Electrical & Computer Engineering     |     Carnegie Mellon

Tuesday, March 19, 12:00-1:00 p.m. HH-1112

Sitaraman Iyer
Carnegie Mellon University

Modeling and Simulation of a CMOS-MEMS Gyroscope

A gyroscope senses the rate of rotation of an object with respect to an inertial frame. A number of MEMS gyroscopes, based upon sensing Coriolis force-induced displacements, have been presented in the past decade. MEMS gyroscopes commonly sense angstrom-scale displacements and sub-atto-farad capacitance changes. It is widely accepted that robust MEMS gyroscopes are difficult to design and manufacture. A quantitative understanding of the sources of non-idealities in MEMS gyroscopes is, therefore, currently required, but has been given inadequate research attention so far.

In this talk we present an approach for understanding and quantifying non-idealities induced by manufacturing variations in a CMOS-MEMS Z-axis gyroscope. Specifically, the non-idealities under consideration are input offset (or bias), acceleration and acceleration squared sensitivity and cross-axis sensitivity. The manufacturing effects we will be considering are die-level width and gap variations, metal mask misalignment and temperature dependent curling of the multilayer CMOS-MEMS structures. NODAS is a library of parameterized mechanical and electrostatic components, such as beam, plate and electrostatic comb, developed at CMU. Behavioral simulation using NODAS is used for gyroscope analysis. Model building efforts contributing to NODAS in the elastic and electrostatic domains as well as design insight resulting from the modeling will be presented. Convergence issues in transient analysis using multi-domain behavioral models encoded in an Analog Hardware Description Language (AHDL) will also be discussed. Analytical equations derived for manufacturing effects on gyroscope non-idealities are found to be consistent with results of behavioral simulations. Design trade-offs and pointers for reduced gyroscope non-idealities deduced using the analyses and simulations will be presented.

Sitaraman Iyer is currently working towards his Ph.D. with Dr. Tamal Mukherjee in the Electrical and Computer Engineering Department at Carnegie Mellon University. He received his B.Tech degree in Electrical Engineering from the Indian Institute of Technology at Mumbai in 1996 and M.S. in Electrical and Computer Engineering from Carnegie Mellon University in 1998. His research interests include design, modeling and simulation of MEMS.