Electrochemical deposition with specific relevance to the microelectronic industry has been investigated at Tyndall for more than 15 years. R&D is focussed on the use of electrolytic and electroless deposition of materials for ICT applications and the microfabrication of electrochemical devices, microbatteries and microfuel cells. We also develop lithographic processes to achieve the desired patterning for selective deposition. The laboratory houses dedicated lithography, deposition and characterisation equipment for advanced materials processing. A wide variety of substrate materials have been investigated including metals, ceramics, polymers, semiconductors and compound semiconductors. We are currently investigating electroless and electrolytic deposition for controllled deposition at the micro/nanoscale. The following shows one aspect of the the electrochemical deposition R&D at Tyndall, templated nanoscale electroless deposition

Anodised aluminium oxide (AAO) and ion beam track etched polycarbonate (PC) substrates are used as templates to deposit metal nanotubes. Single metal tubes have been achieved previously by other researchers. In this collaboration with the Chemistry Derpartment at UCC we investigated coaxial tubes metals and alloys. The results demonstrate the possibility for controlled low cost deposition of metals and alloys as nanoscale deposits in templates

Figure 1. Polycarbonate membrane and the resulting nanotubes formed in this template following electroless processing. Coaxial metals and alloys of CoNIFe inside Ni have been achieved

Recent projects

• Low cost metal contacts for gallium nitride. Enterprise Ireland Proof of Concept, commercialisation fund project (2007)

• Electrodeposited copper composites for advanced IC interconnect. (2007-2010) Irish Research Council for Science Engineering and Technology Embark Partnership scheme scholarship with Intel Ireland.

• Electroless deposition. (2006-2008) Enterprise Ireland Innovation Partnership scheme

Recent publications

1. L.C.Nagle and J.F.Rohan, J. Power Sources, 185 (2008) 411-418. Aligned carbon nanotube composite deposition in platinum for fuel cell catalysts.

2. J.F.Rohan, D.P.Casey, B.Ahern, F.M.F.Rhen, S.Roy, D.Fleming and S.E.Lawrence, Electrochemistry Communications, 10 (2008) 1419-1422. Coaxial metal and magnetic alloy nanotubes in polycarbonate templates by electroless deposition.

3. L.Lewis, D.P.Casey, A.V.Jeyaseelan, J.F.Rohan and P.Maaskant, Applied Physics Letters, 92 (2008) 062113. Electroless nickel/gold ohmic contacts to p-type GaN.

4. C.Ó.Mathúna, T.O’Donnell, R.Martinez, J.F.Rohan and B.O’Flynn, Talanta, 75 (2008) 613-623. Energy Scavenging for Long-Term Deployable Mote Networks

5. W-M.Chen, P.McCloskey, J.F.Rohan, P.Byrne and P.J.McNally, IEEE Transactions on Components, Packaging and Manufacturing Technology, Part A, 30 1 (2007) 144-151, Preparation and temperature cycling reliability of electroless Ni under bump metallization.

6. L.C.Nagle, A.Loughlin and J.F.Rohan, Electrochemical Society Transactions, Vol 2, 6, (2007) 51-59. Electroless cobalt deposition from ammonia borane solutions.

7. L.C.Nagle and J.F.Rohan, Journal of the Electrochem. Society, 153 (11) C773-C776 (2006) Ammonia borane oxidation at gold microelectrodes in alkaline solutions,

8. J.F.Rohan, B.M.Ahern and L.C.Nagle, Electrochemical Society Transactions, Vol 1, Issue 31, 1-9 (2006) DMAB Oxidation for Electroless Deposition from Alkaline Solutions.

9. P.P.Maaskant, M.Akhter, N.Cordero, D.P.Casey, J.F.Rohan, B.J.Roycroft and B.Corbett, Physica Status Solidi (c) 2, No 7, 2907 - 2911 (2005) LED flip-chip assembly with electroplated AuSn alloy.

10. L.C.Nagle and J.F.Rohan, Electrochemical and Solid-State Letters, 8 (5) C77-C80 (2005) Investigation of dimethylamine borane oxidation at a gold microelectrode in base.

11. J.F.Rohan, P.A.Murphy and J.Barrett, Journal of the Electrochemical Society, 152, C32-C35 (2005) Zincate-free, electroless nickel deposition at aluminium bond pads

12. W.M.Chen, P.McCloskey, P.Byrne, P.Cheasty, G.Duffy, J.F.Rohan, J.Boardman, A.Mulcahy and S.C.O'Mathuna, Journal of Electronic Materials, 33 (2004) 900-907. Degradation of electroless Ni(P) under bump metallization (UBM) in Sn3.5Ag and Sn37Pb solders during high temperature storage.

13. J.F.Rohan and G.O’Riordan, Microelectronic Engineering, 65 (2003) 77-85. Characterisation of the electroless nickel deposit as a barrier layer / under bump metallurgy on IC metallisation.

14. J.F.Rohan, G.O’Riordan and J.Boardman, Applied Surface Science, 185 (2002) 289. Selective electroless nickel deposition on copper as a final barrier/bonding layer material for microelectronics applications.

Contact: James Rohan – james.rohan@tyndall.ie | webpage