Resonant MEMS Pressure Sensor in 180 nm CMOS Technology Obtained by BEOL Isotropic Etching

Abstract

This work presents the design and characterization of a resonant CMOS-MEMS pressure sensor manufactured in a standard 180 nm CMOS industry-compatible technology. The device consists of aluminum square plates attached together by means of tungsten vias integrated into the back end of line (BEOL) of the CMOS process. Three prototypes were designed and the structural characteristics were varied, particularly mass and thickness, which are directly related to the resonance frequency, quality factor, and pressure; while the same geometry at the frontal level, as well as the air gap, were maintained to allow structural comparative analysis of the structures. The devices were released through an isotropic wet etching step performed in-house after the CMOS die manufacturing, and characterized in terms of Q-factor vs. pressure, resonant frequency, and drift vs. temperature and biasing voltage.

Design, fabrication, characterization and reliability study of CMOS-MEMS Lorentz-force magnetometers

“…Vertical metal walls that stop the advance of vHF can be created this way. Although via detaching problems have been observed with other release agents 47 , vHF has never caused these issues in our experience. This technique opens a myriad of possible structures for CMOS-MEMS design.…”

A Test Setup for the Characterization of Lorentz-Force MEMS Magnetometers

“…The proposed testing setup is based around an impedance analyzer for various reasons: availability in laboratories doing research on MEMS devices, ease of use and steep learning curve, and the convenient measurement and data processing automation by using scripts. Most importantly, though, is the fact that an impedance analyzer allows the characterization of standalone devices in electrical units directly related to the device: capacitance change under a DC voltage sweep (commonly known as C-V curve), and resonance measurement in conductance (G) and susceptance (B) or impedance (Z) [10], [11], [13], [39]. From such measurements, together with the device geometry information, other parameters can be derived, such as gap (g) and gap variation (A z ), quality factor (Q), device output current (i s ), and sensitivity in different units (as shown in Section II) to name some.…”

“…In a similar direction, CMOS-MEMS [6], [7] devices have been proposed as a solution to not only integrate MEMS magnetometers together with accelerometers and gyroscopes, but to manufacture all these devices on the same electronics die. Following such approach, our research group has developed CMOS-MEMS accelerometers [8], [9], pressure sensors [10], [11], and Lorentz-force magnetometers [12], [13] using the oxide and metal layers available in the Back-End-Of-Line (BEOL) of standard CMOS processes. Like in micro-lithography, the passivation layer is used as a mask that protects the die while a passivation window over the MEMS devices allows the etching acid to etch away the surrounding oxide and release the structures.…”

Review on Carbon Nanomaterials-Based Nano-Mass and Nano-Force Sensors by Theoretical Analysis of Vibration Behavior

“…Regarding force sensors, for manipulating nano particles, biomolecular or cells, development of high sensitivity force sensors with mechanical types [ 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ], electrical types [ 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 ], and optical types [ 65 , 66 , 67 , 68 ], it has been a great challenge for advanced micro/nano-assembly and bio-engineering. Willemsen et al [ 49 ] summarized the works of the detection of biomolecular interaction forces using AFM with silicon nitride probes by that time, in which the AFM probes were considered as force sensors that could detect the interaction forces between individual molecules in nN (10 −9 N) range by mechanical evaluations, such as strain change or frequency shift.…”