11.5: A MEMS-based vacuum gauge for measuring pressure and out-gassing rates in miniaturized vacuum microelectronic devices

Cr/Au meander-shaped resistors were fabricated on 200nm thick square silicon nitride diaphragms on silicon with diaphragm dimensions of 0.775mm, 1.025mm, 1.275mm, 1.775mm, and 2.275mm. At 760Torr, the resistors were heated to about 20°C–60°C above ambient by Joules heating and the resistances were monitored as a function of pressure from 760Torr to 2×10 −4 Torr. As expected from kinetic theory, the sensitivity of the gauges shifted from high to low pressure with increasing diaphragm size (distance from the heat source to the cold junction). Measurements were taken at powers ranging from 0.6mW to 6mW. The sensors were applied to measure potential vacuum bursts due to outgassing events in field emitters and to measure the pressure inside of glass capillaries.