International Journal of Automation and Smart Technology (Nov 2013)

Residual Stress of Curvature Sapphire Substrate with GaN Film Released by the Application of Trench Structures

  • Ming-Han Liao,
  • Jyh-Jone Lee,
  • Chih-Hua Chen,
  • Ssu-Chieh Kao,
  • Kuan-Chou Chen,
  • Cho-Fan Hsieh

DOI
https://doi.org/10.5875/ausmt.v3i4.202
Journal volume & issue
Vol. 3, no. 4
pp. 239 – 243

Abstract

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Serious wafer curvature and residual stress are formed during the growth of an epi-GaN layer on Sapphire substrates due to the different thermal expansion coefficients in these two materials. By using theoretical analysis and a simulation model using the finite element method to describe the realistic shape of wafer curvature on epi-GaN wafers, we examine the influence which different thickness and thermal expansion coefficients in the top epi-GaN layer have on wafer curvature reduction. In addition a new process to reduce wafer curvature and to relax residual stress is proposed. With an additional laser treatment on a sample surface after the growth of the top epi-GaN layer on a Sapphire substrate has taken place, the wafer curvature can be reduced to ~ 37 mm from the original ~ 45 mm in 2 inch wafers with an optimized surface structure design.

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