SELECTION OF GLASS, ANODIC BONDING CONDITIONS AND MATERIAL COMPATIBILITY FOR SILICON-GLASS CAPACITIVE SENSORS

This paper examines the process of anodic bonding with regard to the fabrication of silicon-glass capacitive sensors. Various glasses are assessed in terms of the suitability of their physical properties and results are presented on flatness control of these glasses when bonded to silicon at different temperatures. Many of the problems which can typically affect silicon-glass sensors are examined and explained in terms of the anodic bonding process. Effects such as the electrolysis of the glass and the transport of the oxygen produced in this process are discussed and design considerations for minimising deleterious effects of this oxygen are presented. We demonstrate the process of selection of glass, bonding parameters and other material selection by reference to a device on which we are currently working.