SPIE Advanced Lithography Symposium 2018 – day 1

The plenary session Monday morning began with awards.  We recognized four new SPIE fellows from our community:  Jason Cain, Alexander Starikov, Peter Trefonas, and Reinhard Voekel.  Congratulations!  We had no presentation of the SPIE Frits Zernike Award for Microlithography this year, for a very sad reason.  Just before the award committee was to vote on the winner, one of the nominees for the award, Nick Cobb, died.  (I’m on that committee.)  So instead of making a Frits Zernike award this year, we decided to honor Nick with a special mention and the establishment of the Nick Cobb Memorial Scholarship (thanks to the generation contribution of Mentor Graphics and a matching contribution by SPIE).  It was very touching to see Nick’s family there for this special recognition.

The three plenary talks were all interesting, and each as different from the other as they could be.  Yan Borodovsky came out of retirement to discuss his views on the biggest challenges still facing EUV lithography as it nears high volume manufacturing (HVM).  I liked this quote about EUV:  “It’s not about if, or even when, but how well?”  Yan focused on the quality problems of EUV in two major areas.  First, the EUV mask is a complex phase shifting mask with unintended phase shifts.  Controlling and managing these phase shifts is critical and difficult.  Second, stochastic defects “must be eliminated for EUV HVM” according to Yan.  How to do this in the short term is unclear, but since these stochastic failures increase dramatically as feature size decreases, the long-term solution is even more problematic.  Yan suggested that the only practical approach is to live with them by moving our logic computing devices to some type of fault-tolerant architecture, such a neuromorphic computing or fine-grained cores (thousands of small cores, so that if one or a few go bad you still have a valuable chip).  I’m not sure how long it will take to move away from the standard Von Neumann computing architecture, but it won’t happen in the next few years, that is sure.

Dan Hutcheson gave his typically upbeat assessment of the future of Moore’s Law – somehow the community will overcome the technical hurdles because the economic incentives to do so as so compelling.  But of course, this will not be true forever.  Dan’s opinion was that trying to predict when the end might come would be self-defeating by reducing one’s motivation to forestall that end.  I don’t agree, but I understand his point.

While Dan’s talk gave a 40,000-foot view of the economics of lithography, Stephen Hsu’s plenary talk dove into the gory details of OPC and RET (resolution enhancement technology) from ASML’s perspective.  The many innovative technologies developed by ASML to improve NILS (normalized image log-slope, a measure of aerial image quality) will result in reduction in stochastic problems, but it is clear that this will not be enough.  Thus, Stephen reminded us that “more resist improvement is needed for EUV.”  To that I counter that more improvement in the EUV source is in fact what is needed, and no call to improve resists should be unaccompanied by a call to improve source power.

George Gomba gave the first keynote address of the EUV conference and he made the same mistake as Stephen Hsu:  admitting that EUV photon shot noise was a big problem and then calling on resist improvements as the required solution.  In then end, however, he accurately described the three major unsolved problems in EUV as stochastic failures, mask defectivity, and meeting the source power roadmap going forward.

Following George was the second keynote by Chris Ober of Cornell, talking about his group’s approach to developing EUV resists.  Unfortunately, in a parallel conference Geert Vandenberghe of imec was also giving a review of the status of EUV resists.  The lack of coordination between parallel sessions in different conferences is a perennial complaint of mine.

In the afternoon I attended the joint EUV and resist session.  I have to admit a great thrill at seeing Fractilia’s roughness measurement product, MetroLER, used so effectively in nearly all of the papers in that session.  TEL and imec gave four of the five talks in the session, and both are users of MetroLER.  Thus, my view of those papers is quite biased, unlike their measurements, which were quite unbiased.  (Sorry, LER measurement nerd humor). 

The 6pm conference welcome reception was very nice – I liked it being held in an open area of the conventional hall floor rather than in a room, and I like the beer that was available.    After many good conversations at several different hospitality suites, it was back to my room to prepare for my first talk, early the next morning.

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