Commissioning an EUV mask microscope for lithography generations reaching 8 nm

Commissioning an EUV mask microscope for lithography generations reaching 8 nm Kenneth A. Goldberga, Iacopo Mochia, Markus Benka, Amaud P. Allezya, Michael R. Dickinsona, Carl W. Corka, Daniel Zehma, James B. Macdougalla, Erik Andersona, Farhad Salmassia, Weilun L. Chaoa, Vamsi K. Vytlaa, Eric M. Gulliksona, Jason C. DePonteq, M. S. Gideon Jones”, Douglas Van Campa, Jeffrey F. Gamsbya, William B. Ghiorso“, Hanjing Huanga, William Corka, Elizabeth Martina, Eric Van Everyb, Eric Acomeb, Veljko Milanovic°, Rene Delanoa, Patrick P. Naulleaua, and Senajith B. Rekawaa “Center for X-Ray Optics, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 bAdvanced Design Consulting USA Inc., 126 Ridge Rd, Lansing NY 14882, USA °Mirrorcle Technologies, Inc., 2700 Rydin Road, Unit F, Richmond, CA 94804 ABSTRACT The SEMATECH High-NA Actinic Reticle review Project (SHARP) is a synchrotron—based, EUV—wavelength microscope, dedicated to photomask imaging, now being commissioned at Lawrence Berkeley National Laboratory. In terms of throughput, resolution, coherence control, stability and ease of use, SHARP represents a significant advance over its predecessor, the SEMATECH Berkeley Actinic Inspection Tool (AIT), which was decommissioned in September 2012. SHARP utilizes several advanced technologies to achieve its design goals: including the first Fourier- synthesis illuminator on a zoneplate microscope, EUV MEMS mirrors, and high—efficiency freestanding zoneplate lenses with numerical aperture values up to 0.625 (4x). In its first week of operation, SHARP demonstrated approximately 150 times higher light throughput than AIT and a spatial resolution down to 55—nm half—pitch with 0.42 4xNA (i.e. the smallest feature size on our test mask.) This paper describes the current status of the tool commissioning and the performance metrics available at this early stage. Keywords: extreme ultraviolet lithography, EUV, microscope, actinic, mask, reticle, imaging, zoneplate 1. INTRODUCTION We are now commissioning a new, synchrotron—based extreme ultraviolet (EUV, near l3.5—nm wavelength) microscope to support advanced photomask research for the semiconductor industry. The microscope will serve photolithography generations to the year 2020 and beyond, when printed feature sizes are expected to fall below 10 nm. Called SHARP (the SEMATECH High-NA Actinic Reticle review Project), the microscope is designed to emulate the optical properties of current and future EUV lithography tools, enabling the study of mask defects, pattern architectures, optical proximity correction, phase—shifting patterns, and more.' SHARP is the successor to the SEMATECH Berkeley Actinic Inspection Tool (AIT) which was decommissioned in September, 2012 after eight years of operation. Owing to their highly wavelength-specific optical properties, the creation of production-quality EUV masks may come to rely upon dedicated EUV-wavelength mask—blank inspection and pattern-imaging tools. With commercial tools still months to years years from deployment, SHARP was created by an industry/government partnership to provide advanced research and development capabilities. Although rooted in similar technologies, SHARP is designed to surpass the AIT in almost every performance metric. The AIT was the first EUV microscope to achieve diffraction—limited imaging with zoneplate lenses} and the first to offer an array of user—selectable zoneplate lenses, with different optical properties. To accomplish its goals, SHARP utilizes several advanced short—wavelength optical elements and systems. SHARP is the first EUV microscope to combine lossless, customizable coherence control‘ with zoneplate-lens imaging; and, it is the first to use a dynamic, MEMS—based EUV mirror element. In SHARP nearly 30 times more lenses will be available, providing customized