Abstract
MEMS-Based Integrated Microsystems for Inertial Sensing and All-Optical
Networks
Recent advances in the development of MEMS-based microsystems have not
only been driven by the steady demand for miniaturization and higher
performance at lower cost, but also has been impelled by the large
variety of applications that are enormously affected by these systems.
These applications are spread in a broad range including health care,
automotive, wireless and optical communication, industrial and process
control, instrumentation, military, and consumer market. The impact of
MEMS microsystems is not just limited to reducing overall size, cost,
weight, and power dissipation; they open up new market opportunities, or
enhance the overall performance by making formation of large arrays of
transducers and/or distributed microsystems feasible. A clear example
of a new enabled market by MEMS arrays is micromirrors and other
micro-electromechanical devices for all-optical network switching and
wavelength management. While advanced CMOS and MEMS fabrication
processes have been the key enabling technologies of these microsystems,
the increasing functionality and complexity demands novel and innovative
system engineering, packaging and integration approaches as well. This
talk uses two examples to present how novelty and co-design at all these
aspects needed for high-performance microsystems to fulfill the
applications.
The first MEMS microsystem is a high precision silicon accelerometer
that resolves 10 ppm of earth gravitational force while providing a
direct digital output. Novel device structures, and combined surface
and bulk micromachining fabrication technology are used to form the
capacitive sensing element. The microsensor is operated in an
electromechanical oversampled sigma-delta modulator loop to readout the
sensor, servo-control it, and provide digital output over a 95dB dynamic
range. This system uses the mechanical characteristic of the sensor as
the first sigma-delta loop integrator, in addition to a novel fully
differential interface IC with <300uV offset resolving better than 6aF
capacitance change on a 10pF base capacitance. The new generation of
these inertial microsystems including microgyroscopes use controlled
vibration and temperature micro-environments formed at chip-level to
insert them in harsh-environment applications with over 20,000 g of
shock and -60 to 100 C temperature range. The key to this on-going
development is batch-fabricated environmentally-isolated micro-packages
and wafer-level vacuum packaging technologies.
The 2nd MEMS microsystem is a large port count (>400) transparent
cross-connect optical switch. In addition to novel electrostatic
microactuators for actuation voltage reduction and range improvement, an
integral part of this microsystem is an ultra-high density scalable
robust digital control scheme implemented on a mixed-signal
mixed-voltage CMOS chip. The control chip provides closed-loop
high-precision 2-D free-space beam-steering of the two-axis gimbaled
micromirrors, and hence relaxes the MEMS manufacturing tolerances by
reducing their effects on the overall system performance. The control
algorithm is a modified sliding-mode control scheme which is robust. It
also enables operation of the micromirrors beyond their "pull-in" limit.
Furthermore the chip addresses the interconnect congestion problem for
large port count switches by utilizing a serial digital bus.
About Navid Yazdi
Navid Yazdi is currently a visiting research scientist at the University
of Michigan. He received the B.S. degree in 1988 from the University of
Tehran, Tehran, Iran, the M.S. degree in 1993 from the University of
Windsor, Windsor, Canada, and the Ph.D. degree in 1999 from the
University of Michigan, Ann Arbor, all in electrical engineering.
From
1998 to 2000 he was a full-time tenure-track faculty member at Arizona
State University, where he established a research group focusing on
integrated microsystems with several projects funded by NSF, DARPA, and
semiconductor industry on MEMS sensors and actuators, and analog/digital
VLSI circuitry.
From 2000 to 2003 he was Director of Electronics at
Corning IntelliSense Corporation (CISC). He joined CISC after taking a
leave from Arizona State University. At CISC he created and managed the
control electronics group and focused his effort on precision MEMS
interface electronics and mixed-signal control ASICs for optical
cross-connect and wavelength management products.
Dr. Yazdi has
published over 35 journal articles and refereed conference papers in the
past 10 years on MEMS devices and fabrication technologies, mixed-signal
VLSI circuits and MEMS interface circuitry, and wireless microsystems.
He also holds several US patents on MEMS accelerometers and their
manufacturing process, and closed-loop control of MEMS. Dr. Yazdi is a
member of Tau Beta Pi. He received the University of Michigan College
of Engineering Graduate Student Achievement Award in 1998 for excellence
in scholarship, research, and service.
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