Proposal of a new structural thermal vacuum sensor with diode-thermistors combined with a micro-air-bridge heater

New structural Pirani gauge-type thermal vacuum sensor with a microheater and two pn junction diodes, Th-A and Th-B, as a high-sensitive temperature sensor working like a thermistor formed on a micro-air-bridge (MAB) is proposed. The MAB is separated into two regions of A and B. The Th-A and the Th-B can measure temperatures of the region A and the region B connected to the region A with thermal resistance, respectively. The microheater is formed in the region A and can maintain its temperature by feedback control. The diode-thermistor, Th-C, formed on the SOI substrate is provided to measure the ambient temperature Tc. Principle of this Pirani gauge-type thermal vacuum sensor is based on the measurement of the pressure-dependent thermal conductivity of gaseous media due to the heat exchange between the heated MAB (suspended film) and surrounding gas in vacuum. This has more than two orders of magnitude measurable pressure range (2×10−3–1×105 Pa) compared with traditional Pirani vacuum sensor, and has very fast response and low power consumption.