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Public Lecture - Development of diffusion barrier materials for future generation electronic devices


Miniaturization in semiconductor devices calls for more effective use of materials within the decreasing dimension. This has provided good opportunities for materials innovation. In this talk, I will present two examples to showcase our recent work on new diffusion barrier materials. The first example is the soldering metallization material. It is well known that Ni and its alloys possess a lower reaction rate with Sn than Cu and Cu alloys, making them materials of choice in the lead-free era. Electroless Ni-P has been extensively studied due to its attractive advantages such as coating uniformity, good selectivity and low coating stress. Soldering reaction between lead-free solders and Ni-P, in terms of intermetallic compounds (IMC) morphology and growth kinetics has been thoroughly studied, and so does the joint strength degradation with thermal treatment. It is generally understood that soldering reaction with Ni-P results in complex interfacial IMC layers with voids in the Ni3P layer. Voiding speeds up the interface reaction which in turn affects the long term reliability of the solder joint. We have applied a ternary electroless Ni-W-P (6~7 wt. % of P and 15~18 wt. % of W) alloy and compared its soldering reaction with the binary Ni-P (6~7 wt. % of P) metallization. Ni-W-P was found to have significantly slowed down the reaction rate. The second example is copper diffusion barrier for the future generation back-end-of-line (BEOL) technology. Conventionally, nitrides (TiN, TaN) have been used as the diffusion barrier with reliable performance. Looking beyond the 45 nm technology node with shrinking barrier thickness, the electrical resistivity of the barrier layer has to be further reduced in order to minimize the resistance-capacitance delay (RC delay), a key factor for the device speed. We have turned into amorphous metallic thin films for solution. Examples with Ta-based thin films (Ta-Ni, Ta-Ti, Ta-Cr) have been prepared by magnetron sputtering. The thermal stability and barrier breakdown mechanisms have been studied. Highly stable and good barrier performance has been observed, particularly in Ta-Ni.


Speaker Biographical Sketch

Prof. Chen obtained his BEng, MEng, and PhD in 1984, 1987, and 1997, respectively. He started his academic career as an Assistant Lecturer at Hefei University of Technology, China in 1987 after obtaining his MEng degree. In 1992, he was awarded a one-year visiting scholarship to work in the University of Reading, U.K. After completing the visit, he was financially supported by the Overseas Research Scholarship (ORS) awarded by the Committee of Vice Chancellors and Principals (CVCP) in the UK, and a European Union research grant to pursue his PhD under the supervision of Prof. Tony Atkins. In 1997, he went to Singapore, joining the newly founded Institute of Materials Research and Engineering (IMRE), a national research institute fully funded by the Singapore government. In March 2000, the passion for education brought him back to the academe to become a teacher again in Nanyang Technological University (NTU). He is currently an Associate Professor & Assistant Chair (Undergraduates) in the School of Materials Science and Engineering, and the Director of Advanced Materials Research Centre of NTU. He has graduated 15 PhD and 1 MEng students, and is currently supervising another 10 PhD and 1 MEng students. His general research interests are in these two areas: 1) Thin films & nano-materials for environmental, clean energy, and electronics applications; 2) Mechanical behavior of thin films and composites. Chen Zhong currently serves as an editor / editorial board member for 5 international journals. He has also served as a reviewer for more than 50 academic journals (e.g. Adv. Materials, Acta Materialia, App. Phys. Letters, The J. Phys. Chemistry, etc.) and a number of research funding agencies including European Research Council (ERC). He is an author of 3 book chapters, over 140 SCI journal papers, and 6 international patents. For more details of his teaching and research activities, please visit his website: http://www.ntu.edu.sg/home/aszchen/.


Date: 4 Mar 2013 (Monday)
Time: 3:00pm – 3:45pm
Venue: G6302, 6/F, Academic Building 1, City University of Hong Kong,
83 Tat Chee Avenue, Kowloon Tong, Kowloon,
Hong Kong.
Fee: Complimentary
Language: English
Enquiry Tel: 2784 4245

For seat reservation, please fax the Registration Form to (852)-2788 7579 on / before 2 Mar 2013.