2000-Atmosphere Chip-Scale Packaged Bulk-Type Pressure Sensor with Dual-Cavity Induced Stress Amplification

Characterized up to a pressure of 200 MPa, a bulk-type single-cavity pressure sensor with a sensitivity of
$79 \mu \mathrm{V}/\mathrm{V}/\text{MPa}$
was previously reported. However, the capability of such a construction had not been fully realized since the pressure sensitivity was limited by the bulging of the surface on which the piezoresistive sensors were constructed. Presently reported is an improved dual-cavity design that incorporates a pressure sensing middle plate sandwiched between two vacuum-sealed cavities. Guided by finite-element analysis, the thickness of the sensing plate and the height of the cavities have been optimized. Over the same pressure range of 200 MPa, the new sensor exhibits a pressure sensitivity of
$200\ \mu \mathrm{V}/\mathrm{V}/\text{MPa}$
. This is 2.5× higher than that of the single-cavity design. In addition, a new chip-scale packaging scheme is proposed, providing silicon columns functioning as both electrical leads and stress-relieving structures.