Improving aspect ratio for extreme ultraviolet (EUV) pattern via encapsulating Si-containing gradient block copolymer

Abstract

The Extreme-Ultraviolet lithography technology is receiving the most attention among the candidates for lithography at the level of 10nm or less due to its excellent pattern resolution and reduced number of processes. However, there are many technical challenges in the practical use of the above technologies. Among them, it generates strong EUV source with a so short wavelength of 13.5nm. Energy and wavelength are inversely proportional, and ultra-short light source hits the wafer surface more strongly. At this time, defects that cause the atomic nuclei of the reactive material contained in the photoresist to protrude or induce a completely new atomic bond are generated. In addition, as the wavelength decreases, the thickness of photoresist decreases, which makes it difficult to use as an etching mask. In this study, we try to solve this problem by using the synthesis and self-assembly of a gradient block copolymer containing a silicone block. This block copolymer has a block containing silicone called 4-(tert-butyldimethylsilyloxy)-styrene, and is easy to use as a mask. The other block is made of poly (styrene-gradient- pentafluorostyrene) designed and synthesized so that the region in which the vertically oriented lamella is preferred appears, and thus has the advantage that vertical orientation is easier than other block copolymers. The above block copolymer was applied to the EUV pattern, and as a result, it was confirmed that a vertically aligned lamella was formed on the pattern and an aspect ratio that was about twice as high as that of the existing photoresist was achieved.