A MEMS-based temperature-compensated vacuum sensor for low-power monolithic integration

Abstract

This paper presents a MEMS resonator-based vacuum sensor with a low-power transimpedance amplifier and a mixer-based frequency-to-digital converter. The MEMS resonator is fabricated in a CMOS-compatible process, and a 130 nm CMOS technology is used to design the integrated circuitry. The vacuum sensor operates in the pressure range from 10 to 1200 mbar with a resolution of ~2 mbar. The system is temperature-compensated between -10°C and 60°C. The simulated power consumption of the entire system is less than 495 W from a 1 V supply. I. INTRODUCTIONVacuum sensors are essential to monitor pressure levels in a variety of applications, e.g. aerospace, automotive, medical, etc. These sensors must be accurate in the presence of environmental variations, e.g. of temperature, while still providing a low-power, low-cost, and compact solution, especially in mobile applications. A MEMS beam resonator, whose frequency of vibration shifts with ambient pressure variations, was designed to ensure accuracy over a wide range of temperatures. The MEMS process used to fabricate this resonator is fully compatible with standard CMOS technology, allowing for a single-chip solution with features such as temperature compensation and auto-calibration. This work expands on the previously demonstrated concept of mixing resonant frequencies [1, 2] to create a low-power integrated pressure sensor system. The system offers accurate and reliable performance over a wide temperature span, while still exhibiting the sensing range of many commercial sensors, e.g. [3]. A resonant sensor was chosen for its numerous advantages compared to other sensor types such as piezoresistive or capacitive diaphragm-based sensors and Pirani gauges. Since resonant sensors rely on variations in frequency as opposed to amplitude, they are less susceptible to noise and interference [4,5]. This translates into measurements with a high degree of accuracy, as well as increased sensitivity and resolution. Resonant sensors also exhibit better long-term stability than piezoresistive and capacitive counterparts [6], both of which involve diaphragms that are susceptible to wear and tear. Moreover, resonant sensors are less prone to hysteresis effects, which can adversely affect other sensor types [5].This paper first discusses the MEMS resonator sensor, then describes the sensing system, and finally presents the simulation results.

RF-MEMS Components and Networks for High-Performance Reconfigurable Telecommunication and Wireless Systems

“…The protective lid serves to prevent microsystems-based components from harmful environmental factors, but also to establish optimal conditions for their functioning. For example, MEMS resonators exhibit very high Q-factor when operated in a vacuum [15]. Moreover, the package has also to ensure the redistribution of the electrical signals between the RF-MEMS device and the external world.…”