- High density interconnection
- Submicron wire and nanowire based anisotropic conductive film
- Nanotube-nanowire composites
Innovation in assembly and packaging is accelerating in response to the realization that packaging is now the limiting factor in cost and performance for many types of devices. Near term difficult challenges exist in all phases of the assembly and packaging process from design through manufacturing, test and reliability. Many critical technology requirements are yet to be met and meeting these requirements will require significant investment in research and development. According to ITRS roadmap 2005 the challenges in assembly and packaging technology may be summarised as follows:
- 3D Packaging which includes bumpless interconnect architecture, thermal management, high frequency and high current density issues.
- Small die with high pad count and high current density packages, which includes Electromigration, thermal/mechanical reliability modelling, whisker growth and thermal dissipation issues.
- Flexible System Packaging Conformal, which includes low cost interconnection, small and thin die assembly
The limitations of the present generation anisotropic conductive film (ACF) are as follows:
- Decreasing Bond pad size and separation (1500 µm2 pad area and 10 µm separation between bond pads are required for 3 µm particle diameter).
- Particle distribution is highly random in ACF, hence chances of x-y plane conduction increases.
- When the ACF has too many or too large particles, there can be short-circuiting between two adjacent bumps. When the gap between the bumps is very small, typically (15 to 20 µm)2.
- Process limitations: Coplanarity.
The solution for the above-mentioned limitations is the z-axis engineering for anisotropic conduction in Φ20/20 scenario.
The novelty of the our approach is to synthesize the interconnection layer using optimum combination of nanowire and dielectric materials where the wires will be homogenously distributed and to assess the layer performance as an interconnection medium for future 3D Si interconnection, requiring excellent thermal behaviour and high frequency signal transmission capability. From application point of view, nanowires will be used for first time in packaging. Reliability (Fatigue and Fracture) testing of copper nanowire array based package is new and it will open up a lot of future applications, mainly in the field of miniaturized flexible medical implants.
In order to achieve some of the above-mentioned challenges we focus on the innovative nanowire/ nanotube composite to be used as next generation anisotropic/ isotropic conductive film. Fig. 2 shows the cross sectional SEM image of aligned submicron wire ACF. Fig. 3 shows the cross section of the submicron wire ACF bonded on Tyndall test chip where a single bond pad can be observed which shows that the copper wires are more bent above the bond pad than beside it.
- Kafil M. Razeeb, Lorraine Nagle, John Barton, Paul Tassie, Brendan O’Flynn, James Rohan and Cian O’Mathuna, 3D Interconnection by FIB Assisted Pt Deposition and Electroless Nickel Deposition on the Sides and Edges of an I-Seed, 56th Electronic Components & Technology Conference (ECTC 2006), 30 May-2 June, 2006, San Diego, CA, USA, pp. 1308-1311. [download pdf]
- Frank Stam, Kafil M. Razeeb, Siti Salwa, Alan Mathewson, Micro-nano interconnect between gold bond pads and copper nano-wires embedded in a polymer template, 59th Electronic Components & Technology Conference (ECTC 2009), 26-29 May, 2009, San Diego, CA, USA, pp. 1470-1474. [download pdf]
- Peter Ramm, Armin Klump, Josef Weber, Maaike Tralko Nicolas Litear , Walter De Radt, Thomas Fritzish, Thierry Hilt, Pascal Couderc, Christial Val , Alan Mathewson, Kafil M. Razeeb, Frank Stam, The European 3D Technology Platform (e-Cubes), Future Fab international, 34, 103- 116, 2010. [download pdf]
- Ju Xu, Lan Chen, Alan Mathewson and Kafil M. Razeeb, Ultra Long Metal Nanowire Arrays on Solid Substrate with Strong Bonding, Nanoscale Research Letters, 6, 525, (2011). [download pdf]
- Ju Xu, Eric Dalton, Alan Mathewson, Suresh K. Sitaraman and Kafil M. Razeeb, Large area ultra long metal nanowire arrays on solid substrate and applications, 2nd Nano Today Conference, Hawaii, USA, 11-15 December, 2011.
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