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Abstract:
Hydrogen silesquioxan (HSQ) is a well-investigated negative tone inorganic resist [1,2] which is known for its capabilities for high resolution electron beam lithography (EBL) and its stability against dry etching [3]. In this paper, we introduce a process to create dense structures by EBL utilizing a layer of polymethyl-methacrylate (PMMA) as sacrificial layer beneath a HSQ layer. The sacrificial layer allows a simple lift-off process to remove the HSQ with organic solvents and thus avoids the use of hydrofluoric acid (HF) containing etchants, which is the commonly used HSQ remover [4]. The described double layer resist system allows patterning on substrates that are not HF compatible such as glass or oxide compounds, achieving a high resolution down to the sub-10 nm regime. Despite the use of a double layer resist, this process is applicable for arbitrarily large areas due to the remaining PMMA underneath the HSQ and the avoidance of undercuts. (C) 2013 Elsevier B.V. All rights reserved.
