TX and San Jose, CA (6 July, 2005) - Copper resistivity
will remain a challenge for the semiconductor industry,
but chip designers are likely to use hierarchical
design workarounds to modify the metal for linewidths
at the 45 nm technology node, according to participants
at an industry workshop sponsored by SEMATECH and
Novellus Systems, Inc. (Nasdaq NM: NVLS).
Commenting on the recently concluded Copper Resistivity
Workshop in Burlingame, CA, SEMATECH and Novellus
interconnect specialists shared insights on results
of the recent meeting, which drew approximately 160
engineers. The industry-wide workshop, co-sponsored
by SEMATECH and Novellus, focused on ways to extend
the use of copper in advanced semiconductors in the
face of increasing copper resistivity at linewidths
below 90 nm.
"Due to the fundamental laws of physics, copper
resistivity is bound to increase and will result
in several critical issues that need to be addressed," said
Andreas Knorr, conference co-chair and manager of
the Advanced Materials Development Program in SEMATECH's
Interconnect Division. "Various process refinements
could alleviate perhaps 5 to 15 percent of the problem,
provided that chip manufacturers are willing to accept
added cost and design complexity."
Below 90 nm linewidths, copper resistivity rises
dramatically because of increased electron scattering
on grain boundaries and interfaces. These resistivity
increases can sharply diminish or wipe out the capacitance
benefits of low-k dielectric materials, which have
long been an industry focus.
"The increase in resistivity of an ultrathin
wire was of academic interest long before the first
IC", said Ron Powell, conference co-chair and
Novellus fellow. "But we have been so successful
at scaling down CMOS devices and wiring that we now
have to consider the practical impacts of these 'size
effects' as well."
"Ironically, the switch from aluminum to copper
wiring has accelerated the problem, since size effects
show up in copper at closer-in technology nodes.
Regardless of how the situation came about, it is
likely to be addressed by a synergistic combination
of materials, process and design changes," Powell
added. "Novellus and SEMATECH therefore conceived
of a cross-functional workshop to raise awareness
of the problem and drive a solution."
the resistivity workshop, experts sought to build
consensus on the contributions and root causes
of metal line resistivity increases at wire widths
below 90 nm, discuss the performance and reliability
impact of these surges and consider potential solutions
with innovative approaches to materials, process
and integration, and circuit design. Industry analyst
Dan Hutcheson of VLSI Research praised the conference
as "truly problem focused," adding that
it was "chock full of ideas with lots of theoretical
detail to understand the mechanisms backed up with
real research into potential solutions."
and Powell said the workshop highlighted two promising "process fixes" that
could moderately mitigate the effects of resistivity:
* Minimize the volume that diffusion barriers occupy
by making them ultra-thin
* Enlarge copper grains to diminish boundaries
and encourage unimpeded electron flow.
While participants believed that designers using
hierarchical design rules will be able to work around
the resistivity increase to reach the 45 nm node,
they warned that it will be critical to minimize
line resistance differences induced by process variation.
These differences originate mostly with lack of adequate
critical dimension (CD) control and dishing and erosion
problems caused by chemical-mechanical polishing
(CMP), resulting in line cross-section variations.
Also, workshop experts cautioned that reliability
in fine lines will be a critical issue due to generally
smaller grain sizes, and higher ratios of metal surface
area to metal volume.
"The ultimate solutions will probably come
in the form of short lines and a move to three-dimensional
interconnect," said Sitaram Arkalgud, SEMATECH's
Interconnect director. But he added that despite
copper's inherent problems, the workshop revealed
scant support for returning to the metal it replaced
several years ago.
"The entire audience was asked if they planned
to move back to aluminum, and the answer was a resounding
'No,' " Arkalgud recalled. "Only one person
suggested that it was even a possibility."
said SEMATECH will continue to guide member companies
and the industry in seeking effective resistivity
solutions for the subsequent 32 nm and 22 nm technology
nodes, including exploration of shorter lines 3D
architecture. "Effective interconnect is vital
to remaining on the Roadmap, and we'll be exploring
a variety of options to make sure we can offer effective
solutions at the right time," Arkalgud said.
Alers, principal engineer at the Novellus Customer
Integration Center, said: "Novellus
will continue to work with university groups to generate
fundamental understanding of scattering mechanisms
at copper interfaces, to model the impact of size
effects on overall interconnect performance, and
to stimulate out-of-the-box solutions. We will also
be driving new processes into the industry that,
among their other benefits, will reduce effective
copper resistivity. For example, expect to see more
use of ultrathin diffusion barriers deposited by
ion induced atomic layer deposition (i-ALD) to maximize
copper volume, and electrodeposition chemistries
and annealing procedures to produce large copper
grains in narrow trenches."
"Safe Harbor" Statement
Under the Private Securities Litigation Reform
Act of 1995:
statements regarding (i) the ongoing challenge
presented by copper resistivity and likely design
workarounds; (ii) the use of synergistic materials,
process and design changes to address "size
effects"; (iii) the ability to mitigate resistivity
by minimizing volume occupied by diffusion barriers
and enlarging copper grains; (iv) the use of hierarchical
design rules to reach the 45 nm node; (v) short lines
and three-dimensional interconnect as a solution
to resistivity; (vi) Novellus' commitment to work
with university groups to increase understanding
of scattering mechanisms, to model "size effects" and
stimulate solutions; and (vii) expected use of ultrathin
diffusion barriers and electrodeposition chemistries
and annealing procedures; that are not purely historical
data, are forward-looking statements. The forward-looking
statements involve risks and uncertainties, including,
but not limited to, the inability to solve resistivity
challenges through and technical difficulties with
design workarounds, synergistic solutions, minimizing
diffusing barriers or enlarging copper grains; Novellus'
inability to generate solutions from scattering mechanisms
or "size effects" models; and unanticipated
difficulties precluding the use of ultrathin diffusion
barriers and electrodeposition chemistries, as well
as other risks indicated in our filings with the
Securities and Exchange Commission (SEC). Actual
results could differ materially. We do not assume,
and expressly disclaim, any obligation to update
this information. For more details, please refer
to our SEC filings, including our Annual Report on
Form 10-K for the year ended December 31, 2004, our
Quarterly Report on Form 10-Q for the quarter ended
April 2, 2005, and our Current Reports on Form 8-K
filed or furnished April 7, 2005, April 18, 2005,
April 29, 2005, and May 5, 2005.
Novellus Systems, Inc., an S&P 500 company, manufactures,
markets and services advanced deposition, surface
preparation and chemical mechanical planarization
equipment for today's advanced integrated circuits.
Our products are designed for high-volume production
of advanced, leading-edge semiconductor devices at
the lowest possible cost. Headquartered in San Jose,
Calif., with subsidiaries throughout the United States,
as well as in the United Kingdom, France, Germany,
the Netherlands, Ireland, Italy, Israel, India, China,
Japan, Korea, Malaysia, Singapore and Taiwan, we
are a publicly traded company on the Nasdaq stock
exchange (Nasdaq: NVLS) and a component of the Nasdaq-100
Index®. Additional information about Novellus
is available on our home page at www.novellus.com <http://www.novellus.com>.
SEMATECH is the world's catalyst for accelerating
the commercialization of technology innovations
into manufacturing solutions. By setting global
direction, creating opportunities for flexible
collaboration, and conducting strategic R&D,
SEMATECH delivers significant leverage to our semiconductor
and emerging technology partners. In short, we
are accelerating the next technology revolution.
For more information, please visit our website
at www.sematech.org <http://www.sematech.org>.
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Dan McGowan Pushpita Prasad