The 57th International Conference on Electron, Ion and Photon Beam Technology and Nanofabrication (EIPBN, aka three-beams, aka triple-beam) was held this week in Nashville. The conference moves to a new location each year, and I have to admit that my decision to attend is extremely dependent on its location. I had never been to Nashville before, so here I am. The attendance of 400 was down from last year, so I suspect that many enjoyed last year’s location in Hawaii better.
A word about the venue this year. It was at the Gaylord Opryland Resort, outside of town but right next to the Grand Ole Opry (and a Mall). The place is huge, with nearly 3000 rooms and numerous themed areas, and resembles a Las Vegas resort, but with country music instead of casinos. It has everything one would expect: artificial waterfalls, indoor palm trees, fountain and light shows, and plenty of shopping opportunities. And it realizes every southerner’s dream: the outdoors is air-conditioned.
Compared to this Disneified resort, the actual city of Nashville looks run down and dingy. Broadway (the equivalent of Sixth Street in Austin) is lined with dive bars and free music. I loved it. I found a group of recent PhDs with similar tastes and we managed to try quite a few local beers (Yazoo Pale Ale was my favorite) and catch some amazing music. I was glad for the opportunity the see the other famous music town in America (Nashville deserves its claim to second place, after Austin, as the Music Capital).
Thursday night was the conference banquet, and we were treated to a dinner on a Cumberland River paddle boat. In keeping with the theme, the boat was huge, and the entertainment was a Las Vegas-style review of country music. The quality of the entertainment was surprisingly good, until the last song – a jingoistic God Bless America number that was heavy on the cheese and that left the very international audience wondering how to react. But I guess it is impossible to end a country music montage without providing proof that country music fans are the best Americans.
As I say every time I write about the 3-beams conference, its value lies in its themed diversity. While I have focused in my career on lithography for high volume chip manufacturing, an unforgiving technology niche that demands ultra-high performance and ultra-low unit cost in equal measures, this conference focuses on the needs of flexible, low volume fabrication. High resolution is usually important, but the need to make only a few things rather than a billion things changes the optimization dramatically. There is no convergence to one best solution, but rather an organic and eclectic mix of possibilities. It is a broadening experience to attend.
I heard nothing earth shattering this year, and I certainly listened to some pretty bad talks. But there were a few really good ones as well. I liked Hiroshi Fukuda-san’s poster paper on analyzing LER measurements, though I didn’t understand it (I’ll need to study the written paper). I enjoyed hearing about David Czaplewski’s method for measuring electron beam lithography backscatter – an impressive show of rigorous engineering that is so frequently lacking in this field. Pieter Kruit’s progress report on Mapper did not leave me encouraged, and neither did Tony Yen’s report on EUV mask defectivity. Both areas are progressing, but too slowly.
Virtually every conference I attend produces a soap-box moment for me, and this one has been a long time coming. While I admire the many interesting approaches that researchers have tried over the years to improve resolution in optical printing, I get tired of hearing about how their latest new technique is finally “beating the diffraction limit” and enabling feature sizes that are smaller than could be had with conventional imaging techniques. The “diffraction limit” of conventional imaging is invariably described as half the wavelength (/2), and then the researcher will show an isolated feature (usually of very poor quality) with a size of /5, or possibly down to /8, as demonstration of blowing past the limits. Regardless of how interesting the approach may be, I can’t help but get riled up when I hear such language.
First, a diffraction limit of /2 is the smallest pitch that can be printed, not the smallest feature, and it assumes imaging in air, even though immersion imaging is the standard in lithography today. The smallest half-pitch that we print in lithography manufacturing today is /5 in size, using perfectly conventional imaging. And of course we make a billion features at this size for a dollar. If we want to print an isolated feature, we can easily thin that line to a size of /10, again while staying within the confines of the diffraction limit. (And this is before we start down the path of double patterning.) It is very rare when some university research project using an exotic optical approach produces something as good as, let alone better than, what is routine in the semiconductor manufacturing world. The diffraction limit defines the smallest pitch (the distance between two features) that can be printed. There is no diffraction limit to the smallest individual feature that can be made – that is just a matter of control, and chip makers are very, very good at control.
So, my advice to all you researchers looking for the next big thing in lithography: go for it. Keep doing good work, exploring new ideas, and learning about what light and nonlinear materials can do. It’s really cool stuff. But be careful when you say you are beating some limit, or doing better than “conventional” lithography, because the limits aren’t so limiting, and “conventional” lithography can do some amazing things.
And so ends my report on the 57th 3-beams conference. I gave a paper as well, and I am happy with the outcome. Now I am going back to Austin, and I mean no disrespect when I say that the barbeque and the beer and the music is better there than Nashville. I probably shouldn’t compare, because Nashville is rightly proud of what it has to offer. But I am glad to be going home.
