Enabling Sub-10nm Lithography with Atomic Layer Deposition and Block Copolymer Self Assembly

Block copolymer lithography, an alternative lithographic technique by which self-assembled patterns made from block copolymer thin films are used as lithographic masks, has achieved a high enough level of maturity to be considered for nanofabrication in magnetic recording bit patterned media and in some applications in the semiconductor industry. As the demand for lithographic dimensions squeezes into the single-digit nm scale, pairing block copolymer materials that segregate at these dimensions with adequate pattern transfer techniques is increasingly difficult. For example, PS-b-PMMA, the most mature block copolymer system can only form line/space patterns with pattern transfer above 10 nm. Other promising materials like P2VP-PS-P2VP triblocks, however, lack sufficient etch contrast for reactive ion etching. Here, we present a nanofabrication strategy that integrates atomic layer deposition, ALD, with block copolymer lithography to enable fabrication of sub-10nm features for high density magnetic storage. The selective, cyclic and self-terminating nature of the materials synthesis within ALD reactors provides powerful nanofabrication tools. In particular, two of these tools stand out as enablers for high density patterning: First, the chemical selectivity of the organometallic precursors has facilitated selective synthesis inside porous polymeric materials. Second, the conformality afforded by the self-terminating nature of the ALD reactions has proven to be ideally suited for feature doubling in self-aligned double patterning, SADP. Integrating these powerful tools with block copolymer lithography opens new possibilities in two fronts: On the one hand, it is possible to generate hybrid nanocomposites with nanometer-scale resolution and high etching contrast. This is particularly useful for high resolution block copolymer materials for which no natural etch contrast exists such as P2VP-PS-P2VP triblocks. On the other hand, it is possible to use the already sub-lithographic features obtained by standard PS-b-PMMA block copolymer lithography as the starting point for an additional density multiplication using spacer lines grown by ALD for SADP. Be it for selective infiltration synthesis in block copolymer patterns or for the precise conformal growth in nanostructures made from block copolymers, ALD is likely to emerge as an ideal complimentary technique to block copolymer self assembly to enable sub-10nm lithography.