Oxycarbide Films Research Articles

Analysis of (Cr,Mo) Oxycarbide Films Grown on Stainless Steel via Metalloorganic Chemical Vapor Deposition

A mixture of hexacarbonyl of chromium and molybdenum ((Cr,Mo)(CO)6) was used to deposit oxycarbide films on stainless steel at temperatures of 175°–450°C. Through the analysis of deposition kinetics in various temperature regions, the controlling mechanism was determined to be exothermic surface reactions. Activation energies of the low- and medium-temperature regions were determined to be 71.2 and −60.1 kJ/mol, respectively. Some properties including densities, composition, and crystalline phases of the films were investigated. Results revealed that the chromium content of coating products increased as the temperature increased. The dominating surface reactions switched as temperature increased, because of the increase of chromium content in the precursor gas. Hence, the coating rate and density increased to a maximum, then decreased as the coating temperature was increased to 275°C. Deposited phases were determined by X-ray diffractometry, and the relationship with film density phases has been discussed, using their microstructural textures from scanning electron microscopy micrographs. Corrosion resistance was measured by an electrochemical method. The films obtained in the low- and medium-temperature regions improved the corrosion resistance of stainless-steel substrates by a factor of 24. In addition, the latter case showed the effect of passive protection and was an optimized selection for corrosive protection. The relationship of the improvement of corrosion resistance, physical properties, and the contribution of composed phases was discussed.

Photoacid catalyzed sol–gel process

The hydrolysis of compounds containing alkoxysilyl moieties catalysed by UV-generated protic acids, followed by condensation of in situ generated silanol groups, is proposed as an effective approach to formation of hard, silicate-type materials by a sol–gel process. It gives highly thermally stable materials which can be of value as precursors to silicon oxycarbide films. The effectiveness of the photocatalyst used in the process depends on the type of anion and seems to be limited, in some cases, by Si–F bond formation.

Structural Analysis of Heat-Treated Chromium Oxycarbide Films

Chromium oxycarbide (Cr2CO) films were deposited on stainless steel and copper plates via plasma-assisted chemical vapor deposition. The films were heated to 1073 K under high-vacuum conditions, to examine the high-temperature stability of the films. X-ray diffractometry revealed that the films decomposed to a mixed structure of Cr2O3 and Cr3C2. Thermogravimetric analysis and differential thermal analysis revealed that the decomposition occurred in the temperature range of 858-910 K.

Chromium Oxycarbide Thin Films Prepared by Inductively Coupled Radio-Frequency Plasma-Assisted Magnetron Sputtering

Chromium oxycarbide films were prepared on SUS 304 stainless steel at temperatures of ∼673 K using the inductively coupled radio-frequency plasma-assisted magnetron-sputtering technique. An inductively coupled 13.56 MHz electromagnetic field with a power of 40 W was supplied to excite the glow discharge, and a direct-current power of 700 W was supplied to sputter a 99.9% chromium target in an Ar/CO2/CH4 mixture and in Ar/CO mixture. Electron probe microanalysis revealed that the film contained chromium, oxygen, and carbon. Vickers microhardness of the film was determined to be >1.96 × 1010 Pa. X-ray diffractometry measurements revealed that the film structure was cubic, and the lattice constant was a0= 0.42 nm. This structure was almost the same as that of chromium oxycarbide, Cr2CO, (rock-salt structure, lattice constant of 0.413 nm). The corrosion resistance of the SUS 304 stainless steel to 1 kmol/m3 H2SO4 at 293 K was improved by coating it with a Cr(C,O) film to a thickness of 5.92 μm.

Structural and mechanical properties of tungsten oxycarbide films synthesized by inductively coupled RF plasma-assisted magnetron sputtering

Tungsten oxycarbide films were synthesized on SUS 304 stainless steel at a temperature of 673K in a mixture of carbon dioxide, methane, argon and helium by an inductively coupled RF plasma-assisted magnetron sputtering method. The hardness of the films was determined to be more than 20GPa using a micro-Vickers hardness testing machine. The structure of the film was investigated in detail by X-ray diffraction. It is found that the films with a high micro-Vickers hardness, near stoichiometrical composition of W2CO, and a small lattice constant, have a strong X-ray peak intensity characterized by a highly oriented (110) plane and a large crystallite size.

誘導結合型高周波プラズマ支援マグネトロンスパッタリング法による金属オキシカーバイドの合成

Metal oxycarbide thin films, such as chromium oxycarbide, molybdenum oxycarbide and tungsten oxycarbide films have been synthesized on SUS 304 stainless steel for hard coating at a temperature of 673 K with metal, carbon dioxide and methane by an inductively coupled radiofrequency plasma assisted magnetron sputtering method. The maximum micro-Vickers hardness of the films is more than 20 GPa. X-ray diffraction measurements reveal that the structure of the oxycarbide films is cubic and the lattice constant of them is 0.42-0.43 nm. The films showing a high micro-Vickers hardness are composed of [110] orientated crystallites.

Sealing of Porous Low-k Dielectrics

The ongoing evolution from to insulator materials with lower dielectric constant, k, through the introduction of pores, brings new challenges in terms of processing and reliability. Porosity enhances penetration of undesired chemical species. A method of sealing microporous low-k dielectric chemical vapor deposited silicon oxycarbide films using UV-ozone induced oxidation has been investigated. The film thickness, refractive index, porosity, pore size, and sealing as a function of exposure time have been characterized by ellipsometry. The films are sealed without modification of the underlying porosity, an essential first step in integrating porous materials. © 2003 The Electrochemical Society. All rights reserved.

Interfacial Properties Between CVD Diamond and Titanium

The role of carbide and oxy-carbide films in the adhesion of diamond films on commercial pure Ti metal, and a Ti, 6%Al, 4%V substrates was examined. It was found that the carbon to oxygen ratio in an oxy-carbide structure formed at the interface broadly correlates with the adhesive strength of the diamond/substrate bond. Deposition experiments with substrates including titanium and its alloys, suggest the nature of the substrate is important in aiding carbide and subsequently, diamond formation. XPS depth profiling for Ti-6Al-4V indicates that the mode of TiC formation on pure Ti and Ti-6Al-4V is significantly different because of the segregation of aluminium. This contributes to a change of TiC stoichiometry and morphology. SIMS depth profiles also show that the interfacial surface on Ti-6Al-4V contains several percent of aluminium and nitrogen, both at the outermost surface and in the interior of the interfacial layer. The aluminium is enriched at the surface as compared with the bulk concentration.

Fabrication of Novel TFT LCD Panels with High Aperture Ratio Using a-SiCO:H Films as a Passivation Layer

AbstractFabrication of a novel TFT-LCD panel, using amorphous silicon oxycarbide (a-SiCO:H) films as a passivation layer, was successfully demonstrated for the first time. The a-SiCO:H low-k films were deposited using a standard PECVD (plasma-enhanced chemical vapor deposition) reactor from a gas mixture of trimethylsilane[Si(CH3)3H] and N2O. The resulting films have a dielectric constant between 2.7 and 3.5 and high optical transmittance in the range of visible lightThe transfer characteristics of the TFT's having a-SiCO:H as a passivation layer were comparable with that of a conventional TFT with a PECVD-grown SiNx passivation layer. Stability of the resulting TFT was performed under prolonged bias conditions, and the source-drain current was fairly constant over the test period. The LCD panel with the a-SiCO:H passivation layer showed 30% higher brightness than that of the standard panel.

Low dielectric constant a-SiOC:H films as copper diffusion barrier

A low-k dielectric barrier based on silicon oxycarbide for copper damascene processes has been developed in this work. The optimal process conditions that allow the deposition of silicon oxycarbide films with a dielectric constant of 3.74 and copper diffusion depth of 290 Å after thermal stress at 400 °C for 3 h has been identified. Copper diffusion depth is defined as the copper and dielectric interfacial region with three-order magnitude reduction in copper concentration. A multilayered structure consisting of black diamond/SiOC/Cu/TaN/Si is fabricated. 3-methyl silane and oxygen in varying concentration is used for the deposition of SiOC using plasma enhanced chemical vapor deposition. The composition of the films is studied by Fourier transform infrared spectroscopy. Dielectric constant and dielectric breakdown of the films are also evaluated. Secondary ion mass spectrometry is employed to investigate the copper diffusion property of the films. The electronic component of the dielectric constant has been found to be most significant in affecting the overall dielectric constant in SiOC films.

Inorganic Si-O-C Antireflection Coating at 193 nm for Cu Dual Damascene Process

Silicon oxycarbide (SiOC) films have been investigated as nitrogen (or amine)-free dielectric antireflection layer for a dual damascene structure at 193 nm. Films were deposited by plasma enhanced chemical vapor deposition using trimethylsilane and oxygen. As the oxygen flow rate increased, both the refractive index and extinction coefficient decreased. It was found that reflectance was less than 10% for optimum SiOC, which is comparable to silicon oxynitride. Oxygen plasma treatment converted the top surface of SiOC to silicon oxide. The thickness of the oxide layer increased with the treatment time, however it saturated around 10 nm with treatment times above 90 s. The oxide layer was found to act as a passivation layer stabilizing the SiOC film. It showed reflectance of less than 5% and was successfully utilized as the antireflection layer for a dual damascene structure with no photoresist poisoning. © 2002 The Electrochemical Society. All rights reserved.

Controllable Change of Porosity of 3-Methylsilane Low-k Dielectric Film

A method for controllable increase of porosity of low-k silicon oxycarbide films (SiOCH), deposited by oxidation of 3-methylsilane, has been developed using etching of the SiOCH film by diluted HF solution. The modified SiOCH film is characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and ellipsometric porosimetry. It is found that the chemical composition of the modified SiOCH film remains almost the same during etching. No significant thickness loss is observed, while the pore radius and the film porosity increase with HF dip time. It was concluded that the increase of the pore radius is caused by isotropic etching inside the pores as well as at the film surface. The very low etch rate of SiOCH film by diluted HF and the large difference between the pore radius and the film thickness allows an increase in the porosity without significant thickness loss. This method is a way to prepare ultralow-k dielectric films with higher chemical stability as compared to oxide and silesquioxane-based porous materials. © 2000 The Electrochemical Society. All rights reserved.

Hardness and adhesive properties of (Cr, Mo) oxycarbide films on stainless steel via vapor deposition

A hexacarbonyl of chromium and molybdenum [(Cr, Mo) (CO)6] was used as an oxycarbide source for the coating on stainless steel 304 (SS304) at temperatures from 175 °C to 450 °C. Hardness of the films was determined from a microindentation technique through a similar calculation after Thomas (1987). Intrinsic hardnesses of the films formed at low and medium temperatures were determined to be 8.61 and 2.75 GPa, respectively. Both of them are larger than that of SS304 substrate, 1.75 GPa. Adhesive strength of the films was measured by the scratching test. The results reveal that the adhesive strengths of the films formed at low, medium, and high temperatures are 2.8 N, 37.6 N, and 36.0 N, respectively. Two different fracture modes after scratching were found for the films obtained at various temperature regions. A spalling-off type or a deformation failure with many cracks and deformation bands beside the striation was found.

Transport properties of doped silicon oxycarbide microcrystalline films produced by spatial separation techniques

This paper presents results of the role of the oxygen partial pressure used during the deposition process on the transport properties exhibited by doped microcrystalline silicon oxycarbide films produced by a Two Consecutive Decomposition and Deposition Chamber system, where a spatial separation between the plasma and the growth regions is achieved. This paper also presents the interpretative models of the optoelectronic behaviour observed in these films (highly conductive and transparent with suitable properties for optoelectronic applications) as well as the interpretation of the growth process that leads to film's microcrystallization.

Role of oxygen partial pressure on the properties of doped silicon oxycarbide microcrystalline layers produced by spatial separation techniques

The aim of this work is to present experimental data concerning the role of the oxygen partial pressure during the production process on the properties (structure, morphology, composition, and transport properties) exhibited by doped microcrystalline silicon oxycarbide films. The films were produced by a two consecutive decomposition and deposition chamber system, where a spatial separation between the plasma and the growth regions is achieved. The films produced by this technique are highly conductive and highly transparent with suitable properties for optoelectronic applications requiring wide band‐gap and low‐conductivity materials.

The Structure and Composition of Doped Silicon Oxycarbide Microcrystalline Layers Produced by Spatial Separation Techniques

ABSTRACTThis work presents experimental data concerning the role of the oxygen partial pressure used during the preparation process, on the structure, composition and optoelectronic properties of wide band gap doped microcrystalline silicon oxycarbide films produced by a TCDDC system [1].

Atmosphere effects in the processing of silicon carbide and silicon oxycarbide thin films and coatings

Silicon carbide and silicon oxycarbide films were prepared from solutions of polycarbosilane and methyldimethoxysilane + tetraethoxysilane, respectively, and deposited on different substrates (Si wafers, stainless steel plates, sapphire and SiC fibers). The coatings were heated at different temperatures and in different atmospheres, such as regular grade argon, ultra high purity and argon vacuum. The films were characterized using different techniques (FT-IR, XRD, SIMS, Ellipsometry). The influence of the processing parameters (heat treatment temperature and atmosphere) on the final microstructure of the coatings is discussed in this article.