Corner rounding to strengthen silicon pressure sensors using DRIE

In this work, we optimize an existing piezoresitive silicon pressure sensor by realizing rounded structural edges instead of the sharp edges typical for KOH-etching of the sensor membrane. The advantages of an edge featuring a diameter are estimated by FEM-simulation. Based on simulation results we developed a combination of KOH and plasma etching process to obtain edges with a radius of 5 mum. The experimentally determined difference between the failure pressure of the standard sensors of approx. 3 bar and of the modified sensors of approx. 8 bar is 5 bar. This substantial increase in failure pressure extends the working range of the pressure sensor without compromising its sensitivity or signal quality. The new process requires only minor changes of the old process and is suitable for mass production of micro pressure sensors.