Monolithic integration of capacitive sensors using a double-side CMOS MEMS post process

Abstract

This study presents a novel double-side CMOS (complementary metal-oxide-semiconductor) post-process to monolithically integrate various capacitance-type CMOS MEMS sensors on a single chip. The CMOS post-process consists of three steps: (1) front-side bulk silicon etching, (2) backside bulk silicon etching and (3) sacrificial surface metal layers etching. Using a TSMC 2P4M CMOS process and the present double-side post-process this study has successfully integrated several types of capacitive transducers and their sensing circuits on a single chip. Monolithic integration of pressure sensors of different sensing ranges and sensitivities, three-axes accelerometers, and a pressure sensor and accelerometer are demonstrated. The measurement results of the pressure sensors show sensitivities ranging from 0.14 mV kPa −1 to 7.87 mV kPa −1. The three-axes accelerometers have a sensitivity of 3.9 mV G −1 in the in-plane direction and 0.9 mV G −1 in the out-of-plane direction; and the accelerated measurement ranges from 0.3 G to 6 G.

Low-power Sensor Interfacing and MEMS for Wireless Sensor Networks

“…We will not go into the details of the process here for the sake of simplicity. The CMOS-MEMS process demonstrated here is inspired by previous work done at some universities (Ramstad, 2007;Sun et al, 2009). For low-power applications it is interesting to try to integrate MEMS in a deep sub-micron CMOS process.…”

Single-Side Fabrication of Multilevel 3-D Microstructures for Monolithic Dual Sensors

“…If the two sensors need to be monolithically integrated, multi-level 3D micro-structures will be inevitably fabricated in the same chip. Great efforts have been made to on-chip integrate a pressure sensor with an accelerometer by various fabrication approaches, such as silicon bulk-micromachining [3], MEMS-CMOS bonding process [4], double-side CMOS MEMS post process [5]. In the works of [2]- [5], Cross-sectional schematic of the six-level microstructured TPMS sensor.…”

Novel TPMS sensing chip with pressure sensor embedded in accelerometer

“…Various approaches, such as surface-micromachining [8], bulk-micromachining [9], double-side CMOS post process [10], and MEMS-CMOS bonding process [11], have been developed to integrate pressure sensor and accelerometer on the same chip. However, these side-by-side sensors integration approaches usually need larger space and hence limits the further shrinkage of chip size.…”