CMOS-compatible high-temperature micro-heater: microstructure release and testing

Several practical issues in the fabrication and high-temperature operation of micro suspended hearing structures compatible with standard CMOS technology are reported. Suspended microstructures are fabricated in a standard CMOS process and are released by post-process silicon etching. Addition of 15 vol% of isopropyl alcohol (IPA) to 25-wt% tetra-methyl ammonium hydroxide (TMAH) is found to greatly increase yield of the post-process release etch. Electrothermal properties of the polysilicon are investigated during high-temperature operation. Significant thermally induced drift (reduction) 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 at a temperature estimated to be around 1000 degree C.