Experimental investigations of anisotropic etching of Si in tetramethyl ammonium hydroxide

Anisotropic etching of silicon in tetramethyl ammonium hydroxide (TMAH) is receiving attention as a relatively nontoxic alternative anisotropic etchant for silicon (Si), for the fabrication of microelectromechanical systems, sensors, and actuators. This work presents experimental investigations on several aspects of anisotropic etching of Si in TMAH. The effects of temperature and concentration on etch rates of {100} and {110} wafers are characterized. Several previously unreported experimental findings aimed at better understanding the atomic level mechanisms are presented: underetch-rate variation with mask-edge deviation, an investigation of stirring, and a subtle effect of applied bending stress.