Novel TPMS sensing chip with pressure sensor embedded in accelerometer

Abstract

This study reports the design architecture to embed piezoresistive pressure sensor into accelerometer (PinG sensor) on a single chip by using the cavity-SOI process. The monolithic sensing chip can find various applications such as tire pressure monitoring system (TPMS), etc. The merits of the presented design includes significant chip size reduction by integrating the diaphragm of pressure sensor into the proof-mass of accelerometer, as well as better manufacturability through combining piezoresistor (PZR) process and CSOI process. Preliminary tests demonstrated the feasibility of detecting both pressure and acceleration using the presented PinG sensor. This design architecture is also applicable for other sensors integration.

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

“…And the input-acceleration induced cross-sensitivity at the pressuresensor is only 1.32µV/g, i.e., the cross-influence is about 13.8Pa/g. Thanks to the specific design of the suspended pressure-sensing structure from the stress-free proof-mass end, the influence of input acceleration to the pressure sensor is effectively eliminated, with the "G-to-P" cross-talk being 36 times better than that of the reported PinG sensor [6]. We also test the amplitude-frequency characteristic of the accelerometer, resulting in −3dB bandwidth of about 4kHz, indicating that the precisely fabricated gap distance between Level-5 and Level-6 agrees well with design for air-damping control.…”

“…In order to significantly shrink the chip-size, a PinG layout is recently developed and illustrated in Generation-2 of Fig. 1, where the pressure sensor is embedded inside the mass of the accelerometer [6]. Although this PinG structure is helpful for shrinking the device-size, the fabrication process becomes more complex, where the fabrication employs expensive cavity-SOI process, complicated double-sided bulk-micromachining and anodic wafer-bonding.…”

A Wafer-level pressure calibration method for integrated accelerometer and pressure sensor in TPMS application

“…The process starts with a SOI wafer with buried cavity; the pressure on buried cavity (P 0 ) is defined in this step. The buried cavity is used for embedded pressure sensor to reduce device size [6] [7]. The fabrication process can be divided into three parts: CMOS compatible process, front side and back side etching, and packaging.…”

A monolithic integration multifunctional MEMS sensor based on cavity SOI wafer

“…Compare to normal piezoresistive silicon pressure sensors, the cavity SOI Technology with thin device layer can lead to a much smaller and thinner single crystal silicon piezoresistive absolute pressure sensor [5] [6]. But normal discrete sensor design still needs large space for bonding pads and other connect parts.…”

“…Normal piezoresistive composite sensor designs integrated accelerometer and pressure in chip scale, but those discrete sensor designs still need independent space for each sensor [4]. By embedding pressure sensors which are designed on buried cavity to the accelerometer's mass block, the chip size can be significantly shrunk to 2.3×2.3mm 2 with 0.156mV/g/V to acceleration [5]. But in existing embedding designs, the cantilever structure has gaps between slender beams and frame, which is easily to be blocked by particles in environment.…”