Optical micro-paddle beam deflection measurement for electrostatic mechanical testing of nano-scale thin film application to MEMS

Chi Jia Tong, Ya Chi Cheng, Ming Tzer Lin, Kuan Jung Chung, Jiong Shiun Hsu, Chung Lin Wu

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17 Citations (Scopus)

Abstract

The authors describe their design for a paddlelike cantilever beam sample to relieve non-uniform stress distribution in beam-bending tests of the mechanical properties of thin film applications to MEMS. We added the sample to a custom-designed system equipped with an electrostatic panel and optical interferometer. The system overcomes problems associated with using nano-indentation for testing, and reduces errors tied to the amount of contact force required to bend the beam. Accurate paddle cantilever beam deflection was obtained using a four-step phase-shifting process with a Michelson interferometer. Film strain was determined using a simple force equilibrium equation. Residual stresses were measured at -41.3 MPa for 150 nm silver film, -3.2 MPa for 150 nm gold film, and - 16.8 MPa for 150 nm copper film. We observed residual stresses for copper films at different thicknesses. The results indicate high tensile stress forms during the early deposition stage for thin copper film due to grain coalescence, and a decrease in stress with an increase.

Original languageEnglish
Pages (from-to)1131-1137
Number of pages7
JournalMicrosystem Technologies
Volume16
Issue number7
DOIs
Publication statusPublished - 2010 Jul 1

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All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Hardware and Architecture
  • Electrical and Electronic Engineering

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