The opening remarks for the symposium revealed what was already obvious – the six conferences that make up ALP are doing very well.  There were 536 abstracts submitted and registration stood at 2200 attendees, both excellent numbers indicating a thriving meeting.  I was very excited to see Hank Smith of MIT accept his Frits Zernike Award for Microlithography.  Hank may be best known for his significant work on X-ray lithography in the 1970s and 80s, but his contributions to phase-shifting masks and numerous nanolithography approaches have also been important.  And as his award citation pointed out, the legacy of his students greatly extends the reach of his influence.  Congratulations, Hank!

This year the four plenary talks are spread over two days, with the first two on Monday.  Shien-Yang Wu of TSMC gave an obligatory nod to Artificial Intelligence in his talk about technological progress at the world’s leading semiconductor company.  I don’t blame him for his excitement about AI, since it is expected to add up to $200B to annual semiconductor revenue by 2030, with TSMC destined to take the lion’s share.  His talk touched on several important themes:  the growing role of packaging in keeping the evolving Moore’s Law alive; the challenge of power consumption as AI tries to consume all the data in the world; the trend toward verticality in logic transistors; the many innovations beside lithography scaling that contribute to transistor density improvements.

Subramanian Iyer of UCLA went deeper into one of those topics in his plenary on strategic directions for packaging.  I liked his description of the dual purpose of packaging as “protect and serve”:  protect the chip mechanically and from the environment while serving up electrical connections to other chips.  The key trends in packaging are all about the optimization between increasing the functionality of a monolithic chip (with the higher costs that come from a larger die) and the performance loss that comes from the limitations in I/O when that functionality is spread between chips.  This optimization can be improved by reducing the limitations of the “serve”, getting the signals on and off the chips.  This can be done by making the packaging interconnections (such as the bump pitch) closer in size to the pitch of the top wiring level of the chip (that is, closer to 1 micron from today’s 10 microns) and by reducing the length of the interconnects (bringing the chips closer to each other) so that those interconnects become wires rather than transmission lines.

The opening of the metrology conference began with a touching tribute to Ben Bunday, who died suddenly last August at the age of 55.  Ben was a constant presence at this conference for 25 years, with 104 SPIE papers (two of which won the Diana Nyyssonen Best Paper Award) and 15 years as a member of the metrology conference program committee.  I count Ben as an important colleague (we wrote many papers together and were planning one for 2025) and remember him as a friend.  The standing ovation for him at the end of the tribute was fitting.

Master Younghoon Sohn of Samsung gave a keynote talk in the metrology conference on the evolution of eBeam MI (metrology and inspection) technology.  He described the purposes of MI as monitoring process defects and quantifying the process window.  The talk was structed as an increase in “dimensionality” of SEM metrology, from a 2D top-down SEM image, to a 4D description of a material property in 3D space, to the “next” level of monitoring that 4D description over time.  His mention of my favorite subject was this: “Roughness? Defining the accuracy is quite difficult.”  Very true.

I snuck over to the patterning materials conference to watch Mihir Gupta give a review of imec’s approach to resist evaluation.  Imec has pioneered the addition of the “failure free latitude” to the conventional RLS trade-off (resolution, line-edge roughness, and sensitivity) and Mihir provided some valuable details of their method.

Back at the metrology conference in the afternoon, Applied Materials gave a pair of presentations exhibiting the triumph of marketing over science.  One talked of “True Metrology” and the measurement of the “True CD”.  Really?  Their use of these terms would make any true metrologist cringe.  The “True Value” of a measurand is inherently unknowable, requiring instead a comparison to a reference and an estimated bounding of the errors in the measurement.  This is Metrology 101, and nothing like this was described or even hinted at.  What the paper was about was the use of 150 V in the SEM to reduce resist shrinkage (compared to 500 V).  But to describe a measurement with lower shrinkage as the “True CD” is a distortion of not only what was done, but what is possible.

The other paper by Applied in that session was even worse:  Anna Levant’s talk “Beyond 3 Sigma: roughness metrology evolution at the last 20 years (in memory of Ben Bunday)”.  Purporting to be a review paper of roughness metrology this talk was instead an attempt to rewrite history and claim leadership (or even significant contributions) in roughness metrology by Applied Materials.  Besides “True CD” they have added another nonsensical term to the lexicon: the “noiseless PSD”.  This would just be another fluff paper, not worthy of ire, if it were not for the transparent and grotesque attempt to gain credibility for themselves through the memory of Ben Bunday.  The authors should be ashamed.

So as not to end this post on a sour note, I’ll mention the last presenter I saw giving the last paper of the optical and EUV conference, Tim Brunner.  Tim told me he was retiring next month, so this is likely his last SPIE presentation after 43 years of contributions.  (His first paper, from 1982, was in Optical Microlithography I: Technology for the Mid-1980s.)  Like many, I have been a Tim Brunner fan since I first heard him speak.  He is a paragon of sound reasoning, clear exposition, and good science.  He is also often quite funny, invariably inciteful, and frequently timely in his contributions, which are almost always important.  Tim, you are appreciated, and you will be missed.