Experimental study of mask line edge roughness transfer in DUV and EUV lithography patterning process

Abstract

In this paper, the effects of mask line edge roughness (LER) transfer in both deep ultra-violet (DUV) and extreme ultra- violet (EUV) lithography patterning is studied experimentally. In order to understand how the mask LER transfers in the wafer printing process under both DUV and EUV lithography, an optical mask with programmed LER was fabricated. The EUV mask was further fabricated by using the optical mask via optical lithography pattern transfer. The programmed LER on both optical mask, EUV mask, and printed resist images were characterized, measured, and compared. The data analysis showed that the mask LER in both DUV and EUV cases transferred to wafer with a scaling factor much less than one regardless of lithographic k 1 -factors. The LER transfer does not resemble the case of mask CD error transfer, in which scale factors greater than one for small lithographic k 1 -factor occur. The primary reason for the difference is that the amount of mask LER transferred to the wafer strongly depends on the total area of the LER, i.e. depends on both vertical and horizontal dimension of the LER. This case is very similar to that of a single mask defect transfer.