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An Introduction to MEMs Engineering - Nadim Maluf and Kirt Williams Part 7

Tham khảo tài liệu 'an introduction to mems engineering - nadim maluf and kirt williams part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 100 MEM Structures and Systems in Industrial and Automotive Applications Figure 4.16 Illustration of a bulk micromachined capacitive accelerometer. The inertial mass in the middle wafer forms the moveable electrode of a variable differential capacitive circuit. After accelerometer product catalog of VTI Technologies of Vantaa Finland. pattern information is encoded in each of the three masking layers. Timed etching simply translates the encoded information into a variable topography in the silicon substrate. The end result is a thin support hinge member with a much thicker inertial mass. The recesses on either side of the mass form the thin gaps for the two-plate sense capacitors. Silicon 2. Deposit and pattern three masking layers anisotropic etch silicon 1. Etch recess cavities in silicon 4. Remove second masking layer anisotropic etch silicon Figure 4.17 Process steps to fabricate the middle wafer containing the hinge and the inertial mass of a bulk micromachined capacitive accelerometer similar to the device from VTI Technologies. After 20 . 3. Remove first masking layer anisotropic etch silicon Sensors and Analysis Systems 101 Capacitive Surface Micromachined Accelerometer Surface micromachining emerged in the late 1980s as a perceived low-cost alternative for accelerometers aimed primarily at automotive applications. Both Robert Bosch GmbH of Stuttgart Germany and Analog Devices Inc. of Norwood Massachusetts offer surface micromachined accelerometers but it is the latter company that benefited from wide publicity to their ADXL product family 21 . The Bosch sensor 22 is incorporated in the Mercedes Benz family of luxury automobiles. The ADXL parts are used on board Ford General Motors and other vehicles as well as inside joysticks for computer games. The surface micromachining fabrication sequence illustrated in Chapter 3 is fundamentally similar to both sensors though the Bosch device uses a thicker 10--um polysilicon structural element. Unlike most .