In situ plasma monitoring of PECVD nc-Si:H Films and the influence of dilution ratio on structural evolution

Yu Lin Hsieh, Li Han Kau, Hung Jui Huang, Chien Chieh Lee, Yiin Kuen Fuh, Tomi T. Li

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

We report plasma-enhanced chemical vapor deposition (PECVD) hydrogenated nano-crystalline silicon (nc-Si:H) thin films. In particular, the effect of hydrogen dilution ratio (R = H2/SiH4) on structural and optical evolutions of the deposited nc-Si:H films were systematically investigated including Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR) and low angle X-ray diffraction spectroscopy (XRD). Measurement results revealed that the nc-Si:H structural evolution, primarily the transition of nano-crystallization from the amorphous state to the nanocrystalline state, can be carefully induced by the adjustment of hydrogen dilution ratio (R). In addition, an in situ plasma diagnostic tool of optical emission spectroscopy (OES) was used to further characterize the crystallization rate index (Hα*/SiH*) that increases when hydrogen dilution ratio (R) rises, whereas the deposition rate decreases. Another in situ plasma diagnostic tool of quadruple mass spectrometry (QMS) also confirmed that the "optimal" range of hydrogen dilution ratio (R = 30-40) can yield nano-crystalline silicon (n-Si:H) growth due to the depletion of higher silane radicals. A good correlation between the plasma characteristics by in situ OES/QMS and the film characteristics by XRD, Raman and FTIR, for the transition of a-Si:H to nc-Si:H film from the hydrogen dilution ratio, was obtained.

Original languageEnglish
Article number238
JournalCoatings
Volume8
Issue number7
DOIs
StatePublished - 1 Apr 2018

Keywords

  • Fourier-transform infrared spectroscopy (FTIR)
  • Nc-Si:H
  • Optical emission spectroscopy (OES)
  • PECVD
  • Plasma diagnostics
  • Quadruple mass spectrometry (QMS)
  • RF-PECVD
  • X-ray diffraction spectroscopy (XRD)

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