| Taiwan foundry United
Microelectronics Corp. (UMC) has fabricated a
voltage-controlled oscillator (VCO) with a
record-setting fundamental operating frequency of
105GHz using its 0.13µm RFCMOS process technology.
The chip was developed by the Silicon Microwave
Integrated Circuits and Systems Research Group
(SIMICS), Department of Electrical and Computer
Engineering at the University of Florida,
Gainesville.
Until now, the highest recorded fundamental
operating frequency for CMOS circuits was a 103GHz
oscillator fabricated using a 90nm CMOS process
that consumed about four times more power. The new
effort by the University resulted in the 105GHz
VCO as well as a second 99GHz VCO with a tuning
range of 2.4GHz, using the 0.13µm process. The
effort signifies that VCOs for the 94GHz
industrial scientific medical band and imaging as
well as 60GHz WLAN and 77GHz radar applications
can be implemented using UMC's process. VCOs are
used in virtually all RF and wireless systems.
Patrick T. Lin, chief system architect at UMC,
stated, "Compared to other technologies used in
producing these types of circuits, CMOS delivers
the best combination of high performance with low
power and low cost for high-volume applications.
This latest achievement with the University of
Florida demonstrates in working silicon that our
RFCMOS process technology is readily able to
support very high frequency designs."
"Developing ICs of this caliber in 0.13µm CMOS
is a huge milestone," added Professor Kenneth O
from the University of Florida. "If we incorporate
frequency doubling techniques, we should be able
to generate signals with frequencies of 200GHz and
higher. This has the potential to open up
far-infrared to CMOS. UMC's role in our
development was pivotal as this leading foundry
provided the process and parameters that brought
the chip to silicon quickly and easily."
105GHz-99GHz VCOs
The 105GHz VCO
utilizes a cross-coupled NMOS transistor core. The
transistor structure of the LC resonator-based VCO
chip has been optimized to reduce parasitic
capacitances, which limits the maximum operating
frequency. An accumulation mode MOS varactor has
been optimized to achieve Q values of
approximately 6 at 105GHz or about 630 at 1GHz,
which is critical for achieving low power
consumption and reducing noise. The 99GHz VCO core
consumes 15 mW. The phase noise at 10MHz offset
from the carrier varies between -101 to -103dBc/Hz
over the 2.4GHz tuning range. The circuits were
developed with the support of Darpa and announced
at the 2005 VLSI Symposium on Circuits in a paper
authored by Chang-Hua Cao, Ph.D candidate at the
University, and Kenneth O.
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