Kenneth Goldberg, CXRO Deputy Director
SHARP Microscope Principal Investigator
The other day, I was looking up something on the web with my iPhone and my wife joked, "Remember, before the internet, when you had to just sit there and wonder...?" Indeed, I literally grew up with computers and now take them for granted, but I also know that there's a phenomenal triumph of science and optics underpinning every device. It wouldn't be an overstatement to compare the sustained, ongoing development of (chip-making) photolithography to the greatest technological achievements in human history.
The microprocessor turned 40 years old in November of 2011. So within my lifetime, the semiconductor industry has touched and transformed nearly every aspect of our lives. As a scientist, I am excited to contribute something valuable to that ongoing process through my work in extreme ultraviolet (EUV) photolithography. EUV (using 13.5-nm-wavelength light) is the successor to today's deep-ultraviolet (DUV) lithography (193 nm). It is expected to come into production within the next few years, printing successively smaller generations of circuit patterns with 16-, 11-, and 8-nm feature sizes.
In lithography, photomasks (also called "masks" or "reticles") carry a master copy of the complex circuit patterns that get transferred onto a chip, and mask defects are a major concern. A defect caused by a stray particle on the surface, an unexpected kink in the master pattern, or subtle imperfections in the underlying substrate, can short-circuit a chip, or ruin a whole batch.
Success requires lithographers to find and then remove or repair defects before they cause problems; but consider the difficulty. On a 6-inch-square EUV mask, critical defects can be just 10–40-nm wide and 1–2-nm tall— comparable in relative size to a few errant tortillas dropped somewhere in California. Worse, they can be transparent, phase-shifting tortillas in some cases. Since EUV masks are finely tuned for EUV wavelengths, the usual inspection modes—electron and atomic force microscopy, DUV inspection, etc.—cannot reliably gauge the impact of defects, once found. For the smallest defects, EUV mask imaging is essential, and that's where we contribute.
The US national laboratories have unique tools like ultra-bright synchrotron light sources and expertise that industry can call upon for critical help. Creating cutting-edge research tools based on exotic EUV optical systems is a specialty of my group, the Center for X-Ray Optics at Lawrence Berkeley National Laboratory (LBNL). We control and focus EUV light using curved-mirror lenses specially coated to reflect EUV light, and tiny holographic lenses called Fresnel zoneplates that bend light by diffraction.
In one such collaboration, LBNL is extending its long partnership with a consortium of leading semiconductor manufacturers to create a new EUV microscope capable of several generations of EUV mask research. With customizable coherence control and selectable magnifications and numerical aperture values, our new SHARP microscope (the Semiconductor High-NA Actinic Reticle Review Project) will flexibly emulate the conditions of current and future EUV printing tools. With an ability to study defects once considered too small to detect, SHARP will answer pressing research questions about mask defect printability and repair, mask architecture, materials, contamination and cleaning, and more. It will be ready at the end of 2012, several years ahead of commercial mask-imaging tools. SHARP will give researchers a unique, early look at the future of EUV lithography, so they will no longer have to sit and wonder.
Additional information
With sales of some $51 billion a year, semiconductors are the United States' second largest export product. Developing technology to produce and test the next generation computer chips is one of industry's core missions. For over a decade, semiconductor companies have sponsored photolithography-related research at Berkeley Lab through the Center for X-Ray Optics, including world-leading programs in optics, masks, and materials--most conducted on three CXRO beamlines at the Advanced Light Source.
Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 12 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit www.lbl.gov.
Dr. Kenneth Goldberg is the deputy director of Lawrence Berkeley National Laboratory's Center for X-Ray Optics. He specializes in the development of technologies for EUV and soft x-ray wavelengths, including lithography, mask inspection, and interferometry. Dr. Goldberg is the principal investigator of the SEMATECH Berkeley Actinic Inspection Tool (AIT), an EUV reticle-imaging microscope; and he is a co-creator of the SEMATECH Berkeley Micro-Exposure Tool (MET). Dr. Goldberg received an A.B. degree in Physics and Applied Math, and a Ph.D. in Physics from the University of California, Berkeley. He has authored and co-authored over 160 publications, and has received 12 patents.
