INITIAL DEFORMATION OF SINX/AL CANTILEVERS ACCORDING TO THERMAL BUDGET FOR MEMS SENSORS

Mechanical properties of MEMS devices are specified by their structure and process parameters, such as temperature, films thickness, deposition conditions, etc. These features, in particular, the deposition temperature and post deposition treatments, determine the residual stress in the films, which affect the initial deformation, stability of parameters, sensitivity and reliability. Prediction, control and minimization of residual stress are an important part of the structural and technological design of MEMS devices. The effect of post deposition thermal treatment on the residual mechanical stress of SiNx, Al and SiNx/Al films is studied. It is shown that the tensile stress in Al film is critical for residual mechanical stress of the SiNx/Al structure and increases with the increase of temperature and time of post annealing. This allows to control the post annealing conditions and the process temperature budget to compensate the compressive stress in SiNx films and to minimize the summary residual stresses and initial deformations of SiNx/Al structure. The residual stress of the bilayer SiNx/Al structure has little effect on the film thickness, but the ratio of SiNx and Al thicknesses is significant for the thermal deformation of SiNx/Al microcantilever.