A Novel Barometric Pressure Sensor Based on Piezoresistive Effect of Polycrystalline Silicon

Abstract

In this work, we propose a novel barometric pressure sensor based on the piezoresistive effect of polycrystalline silicon (Poly-Si). Key process steps for the fabrication of the barometric pressure sensor are explained. A sealed cavity is formed under the insulator diaphragm, and piezoresistors composed of 0.35 ㎛ thick Poly-Si is formed on the diaphragm. The distance between the diaphragm and the silicon substrate in the cavity is 2 ㎛. The Poly-Si is doped by implanting boron ions at a heavy dose and the effect of the dose is investigated. In this sensor, the stress and strain of diaphragm induced by an external atmospheric pressure are read by the piezoresistance change of the Poly-Si. The displacement of the diaphragm showed 0.17 ㎚ change at 1 h㎩. The changes in the strain applied to the Poly-Si on the diaphragm lead to a change in piezoresistance. The change in piezoresistance is amplified using a Whetstone bridge circuit fabricated on the same chip. The barometric pressure sensor has a sensitivity of 2.5 ㎶/h㎩ at a boron dose of 5×1015 ㎝SUP-2/SUP