1 July 2004 Buried polysilicon hot-wire anemometer with integrated bulk micromachined channel
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We describe the design, fabrication, and characterization of a buried polysilicon hot-wire anemometer with an integrated micromachined channel for fluid flow sensing. Hot-wire flow sensor elements and bulk micromachined channels are fabricated separately on device and channel wafers. The direct silicon wafer bonding technique is then used to integrate the flow sensors and channels. This is made possible by fabrication of the polysilicon resistor flow sensing element in a trench. Heavily doped polysilicon connections are also recessed into the device wafer. The attraction of using polysilicon for the flow sensing element and connections is the ability to adjust the resistivity and temperature coefficient of resistance (TCR) by control of the dopant concentration. The effect of doping on both these parameters is characterized in detail to enable selection of the appropriate doping concentration for each region of the device. Light doping is preferred for the resistor element, since this ensures high thermal sensitivity, while heavy doping is used to provide low resistance connections. The materials allow use of standard high-temperature fabrication processes compatible with standard integrated circuit (IC) technology and micromachining techniques, including silicon bonding. This offers the ability to integrate other microfluidic components and electronic control circuits.
© (2004) Society of Photo-Optical Instrumentation Engineers (SPIE)
Hao Zhao, Hao Zhao, John H. Montgomery, John H. Montgomery, S. J. Neil Mitchell, S. J. Neil Mitchell, Harold S. Gamble, Harold S. Gamble, } "Buried polysilicon hot-wire anemometer with integrated bulk micromachined channel," Journal of Micro/Nanolithography, MEMS, and MOEMS 3(3), (1 July 2004). https://doi.org/10.1117/1.1758726 . Submission:

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