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Open AccessArticle

In Situ Plasma Monitoring of PECVD nc-Si:H Films and the Influence of Dilution Ratio on Structural Evolution

1
Department of Mechanical Engineering, National Central University, Taoyuan 32001, Taiwan
2
Opto-mechatronics Engineering, National Central University, Taoyuan 32001 Taiwan
3
Optical Science Center, National Central University, Taoyuan 32001 Taiwan
*
Author to whom correspondence should be addressed.
Coatings 2018, 8(7), 238; https://doi.org/10.3390/coatings8070238
Received: 12 April 2018 / Revised: 25 June 2018 / Accepted: 2 July 2018 / Published: 6 July 2018
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. View Full-Text
Keywords: PECVD; plasma diagnostics; nc-Si:H; RF-PECVD; Fourier-transform infrared spectroscopy (FTIR); quadruple mass spectrometry (QMS); optical emission spectroscopy (OES); X-ray diffraction spectroscopy (XRD) PECVD; plasma diagnostics; nc-Si:H; RF-PECVD; Fourier-transform infrared spectroscopy (FTIR); quadruple mass spectrometry (QMS); optical emission spectroscopy (OES); X-ray diffraction spectroscopy (XRD)
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Hsieh, Y.-L.; Kau, L.-H.; Huang, H.-J.; Lee, C.-C.; Fuh, Y.-K.; Li, T.T. In Situ Plasma Monitoring of PECVD nc-Si:H Films and the Influence of Dilution Ratio on Structural Evolution. Coatings 2018, 8, 238.

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