I don’t quite understand it, but it is a thing:  many attendees take a picture of every slide of every talk they attend.  Maybe it is for trip reports they are required to produce?  I’ve learned to tune it out so that this behavior no longer interferes with my ability to concentrate on the presenter (mostly).  Last year at the Photomask and EUV Lithography conference I put a link on my first slide so that attendees could download the slides rather than taking pictures of them.  This year, IBM has done one better – every talk they are giving at this conference has a QR code on the title slide that goes straight to the slides for viewing or download.  Genius!  I hope this becomes a permanent trend copied by all.

Wednesday saw some very good talks.  Nischal Dhungana of the University of Grenoble used CD-SAXS (small angle x-ray scattering) to measure linewidth roughness (LWR) of a group of line/space features.  I have to admit I didn’t follow how it works, but since the SAXS measurement is done in the Fourier Plane the output is (after some sorting) an almost direct measurement of the PSD (power spectral density).  Much work remains, so we’ll have to see where this goes.

Erik Simons of Nearfield Instruments described a very interesting approach to make Atomic Force Microscope (AFM) measurements of extremely small features with much higher accuracy.  In order to measure small trenches, the AFM probe must be long and narrow to fit in the trench.  But a long, narrow probe will bend when near the sidewall of a feature due to Van der Waals forces, causing considerable error in the data.  Their solution is to measure the twisting of the cantilever holding the probe with a laser, then model the additional bending of the probe given that data.  Knowing the bending allows the data to be corrected.  I don’t know how this might affect tip shape deconvolution (a point that Simons skipped over and a perennial difficulty for AFMs), but they seem to be on a roadmap to better accuracy.

Roberto Fallica of imec studied line wiggling, a problem of growing importance as line/space feature sizes shrink, using the PSD of the pattern placement roughness (PPR).  Most line wiggling metrics make use of the LER and LWR, so I’ll have to think more about the information available in the PPR.  Dario Goldfarb of IBM showed how High-NA EUV patterning of arrays of holes produced very low local CD uniformity (LCDU).  Numbers less than 1.5 nm are very encouraging.

Kevin Dorney of imec did such a good job with his talk on the effects of the environment on metal oxide resists that I did not even mind seeing dozens of IR spectra.  The systematic way that imec has worked on this important puzzle shows how science should be done.  Varun Kakkar of ASML looked at the correlation between contact hole LCDU and another important stochastic effect, local pattern placement errors (LPPE).  LPPE characterizes the deviation of the center of each hole from a perfect grid and can be correlated with LCDU.  I’m not sure why that correlation matters, but I’m going to think about it.  Wongi Park of Samsung showed in the next talk that any measurement of LPPE must include the measurement and removal of SEM distortion if accuracy in to be expected.  He showed removal of only low-order terms (translation, rotation, and magnification), but higher order effects can also be removed with enough data.

I ended the day by going to Robert Bristol’s first talk as a Fractilia employee.  Since I am a coauthor on the paper (and Robert’s boss), my opinion is definitely biased, but I think he did a great job.  And it was an important topic.  Working with Nanya on a DRAM manufacturing process we found a good stochastics metric that correlates well with end-of-line yield:  line segment unbiased LCDU.

The poster session was massive (almost overwhelming), but spread out enough so that it was easy to move around and enjoy the posters.