Improving the Lithographic Performance of Tetranuclear Organotin Resist via Additives with Active Ligands

Abstract

A series of tetranuclear organotin clusters (Sn-mCl, Sn-opy, Sn-mMe, and Sn-dMe) with different carboxylate ligands (mCl, meta-chloromethylbenzoate; opy, picolinate; mMe, meta-methylbenzoate; dMe, 3,5-dimethylbenzoate) were synthesized and characterized. Evaluations on thermostability and film-forming capability demonstrate the potential of Sn-opy cluster and the mixture of Sn-opy with Sn-mCl cluster additive (m₁/m₂ = 9 : 1, designated as Resist-91) as negative-tone non-chemically amplified resist (n-CAR) materials. The lithographic performances of Resist-91 and Sn-opy resist were evaluated by using electron beam lithography. Sn-opy resist can only resolve the best 22 nm half-pitch (HP) pattern at 2000 μC·cm^–2. Resist-91 exhibits superior lithographic performance and resolves 20 nm HP patterns at 1450 μC·cm^–2, demonstrating a significantly improving of the sensitivity and resolution by the introduction of Sn-mCl. Further extreme ultraviolet lithography demonstrates the capability of Resist-91 to form 20 nm HP patterns at a dose of 39 mJ·cm^–2, with the best Z-factor of 2.1 × 10^–7 mJ·nm³ among ladder-shaped tetranuclear organotin resists. Extensive mechanistic analysis of Resist-91 and model films demonstrates the substitution of Cl atom by pyridine ligand, and the generation of a network consisting of tin oxides and organics with the assistance of Sn-mCl cluster, highlighting the critical role of additives with active ligands.

Keywords

Tin-based resist / Organotin cluster / Cluster compounds / Tin / Benzyl chloride / Electron beam lithography / Extreme ultraviolet lithography / Photochemistry

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