Technology Ga a s
Manufacturing at the legendary Ft Collins fab
(a)
Avago developed WaferCap at its Ft
Collins, CO, facility. Hewlett-Packard
first owned this chip-making fab, MMIC wafer
but it was transferred to its spin-off
RF in RF out
(b)
Agilent Technologies in 1999, and
cap wafer
became part of Avago Technologies in
December 2005.
For more than 30 years the facility
RF in RF out
has been responsible for leading-edge,
MMIC wafer
flagship central processor unit Fig. 1. Typical radio-frequency packages feature bond wires and
manufacturing, support chips, NMOS, silicon and GaAs wafer-scale packaging. active circuits encapsulated in high-dielectric-loss polymers,
CMOS, bipolar, CMOS image sensor and Today, Avago’s captive manufacturing which increase parasitic loss and degrade device
other technologies. This roll call has facility allows the co-development of performance (a). Avago’s WaferCap technology features a
occurred despite significant outsourcing design and focused manufacturing shorter lead length that cuts inductance and its variability (b).
of US semiconductor manufacturing capability, which can combine to match
capacity over the same time period. the needs of the pending design. This via for electrical contact to circuitry
More recently, business needs have approach cuts the turnaround times that
required new technologies including occur in development and ultimately
MEMS and advanced RF GaAs, and ensures a faster time to market.
diffusion pad metal solderable metal
barrier
solderable metal and underlying pad metal.
Soldered parts that have been attached to the
pads in this manner have passed several qualifica-
tion tests, including multiple reflow and shear, drop, Avago Technologies’ WaferCap die have dimensions that are
cycle bending, vibration and thermal cycle. the same as many passive components and they can be
mounted on printed circuit boards using similar processes.
RF performance advantages
Our WaferCap design provides short lead lengths, vide broadband amplification to signals transmitted
minimal inductance with low variability and RF through coaxial cable for cable TV, or deliver ampli-
transitions with minimal parasitic loss, thanks to fication in base stations and instrumentation.
routing of input and output signals along the back- We have started by incorporating our
side of the device wafer through via holes. This is enhancement-mode PHEMT technology into Wafer-
a massive improvement over conventional plastic Cap products. This creates high dynamic range, ultra-
packages, which have higher parasitic losses that low-noise integrated circuits with high gain, which
degrade performance. Their inferiority results from can operate from a single positive DC supply.
the high-dielectric-loss carbon polymer that encap- Our next step will be to design additional prod-
sulates bond wires and active circuits. Our approach ucts into the 0402 package format. Customers are
also delivers a greater consistency of the lead design, currently evaluating some of these parts (see table 1,
which removes the need to tune wire bonds. p21, for details), which could form the building
Device modeling suggests that our devices can blocks of circuits targeting specific applications.
form amplifiers operating in the 17–33 GHz range Further down the road we will be launching a
(Microwave Journal August 2008). These simula- two-pronged process development program. One
tions show that our chips are capable of operating aim is to extend our WaferCap technology to include
well beyond 50 GHz and we believe that they have other types of transistor, such as enhancement-mode
the potential to stretch to 100 GHz. and depletion-mode HEMTs. We are also aiming to
We have investigated several applications that can extend it to other standard package sizes. Going
derive the biggest benefit from the unique proper- smaller will cut costs, while increasing size promises
ties of WaferCap technology. Three different ampli- more integration and greater performance. We’re
fier designs have been developed – a 1–12 GHz 50 Ω planning to release products based on this develop-
gain block, a 0.5–6 GHz bypass low-noise amplifier ment in 2009, which will allow our cus tomers to
(LNA) and a 1–6 GHz low-voltage LNA. We have enjoy more benefits from this technology. l
recently detailed each of these designs at the Euro-
About the author
pean Microwave Conference, which was held in
Jim Roland is a process
Further reading
integration engineer at Avago
Amsterdam, the Netherlands, on October 27–31. An interactive video presentation describing
Technologies. He is
These three amplifiers could serve many commer- Avago’s WaferCap technology can be seen at www.
responsible for developing
cial wireless applications in the 0.5–12 GHz range. avagotech.com/pages/products/wsd-vmmk/. More
new or evolved processes for
However, we believe that they will also prove their information is available at www.avagotech.com/
manufacturing. worth in other markets. They could be used to pro- pages/wafercap.
22 compoundsemiconductor.net December 2008 Compound Semiconductor
CSDec08AVAGO 21,22.indd 22 18/11/08 12:20:43
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