23 October 2015 Film loss-free cleaning chemicals for EUV mask lifetime elongation developed through combinatorial chemical screening
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Abstract
EUV masks include many different layers of various materials rarely used in optical masks, and each layer of material has a particular role in enhancing the performance of EUV lithography. Therefore, it is crucial to understand how the mask quality and patterning performance can change during mask fabrication, EUV exposure, maintenance cleaning, shipping, or storage.

SPM (Sulfuric acid peroxide mixture) which has been extensively used for acid cleaning of photomask and wafer has serious drawback for EUV mask cleaning. It shows severe film loss of tantalum-based absorber layers and limited removal efficiency of EUV-generated carbon contaminants on EUV mask surface.

Here, we introduce such novel cleaning chemicals developed for EUV mask as almost film loss free for various layers of the mask and superior carbon removal performance. Combinatorial chemical screening methods allowed us to screen several hundred combinations of various chemistries and additives under several different process conditions of temperature and time, eventually leading to development of the best chemistry selections for EUV mask cleaning.

Recently, there have been many activities for the development of EUV pellicle, driven by ASML and core EUV scanner customer companies. It is still important to obtain film-loss free cleaning chemicals because cleaning cycle of EUV mask should be much faster than that of optic mask mainly due to EUV pellicle lifetime. More frequent cleaning, combined with the adoption of new materials for EUV masks, necessitates that mask manufacturers closely examine the performance change of EUV masks during cleaning process.

We have investigated EUV mask quality changes and film losses during 50 cleaning cycles using new chemicals as well as particle and carbon contaminant removal characteristics. We have observed that the performance of new chemicals developed is superior to current SPM or relevant cleaning chemicals for EUV mask cleaning and EUV mask lifetime elongation.
© (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jaehyuck Choi, Jaehyuck Choi, Jinsu Kim, Jinsu Kim, Jeff Lowe, Jeff Lowe, Davide Dattilo, Davide Dattilo, Soowan Koh, Soowan Koh, Jun Yeol Choi, Jun Yeol Choi, Uwe Dietze, Uwe Dietze, Tsutomu Shoki, Tsutomu Shoki, Byung Gook Kim, Byung Gook Kim, Chan-Uk Jeon, Chan-Uk Jeon, } "Film loss-free cleaning chemicals for EUV mask lifetime elongation developed through combinatorial chemical screening", Proc. SPIE 9635, Photomask Technology 2015, 96350C (23 October 2015); doi: 10.1117/12.2197226; https://doi.org/10.1117/12.2197226
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