Nanopore patterning using Al<inf>2</inf>O<inf>3</inf> hard masks on SOI substrates

Xiaofeng Wang, Michael Goryll

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Aluminum oxide Al<inf>2</inf>O<inf>3</inf>, deposited using amorphous atomic layer deposition (ALD), is a very promising material to be utilized as a hard mask for nano-patterning. We used an aluminum oxide hard mask on a silicon-on-insulator (SOI) substrate to implement a sub-100 nm nanopore process. The transfer of nanoscale patterns via dry etching of the Al<inf>2</inf>O<inf>3</inf> thin film was investigated by comparing etch profiles, etch rates, and selectivity of Al<inf>2</inf>O<inf>3</inf> over PMMA resist, using different gas chemistries such as Cl<inf>2</inf>, Ar, Ar/BCl<inf>3</inf> mixtures, and BCl<inf>3</inf> plasma. A selectivity of 1:4 was observed using an inductively coupled plasma reactive ion etching (ICP-RIE) tool with BCl<inf>3</inf> plasma, and the sub-100 nm nanopore patterns were anisotropically transferred to the alumina layer from a 250 nm PMMA layer. The dense and inert Al<inf>2</inf>O<inf>3</inf> hard mask showed exceptional etch selectivity to Si and SiO<inf>2</inf>, which allowed the subsequent transfer of the nanopore patterns into the 340 nm-thick Si device layer and made it possible to attempt etching the 1 μm-thick buried oxide (BOX) layer. Using chlorine chemistry, nanopores patterned in the Si device layer showed excellent anisotropy while preserving the original pattern dimensions. The process demonstrated is ideally suited for patterning high aspect ratio nanofluidic structures.

Original languageEnglish (US)
Article number075020
JournalJournal of Micromechanics and Microengineering
Issue number7
StatePublished - Jul 1 2015


  • alumina hard mask
  • dry etch
  • nanopore patterning

ASJC Scopus subject areas

  • Mechanical Engineering
  • Electrical and Electronic Engineering
  • Mechanics of Materials
  • Electronic, Optical and Magnetic Materials


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