Tetra-Methyl Ammonium Hydroxide (TMAH) Preferential Etching for Infrared Pixel Arrays

摘要

An infrared scene simulator employs a silicon-based micromachined Complementary Metal Oxide Semiconductor (CMOS) electronic-driven array of miniature infrared heater elements. The IR pixel array is based upon the suspension of micro-heaters over a micromachined cavity in the silicon substrate. A polysilicon resistor is used as the infrared emitter. To create IR scene generators with sufficient resolution, a large number of micro-heaters need to be produced in an array. A CMOS/microelectromechanical systems (MEMS) approach to creating these scene generators was chosen as cost effective. The CMOS electronics are produced at a commercial or otherwise standard foundry, and the resultant wafers are put through a post-processing etch step to create monolithic thermal pixel arrays (TPAs). A post-processing etch needs to completely isolate the heaters, and not affect the CMOS electronics in any way. The silicon etchant that was used as a method of thermal isolation was a tetra-methyl ammonium hydroxide (TMAH) solution.