Saturday, June 27, 2015

Nanopore patterning using ALD Al2O3 hard masks on SOI substrates

Nice to see some work using ALD hard masks from Arizona State University. For really advanced High-k ultra hard to etch hard masks check out this work by Fraunhofer CNT on zirconia ALD hard masks : High Resolution Patterning by Dual Hard Mask Scheme

Nanopore patterning using Al2O3 hard masks on SOI substrates

Xiaofeng Wang and Goryll 
2015 J. Micromech. Microen Michael g. 25 075020


Aluminum oxide Al2O3, 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 Al2O3 thin film was investigated by comparing etch profiles, etch rates, and selectivity of Al2O3 over PMMA resist, using different gas chemistries such as Cl2, Ar, Ar/BCl3 mixtures, and BCl3 plasma. A selectivity of 1:4 was observed using an inductively coupled plasma reactive ion etching (ICP-RIE) tool with BCl3 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 Al2O3 hard mask showed exceptional etch selectivity to Si and SiO2, 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.

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