Anisotropic etching of silicon for accelerometer chip fabrication

Anisotropic etching of (100) single crystal silicon (SCS) in potassium hydroxide (KOH) -- water solutions and Ethylene diamine pyrocatechol (EDP) -- water solutions has been investigated for fabrication of a seismic mass -- spring structure used in inertial accelerometers. The vertical anisotropic etching rate and lateral undercut rates have been experimentally determined in both the cases. For EDP the effect of temperature on the etching rates have been found to follow an Arrhenius type of temperature dependence. The activation energies vary from 0.17 eV to 0.58 eV for EDP solutions of varying concentration. The effect of addition of iso-propyl alcohol to KOH have resulted in reduction of etching rates. The basic design rules for etching a seismic mass structure with vertical end walls on (100) silicon wafer are highlighted.