On-Chip Integration of Pressure Plus 2-Axis (X/Z) Acceleration Composite TPMS Sensors with a Single-Sided Bulk-Micromachining Technique.

Jiachou Wang,Fang Song

doi:10.3390/mi10070473

Abstract

A novel on-chip integration of pressure plus 2-axis (X/Z) acceleration composite sensors for upgraded production of automobile tire pressure monitoring system (TPMS) is proposed, developed, and characterized. Herein, the X-axis accelerometer is with the cantilever beam-mass structure and is used for automatically identifying and positioning each of the four wheels. The IC-Foundry-Compatible low-cost batch fabrication technique of MIS (i.e., Micro-openings Inter-etch and Sealing) is employed to only fabricate the device from the front side of (111) silicon wafer, without double-sided micromachining, wafer bonding, complex Cavity-SOI (Silicon on Insulator) processing, and expensive SOI-wafer needed. Benefited from the single-wafer front-side fabrication technique on ordinary single-polished wafers, the fabricated composite TPMS sensor has the advantages of a small chip-size of 1.9 mm × 1.9 mm, low cross-talk interference, low-cost, and compatible process with IC-foundries. The fabricated pressure sensors, X-axis accelerometer and Z-axis accelerometer, show linear sensing outputs, with the sensitivities as about 0.102 mV/kPa, 0.132 mV/kPa, and 0.136 mV/kPa, respectively. Fabricated with the low-cost front-side MIS process, the fabricated composite TPMS sensors are promising in automotive electronics and volume production.

Highlights

Silicon-based pressure sensor and accelerometer have been intensively developed and widely used in industry and costumer application due to their tiny size, low cost, and linear output property [1]
With the rapid development of science and technology and the improvement of people’s living standards, today, for further improving vehicle safety and comfort, an additional X-axis accelerometer is proposed and integrated into the composite tire pressure monitoring system (TPMS) sensor for automatic identifying and positioning each of the four wheels, even if the wheel positions are mutually exchanged in the 4S shops
The worry lies in that the users would like to enjoy the improved function, but do not want to pay more for it, thereby the only way to avoid the additional cost and reduce the device size is to realizing monolithic integration of the three sensors in a cheap non-SOI (Silicon on Insulator) wafer

Summary

Introduction

Silicon-based pressure sensor and accelerometer have been intensively developed and widely used in industry and costumer application due to their tiny size, low cost, and linear output property [1]. The worry lies in that the users would like to enjoy the improved function, but do not want to pay more for it, thereby the only way to avoid the additional cost and reduce the device size is to realizing monolithic integration of the three sensors in a cheap non-SOI (Silicon on Insulator) wafer. Many reported composite TPMS sensors have consisted of only a pressure sensor and a Z-axis accelerometer, and formed by the hybrid packaging scheme or the on-chip integrating scheme. To solve the aforementioned problems, this study proposes and develops an IC-Foundry-Compatible low-cost batch fabrication technique to realize monolithic integration of pressure plus two-axis (X/Z) acceleration sensors in cheap non-SOI silicon wafers. The design, fabrication, and the characterization of the composite TPMS sensor will be detailed

Design

Pressure Sensor

X-Axis Accelerometer

Fabrication

Conclusions