Study on Fusion Mechanisms for Sensitivity Improvement and Measurable Pressure Limit Extension of Pirani Vacuum Gauges With Multi Heat Sinks

Abstract

Sensitivity improvement and measurable pressure limit extension of Pirani vacuum gauge are urgent needed for meeting the rapid growing requirements in ultra-low and wide-range pressure applications. However, the adjustable range of measureable pressure of the Pirani vacuum gauge is limited to only several orders of magnitude of vacuum range. In this work, a fusion method was proposed to improve the sensitivity and extend the measurable pressure limit of the wafer-level packaged Pirani gauge for meeting the wider applications. An analytical temperature model was presented for estimating the electrothermal behavior of the suspended micro-heater with multi heat dissipation paths. The results calculated by the model are validated by the test results of Pirani gauges with both three and four heat sinks. The results indicate that the model for Pirani gauge with one heat sink structure will no longer make sense for devices with multi heat sinks. The electrical fusion of the Pirani gauges with these structure parameters extends dynamic range from 1 ~ 104 Pa to that of $6 \times 10^{-2} \sim 10^{4}$ Pa, which generates one more sensitivity peak compared to one single device. The sensitivity peaks are $5.7 \times 10^{3}$ K/W/decade and $3.4 \times 10^{3}$ K/W/decade around the upper and lower limits, respectively. [2019-0201]