Mechanical integrity failure of bulk-micromachined Si wafers: Influence of structure geometry and wafer handling

Mechanical stability and strength of bulk-micromachined silicon wafers has been studied to optimize the fabrication sequence and design for maximum yield. The effects of geometry parameters (e.g. fill factor, membrane thickness) were investigated. Results show that under the condition of reasonable geometries (limited etch depth) and a proper wafer handling the bulk-micromachined trenches and recesses do not cause any significant decrease in the mechanical-integrity-failure related yield. Very thin (<10 μm) Si membranes, on the other hand, are very sensitive to any mechanical loads and more elaborated fabrication sequence is required to guarantee a reasonable yield