Cu/Sn interfacial reactions: Thin-film case versus bulk case

King-Ning Tu*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

156 Scopus citations


The interfacial reaction between Cu and Sn is of interest in both thin-film cases and bulk cases. Currently, it has been found that a film of Cu containing about 1 at.% Sn possesses the best resistance to electromigration among all the Cu alloy films studied so far. How to alloy Sn into Cu thin films by interdiffusion is of technological interest in ULSI wiring. The bulk cases are of interest because of the application of solder bumps as interconnects in the packaging of high-power devices and because of the environmental concern of Pb-bearing solders. The most promising Pb-free solders are Sn based, and Cu - Sn compound formation is essential to achieve a solder joint. This paper reviews the interfacial reaction in bimetallic Cu - Sn thin films. The spontaneous growth of Sn whiskers accompanying the reaction is also presented. With regard to soldering reactions, the growth of scallop-type rather than layer-type Cu-Sn compounds is analyzed. This growth is accompanied by a ripening reaction among the scallop-type grains. A comparison between the thin-film reaction and the soldering reaction is given.

Original languageEnglish
Pages (from-to)217-223
Number of pages7
JournalMaterials Chemistry and Physics
Issue number2-3
StatePublished - 1 Jan 1996


  • Bimetallic thin films
  • Copper-tin compounds
  • Interfacial reactions
  • Solders
  • Tin-based solders

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