{"id":558,"date":"2018-02-28T09:01:58","date_gmt":"2018-02-28T15:01:58","guid":{"rendered":"http:\/\/life.lithoguru.com\/?p=558"},"modified":"2018-02-28T09:01:58","modified_gmt":"2018-02-28T15:01:58","slug":"spie-advanced-lithography-symposium-2018-day-2","status":"publish","type":"post","link":"https:\/\/lithoguru.com\/life\/?p=558","title":{"rendered":"SPIE Advanced Lithography Symposium 2018 \u2013 day 2"},"content":{"rendered":"

Midway through the week, my first impressions have solidified into a clear view of the conference themes.\u00a0 I think we can call this the year of stochastics.\u00a0 Five years ago it was hard to get anyone to listen when you talked about stochastic effects in lithography, but today it seems to be the only thing people are talking about.\u00a0 What has changed?\u00a0 EUV lithography is close enough to reality that people can imagine, and even visualize, using EUV to make something other than test images for their SPIE paper.\u00a0 We can visualize making devices, devices that must yield.\u00a0 And it is not a pretty picture.\u00a0 For years we talked about progress in all the other areas of EUV lithography, with a parting comment that \u201cEUV resists must improve\u201d to fix the stochastic effects.\u00a0 But now it is clear that we must attempt to make devices with the resists we have today, and no miracles are on the horizon.<\/span><\/p>\n

The other thing that has changed is the shift in emphasis from stochastic-induced roughness to stochastic-induced defects.\u00a0 It is hard for us lithographers to understand how an extra nanometer of linewidth roughness might affect our devices, but it easy for us to understand the implications of a missing contact hole.<\/span><\/p>\n

I started my day in the Metrology conference with a session dedicated to LER\/LWR measurement.\u00a0 Gian Lorusso introduced the \u201cimec protocol\u201d, his attempt to standardize the measurement of roughness (full disclosure:\u00a0 I was a coauthor).\u00a0 He began by describing an exercise imec performed where they sent a set of identical wafers to 13 companies and asked them to measure the linewidth roughness and send back the results.\u00a0 The answers he received varied by +\/- 30%.\u00a0 The need for standardization in measurement is obvious.\u00a0 The main problem is bias in the measurements due to SEM noise (and how that bias varies with measurement conditions), so the most important recommendation is to always use unbiased measurements.\u00a0 He also described how the ITRS recommended measurement approach has become outdated with today\u2019s low correlation length processes:\u00a0 a 2-micron line length is no longer needed.\u00a0 Gian\u2019s paper is extremely important, and I hope that the imec protocol is widely followed from now on.<\/span><\/p>\n

My first paper of the conference was in this same session, which included simulation results that were finished the night before (cutting things just a little too close!).<\/span><\/p>\n

It may seem like I am pitching too many papers that I was a co-author on, but I am going to do it anyway.\u00a0 Charlotte Cutler of Dow gave an excellent talk on her use of power spectral density analysis to improve resist materials.\u00a0 As a resist maker, Dow regularly measures features after the lithography step (in industry jargon, ADI:\u00a0 after develop inspect), but has little access to after-etch results since those depend heavily on each customer\u2019s etch process.\u00a0 But when it comes to roughness, it is the after-etch performance that matters.\u00a0 So, Charlotte needs to correlate her ADI measurements to after-etch results.\u00a0 Traditionally, that has meant looking at the ADI 3-sigma roughness with the assumption that a low ADI 3-sigma roughness would translate into a low after-etch 3-sigma roughness.\u00a0 Alas, it often does not.\u00a0 To explore why, she created two matrices of resist formulations and measured the power spectral densities of the roughness of each of them.\u00a0 She found that while after-develop 3-sigma roughness was not a good predictor of after-etch 3-sigma roughness, the after-develop unbiased PSD(0) was.\u00a0 I predicted last year that this approach would work (in my EUVL Symposium paper), and it is very gratifying to see this prediction proved out experimentally.<\/span><\/p>\n

There seem to be fewer ASML papers at the conference this year (is it my imagination?), but I did catch Jan von Schoot talking about their plans for a high-NA EUV scanner.\u00a0 Every time I see drawing of this tool, or pictures of the lens manufacturing facility under construction at Zeiss, I am amazed at how massive and complicated this tool will be.\u00a0 Perhaps it is designed to make the NXE:3400 seem only moderately complex.<\/span><\/p>\n

I walked around the poster session (much smaller than in years past), and saw quite a few good ones.\u00a0 The conference is now half-way over, but I won\u2019t say it is a downhill ride from here.\u00a0 Wednesday will be exciting!<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

Midway through the week, my first impressions have solidified into a clear view of the conference themes.\u00a0 I think we can call this the year of stochastics.\u00a0 Five years ago it was hard to get anyone to listen when you talked about stochastic effects in lithography, but today it seems to be the only thing […]<\/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-558","post","type-post","status-publish","format-standard","hentry","category-microlithography"],"_links":{"self":[{"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=\/wp\/v2\/posts\/558","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=558"}],"version-history":[{"count":1,"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=\/wp\/v2\/posts\/558\/revisions"}],"predecessor-version":[{"id":559,"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=\/wp\/v2\/posts\/558\/revisions\/559"}],"wp:attachment":[{"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=558"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=558"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/lithoguru.com\/life\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=558"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}