Thermally-Driven Angular Rate Sensors in Standard CMOS


The complete design cycle for micromachined angular rate sensors is presented. Original analysis is combined with previously published results culled from a diverse spectrum of sources, and form a complete treament of the pertinent design issues. Main functional components (actuator, oscillating mass, transducer and interface circuit) are introduced with desgin analysis and methodologies, and the dependence of component and sensor performance on operating frequency is discussed in detail.  System-level issues such as electrical noise, mechanical and thermal error sources, and the use of feedback control are also addressed. A general introduction to resonant systems, and angular rate sensors in particular, is also presented.  A discussion on the design of complex systems is given, and the angular rate sensor system is used to illustrate the design principles conveyed.  The concept of design hierarchies is used to decompose the complex functional system of the angular rate sensor in a manner similar to that used in VLSI.

System-level and component designs are presented for the mechanical portional of a micromachined angular rate sensor fabricated in a standard commerical CMOS process.  The sensor consists of a thermal actuator coupled to a spring-mass system.  Actuator performance is characterized, and generated force and displacements are correlated to theory as functions of actuator dimensions.  Generated forces are quite high (typically 100-200uN), while actuator deflections are small (on the order of tens of nanometers) due to a very high structural stiffness of the actuaor for axial deformations. Residual stress in the actuator structure is also examined.  A thorough analysis of sensor dependence on drive frequency is undertaken, and preliminary design analysis is presented for the spring-mass system.  Resonant frequency of the spring-mass oscillator is calculated for vaious configurations, and a novel analysis relating Q factors to system design parameters and device operating conditions is presented. Finally, a brief discussion of future work is given.

Michael Dean Pottenger
Publication date: 
December 31, 1995
Publication type: 
Master's Thesis
Pottenger, M. D. (1995). Thermally-driven Angular Rate Sensors in Standard CMOS. (n.p.): University of Southern California.

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