Journal of Materials Research

Articles

Effect of film chemistry on refractive index of plasma-enhanced chemical vapor deposited silicon oxynitride films: A correlative study

S. Naskara1, S.D. Woltera2 c1, C.A. Bowera3, B.R. Stonera4 and J.T. Glassa5

a1 RTI International, Center for Materials & Electronic Technologies, Research Triangle Park, North Carolina 27709; and Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708

a2 Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708

a3 RTI International, Center for Materials & Electronic Technologies, Research Triangle Park, North Carolina 27709

a4 RTI International, Center for Materials & Electronic Technologies, Research Triangle Park, North Carolina 27709; and Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708

a5 Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708

Abstract

Thick SiOxNy films were deposited by radiofrequency (rf) plasma chemical vapor deposition using silane (SiH4) and nitrous oxide (N2O) source gases. The influence of deposition conditions of gas flow ratio, rf plasma mixed-frequency ratio (100 kHz, 13.56 MHz), and rf power on the refractive index were examined. It was observed that the refractive index of the SiOxNy films increased with N and Si concentration as measured via x-ray photoelectron spectroscopy. Interestingly, a variation of refractive index with N2O:SiH4 flow ratio for the two drive frequencies was observed, suggesting that oxynitride bonding plays an important role in determining the optical properties. The two drive frequencies also led to differences in hydrogen concentration that were found to be correlated with refractive index. Hydrogen concentration has been linked to significant optical absorption losses above index values of ∼1.6, which we identified as a saturation level in our films.

(Received January 14 2008)

(Accepted February 14 2008)

Key Words:

  • X-ray photoelectron spectroscopy (XPS);
  • Optical properties;
  • Dielectric

Correspondence:

c1 Address all correspondence to this author. e-mail: woltersd@duke.edu

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