Performance enhancement of Pirani gauge on silicon-on-insulator wafer with simple fabrication process

A micro-Pirani gauge, operating in the range of vacuum to atmospheric pressure, is designed, fabricated and characterized. The proposed micro-Pirani gauge is fabricated on a commercially available silicon-on-insulator (SOI) wafer with a simple micromachining technique. Since the micro-Pirani gauge has one heater with triple heat sinks, a new mathematical model is developed and validated with the experimental results. By using the mathematical model, the design parameters-thickness, width, and length of the heater and the gaps between the heater and heat sinks-are optimized for attaining a wide operating range of 0.05-760 Torr. The heater dimensions and gaps in the optimized micro-Pirani gauge are as follows: thickness of 1.5 μm, width of 3 μm, and length of 350 μm for the heater, and gaps of 0.6 and 1 μm in the lateral and vertical directions, respectively. The total area of the micro-Pirani gauge, including the four bond pads, is 950 × 700 μm2.