Overview of the MEMS Pirani Sensors

Abstract

Vacuum equipment has a wide range of applications, and vacuum monitoring in such equipment is necessary in order to meet practical applications. Pirani sensors work by using the effect of air density on the heat conduction of the gas to cause temperature changes in sensitive structures, thus detecting the pressure in the surrounding environment and thus vacuum monitoring. In past decades, MEMS Pirani sensors have received considerable attention and practical applications because of their advances in simple structures, long service life, wide measurement range and high sensitivity. This review systematically summarizes and compares different types of MEMS Pirani sensors. The configuration, material, mechanism, and performance of different types of MEMS Pirani sensors are discussed, including the ones based on thermistors, thermocouples, diodes and surface acoustic wave. Further, the development status of novel Pirani sensors based on functional materials such as nanoporous materials, carbon nanotubes and graphene are investigated, and the possible future development directions for MEMS Pirani sensors are discussed. This review is with the purpose to focus on a generalized knowledge of MEMS Pirani sensors, thus inspiring the investigations on their practical applications.

A combined MEMS thermal vacuum sensor with a wide pressure range

“…With the development of micromachining technology, the microelectromechanical systems (MEMS) thermal vacuum sensors demonstrate advantages of small size, fast response and low power consumption. Compared with MEMS piezoresistive and capacitive vacuum sensors, they do not need a vacuum cavity in terms of structure and pose a relatively wide pressure range with regard to performance [3,4], so they have been widely applied in many academic and industry fields [5,6].…”

Charge Density-Based Pyroelectric Vacuum Sensor

“…A typical Pirani gauge and thermistor gauge measure the change in filament temperature with pressure through the change of the resistance, and a thermocouple gauge measures the temperature of filament by means of a thermocouple [ 14 ]. The thermal conductivity vacuum gauges have experienced an improvement from having large volumes and difficulty in mass production to miniaturization of gauges by introducing MEMS (Micro-Electro-Mechanical-Systems) technology [ 15 – 17 ]. However, the MEMS thermal conductivity gauges have complex structures, and the fabrication process of some devices may be incompatible with the CMOS (the complementary metal oxide semiconductor) process, which increases the cost of gauges and relatively reduces their performance [ 17 ].…”

“…The thermal conductivity vacuum gauges have experienced an improvement from having large volumes and difficulty in mass production to miniaturization of gauges by introducing MEMS (Micro-Electro-Mechanical-Systems) technology [ 15 – 17 ]. However, the MEMS thermal conductivity gauges have complex structures, and the fabrication process of some devices may be incompatible with the CMOS (the complementary metal oxide semiconductor) process, which increases the cost of gauges and relatively reduces their performance [ 17 ]. Therefore, it is necessary to develop new types of vacuum sensors with a simple fabrication process.…”

Knudsen force based double beam MEMS vacuum pressure sensor

“…Micro Electro Mechanical Systems (MEMS) technology has led to the development of miniature vacuum sensors with many advantages over conventional vacuum gauges such as lower power consumption, higher measurement sensitivity, improved dynamic range, smaller volume, and lower fabrication costs. The common type of MEMS vacuum pressure sensor is based on thermal conductivity or membranebased measurements like a, Pirani gauge [2], ionisation gauge [3] or based on change in resonance frequency [4]. Touch mode capacitive vacuum pressure sensors to detect absolute [5] and differential vacuum pressures have also been reported * Author to whom any correspondence should be addressed.…”