A micromachined Knudsen pump for on-chip vacuum

This paper describes a single-chip micromachined implementation of a Knudsen pump-a type of vacuum pump that works by the principle of thermal transpiration, has no moving parts, and consequently offers high reliability. A 6-mask process was used to fabricate the pump from a glass substrate and a silicon wafer. A single stage pump and two integrated pressure sensors occupy 1.5 mm/spl times/2 mm. Measurements show that this device can evacuate a cavity to 0.46 atm while operating at atmospheric pressure and using 80 mW input power. Temperature measurements show thermal isolation on the order of 10/sup 4/ K/W between the polysilicon heater used to operate the pump and the rest of the device.