CMOS MEMS capacitive absolute pressure sensor

Abstract

This paper presents the design, fabrication and characterization of a capacitive pressure sensor using a commercial 0.18 μm CMOS (complementary metal-oxide-semiconductor) process and postprocess. The pressure sensor is capacitive and the structure is formed by an Al top electrode enclosed in a suspended SiO 2 membrane, which acts as a movable electrode against a bottom or stationary Al electrode fixed on the SiO 2 substrate. Both the movable and fixed electrodes form a variable parallel plate capacitor, whose capacitance varies with the applied pressure on the surface. In order to release the membranes the CMOS layers need to be applied postprocess and this mainly consists of four steps: (1) deposition and patterning of PECVD (plasma-enhanced chemical vapor deposition) oxide to protect CMOS pads and to open the pressure sensor top surface, (2) etching of the sacrificial layer to release the suspended membrane, (3) deposition of PECVD oxide to seal the etching holes and creating vacuum inside the gap, and finally (4) etching of the passivation oxide to open the pads and allow electrical connections. This sensor design and fabrication is suitable to obey the design rules of a CMOS foundry and since it only uses low-temperature processes, it allows monolithic integration with other types of CMOS compatible sensors and IC (integrated circuit) interface on a single chip. Experimental results showed that the pressure sensor has a highly linear sensitivity of 0.14 fF kPa −1 in the pressure range of 0-300 kPa.

MEMS capacitive pressure sensor monolithically integrated with CMOS readout circuit by using post CMOS processes

“…To date, various CMOS-MEMS devices have been implemented by using post-CMOS process such as inertial sensors, magnetometers and pressure sensors, etc. [8][9][10][11].…”

Characterization of CMOS-MEMS Resonant Pressure Sensors

“…[3]- [6]. The capacitive MEMS pressure sensors are the most widely used pressure sensor types, as they show excellent noise performance, exhibit low power consumption and permit easy integration with processing circuitry [4], [6], [7].…”

“…For example, Narducci et al reported a capacitive pressure sensor using Al metal layers of a commercial CMOS process as sensing electrodes [6]. Cheng et.…”

Weaving of Fabric for Meter-Scale Floor Touch Sensors Using Automatic Looming Machine

“…(5,6) However, meter-scale touch sensors are difficult to fabricate using the current sensor manufacturing technology. (11)(12)(13) The critical problem of meter-scale floor touch sensors is their size: the sensors are not several millimeters squared (11)(12)(13) but several meters squared. The existing fabrication technology of silicon-based micromachining provides 5-mm-wide small pressure or touch sensors with high accuracy, but they must be at least 30 cm (12,13) owing to the silicon wafer size and the chamber size of machining tools.…”