a silicon - on - insulator substrate is anodically bonded to a glass substrate in a mems structure with or without electrically bypassing the insulator layer by electrically comprising the silicon layers . the insulator layer serves as an etch stop to create a well - defined , thin silicon membrane for a sensor . a second glass substrate is anodically bonded to the other side of the soi substrate , and debonding of the existing anodic bond prevented by eliminating any potential drop across the existing bonded surface .