Microstructure release and test techniques for high-temperature micro hotplate

We report several practical issues in the fabrication and high-temperature operation of micro suspended heating structures compatible with standard CMOS technology. Suspended microstructures are fabricated in a standard CMOS process and are released by post-process silicon etching. TMAH at 25 wt% with 15 vol% of IPA is found to greatly increase yield by reducing mechanical disturbances during etching. Electro-thermal properties of the polysilicon are investigated during high-temperature operation. Significant thermally-induced negative drift in resistance at high temperatures is found, and the impact on temperature control is discussed. Thermal isolation is found to be about 50 K/mW, and reliable operation is observed near 1000/spl deg/C.