Hot-wire plasma enhanced chemical vapour deposition system for preparation of silicon carbide thin films / Aniszawati Azis
This research offers insights on the function of a home-built plasma enhanced chemical vapor deposition (PECVD) system in the preparation of silicon carbide (SiC) thin films. The work started with designing and building a reaction chamber for the PECVD system that would utilize radio frequency (R...
| Summary: | This research offers insights on the function of a home-built plasma enhanced
chemical vapor deposition (PECVD) system in the preparation of silicon carbide (SiC)
thin films. The work started with designing and building a reaction chamber for the
PECVD system that would utilize radio frequency (RF), direct current (DC) and hotwire
(HW). The first phase of the work ensured that the PECVD system is capable of
producing good quality and reproducible silicon carbide thin films via independent
deposition techniques namely RF-PECVD, DC-PECVD and HW-CVD. The effects of
methane to silane gas flow rate ratio on the deposition rate, optical energy gap, Si-C and
Si-H bonding configurations and formation of any crystalline structures were
investigated. Analytical study revolved around the results obtained from Optical
transmission spectroscopy, Fourier transform infrared (FTIR) spectroscopy, micro-
Raman scattering spectroscopy and X-Ray diffraction spectroscopy. Based on the
findings from the first phase of the work, the research was then proceeded to the next
phase of the work where a hybrid deposition technique comprising DC-PECVD and
HW-CVD was introduced and applied. The study for these films involved the effects of
applied DC voltage and the role of hydrogen in the growth and deposition process of
silicon carbide thin films. Results of this work demonstrated that the optical energy
band gap of the silicon carbide films prepared by all techniques could be increased by
increasing the methane to silane gas flow rate ratio. These results were consistent with
published results and the variation of the properties of the films was consistent with the
deposition kinetics of silicon carbide. The system is tunable to produce silicon carbide
films with a wide range of optical energy band gap from 1.63 eV to 3.26 eV. The film
deposition rate is affected in contrary manners for different techniques and does not
show direct effect on carbon incorporation nor crystallization of the film. However, by
the multiple ranges of deposition parameters allowed by the system built in this work, a
variety of silicon carbide thin film could be produced. RF-PECVD technique provides
silicon rich amorphous silicon carbide films with deliberately high optical energy band
gap. DC-PECVD technique displayed low deposition rate as compared to the other
techniques but produces silicon carbide films with relatively high optical energy band
gap and more ordered structure with traces of silicon nanocrystallites. Silicon carbide
films prepared by HW-CVD technique exhibit enhanced properties such as increasing
value of optical energy band gap and more amorphous structure with increased methane
to silane gas flow rate ratio. The new HW-PECVD technique demonstrated in this
system has succeeded in preparing silicon carbide thin films and provided a minimum
optical energy band gap of 2.05 eV. The optical energy band gap could be increased by
applying lower DC voltage. The new deposition system is also made feasible to
hydrogen applications. It was observed that nanocrystallite structures were formed and
were embedded in amorphous SiC film matrix with longer hydrogen surface treatment
time. |
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