Pressure Sensors from Silicon Carbide.(Brief Article)

Pressure sensors that contain thin diaphragms made from the 6H polytype of silicon carbide (6H-SiC) have been developed at the John H. Glenn Research Center at Lewis Field (Cleveland, OH; Tel: 216/433-3484). These are prototypes of pressure sensors for use at high temperatures in engines, power plants, material processing systems, and numerous other applications. They were made by micromachining.

The wide bandgap (3.0-v), high-breakdown electric field (2.5-mV/cm), and high electron saturation speed (2 107 cm/sec.) of 6H-SiC make it a superior candidate material for high-temperature electronic devices. In addition, SiC exhibits excellent thermal and mechanical properties at high temperatures and large coefficients of piezoresistance - a combination of properties that makes this material suitable for high temperature electromechanical sensors.

The prototype SiC pressure sensors were batch-fabricated by micromachining and demonstrated to work at temperatures from ambient up to 500C. The 6H-SiC starting material (wafers) have micropipes in them. The processing conditions applied in this work plugged the micropipes, thereby making the 6H-SiC material useable.

The SiC pressure sensors offer the following five major advantages in addition to those mentioned above:

* Junction leakage, which renders silicon ...