Preparation and Deposition Mechanism of a ‐ SiC :  H  Films by Using Hexamethyldisilane in a Remote  H 2 Plasma

Abstract

Characterization of a-SiC:H films deposited by hexamethyldisilane (HMDS) in remote hydrogen plasma is carried out and a reaction model for film deposition is presented. The Si/C ratio increases from 0.6 to 1.3 while the optical bandgap decreases from 3.3 to 2.1 eV with an increase in substrate temperature from 30 to 600~ When the chemical aspect of the deposition process is concerned it was found that atomic H decomposes the HMDS molecule via a chemical reaction. UV radiation appears to be inactive during the deposition process. It is proposed that the most susceptible bond for the initial breakup is the St--St bond in the HMDS molecule. We assume that the other possible bond for the initial break up is C~H. A reaction model for the deposition of a-SiC:H is presented by considering Me2Si:CH2 as the film-forming precursor.There are many reports in the literature on the preparation and characterization of a-SiC:H films in glow-discharge plasmas as well as discussions on the deposition mechanism. 1-9 In most of those works SiHJCH4 or Sill4/ C~H2 mixtures diluted in H2 were used. ~-4'~~ However, a major problem in the use of Sill4 as an Si source is the necessity of a carefully designed safety precautionary tubing system combined with expensive leak detectors because of its high pyrophoric nature. Therefore, the search for novel monomers which are neither pyrophoric nor toxic for the fabrication of a-SiC:H is significant. Some recent publications report the ability for depositing a-SiC:H films by using relatively novel carbosilane monomers such as tetramethylsiline, I~ trimethylsilane, ~2 disilylmethane, 7 disilane, 8 etc. The other advantage of these materials is that some of these precursor gases can be used as silicon and carbon sources; therefore, the use of hydrocarbon gases as a carbon source is not needed. When these gaseous monomers diluted in H2 or in other inert gases (e.g., Ar, He) are introduced into a glow-discharge plasma different kinds of ionic and atomic states are generated in addition to the vacuum ultraviolet (VUV) radiation, hence the path of the deposition process is complicated and difficult to explain. This is because, both VUV radiation 13'~4 and excited atomic or/and ionic states ~8 can initiate the filmforming reaction. In contrast, remote plasmas have only a few reactive radicals compared to direct plasmas. I~ Moreover, in remote-plasma chemical vapor deposition (RPCVD) the monomer can be selectively activated by either UV ra,diation or atomic states generated in the plasma region. Therefore, the reaction process of the deposition is somewhat more explainable or at least a model for the deposition process can be proposed. Some previous reports have pointed out that the surface quality of RPCVDs is better compared to that of direct-plasma CVDs, since the deposition is carried out in an electron and ionic state-free environment. ~7-2~ In direct-plasma CVDs the growing film usually contains microscopic damage due to the continuous bombardment of electrons and charged particles. 17-21 We ha...

Growth Mechanism and Chemical Structure of Amorphous Hydrogenated Silicon Carbide (a‐SiC:H) Films Formed by Remote Hydrogen Microwave Plasma CVD From a Triethylsilane Precursor: Part 1

“…2) and the resulting near-zero value of the apparent thermal activation energy, E a , calculated from the slope of the Arrhenius plot suggests that film growth is independent of the substrate temperature, and the rate of the process is mass transport-limited. Similar results, showing E a ¼ 0, are reported for RHP-CVD from the dimethylsilane, [6,9] trimethylsilane, [6,9] hexamethyldisilane, [3,5,6,9,12] and tetrakis(trimethylsilyl)silane [2,4,5] precursors.…”

“…[1] They are used in semiconductor technology, e. g., in p-i-n solar cell devices as wide bandgap intrinsic layers in multifunction solar cells, a wide bandgap p-type window layer for a-Si:H or a-SiGe:H cells, or as components in thin film visible light emitting diodes. [1] Of the various CVD methods used for the formation of a-SiC:H films, RHP-CVD is an extremely useful technique because it offers well-controlled growth conditions, free of film damaging effects like charged-particle bombardment or high-energy ultraviolet irradiation, [2][3][4][5][6][7] which inherently contribute to the conventional direct plasma CVD (PCVD) process. [7,8] .…”

“…They included dimethylsilane, Me 2 SiH 2 , [6,9] trimethylsilane, Me 3 SiH, [6,9] hexamethyldisilane, (Me 3 Si) 2 , [3,5,6,[9][10][11][12] tetrakis(trimethylsilyl)silane, (Me 3 Si) 4 Si, [2,[4][5][6]9] and (dimethylsilyl)(trimethylsilyl)methane, Me 3 SiCH 2 SiHMe 2 . [6,9,13,14] The present work deals with the fabrication of a-SiC:H films by RHP-CVD using triethylsilane, Et 3 SiH, (TrES) as the single-source precursor. TrES was chosen due to the following features.…”

Synthesis of Si–C–N coatings by thermal Plasmajet chemical vapour deposition applying liquid precursors

“…For a remote plasma CVD process, using the precursor hexamethyldisilane, deposition rates lower than 2 nm h À1 are reported. 7 However, the coatings manufactured in this process show a perfect interface between substrate and surface, because there is no bombardment of electrons or heavy particles, as in processes that use a plasma on the substrate surface. Additionally, a significant improvement concerning the homogeneity of the coatings thickness distribution is achieved.…”

“…Usually 200 to 400°C is sufficient, [8][9][10][11][12] and for remote plasmas the substrate temperatures can be kept at 30°C. 7 However, when a silicon precursor with bonds between silicon and hydrogen is applied, low substrate temperatures favour the transfer of hydrogen into the coating structure, which leads to inferior mechanical properties. For coatings manufactured from SiH 4 and different carbon precursors, hydrogen contents up to 41 at.% are reported.…”