Characterization of pad-wafer contact and surface topography in chemical mechanical planarization using laser confocal microscopy

Ting Sun, Yun Zhuang, Leonard Borucki, Ara Philipossian

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

In this study, an optical method using laser confocal microscopy was developed to measure the surface contact area and topography of pads under a dry and static condition. A custom-made pad sample holder with a sapphire window and a miniature load cell was used to collect pad surface contact images at controlled loads. By extracting the black spots in the collected images, pad contact area and contact summit density were obtained. The analysis of a post polishing pad sample (8;289×921 μm2) showed that the contact area increased from 0.026 to 0.045% when the pressure increased from 2 to 4 psi and increased further to 0.059% when the pressure increased to 6 psi. The contact summit density also exhibited a linear increase with the applied pressure. The above results were consistent with the Greenwood and Williamson theory, which predicted a linear relationship between pad contact area and contact summit density. Laser confocal microscopy was also used to measure pad surface topography by establishing probability density functions (PDFs) of pad surface height.

Original languageEnglish (US)
Pages (from-to)665011-665014
Number of pages4
JournalJapanese Journal of Applied Physics
Volume49
Issue number6 PART 1
DOIs
StatePublished - Jun 2010

ASJC Scopus subject areas

  • Engineering(all)
  • Physics and Astronomy(all)

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