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Node Infrastructure and Process Update

September 2010

All ANU facility equipment is being accessed by Australian researchers (internal as well external users from academia and industry). Below is a summary of the highlights of our work and process development over the past three months.

The EBL RAITH 150 machine has been intensively used for development work of 3-level masking: ZEP resist/Cr/SiOX where ZEP is used as a mask to etch Cr in the ICP using Cl2:O2 chemistry followed by etching SiOX with Cr-mask that is very resistant to fluorine chemistry. Also, we continued the work on bi-layer PMMA resist for first making plasmonic structures on fused silica for lift-off of a 25nm gold layer, making use of the new e-beam evaporator. These structures have shown plasmonic resonance and are now under thorough evaluation by the external user.

Nano-imprint tests were continued using PDMS mould and sub-µm patterns have been successfully obtained down to 200nm. We also started developing processes of UV-curing using quartz stamps.

Much effort has been made to investigate the various capabilities that the dual frequency PECVD system offers. Standard SiOX and SiNX dielectric layers are now available. Also amorphous Si and poly-crystalline Si can be deposited using SiH4 and He. Moreover stress free (low tensile strain) SiNX dielectric layers can be deposited at 300 and 600°C. Analysis data includes refractive index, optical band-gap, roughness and N/Si ratio (in SiNX).

The ICP system has been accessed by several users (internal and external industry) on a regular basis, using either Cl2-based or F-based processes. Materials like GaAs, AlN and Ge are regularly etched in the system. Our effort in the last period focused on optimising the etching of dielectric layers after optical lithography.

After retro-fitting various accessories to our FIB system it has been heavily used, mainly for general purpose milling processes. An ANU start-up company started making use of the FIB and, recently, we negotiated a preferential rate with them associated with forecasted intensive usage in the coming quarter.

The E-Beam Evaporator has been accessed by a number of ANU users and, more importantly, the first plasmonic structures were successfully made using a lift-off process based on the bi-layers of PMMA (see EBL). This was possible due to the larger distance between source and samples to circumvent excessive heating during evaporation, hence not ruining the achieved undercut of the PMMA bi-layers that facilitates the lift-off process.