fab tool costs with improved equipment productivity
Internationsl Sematech Manufacturing Initiative (ISMI)
cost of new semiconductor fab equipment, both in terms of dollars and
floor space, continues to be a large incentive driving semiconductor
manufacturing productivity improvements. Models show that a 200-mm fab
manufacturing 20,000 wafers per month at the 130-nm node requires an
equipment investment of ~$900 million. In contrast, a 300-mm fab manufacturing
20,000 wafers per month at the 90-nm node requires an equipment investment
of ~$1.4 billion. Finally, a 300-mm fab manufacturing 20,000 wafers
per month at the the 65-nm node is expected to require an ~$1.8 billion
investment is impelling semiconductor manufacturers to remain focused
on maximizing equipment productivity.
Industry leaders are realizing that on their own, they cannot afford
to do the learning necessary to maximize equipment investment. Hence,
partnerships, collaboration, and the sharing of a combined knowledge
set are becoming the norm as manufacturers struggle with the economics
of today's fabs. Further optimization of equipment productivity through
the use of automation and advanced control schemes will lead to reduced
cycle times and defects, thus shortening time to market. Improving equipment
productivity and its associated costs are key areas in which International
Sematech Manufacturing Initiative (ISMI) member companies are focusing
their efforts and support.
is not a new concept to the semiconductor industry. In the 1990s, it
became very apparent to leading-edge technology providers that their
development costs were escalating dramatically as technology was adapting
to the requirements of the International Technology Roadmap for
Semiconductors. To help defray the escalating costs, companies
formed joint development programs and alliances with customers and other
technology leaders in which all involved parties shared the costs of
their projects. Companies also used their membership in consortia such
as IMEC and Sematech to leverage a pool of development monies supplied
by 10 to 15 companies.
a joint development effort or alliance arrangement involves two or three
similar companies whose agreement is fairly narrow in scope. A consortium,
on the other hand, has to satisfy the needs of sometimes very diverse
businesses. Either way, the pooling of funds is used to pursue an outcome
that is shared by all parties involved.
the area of equipment productivity, ISMI, a wholly owned subsidiary
of Sematech, has taken collaboration to the next level. While the fundamentals
of a collaborative effort are still in place, where every ISMI member
provides funding for the unified effort to drive equipment productivity
improvements, members combine their manufacturing experiences to help
shape the continuous improvement program (CIP) solutions provided by
equipment suppliers. A membership champion is appointed to test the
solution in the fab and then share the conclusions with all the other
participants. This procedure results in a win-win situation for the
consortium and the supplier. Membership resources are conserved by centralizing
the effort to test the solution, and suppliers receive a single, prioritized
response from ISMI's members as to where improvement is needed.
the first annual ISMI Symposium for Manufacturing Effectiveness in 2004,
Varian Semiconductor Equipment Associates (Gloucester, MA) demonstrated
how collaboration with ISMI had been integrated into the company's CIP.
Illustrating the CIP input process, the schematic diagram in Figure
1 shows how an ISMI/Varian equipment productivity improvement team (EPIT)
has direct input into the company's CIP activities. The team, relying
on input from ISMI members, sought to make software improvements (beam
tuning and bug identification), hardware improvements (reliability and
wafer handling), and process improvements (yield enhancement, source
life, particle reduction).1
1: Collaborative learning integration process for continuous equipment
improvement. (Illustration courtesy of Varian Semiconductor Equipment
improvements, the E-series roplat cable and Productivity Plus, were
in part a result of the EPIT's productivity
and cost of ownership (COO) reduction efforts. The E-series roplat cable
improvement involved reengineering the two electrical cables that connect
to the roplat cable into a single flexible ribbon cable to eliminate
particle or reliability issues that were caused when the cables came
loose or broke. While cable issues arose once a month before the modification,
they were reduced to once every 18 months thereafter.
Plus achieved a needed throughput improvement without increasing tool
footprint. It was accomplished by installing an optional additional
pick arm on a tool to reduce the mechanical wait time associated with
wafer movement from the cassette to the orienter, the orienter to the
platen, and the platen to cassette. This option is especially advantageous
in short-duration implant processes, providing up to 30% greater throughput.
Modeling indicated that a 20% throughput improvement could be achieved
with normal fab implant loading at a member company's site.
examples of win-win collaboration demonstrate how suppliers can provide
needed improvements that make their products more cost competitive while
all ISMI member companies can enjoy the benefits of mutual support to
solve technology issues, enabling them to become early adopters of new
hardware. Varian highlighted four key advantages of collaborating with
Access to open discussion on best-known methods.
return on investment (ROI) in the form of "golden nuggets."
Exposure to technology issues from nonmember companies through CIP presentations.
The establishment of EPIT members' equipment performance as a benchmark
for the industry as a whole.
issues addressed in this collaborative environment are both strategic
and tactical. They encompass software and hardware inadequacies, where
solutions will benefit multiple member companies. Some examples include:
mean time between wet cleans by extending part lifetimes. This
goal can be achieved by using different materials or redesigning parts
to improve particle performance. For example, by optimizing the slit-valve
O-ring material used in chemical vapor deposition processes, coupled
with adjusting slit-valve operation, a 50% reduction in baseline particle
performance was achieved.
software solutions that enable equipment to recover from processing
Addressing across-wafer uniformity. A supplier developed
integrated hardware and software solutions to improve across-wafer uniformity
issues, which reduced edge-die yield loss to within 1% of the center-wafer
Improving electrostatic chuck (ESC) critical dimension (CD) uniformity.
Another supplier improved ESC CD uniformity by providing a best-known
method that reduced CD shift from 0.03 to <0.01 Ám on a 0.4-Ám feature.
to develop a multicompany consensus and encouraging supplier engagement
has proven to be a most effective tool for driving equipment productivity.
When multiple end-users jointly decide where to focus their activities,
equipment suppliers can justify particular CIP activities. Although
each company has to deal with its own protocol for incorporating solutions
into their fabs, the bottom line for suppliers is that a solution has
been provided that addresses the needs of several end-users.
to a consortium enables participants to leverage their combined knowledge.
Benchmarking results of member companies' equipment performance are
a valued commodity for driving equipment productivity. Protected by
legal restrictions on further distribution, member companies share equipment
performance data using the SEMI E10 reporting methodology to understand
best-of-breed manufacturing capabilities. This process is supported
by equipment experts from the member companies who work in teams to
seek equipment productivity opportunities.2
teams focus on equipment productivity issues while keeping cost-, process-,
and recipe-specific information confidential. This procedure enables
participants to share equipment software and hardware experiences. At
ISMI, these stories are called golden nuggets, concrete information
gathered by participants in team meetings (as pictured in Figure 2).
2: A 2004 EPIT team face-to-face meeting.
nuggets are stored in a database that is available to all ISMI members.
That database contains more than 2300 entries from 33 different equipment
projects undertaken in the past six years. Entries cover tools used
in all processes, including furnace applications, wet processing, etch,
deposition, lithography, ion implant, chemical-mechanical polishing,
and metrology. To make them easy to find, the data are categorized.
Every entry contains information on the advantages expected from a modification,
including COO, throughput, availability, reliability, and uptime improvements.
Table I lists some
examples of golden nuggets.
the effectiveness of a modification is demonstrated, the results are
relayed to the team and compiled in a searchable database for subsequent
use. This golden nuggets database has become a benchmarking instrument
that highlights the power of information sharing in the program.
the Cost-Reduction Envelope
they compete in the marketplace, fabs are constantly pressured to reduce
costs. Once a fab's equipment depreciation base is set, cost-reduction
efforts focus on the outflow of "green" dollars—actual cash being
spent to support the equipment set. Consumable parts quickly become
a focus of cost-reduction measures, driving the effort to improve part
lifetimes and leading to improved equipment productivity. At this stage,
fabs either purchase parts from the original equipment manufacturer
(OEM) or eventually turn to second-source suppliers. Increased equipment
output, improved defect density, and higher overall equipment effectiveness
are common leverage schemes for lowering costs. While all IC manufacturers
rely on these methods, they do not have the capacity to address all
of them independently, leading to missed opportunities.
an effective method for improving equipment productivity has been the
use of beta sites, where suppliers and end-users collaborate to test
solutions. Eventually, successful work performed at beta sites makes
its way into the marketplace in the form of products. Confidentiality
agreements between suppliers and evaluators often postpone the availability
of a solution in the marketplace.
positive results often migrate into marketing literature, the evaluation
source is not identified, limiting other suppliers' ability to collaborate
directly with the evaluator about the project.
contrast, when OEMs or second-source suppliers within the consortium
perform work at beta sites, they can share both positive and negative
results with other consortium members in a timely fashion. Over the
course of an evaluation, the participants share written reports that
describe the project, chart the expected results, catalog observations
from installation through execution, and rate the evaluation.
one case, a supplier-sponsored improvement package involving a new chamber
body design and a new valve to improve particle performance on an aluminum/copper
0.5% metal etch tool was evaluated. The beta site results were compared
with a control group of seven other tools that were configured without
the upgrade at an ISMI member company's facility. To determine the effectiveness
of the tool reconfiguration, data were gathered on in-line blanket-wafer
particle levels, product-wafer particle levels, mean time between wet
cleans (MTBCs), and mean time between failures (MTBFs). Product-wafer
particle results were obtained using an AIT II patterned-wafer inspection
system from KLA-Tencor (San Jose). The evaluation, which received a
rating of 8 out of 10, concluded:
The in-line blanket-wafer particle data baseline degraded
as a result of the beta site installation, the reasons for which were
detailed in the report.
Depending on the product type, in-line product-wafer defect density
improved by approximately 35%.
MTBC improved from 200 to 300 hours.
advantage of the beta site program is that participants also gain access
to reports on unsuccessful beta site evaluations, especially those based
on input from consortium members. For example, a supplier proposed replacing
the turbo molecular pump in an etch tool that was thought to be a key
source of particles streaming back into the metal etch chamber. However,
participants in the evaluation could not collect particle data because
of interface problems at the site. After multiple attempts were made,
other data from the site became available and the test was aborted.
and the previous example highlight the advantage of sharing beta site
information, both good and bad. The credibility of beta site evaluations
is enhanced when participants share objective evaluation results of
beta equipment performance, making them available to other consortium
members for discussion.
end-users cannot continue to lower costs by buying replacement parts
directly from OEMs, they seek to identify and qualify lower-cost, second-source
parts suppliers. The marketplace eventually reacts, and companies emerge
to fill the demand. That trend can be seen most clearly in the automobile
industry, where common high-turnover parts such as bulbs, belts, filters,
and brakes quickly enter the market and become alternatives to high-cost
dealer offerings. This trend has also occurred in the semiconductor
equipment replacement-parts sector. In contrast to the auto industry,
however, specialized technical proficiency is required to manufacture
IC tool replacement parts, leading to higher cost margins.
is another area in which consortium membership is advantageous. Although
information on parts costs is not shared among members, shared knowledge
of the areas in which companies are purchasing spare parts from second-source
providers can be a powerful cost-reduction tool. This activity also
provides visibility to qualified second-source parts suppliers. The
OEMs and their OEM parts suppliers are reacting to the loss of market
share by making price concessions and providing end-users with previously
unavailable customized solutions, such as reworked-parts programs.
to become best of breed can help to improve equipment productivity in
other areas as well. The use of in-house organizations versus service
contracts to support equipment maintenance, quartz cleaning, parts stocking,
pump rebuilding, and gas services can have an impact on overall cost
and equipment productivity.
ISMI workshops have been formed in which consortium members can discuss
their companies' operational strategies. The end result is a benchmarking
tool that is available to ISMI member companies as they strive to make
their fabs best of breed for equipment performance. These workshops
have focused on the advantages of single-source procurement and maintenance
of support equipment such as pumps, the use of complete outsourcing
versus in-house activities, OEM service contracts and future-use strategies,
and second-source parts use.
integration of metrology data systems, statistical process control (SPC),
and fault detection and classification (FDC) into the fab will play
a key role in identifying equipment problems and reducing mean time
to detection. Residual-gas analysis, arc detection, optical emission
spectroscopic monitoring, and downstream sensors for detecting particle
excursions have become the norm for extracting consistently high-quality
data from process equipment.
addition, by using feed-forward and feed-backward control schemes that
enable engineers to compensate for or fine-tune process recipes, advanced
process control (APC) maximizes the value of equipment output, increasing
process and die yields, eliminating the need for send-ahead wafers,
and reducing rework. Figure 3 illustrates the interaction between SPC,
metrology, process equipment, and process adjustment.
3: Role of statistical process control in detecting process equipment
outputs are also being used to predict maintenance activities and equipment
performance trends, reducing nonscheduled downtime and extending lifetime
estimates of preexisting parts. Multivariate analysis of equipment parameter
data has proven to be an effective technique for providing additional
visibility to equipment performance trends in complicated control schemes.
Translation of the multivariate output signal into a concise set of
corrective actions will further improve equipment effectiveness.
manufacturers' ability to make automated data-driven decisions will
be key to realizing the productivity roadmap.3 However, with
its data-sampling limitations, the use of the SECS/GEM interface to
collect and transmit data without affecting equipment processors' ability
to maintain maximum throughput is beginning to limit fabs' ability to
catch perturbations in equipment performance.4 The development
of Interface A, which has a data-collection rate 10 times greater than
that of SECS/GEM, has been aided by the adoption of four standards that
will create a new dataport for external access to equipment data. The
new interface is scheduled for deployment on 300-mm equipment.5
huge tool investments required by the semiconductor industry continue
to fuel the never-ending drive to improve equipment productivity. Multicompany
alliances are an effective way to lower individual companies' investments
in the learning process, which is necessary for maximizing equipment
performance. Groups of companies can share costs, resources, and knowledge
in order to define, execute, and verify equipment productivity improvements.
Collaboration between equipment suppliers and end-users on CIP projects
creates a win-win business environment. By sharing information on equipment
problems, performance benchmarks, beta site evaluations, second-source
suppliers, and equipment-related success stories, joint company collaboration
can be leveraged to improve equipment productivity and lower bottom-line
costs. Further productivity gains can be achieved by integrating APC
in the fab through the establishment of equipment SPC, FDC, and run-to-run
P Tarvin, "How the EPIT Process Has Helped VSEA to Improve Equipment
Productivity" (paper presented at the First ISMI Symposium on Manufacturing
Effectiveness, Austin, TX, October 26, 2004).
L Peters, "Tighter Equipment Tracking for Efficient Fabs,"
Semiconductor International 27, no. 5 (2004): 34.
B Van Eck, "Facing Factory Productivity Issues in the
Coming Decade," MICRO 23, no. 1 (2005): 31–35.
Semiconductor Equipment Communication Standard/Generic Equipment
S Fulton and H Wohlwend, "Striving to Realize Productivity
in Truly Optimized Fabs," MICRO 23, no. 3 (2005): 29–36.
Marmillion is an IBM assignee to the International Sematech
Manufacturing Initiative, where he manages the equipment productivity
program. Before beginning his role at ISMI, Marmillion spent 24 years
in semiconductor development and manufacturing at IBM in Burlington,
VT, where he focused on dry plasma etch applications. Most recently,
he served as project manager for the 300-mm equipment-procurement
project at IBM's East Fishkill, NY, facility. Marmillion has also
been manufacturing engineering module leader for the start-up of 180-nm
copper back-end-of-line and DRAM surface strap. He received a BA in
chemistry from the University of New York, Potsdam, and is a certified
project management professional. (Marmillion can be reached at 512/356-3094
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