Si-Containing Reverse-Gradient Block Copolymer for Inorganic Pattern Amplification in EUV Lithography

Although extreme ultraviolet lithography (EUVL) has emerged as a leading technology for achieving high quality sub-10 nm patterns, the insufficient pattern height of photoresist patterns remains a challenge. Directed self-assembly (DSA) of block copolymers (BCPs) is expected to be a complementary technology for EUVL due to its ability to form periodic nanostructures. However, for a combination with EUV patterns, it is essential to develop advanced BCP systems that are suited to inorganic-containing EUV photoresists and offer improved resolution limits, pattern quality, and etch resistance. Here, we report a reverse-gradient BCP system, poly[(styrene-gradient-pentafluorostyrene)-b-4-tert-butyldimetilsiloxystyrene] [P(S-g-PFS)-b-P4BDSS] BCP, which enables universally vertically oriented lamellae even in the absence of a neutral layer, while also containing a Si-containing block with high etch resistance. The gradient block, characterized by a gradual compositional transition from the block junction to the tail, plays a crucial role in creating an adequate surface energy contrast that energetically drives the formation of perpendicular lamellae without neutral layer. When used as a pattern height enhancement layer in EUVL, a high aspect ratio (3.29) of patterns was achieved, thereby offering a supplementary solution for next-generation EUVL.