EUV Source Collector Norbert R. Böwering * , Alex I. Ershov, William F. Marx, Oleh V. Khodykin, Björn A. M. Hansson, Ernesto Vargas L., Juan A. Chavez, Igor V. Fomenkov, David W. Myers, David C. Brandt Cymer Inc., 17075 Thornmint Court, San Diego, CA USA 92127-1712 ABSTRACT A collector subsystem has been designed, built, and tested. The subsystem consists of a 320mm diameter ellipsoidal collector coated with a graded multilayer, mounting mechanics, thermal management capability, and a collector protection system. The EUV light emission can be collected with a solid angle of 1.6 sr. Collector substrates have been developed with the goal of offering both optical surface quality to support high multilayer mirror (MLM) reflectivity and material compatibility for long-term operation in the EUV source system. An interface-engineered MLM coating capable of maintaining high normal-incidence peak reflectivity at 13.5 nm during continuous operation at 400 °C has been developed. The thermal management of the system has been engineered and tested to maintain uniform substrate temperature during operation. Lastly, protection techniques have been developed to provide the collector with a long operational lifetime. Performance data for the entire subsystem are presented. The collector was installed in the source chamber of a laser-produced-plasma EUV source during system integration experiments using a tin droplet target. First results of the collected EUV output at the intermediate focus measured with a power meter and a fluorescence- converter-based imaging system are discussed. Keywords: EUV collector mirror, EUV lithography, EUV light source, laser-produced plasma, multilayer mirror, EUV radiation power, collector lifetime 1. INTRODUCTION EUV light sources generally emit radiation from the generated micro-plasma into all directions. Therefore, it is highly desirable to collect the emitted radiation power as efficiently as possible and redirect it towards the entrance of the illumination system of the lithography exposure tool. In order to keep the size of the mirror within reasonable limits the collector has to be mounted relatively close to the light emission region and thus needs to be protected from debris ejected from the plasma region to insure a sufficiently long mirror lifetime. Consequently, the optical collector is regarded as one of the most critical subsystems for extreme-ultra-violet (EUV) source systems. Since the optical requirements are quite challenging and since the manufacturing process consists of many steps it is a time-consuming process to develop and test a large advanced collector subsystem. For a prototype it is required to prove the full functionality of the entire light source system that includes delivery of EUV radiation to the intermediate focus (IF) position via the collector. In addition to the technical aspects it must also be demonstrated that the manufacturing is economically viable. In summary, the general requirements are that the collector subsystem needs to have high collection efficiency for EUV radiation, high resistance to debris generated by the plasma, have a long lifetime, a reasonable cost, and be exchangeable with consideration of semiconductor industry maintenance standards. For integration with Cymer’s laser-produced plasma (LPP) light source that is currently being developed [1, 2] we have designed, installed, and tested a near normal-incidence sub-aperture collector mirror with 1.6 sr collection solid angle. The mirror is intended for use during continuous operation at temperatures of up to at least 400 °C in conjunction with an LPP using liquid metal droplet targets containing lithium (Li) or tin (Sn) [3]. In this paper we discuss the various aspects of the entire collection subsystem, geometry and opto-mechanical design, and we describe heating tests of the mirror shell as well as lifetime tests on witness samples. We also present data characterizing the mirror substrate and the * NBowering@cymer.com ; phone 1 858 385-6287; fax 1 858 385-5353; www.cymer.com Emerging Lithographic Technologies X, edited by Michael J. Lercel, Proc. of SPIE Vol. 6151, 61513R, (2006) · 0277-786X/06/$15 · doi: 10.1117/12.656462 Proc. of SPIE Vol. 6151 61513R-1