Development and Application of a New Method for Epitaxial Growth of Metals, Alloys and Multilayers by Surface Limited Redox Replacement

Nikolay Dimitrov, SUNY at Binghamton, DMR 0742016

Protocols for coating with ultra thin and continuous Au and Ag layers of Ni films used in electronic circuitry were developed. The work is aimed at alleviating sporadic reliability issues with Pb-free soldering on the Ni. It was found by AFM and CV (Pb UPD) characterization that 20 nm thick Ag layers were best deposited by surface limited redox replacement (SLRR), while the same thickness of Au was best grown by a combination of (initially) defect mediated growth (DMG) and (later on) surfactant mediated growth (SMG).

A detailed scanning probe study of the SLRR mechanism revealed important aspects of the critical role of the underpotentially deposited (UPD) sacrificial layer (SL) in maintaining the quasi-2D growth. It was proven by separating the deposition on (i) surface pre-coated with SL and (ii) bare surface that the SL not only “powers up” the exchange reaction but also serves as “tool” for evenly spreading the growing atoms on the surface (adsorption driven process). CV stripping experiments ascertained the larger portion of deposit expected on the SL pre-coated surface.

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60 ML of Ag grown on Au (111) in Local Cell Configuration

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Dissemination: A large portion of the work on voiding in electro-deposited Cu – Pb-free solder joints that has been (in part) supported by this grant was presented as invited talk by N. Dimitrov at 215th ECS Meeting. Graduate students Yihua Liu (The ECS Travel Award) and Fred Wafula also attended.

Dr. Natasa VasiljevicDepartment of Physics,University of Bristol, UK

Professional Development In November 2008, Lasantha Viyannalage

defended his largely sponsored by this grant Ph.D. thesis “Development of a New Method for Epitaxial Growth of Metals and Multilayer Structures by Surface Limited Redox Replacement in One Pot Configuration”.

During the summer of 2009 Stephanie Geer was appointed on a REU fellowship position with our group. Stephanie was identified as best candidate based on her volunteer work with us last summer.

Development and Application of a New Method for Epitaxial Growth of Metals, Alloys and Multilayers by Surface Limited Redox Replacement

Nikolay Dimitrov, SUNY at Binghamton, DMR 0742016

Understanding, Controlling and Minimizing the Voiding, Sporadically Occurring in Solder

Joints with Electroplated Copper

1000 hrs @ 150oC

Lasantha Viyannalge received his Ph.D. degree in December 2008. For him “INSIDE BINGHAMTON UNIVERSITY” wrote:“An excellent research ambassador for Binghamton, Viyannalage’s success has taken him to seven national and international conferences, as well as national and international research labs.”

Stephanie Geer, a junior student at SUNY Brockport is currently doing REU research with our group for the summer. She has been developing different strategies for plating Sn layer with controllable microstructure for a project aiming at studying post-deposition whiskering occurring spontaneously in Sn electrodeposited films .

Dr. Eric Cotts

Ongoing Collaborations Studies of the SLRR mechanism have been carried

out in collaboration with Dr. Natasa Vasiljevic from University of Bristol, UK.

Work on the catalytic activity of PtxCu(1-x) alloy nanocubes has been performed in collaboration with Dr. Fang’s group at SUNY Binghamton.

Voiding in Cu-solder joints and Sn whiskering have been studied with Dr. Cotts’ group at SUNY Binghamton.