Abstract
Flip chip interconnection of integrated circuits (IC) for packaging applications such as direct chip attachment use Pb-Sn solders as the connection between the die and the substrate. Under bump metallization is typically used to transition from the non-solderable Al bond pad on the IC to a solderable surface such as copper using traditional blanket metal deposition, photolithography and etching procedures. In this study, we report for the first time the use of a novel process for selectively depositing adherent copper directly onto aluminum thin films, eliminating the need for adhesion promoting transition layers and additional patterning steps. Utilizing copper bearing organic solutions and standard electroless and electrolytic copper plating baths, as-deposited and annealed sputter deposited Al-x%Cu (x = 0 to 2) thin films were coated with metallic copper. An increase in the organically deposited copper nucleation site density was observed with increasing copper concentration in the sputtered aluminum/copper thin films. Preliminary results using focused ion beam microscopy indicated that dissolution of the aluminum oxide surface and subsequent deposition of copper by cementation occurs in the non-conducting organic solution at sub-micron reaction lengths. Qualitative adhesion testing of samples resulted in the majority of films passing the tape test. Demonstration of the process using 50-micron diameter vias in BCB coated flip chip test vehicles from MCNC will be presented.
Recommended Citation
M. Fang et al., "Maskless, Direct Deposition of Copper Onto Aluminum Bond Pads for Flip Chip Applications," Materials Research Society Symposium - Proceedings, vol. 515, pp. 85 - 90, Springer, Jan 1998.
The definitive version is available at https://doi.org/10.1557/proc-515-85
Department(s)
Materials Science and Engineering
International Standard Serial Number (ISSN)
0272-9172
Document Type
Article - Conference proceedings
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2024 Springer, All rights reserved.
Publication Date
01 Jan 1998