According to the International Technology Roadmap for Semiconductors, meeting the strict requirements on image placement errors in the sub-45-nm regime may be one of the most difficult challenges for the industry. For Extreme Ultraviolet Lithography (EUVL), the nonflatness of both the mask and chuck is critical as well, due to the nontelecentric illumination during exposure. To address this issue, SEMI Standards P37 and P40 have established the specifications on flatness for the EUVL mask substrate and electrostatic chuck. This study investigates the procedures for implementing the Standards when measuring and characterizing the shapes of these surfaces. Finite element simulations are used to demonstrate the difficulties in supporting the mask substrate, while ensuring that the measured flatness is accurate. Additional modeling is performed to illustrate the most appropriate methods of characterizing the nonflatness of the electrostatic chuck. The results presented will aid in identifying modifications and clarifications that are needed in the Standards to facilitate the timely development of EUV lithography.

Date Published: 30 October 2007
PDF: 11 pages
Proc. SPIE 6730, Photomask Technology 2007, 673014 (30 October 2007);

Published in SPIE Proceedings Vol. 6730:
Photomask Technology 2007
Robert J. Naber; Hiroichi Kawahira, Editor(s)