A free-hanging strain-gauge for ultraminiaturized pressure sensors

The first entirely surface micromachined free-hanging strain-gauge pressure sensor is presented. The sensing element consists of a 80 pm long H-shaped force transducing beam supported at both ends. The H-shape enables the strain-gauge to be a part of the beam without the need for additional layers. The beam is located beneath and attached at one end to a square polysilicon diaphragm and at the other end to the cavity edge. The diaphragm of the fabricated sensor is 2 mum thick and has a side length of only 100 mum. The new design enables a combination of high pressure sensitivity and miniature chip size as well as good environmental isolation. The pressure sensitivity of the sensor with a H-shaped 0.4 mum thick force transducing beam was measured to be 5 muV/V/mmHg. (C) 2002 Elsevier Science B.V. All rights reserved.