Date: Tuesday, May 25, 2021
Time: 11:00 am
Talk Title: Lithography’s Endgame: The Last Wavelength and Moore’s Law 2.0
The extraordinary success story that is Moore’s Law required many technological components to come together at the right times. This presentation will tell this story through the lens of one of the key components: the patterning materials, in particular the photoresists.
Every chip ever produced has used some form of microlithography, usually photolithography, which has historically been the gating technology for how quickly features sizes could be shrunk. Starting with cyclized rubber resists, the industry went on to use DNQ novolak systems for a quarter century, before switching wavelengths from near-UV to 248 and 193 nm, then to 193 nm immersion. Every one of these switches required the invention of a new photoresist platform, new resin systems and even new imaging concepts, such as the use of chemically amplified resists beginning with 248 nm. For the materials scientist, Moore’s Law has historically been a race to the next wavelength. This sequence of more or less frantic developments is coming to an end as we near the physical limits of microlithography. With the introduction of EUV lithography, the finish line of this race is in sight: today’s EUV resists are still far from perfect, and this presentation will cover their issues and the paths forward, but there can be no doubt that with EUV, we have reached what appears to be the Last Wavelength. There will never be a new “next gen” exposure technology after it – lithography has reached its endgame.
At the same time, we are approaching fundamental limits from the device side. Today’s FinFETs are about 40 Si atoms wide, and the thermodynamic limit for irreversible computation may be about 6 Si atoms. While there still is some room, the end of shrink is in sight. Instead, Logic and eventually all devices will follow the path already taken by NAND flash memory and expand into the 3rd dimension. As already seen in 3D NAND, the switch to 3D architectures will end lateral feature size shrink, followed by a relaxation of lithographic design rules: other parts of the process will become the most challenging ones, and photolithography will no longer be the gating technology. Transistor density increases will continue in a new form through 3D stacking: Moore’s Law 2.0.
However, the need for better, faster, cheaper process options will not go away, and bottom up technologies such as DSA, selective or self-aligned patterning, and other processes with atomic level precision will need to continue to be developed. The future will see new non-CMOS device types and possibly even circuits which function according to the laws of relativistic quantum physics, all of which will require new materials and bring new challenges. While photolithography is entering its end game, the job of the material scientists is far from done.
Ralph R. Dammel (*April 29, 1954) received a Ph.D. in Chemistry from the J.W. Goethe University in Frankfurt/FRG in 1986. He has worked for EMD Performance Materials/Merck KGaA or its predecessor organizations in Germany, the US, Hong Kong, and Thailand since then, and is currently employed as Technology Fellow in the CTO Office of Merck KGaA’s Electronics division.
Dr. Dammel is the author of over 200 scientific papers in chemistry and microlithography and is an inventor on over 470 patents in over 100 patent families in the field. His monograph “Diazonaphthoquinone-based Resists” is generally recognized as the definitive book on the subject. In spring 2009, Dr. Dammel was elected as SPIE Fellow. He received the Photopolymer Science and Technology Outstanding Achievement Award in June 2011, SPIE’s Frits Zernicke Award for Microlithography in February 2015, and Merck KGaA’s Science Award in 2020.