Making scanners march in step

by M. David Levenson, editor-in-chief, Microlithography World

Dec. 12, 2008 – Brion Technologies, an ASML company, has developed a suite of products to optimize the performance of diverse scanners so that challenging chip patterns can be manufactured in parallel, on old and new tools, at high volume.

Announced last week at Semicon Japan (Dec. 3), the LithoTuner Pattern Matcher software optimizes standard scanner parameters such as NA, dose, stage tilt, and illumination for customer-selected chip patterns. Another LithoTuner brand product, Pattern Matcher Full Chip, employs Brion’s computational lithography technology to identify critical patterns in a chip design for optimization. Since different features may be more or less problematic on different scanners and under different conditions, Pattern Matcher Full Chip also inputs models of all the scanners and looks for sites with marginal printing performance all through the process windows. Sensitive chip structures are identified and the scanner tuning parameters are optimized for them.

“Pattern Matcher Full Chip optimizes performance “for all the sites on all the chips for all the scanners” using Brion’s computational litho technology, Tom Pye, director of strategic marketing at Brion, told MLW. He reported the company has seen 30%-70% better matching at customer fabs; “at Semicon Japan customers seemed impressed,” he said.

Scanner matching is especially important for products running in large volume or in surges where a large number of chips need to be made in a short time. When that happens, it is not feasible to restrict production to a one “golden” exposure tool that somehow delivers high yield — a second or third tool needs to be run as well and produce the same CDs. That may mean turning the knobs at run time, and possibly setting them differently for different reticles. LithoTuner facilitates software control of all the scanner tuning knobs, as many as 20 for state-of-the art ASML exposure tools. “ASML is the only company that can tie these capabilities together into a holistic lithography approach,” stated Martin van den Brink, EVP of marketing and technology at ASML, in the press release. “LithoTuner shows the benefits of combining computational lithography with detailed scanner knowledge.”

That scanner knowledge is not all available to the customer normally, according to Ron Goossens, director of product marketing at Brion. Some comes from the manufacturer and some is created by Brion’s scanner model-building process, which also captures resist and other data. “Building a scanner model can take weeks,” he explained to MLW, “but once it is built, optimizing a scanner for a given reticle with LithoTuner takes a few hours of pre-processing and the scanner set-up at run-time is done in minutes. Most of our customers have already built the models in order to use other Brion products.”

Rather than having chip designers to accommodate the peculiarities of a fab’s scanner portfolio in a design-for-manufacturing (DFM) paradigm, customers want manufacturing optimized for design (MFD). According to Pye, LithoTuner Pattern Matcher Full Chip facilitates that for Brion/ASML customers. — M.D.L.

Adding knobs for improved matching.
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