VACUUM-SEALED SILICON MICROMACHINED PRESSURE SENSORS

Considerable progress in silicon pressure sensors has been made in rec ent years. This paper discusses three types of vacuum-sealed silicon m icromachined pressure sensors that represent the present state of the art in this important area. The devices are a capacitive vacuum sensor , a surface-micromachined microdiaphragm pressure sensor, and a resona nt pressure sensor. Vacuum sealing for these devices is accomplished u sing anodic bonding, films deposited using low-pressure chemical vapor deposition, and thermal out-diffusion of hydrogen, respectively. Thes e sensors emphasize high sensitivity, small size, and excellent stabil ity, respectively. The silicon-diaphragm vacuum sensor uses electrosta tic force balancing to achieve a wide pressure measurement range.