9 July 2015 Exploring EUV mask backside defectivity and control methods
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The backside of photomasks have been largely ignored during the last several decades of development, with the exception of avoiding gross damage or defects, as almost all problems are far enough out of the focal plane to have minimal effect on imaging. Since EUV masks are reflective, and the column is held in a vacuum, scanners have been designed to utilize electrostatic chucking. With the chucking system for EUV, the requirements for the backside of the mask must be redefined to integrate concerns in substrate design, mask manufacturing, and usage. The two key concerns with respect to an electrostatic chuck are defects and durability. Backside defects can affect imaging, while potentially damaging or contaminating the tool, the mask, or even subsequently used masks. Compromised durability, from either usage or cleaning, can affect the ability of the chuck to hold the mask in place. In this study, these concerns are evaluated in three stages: minimizing defects created during mask fabrication, actions taken upon discovery of defects, and durability of the backside film with continued cleans and chucking. Data incorporated in this study includes: sheet resistance, film thickness, and optical inspection images. Incorporating the data from the three stages of fabrication, disposition, and lifetime will help us define how to structure backside EUV mask handling during mask manufacture and indicate what further solutions are needed as EUV technology transitions into manufacturing.
© (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Christina Turley, Christina Turley, Jed Rankin, Jed Rankin, Louis Kindt, Louis Kindt, Mark Lawliss, Mark Lawliss, Luke Bolton, Luke Bolton, Kevin Collins, Kevin Collins, Lin Cheong, Lin Cheong, Ravi Bonam, Ravi Bonam, Richard Poro, Richard Poro, Takeshi Isogawa, Takeshi Isogawa, Eisuke Narita, Eisuke Narita, Masayuki Kagawa, Masayuki Kagawa, } "Exploring EUV mask backside defectivity and control methods", Proc. SPIE 9658, Photomask Japan 2015: Photomask and Next-Generation Lithography Mask Technology XXII, 965811 (9 July 2015); doi: 10.1117/12.2197383; https://doi.org/10.1117/12.2197383


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