Tuesday was a heavy\nday of stochastics for me. Greg Wallraff\nof IBM got me off to a good start with his interesting simplified Monte\nCarlo-like stochastic resist model. As\nexpected for chemically amplified resists, higher PAG loading had a big effect\non reducing stochastic variability, and higher amounts of photodecomposable quencher\nhad a smaller but noticeable impact. \nAlso as I expected, acid amplifiers only make things worse\nstochastically. All of his simulations\nused a 15nmx15nmx15nm voxel, but I hope he will look into the impact of voxel\nsize on his simulation results. I think\nthat understanding the role of the averaging volume (voxel size essentially) is\none of the biggest gaps in our knowledge of stochastic behavior.<\/p>\n\n\n\n
Andy Neureuther gave\na fantastic talk on the role of dissolution path in determining missing contact\ndefectivity. His algebraic model looked\nvery insightful, and dissolution path plays an underappreciated role in how\nphoton shot noise manifests itself in stochastic defectivity of contacts. Dario Goldfarb of IBM and Patrick Theofanis\nof Intel each showed wonderfully rigorous experimental and simulation studies\n(respectively) of EUV resist exposure mechanisms.<\/p>\n\n\n\n
Peter de Bisschop of imec once again provided the incentive (and the data) for the industry to look more closely at EUV defectivity versus dose, this time by adding pitch variation and challenging us to model the results.\u00a0 Both Synopsis and Mentor used that same dataset to develop models for stochastic defectivity (a work still in progress).<\/p>\n\n\n\n
I gave my paper for\nthe week (comparing the noise sensitivity of different CD-SEM edge detection\nalgorithms), as did two of my coauthors on separate studies. Jen Church of IBM compared LER with\ndefectivity for lines and spaces and LCDU with defectivity for contacts. While she showed that unbiased LER and\nlow-noise LCDU were required, these metrics alone were not enough to predict\ndefectivity or yield. Charlotte Cutler\nof DuPont gave the third in a series of papers she has presented at the\nPatterning Materials conference on using power spectral density (PSD) analysis\nfor resist design. In my completely\nbiased perspective, both of these papers were highlights of the day.<\/p>\n\n\n\n
At the metrology\nconference I enjoyed a talk by the National Metrology Institute of Japan on\nusing AFM as a roughness reference metrology, even though I disagree with some\nof their conclusions. Comparing SEM and\nAFM measurement of the same sample (an etched silicon line), the two measured\nedges matched extremely well except at the high frequencies. The authors attributed these differences to\nSEM noise, but failed to recognize the role of instrument resolution. With an uncharacterized tip size of about\n7nm, their AFM is a much lower resolution instruments (in terms of\nhigh-frequency roughness measurement) and so was unable to see the high\nfrequency variations that are visible in a SEM (admittedly contaminated by SEM\nnoise). I hope the authors will continue\ntheir work be comparing AFM to unbiased SEM measurements, and that they will\nwork to deconvolve the tip shape from the AFM measurements (hopefully using\ndifferent tips with different shapes).<\/p>\n\n\n\n
The final talk I heard was a fantastic one, by Luc Van Kessel, a student at the Technical University of Delft.\u00a0 He studied a subject I have long been fascinated with:\u00a0 how does the 2D surface roughness of the sidewall of a feature translate into the 1D edge roughness observed in a top-down CD-SEM?\u00a0 For his 300V SEM simulations, the observed top-down edge an isolated line was essentially the extreme X-Y points of the 3D feature.\u00a0 Things were a bit more complicated for a small space because of the aspect ratio making the bottom of the space less visible in the SEM.\u00a0 Also, his 500V simulations were only preliminary and could be somewhat different due to the greater penetration distance of those higher-energy electrons.\u00a0 Great work, Luc!<\/p>\n\n\n\n
With Harry Levinson, I ended the day by hosting an all-conference panel called \u201cA toast to lithography\u2019s past:\u00a0 what we learned from technologies not used in HVM\u201d.\u00a0 Hans Loschner gave us the history of the life (and death) of ion-beam projection lithography, Reiner Garreis of Zeiss discussed 157-nm lithography, Alexander Liddle recalled his time working on Scalpel, and I filled in for Tobey Aubrey (who couldn\u2019t make it) to talk about our lessons learned from proximity x-ray lithography.\u00a0 While I enjoyed all of the discussion, I didn\u2019t enjoy the unfortunate logistics.\u00a0 We made the big mistake of scheduling our panel immediately after the EUV retrospective panel.\u00a0 Not only was the EUV panel late to finish (as expected for EUV), but the time to transition between panels was far too short.\u00a0 The topics of the two panels were very similar, but nobody would want to sit through four hours of panel discussions at one time.\u00a0 Lessons learned not only about lithography, but about panel discussions as well.<\/p>\n","protected":false},"excerpt":{"rendered":"
Tuesday was a heavy day of stochastics for me. Greg Wallraff of IBM got me off to a good start with his interesting simplified Monte Carlo-like stochastic resist model. As expected for chemically amplified resists, higher PAG loading had a big effect on reducing stochastic variability, and higher amounts of photodecomposable quencher had a smaller […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[],"class_list":["post-616","post","type-post","status-publish","format-standard","hentry","category-microlithography"],"_links":{"self":[{"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=\/wp\/v2\/posts\/616","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=616"}],"version-history":[{"count":3,"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=\/wp\/v2\/posts\/616\/revisions"}],"predecessor-version":[{"id":619,"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=\/wp\/v2\/posts\/616\/revisions\/619"}],"wp:attachment":[{"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=616"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=616"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=616"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}