LIGHT is the most ubiquitous and extraordinary phenomena in all of science. It flows toward us from glowing screens and from the farthest knowable reaches of space and time ago. No matter the wavelength, no matter the color, light is light. Its elegant path through the universe can be described by the simplest equations and the most complex interactions. Penetrating X-rays, the warmth of the Sun, and the familiar AM radio crackle all share the shades and glimpses of the same underlying physics.
Light carries energy in discrete wave-like packages called photons—quintillions of them arrive in a single blink. Photons are enigmatic yet highly predictable, arriving on our eyes, our cameras, and our detectors in a steady stream or a soft, slow rain. Scientists exploring light employ mathematics, experiments, and analysis to incrementally deepen our understanding. Our work gives rise to greater predictive abilities that we use to create fantastic new tools and techniques for science.
As a scientist working with light, every day is a new gift: time to think and learn; time to build and do; time to test and measure and troubleshoot and rebuild and test again; time to grow and refine and improve over time; and ultimately, time to collaborate and share and pass on, so that others can build upon the work we do, and surpass us.
Since 1993, my research at Lawrence Berkeley National Laboratory (LBNL) has been dedicated to short-wavelength extreme ultraviolet (EUV) and soft x-ray light. This light cannot be seen by the naked eye, yet it is so strongly reactive that it does not propagate a millimeter through the air before becoming extinguished. That extreme reactivity makes possible fantastic probes of material and chemical properties, while the short-wavelength enables us to squeeze it down to create nanometer-scale imaging resolutions and surface-probing interferometers with sub-Å (one ten-billionth of a meter) sensitivity.
All of the conventional elements associated with visible-light optics (lenses, mirrors, prisms, etc.) have to be re-envisioned, re-engineered, and re-designed for highly specialized applications at short wavelength. That is what I do.
I work to create and explore new capabilities and applications of short wavelength light, to bring techniques from other wavelength ranges to the EUV for the first time, and to develop unique tools and instruments at the forefront of my field.
I previously led a research team at the Center for X-Ray Optics (CXRO) that created and now operates a one-of-a-kind extreme-ultraviolet (EUV) microscope called SHARP, a research tool dedicated to improving commercial chip-making technologies. We study aspects of advanced photolithography, the central process used in the mass-production of computer chips. In 2019, 26 years after I began working on EUV Lithography at LBNL with CXRO, EUV lithography reached high-volume manufacturing (HVM) in several facilities worldwide.
In 2016, I joined the LBNL team working to create a major upgrade to the Advanced Light Source, called ALS-U. I led the ALS-U Beamlines and Optical Systems group from January 2017 through May 2019, during the period where the project moved from Department of Energy’s (DOE) Critical Decision 0, CD-0 (feasibility studies), through CD-1 (into preliminary design).
When approved and built, ALS-U will deliver coherent, diffraction-limited EUV, soft x-ray, and tender x-ray light that is orders of magnitude brighter than what we have today. It requires the development of new optical technologies to preserve the quality of the light from the source to the samples. For me, this effort grows from over two decades of work–through numerous projects and collaborations on interferometric wavefront metrology–to create short-wavelength optics, beamlines, mirrors, lenses, and imaging systems capable of performing at the physical limit of nanoscale resolution.
During this time, I was a co-principal investigator on a Department of Energy, Accelerator Research and Development Program (ADRP), four-lab collaboration called Wavefront Preserving Mirrors. My co-PIs were from SLAC National Accelerator Laboratory, Argonne National Laboratory, and Brookhaven National Laboratory.
My previous projects have included the SEMATECH Berkeley Actinic Inspection Tool (AIT), the Berkeley Microfield Exposure Tool (MET), and several other early EUV Lithography research projects, including the Engineering Test Stand (ETS) for the EUV LLC. Using extreme-ultraviolet interferometry, I tested and aligned six different EUV Schwarzschild objectives in a series of early EUV optics demonstration experiments. I have also developed interferometric techniques for the alignment and testing of glancing-incidence Kirkpatrick-Baez mirror pairs used on soft x-ray beamlines. In my work, I have conducted numerous studies on the performance and use of Fresnel zone plate lenses.
Our work is made possible by a talented, dedicated team of engineers and technicians whom we routinely challenge to expand the realm of what’s experimentally possible. My projects have been funded by industry and government agencies who recognize that millions of dollars spent on research can create billions of dollars in real economic value. Those agencies, and numerous program managers and directors within them, are visionary leaders who have repeatedly fought to foster and nurture our work. They deserve profound credit for their essential role in our success and our accomplishments.
For four years, I chaired the SPIE Advanced Lithography—Extreme Ultraviolet (EUV) Lithography conference, concluding in 2019. I was the program committee chair for Experimental Systems of the 6th Diffraction-Limited Storage Ring (DLSR) Workshop, held at LBNL, October 29-31, 2018. I served for four years on the ALS Users Executive Committee—one year as Chairman. I have been section head of EUV Lithography for the annual EIPBN meeting, and on the program committee for the SPIE Advances in X-Ray/EUV Optics and Components section of the SPIE Annual Meeting. I co-chaired the IWXM 2015—International Workshop on X-Ray Optics and Metrology.
Kenneth A. Goldberg
ALS-U Beamlines and Optical Systems (BOSS) Group
Staff Physicist, Photon Sciences Development Group, Advanced Light Source (ALS)
Lawrence Berkeley National Laboratory (LBNL)