In this study, the authors propose transparent conductive oxide layer as a new absorber for extreme ultraviolet lithography mask. The optical constant of indium tin oxide (ITO) at is calculated and the extinction coefficient of ITO is found to be 1.55 times higher than that of TaN, resulting in higher absorption in the absorbing stack. Using an ITO layer in the absorber stack enables to design the attenuated phase-shift masks with smaller height difference of only than the conventional TaN absorber stack of about between high reflecting and absorbing stacks in extreme ultraviolet lithography, indicating that the geometric shadow effect can be significantly reduced.
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American Vacuum Society
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