Megasonic agitation for enhanced electrodeposition of copper
- 318 Downloads
In this paper we propose an agitation method based on megasonic acoustic streaming to overcome the limitations in plating rate and uniformity of the metal deposits during the electroplating process. Megasonic agitation at a frequency of 1 MHz allows the reduction of the thickness of the Nernst diffusion layer to less than 600 nm. Two applications that demonstrate the benefits of megasonic acoustic streaming are presented: the formation of uniform ultra-fine pitch flip-chip bumps and the metallisation of high aspect ratio microvias. For the latter application, a multi-physics based numerical simulation is implemented to describe the hydrodynamics introduced by the acoustic waves as they travel inside the deep microvias.
KeywordsTrench Print Circuit Board Seed Layer Acoustic Streaming Copper Electrodeposition
The authors would like to acknowledge the financial support of the Engineering and Physical Science Research Council (EPSRC) under the grand challenge project entitled “3D-Mintegration” (www.3d-mintegration.com) which is referenced EP/C534212/1. The authors would also like to acknowledge a DTA funding from the UK Engineering and Physical Sciences Research Council (EPSRC) through the Innovative electronic Manufacturing Research Centre (IeMRC).
- Hughes M, Bailey C, McManus K (2007) Multi-Physics modelling of the electrodeposition process. In: EuroSime 8th international conference on thermal, mechanical and multi-physics experiments and simulation in micro-electronics and micro-systems. London, UK, pp 1–8. ISBN 1-4244-1106-8Google Scholar
- Kaufmann JG, Desmulliez MPY et al (2008) Megasonic enhanced electrodeposition. In: Symposium on design, test, intergration and packaging of MEMS/MOEMS, DTIP. Nice, France, pp 370–372Google Scholar
- Nyborg WL (1998) Nonlinear acoustics. In: Hamilton MF, Blackstock DT (eds) Acoustic streaming, chap 7. Academic Press, London Google Scholar
- Puippe J C, Leaman F L (eds) (1896) Theory and practice of pulse plating. AESF, Orlando Google Scholar
- Tian Y, Liu C, Hutt DA, Stevens R (2008) Electrodeposition of indium for bump bonding. In: Proceedings of 58th electronic components and technology conference. Florida, USA, pp 2096–2100Google Scholar