Bulk accelerometers

A representative example in which glass-to-silicon bonding is used are bulk micromachined accelerometers [121]. In this case, glass serves several functions ... 

Fig. 5.1.18 Bulk micromachined capacitive accelerometer chip from VTI Hamlin OY showing a massspring system in the center chip and counterelectrodes on both side chips before and after sealing...

D. Lapadatu, Limits in miniaturisation of bulk micromachined capacitive accelerometers, Ph.D. Thesis, K. Univ. Leuven, Belgium, 1996. 

Fig. 7.1.12 Examples of various automotive-qualified MEMS inertial sensor technologies bulk micromachining (a-c), a) SensoNor Tire Pressure Monitor Sensor that includes an inertial roll switch [90], b) VTI low-g accelerometer [12] surface micromachining (c—g), c) Bosch thick polysilicon lateral accelerometer [91], d) Infineon surface-micromachined pressure sensor [92], e) initial trampoline-style ...

The surface micromachining technique is a CMOS-compatible process and has some advantages over the bulk micromachining one. The most popular microstructure is the so-called comb-drive structures as shown in Fig. 7. Several commercially available sensors with integrated circuit on chip have been developed by using this technique such as accelerometers, gyroscopes, microphones, etc. 

Porous Si shows a much lower thermal conductivity than bulk crystalline Si. The measured difference is more than two orders of magnitude at room temperature, while it exceeds four orders of magnitude at cryogenic temperatures. This makes porous Si very appropriate for use as a local thermal isolation platform on the Si wafer for the integration of sensitive thermal and other devices. Existing devices to date include flow sensors, accelerometers, bolometers, gas sensors. 

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