BCP Lithography Defined Arrays of InAs NWs Grown Using MOVPE with Au Seeds

Abstract: In this report we outline a detailed process flow for a quick and inexpensive implementation of large dense arrays of InAs nanowires (NWs) grown in the reactive ion etching/etched (RIE) pores of a SiO2/SiNx mask on top of an InAs/Si(111) substrate. The self-assembled (hexagonally close-packed) pattern of poly(methyl-methacrylate) (PMMA) cylinders in a poly(styrene) (PS) matrix adopted by a linear diblock poly(styrene-block-methyl-methacrylate) P(S-b-MMA) block-copolymer (BCP) was transferred to the dielectric stack (consisting of a ≈10 nm plasma enhanced chemical vapour deposition/deposited (PECVD) SiNX layer topped by a thin atomic layer deposition/deposited (ALD) SiO2 film) using a two-step RIE procedure. Gold particles were then selectively deposited at the bottom of the etched cylinders by means of electrodeposition and were later used as catalytic seeds in the subsequent metal-organic vapour-phase epitaxy (MOVPE) growth of InAs NWs. The P(S-b-MMA) BCP was used in conjunction with a graftable hydroxyl end-functionalized P(S-r-MMA) brush layer and the conditions for rapid thermal processing (RTP) grafting and various annealing techniques were evaluated. RTP was found to be a rapid, effective and convenient way of performing both the brush layer graft and the BCP anneal. This project was a successful proof-of-concept but each step in the process flow still needs further optimization to improve the fidelity of our version of BCP lithography.