The influence of “starving plasma” regime on carbon content and bonds in a-Si1−xCx:H thin films

Abstract

Differences on carbon content and chemical bonds in a-Si1−xCx:H were observed and analyzed in carbon rich and silicon rich films, deposited by plasma enhanced chemical vapor deposition from mixtures of silane and methane. The influence of the radio frequency low power density regime on the film’s properties was investigated. The content of Si, C, and H in the solid phase was obtained by Rutherford back scattering and forward recoil spectrometry. The bondings were analyzed by Fourier transform infrared spectroscopy. Quantitative analysis on the film’s chemical composition was performed combining the vibrational spectra with the stoichiometry data. The results showed that under “silane starving plasma” conditions, a carbon content as high as 70 at. % is achieved and the main carbon bonds are tetragonal C–H, C–H2, and Si–C.

Microstructure analysis of a-SiC:H thin films grown by high-growth-rate PECVD

“…Fig. 1 evidences that, as already observed by Ambrosone et al [4], the deposition rate in a high power regime can be dependent on the silane flux, as found for 'low power regime' [2,6]. In the present work, the analysis of the dependence of the deposition rate on Rc (given by the slope of the fitting curve) shows that growth rate tends to a non-zero value, even with no silane in the chamber.…”

“…Plasma enhanced chemical vapor deposition (PECVD) operating with silane and methane gas mixtures in the socalled 'low power regime' has been for years the most widely studied technique aimed at growing high-quality hydrogenated amorphous silicon carbide (a-SiC:H) [1,2]. Anyway, this configuration is subject to drawbacks such as a low carbon incorporation efficiency and a low deposition rate.…”

Amorphous silicon carbide films prepared by H2 diluted silane–methane plasma

“…The deposition rate was estimated by dividing film thickness with deposition time. Tauc [14] plot was used to determine the optical band gap energy (E G ) rather than the commonly used E04 estimation [10]. Fig.…”

“…This graphitization process limits the range of attainable values for the optical gap as well as the optimization of other diamond-like properties. Peryra and Fantini [9,10] reported a low plasma power density (typically 50 mW/cm 2 ) regime denominated as ''silane starving plasma'' in PECVD that was responsible for obtaining carbon-rich aSi:C:H films with optical gap as high as 3.7 eV [10]. They argued that the deposition of wide gap materials at silane starving plasma is a particular case of the low power density regimes [11], where the RF power density is sufficient to break SiH 4 molecules, but insufficient for the more stable CH 4 bonds.…”

a‐SiC:H films deposited by PECVD for MEMS applications

“…In a previous work [9], a material close to stoichiometry (x~0.5) was produced, aiming to obtain an amorphous counterpart of crystalline SiC, preserving most of its properties and with structural and chemical order. This has been achieved under "silane starving plasma" conditions [10,11], which promotes preferential bonding of silicon atoms to carbon atoms, thus the resulting material exhibits a local order similar to crystalline SiC.…”