Direct measurement of electromigration-induced stress in interconnect structures

Christopher J. Wilson, Alton B. Horsfall, Anthony G. O'Neill, Nicholas G. Wright, Steve J. Bull, Jonathan G. Terry, J. Tom M. Stevenson, Anthony J. Walton

Research output: Contribution to journalArticlepeer-review

Abstract

This paper reports the first direct experimental measurement of electromigration-induced stress in aluminum interconnects, using a series of microrotating stress sensors. The build-up of stress gradients in interconnect metallization, which is concomitant with backstress, has been previously investigated theoretically, but experimental verification using optical or X-ray techniques has proven more difficult. These initial results show a compressive-stress gradient along the line of stress sensors, consistent with that predicted by conventional mass-transport theory. Additionally, these measurements are in qualitative agreement with the mathematical model proposed by Korhonen et aL (1993), with a reduced-stress and increased-diffusion coefficient. These differences are discussed, and the causes postulated. The limited resolution of previous techniques restricts their ability to obtain a detailed characterization, whereas, in principle, this new technique can be scaled to the end of the International Technology Roadmap for Semiconductors. These preliminary findings suggest that the presented technique will provide a valuable tool for the investigation of back-end-of-line interconnect stress in the future.

Original languageEnglish
Pages (from-to)356-362
Number of pages7
JournalIEEE Transactions on Device and Materials Reliability
Volume7
Issue number2
DOIs
Publication statusPublished - Jun 2007

Keywords

  • backstress
  • electromigration
  • interconnect
  • metallization
  • microelectromechanical system (MEMS)
  • reliability
  • stress
  • stress gradient
  • stress measurement
  • stress sensor
  • X-RAY MICRODIFFRACTION
  • CONFINED METAL LINES
  • ALUMINUM FILMS
  • RESIDUAL-STRESS
  • THIN-FILMS
  • EVOLUTION
  • DIFFUSIVITY
  • GENERATION
  • DEPENDENCE
  • STRAIN

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