Remote hydrogen plasma chemical vapor deposition of silicon–carbon thin‐film materials from a hexamethyldisilane source: Characterization of the process and the deposits

Abstract

Amorphous, hydrogenated silicon-carbon (a-Si:C:H) films were produced by remote hydrogen plasma chemical vapor deposition (RHP-CVD) with hexamethyldisilane (HMDS) as the starting compound. Microwave hydrogen plasma was the source of the atomic hydrogen active species. The susceptibility of particular bonds in the HMDS molecule toward the initiation step was established with tetramethylsilane as a model compound. The reaction mechanisms proposed for the RHP-CVD process revealed the important role of polymerization in film growth. The temperature dependence of the film growth rate implied that the investigated RHP-CVD was a nonthermally activated process. The a-Si:C:H films produced at different deposition temperatures were characterized in terms of their chemical structure, surface and bulk composition, surface morphology, surface free energy, density, corrosion resistance, mechanical properties (adhesion and hardness), and optical properties (refractive index and optical band gap). The deposition temperature appeared to be a key parameter, precisely controlling the structure and properties of the resulting films. Based on the results of these studies, reasonable structure-property relationships were found.

Reactivity of organosilicon precursors in remote hydrogen microwave plasma chemical vapor deposition of silicon carbide and silicon carbonitride thin‐film coatings

“…[28,29] 1,1-Dimethylsilene, Me 2 Si CH 2 , a strongly reactive transient intermediate produced via equation (8), is considered to be an important SiC film-forming precursor. [14,30] The presented activation reactions of the TrMS and HMDS precursors are consistent with the results of our gas chromatography/mass spectrometry (GC/MS) examination of the conversion products sampled from the gas phase during RP-CVD. [30] The GC/MS data revealed the presence of HMDS as the major conversion product of TrMS formed via equations (5) and (7), whereas TrMS predominated among the conversion products of HMDS, thus accounting for equation (6).…”

“…We assume that the energy may be transferred via a three-body recombination reaction of hydrogen atoms, strongly exothermic process, involving the molecule in equation (14). The formation of two dimethylsilene molecules in the activation step of DTMSM [equation (14)] is consistent with the relatively high k m value evaluated for this precursor ( Table 1).…”

“…Their hypothetical reactions resulting in the formation of the SiC and SiCN films are described in our previous reports. [14,30,35] …”

“…[14] The apparatus consists of three major parts: a plasma generation section (made from Pyrex glass tube, 28 mm i.d.) coupled via a resonant cavity and a waveguide with a microwave (2.45 GHz) power supply unit; a remote tube equipped with a Wood's horn photon trap; and a CVD reactor (made of Pyrex glass by HWS, Mainz) containing greaseless conical joints, 20 cm diameter flat flanges sealed with an O-ring and a stainless steel substrate holder (13 cm in diameter) equipped with a heater.…”

“…The susceptibility of particular bonds in the molecules of investigated precursors to react with atomic hydrogen was estimated by our earlier comparative RP-CVD experiments involving some permethylated model compounds, such as tetramethylsilane, [14,17] tetraethylsilane, [18] bis(trimethylsilyl)methane, [17] (dimethylamino)trimethylsilane [19] and hexamethyldisilazne, [20] which are known as effective filmforming precursors for DP-CVD. [21 -23] The inability of these compounds to form films found for all RP-CVD experiments proved that the C-H, C-C, Si-C, Si-N, C-N and N-H bonds are nonreactive, whereas the observed ability of investigated precursors DMS, TrMS, TrES, HMDS, DTMSM, BDMSE, DMADMS, BDMAMS, TDMAS and TMDSN to form films can be attributed to the major role of their Si-H or Si-Si bonds in the activation step of the investigated RP-CVD process.…”