A MEMS-based resistive vacuum gauge with voltage readout

A 20nm thick Ni resistor element was fabricated on a 1μm thick, 400μm wide silicon nitride bridge via bulk micromachining. By applying a given power to the resistor its temperature increases, as the pressure decreases, since fewer gas particles are available to transfer heat away from the resistor. Rather than sensing the resistance change, a thin film thermocouple consisting of 20nm Ni and 20nm Cr was fabricated in the center of the resistor element, allowing the direct measurement of a voltage signal. It will be shown that by fabricating two gauges with different d´s, but identical thermal resistances, the measurable pressure range can be extended from two orders of magnitude to about 4 orders of magnitude. One of these gauges was incorporated into a miniature vacuum chamber with a volume of about 1cm³ to observe potential leakage and pressure bursts from operating a field emitter device in close proximity.