Article

Review: Semiconductor Piezoresistance for Microsystems

Stanford University, Mechanical Engineering, Stanford, CA 94305 USA.
Proceedings of the IEEE (Impact Factor: 4.93). 03/2009; 97(3):513-552. DOI: 10.1109/JPROC.2009.2013612
Source: PubMed

ABSTRACT

Piezoresistive sensors are among the earliest micromachined silicon devices. The need for smaller, less expensive, higher performance sensors helped drive early micromachining technology, a precursor to microsystems or microelectromechanical systems (MEMS). The effect of stress on doped silicon and germanium has been known since the work of Smith at Bell Laboratories in 1954. Since then, researchers have extensively reported on microscale, piezoresistive strain gauges, pressure sensors, accelerometers, and cantilever force/displacement sensors, including many commercially successful devices. In this paper, we review the history of piezoresistance, its physics and related fabrication techniques. We also discuss electrical noise in piezoresistors, device examples and design considerations, and alternative materials. This paper provides a comprehensive overview of integrated piezoresistor technology with an introduction to the physics of piezoresistivity, process and material selection and design guidance useful to researchers and device engineers.

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    • "Commercially available micromachined pressure sensors are by a vast majority based on the piezoresistive effect, where a mechanical deformation causes a change in the electrical resistance of the sensing element which can be translated into a pressure signal. However, temperature dependence of the piezoresistive coefficient, limited pressure range and scalability have ruled out these sensors in many cases [6]. The response, sensitivity and stability are dependent on the fabrication process, which is known to be a costly investment. "
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    ABSTRACT: We present a pressure sensing unit based on a unique corona discharge setup using symmetrical electrode arrangement with simultaneous positive and negative corona generation. The device generates stable corona discharge and enables reliable air pressure measurement in the range of 80-105 kPa, tested with five prototypes. The current-voltage characteristics of bipolar discharge system is analyzed in general form and three governing parameters, namely electrode geometry, electrode distance and discharge current, are studied in relation with absolute pressure. The sensors are driven with constant discharge current as low as 1 μA. The measured sensitivity is in good agreement with theoretical prediction and the sensor stability has been confirmed with 20-h continuous test without sensitivity deterioration. The sensitivity does not depend on the tested temperature range and its variation between devices is small, approximately ±3.0%. The advantage of the proposed system compared with similar corona-based constructions is its stable operation at low current with low power consumption and minimum electrode deterioration, which provides a cost effective and reliable solution. & copy;2015 Elsevier B.V. All rights reserved.
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    • "At higher doping levels, however, TCS drops off faster than sensitivity. Also, the strain and temperature nonlinearities in sensitivity and temperature change of resistance are very much reduced [10] [11]. Here, boron was used for doping p-type silicon and doping level was controlled to be > 8x10 19 /cm 3 for a low TCS. "
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    DESCRIPTION: Strain gauge; bulk micromachining; glass frit bonding; pressure sensor; steel diaphragm
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    • "Clearly, the corner frequency, where the power density of the thermal and flicker noises are equal, shifts toward higher frequencies by increasing the sensor bias. Above the bias voltage of 6V, the PSD mostly follows 1/ f α trend with 1.5 < α < 1.7, which can indicate the introduction of other noise mechanisms in addition to the conductance fluctuation of the material lattice [17]. "
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    ABSTRACT: We present a comprehensive study of the design, modeling, and characterization of an on-chip piezoresistive displacement sensor. The design is based on the bulk piezoresistivity of tilted clamped-guided beams without the need for additional steps to generate doped regions. The sensor is implemented in a one-degree-of-freedom microelectromechanical system (MEMS) nanopositioner, where the beams also function as the suspension system. A standard MEMS fabrication process is used to realize the device on single-crystalline silicon as the structural material. The beams are oppositely tilted to develop tensile and compressive axial forces during stage movement, creating a differential sensing feature. An analytical approach is proposed for modeling and design of the tilted clamped-guided beams. The linearity of the sensor in the differential configuration is investigated analytically. The static, dynamic, and noise characteristics of the sensor are presented, followed by a model-based investigation of the measured dynamic feedthrough. [2015-0030]
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