A transfer technique of stress sensors for versatile applications

This paper reports a transfer process of silicon stress and Pt temperature sensors for versatile requirements. Based on a 3μm thick BCB adhesive layer, a 1.6 mm × 1.6 mm donor chip with stress and temperature sensors, which are fabricated on the silicon-on-insulator wafer using standard MEMS process, is bonded on a target wafer. After the bottom silicon layer and the insulator SiO₂ layer of the donor chip are etched by XeF₂ gas and RIE technique, only about 0.2μm thick top sensor layer and 0.7μm thick aluminum layer used as conducting wires and pads are transferred onto the target wafer for the measurement of its in-plane stresses. Through the transfer process of stress and temperature sensors, the in-plane stresses of the target wafer caused by the fabrication processes or the package processes can be measured.