results, complex isolation topologies such as SWAMI can be modeled using the viscous models in SUPREM-IV.<>