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Oxidation study on as-bonded intermetallic of Copper wire-Aluminum bond pad metallization for electronic microchip

T., Joseph Sahaya Anand and Chua, Kok Yau (2012) Oxidation study on as-bonded intermetallic of Copper wire-Aluminum bond pad metallization for electronic microchip. Materials Chemistry and Physics, 136 (2-3). pp. 638-647. ISSN 0254-0584

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Abstract

In this work, influence of Copper free air ball (FAB) oxidation towards Intermetallic Compound (IMC) at Copper wire-Aluminum bond pad metallization (Cu/Al) is studied. Samples are synthesized with different Copper FAB oxidation condition by turning Forming Gas supply ON and OFF. Studies are performed using Optical Microscope (OM), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and line-scan Energy Dispersive X-ray (EDX). SEM result shows there is a cross-sectional position offset from center in sample synthesized with Forming Gas OFF. This is due to difficulty of determining the position of cross-section in manual grinding/polishing process and high occurrence rate of golf-clubbed shape of oxidized Copper ball bond. TEM inspection reveals that the Copper ball bond on sample synthesized with Forming Gas OFF is having intermediate oxidation. Besides, the presence of IMC at the bonding interface of Cu/Al for both samples is seen. TEM study shows voids form at the bonding interface of Forming Gas ON sample belongs to unbonded area; while that in Forming Gas OFF sample is due to volume shrinkage of IMC growth. Line-scan EDX shows the phases present in the interfaces of as-bonded samples are Al4Cu9 (~3nm) for sample with Forming Gas ON and mixed CuAl and CuAl2 (~15nm) for sample with Forming Gas OFF. Thicker IMC in sample with Forming Gas OFF is due to cross-section is positioned at high stress area that is close to edge of ball bond. Mechanical ball shear test shows that shear strength of sample with Forming Gas OFF is about 19% lower than that of sample with Forming Gas ON. Interface temperature is estimated at 437°C for as-bonded sample with Forming Gas ON by using empirical parabolic law of volume diffusion.

Item Type: Article
Additional Information: Q1 Journal under the Subject Category: Materials Chemistry http://www.scimagojr.com/journalsearch.php?q=17800&tip=sid&clean=0
Uncontrolled Keywords: Copper wire bonding, Aluminum bond pad metallization, Al-Cu Intermetallic, free air ball oxidation.
Subjects: T Technology > TJ Mechanical engineering and machinery
Divisions: Faculty of Manufacturing Engineering > Department of Engineering Materials
Depositing User: Dr. T. Joseph Sahaya Anand
Date Deposited: 26 Mar 2013 04:08
Last Modified: 28 May 2015 03:46
URI: http://eprints.utem.edu.my/id/eprint/6949

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