The effect of corner radius of curvature on the mechanical strength of micromachined single-crystal silicon structures

The burst pressure of typical diaphragm structures is measured for devices that have various radii of curvature at the sharp corner. When pressure is applied to the etched side of the diaphragm, burst pressure is increased by over 50% in devices with radii of curvature as little as 0.2 mu m compared to devices with no measurable radii of curvature. Devices with radii of curvature of 1.5 mu m have burst pressures that are 5* higher than those manufactured with customary methods. Finite element submodeling has been used to simulate the test results, and the models estimate the fracture strength of (100) silicon wafers at 990 kpsi in the (110) direction.<>