Development of Silicon Nanowire-Based NEMS Absolute Pressure Sensor Through Surface Micromachining

This letter reports on a nano-electro-mechanical system (NEMS) pressure sensor with p-doped silicon nanowires (average cross-sectional area ~100 nm
²
) as piezoresistive sensing elements. Taking advantage of surface micromachining, an absolute pressure-sensing device is developed using front-side isotropic etching. In contrast to the previously reported silicon nanowire (SiNW) pressure sensor processed with bulk micromachining through the backside deep reactive ion etching (DRIE), nonlinearity has been reduced to 0.31% (BFSL). In addition, the performance variations across the wafer have been significantly reduced to 6% in comparison with a 33% sensitivity fluctuation across the 8-inch wafer reported in our early work fabricated by a DRIE process. After front-side vacuum sealing, temperature-induced performance degradation has also been minimized. Moreover, the dramatic geometry downsizing (device footprint $\sim 385~\mu \text{m}^{\mathrm {\mathbf {2}}}$ ) validates the scalability of the SiNW-based NEMS sensor. With excellent uniformity, the SiNW-based sensor can be commercially manufactured on an 8-inch wafer at lower cost with high yield.