Polysilicon resonant microbeam technology for high performance sensor applications

Advances have been made in the fabrication and testing of polysilicon resonant microbeams for application to high performance pressure sensors and accelerometers. Fabrication efforts have centered on three issues: interface integrity, sealing with repeatable vacuum levels and polysilicon piezoresistor performance. The interface issue requires an elimination of residues which can weaken the adhesion of polysilicon to silicon and polysilicon to processed polysilicon. An improved seal and pump technique is based on polysilicon sealing and hydrogen permeation. The sensitivity of the U-shaped piezoresistors used as beam deflection sensors can be compromised by lateral impurity diffusions. These problems can be eliminated by geometric design and heat cycle allocation. Testing of polysilicon resonant microbeams has been conducted to determine their characteristics from -60 to +180 degrees C. The results verify the applicability of resonant microbeams to high performance sensor applications. >