Design And Testing Of Highly Robust MEMS Pirani Vacuum Gauge Based On Porous Silicon Thermal Insulation Layer

Pirani vacuum gauge as one of the vacuum sensors,its measurement range covers from rough vacuum to medium vacuum.As an important device for measuring vacuum,its applications include scientific research,semiconductors,aerospace and other fields.In this paper,Micro-Electro-Mechanical System(MEMS)technology is combined with Pirani vacuum gauge,and considering that the suspended thin film structure is mostly used in the research of gas heat conduction vacuum gauge,which is limited by the low strength of thin film structure,there is the risk of thin film rupture and vacuum gauge failure under high temperature and mechanical shock.In this thesis,a highly reliable porous silicon MEMS Pirani vacuum gauge is proposed.Firstly,the working principle of vacuum gauge was carefully analyzed and discussed,and the structure of porous silicon MEMS vacuum gauge was designed based on the derivation of equations.The thermal conductivity,microhardness and elastic modulus of the prepared porous silicon were measured by Raman spectroscopy and nanoindentation local unloading method,and the thermal conductivity of porous silicon was finally measured as 3.26 W/(mK),the microhardness as 0.43 GPa and the effective Young’s modulus as about 7.84 GPa.The application of one of the porous silicon thermal insulation layers greatly improves the robustness of the MEMS vacuum gauge,and its pure solid-state structure can adapt to high-intensity airflow impact.This solid-state,non-hanging film structure of the MEMS Pirani vacuum gauge is mechanically stable and unaffected by strong gas convection impact and mechanical vibration.Then a vacuum gauge test system was built.After testing,the vacuum measurement range of the Pirani vacuum gauge designed in this paper reached 5×10-1～105 Pa,and different vacuum pressure sections were tested separately to obtain the linearity of each vacuum pressure section.degree and sensitivity.Among them:0.5～4 Pa:The linearity is 9.15%,the sensitivity is 5.91 mV/Pa;4～50 Pa:The linearity is 21.03%,the sensitivity is 0.804 mV/Pa;50～200 Pa:The linearity is 10.21%,the sensitivity is 0.86 mV/10Pa;200～700 Pa:The linearity is 8.98%,the sensitivity is 0.13 mV/10Pa;700～1500 Pa:The linearity is 10.97%,the sensitivity is 3.11 mV/KPa;1500～4000 Pa:The linearity is 11.82%,the sensitivity is 8 mV/10K Pa;4000～10000 Pa:The linearity is 17.06%,and the sensitivity is 2.33 mV/10KPa;10000～100000 Pa:The linearity is 8.14%,and the sensitivity is 3.54 mV/100 K Pa.The experimental results show that the full-scale response of the chip is 94.55 mV,and the linearity is good enough to meet the measurement of rough vacuum to medium vacuum.