Mechanical and structural properties of RF magnetron sputter-deposited silicon carbide films for MEMS applications
01 Feb 2012-Journal of Micromechanics and Microengineering (IOP Publishing)-Vol. 22, Iss: 2, pp 025010
TL;DR: In this paper, the authors reported preparation and characterization of silicon carbide (SiC) films obtained by RF magnetron sputtering using a SiC ceramic target, and the residual stress of the films was measured as a function of sputtering parameters.
Abstract: In the present work, we report preparation and characterization of silicon carbide (SiC) films obtained by RF magnetron sputtering using a SiC ceramic target. The films were deposited in Ar ambient without external substrate heating. The residual stress of the films was measured as a function of sputtering parameters. The stress of the as-deposited films was observed to be compressive for the entire range of sputtering parameters used in the present work. Postdeposition annealing at 400 ?C in N2?ambient was useful in reducing the stress in the films. On sequentially annealing the films at higher temperatures (600 and 800 ?C), the nature of the stress changed from low compressive to high tensile. A superhard SiC film with low residual compressive stress (58.7 MPa) was obtained with hardness and Young's modulus values of 49.86 GPa and 363.75 GPa respectively. The x-ray diffraction pattern revealed that the films were either amorphous or nano-crystalline, depending on the deposition parameters and postdeposition annealing temperature. Atomic force microscopy roughness results confirmed good chemical stability of the films in potassium hydroxide and buffered hydrofluoric acid solutions. Several types of micro-structures were fabricated to demonstrate the feasibility and compatibility of these films in MEMS fabrication.
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TL;DR: In this paper, the physical, mechanical and tribological properties of various surface coatings and their impact on the replication efficiency and lifetime of micro/nano-molds that are used in micro-nano hot-embossing and injection molding processes are discussed.
Abstract: Micro/nano hot-embossing and injection molding are two promising manufacturing processes for the mass production of workpieces bearing micro/nanoscale features. However, both the workpiece and micro/nano-mold are susceptive to structural damage due to high thermal stress, adhesion and friction, which occur at the interface between the workpiece and the mold during these processes. Hence, major constraints of micro/nano-molds are mainly attributed to improper replication and their inability to withstand a prolonged sliding surface contact because of high sidewall friction and/or high adhesion. Consequently, there is a need for proper surface coating as it can improve the surface properties of micro/nano-molds such as having a low friction coefficient, low adhesion and low wear rate. This review deals with the physical, mechanical and tribological properties of various surface coatings and their impact on the replication efficiency and lifetime of micro/nano-molds that are used in micro/nano hot-embossing and injection molding processes.
65 citations
TL;DR: An outstanding electrochemical performance of Si@SiC-0.5 is attributed to the SiC phase, which acts as a buffer layer that stabilizes the nanostructure of the Si active phase and enhances the electrical conductivity of the electrode.
Abstract: Here, we propose a simple method for direct synthesis of a Si@SiC composite derived from a SiO2@C precursor via a Mg thermal reduction method as an anode material for Li-ion batteries. Owing to the extremely high exothermic reaction between SiO2 and Mg, along with the presence of carbon, SiC can be spontaneously produced with the formation of Si. The synthesized Si@SiC was composed of well-mixed SiC and Si nanocrystallites. The SiC content of the Si@SiC was adjusted by tuning the carbon content of the precursor. Among the resultant Si@SiC materials, the Si@SiC-0.5 sample, which was produced from a precursor containing 4.37 wt % of carbon, exhibits excellent electrochemical characteristics, such as a high first discharge capacity of 1642 mAh g–1 and 53.9% capacity retention following 200 cycles at a rate of 0.1C. Even at a high rate of 10C, a high reversible capacity of 454 mAh g–1 was obtained. Surprisingly, at a fixed discharge rate of C/20, the Si@SiC-0.5 electrode delivered a high capacity of 989 mAh g...
51 citations
TL;DR: In this article, the impact of various deposition parameters such as the reactive gas flow ratio, plasma power, substrate temperature and chamber back pressure of ICP-CVD deposited a-SiC:H thin films is investigated and the influence on important MEMS-related properties like residual stress, Young's modulus, hardness, mass density and refractive index is evaluated.
Abstract: In this study, the impact of various deposition parameters such as the reactive gas flow ratio, plasma power, substrate temperature and chamber back pressure of ICP-CVD deposited a-SiC:H thin films is investigated and the influence on important MEMS-related properties like residual stress, Young’s modulus, hardness, mass density and refractive index is evaluated. Basically, tailoring of the as-deposited a-SiC:H characteristics is possible to a great extent with residual stress values ranging from −16 up to −808 MPa, Young’s modulus values between 36 and 209 GPa or deposition of layers with hardness values ranging from 5.3 to 27.2 GPa is feasible. Especially the mechanical parameters are strongly linked to both the Si C bond density and the amount of incorporated hydrogen obtained from Fourier transform infrared spectroscopy analyses.
22 citations
TL;DR: In this paper, the formation of 3C-SiC films has been confirmed from low angle XRD analysis, Raman spectroscopy, Fourier transform infrared (FTIR), XPS and dark and photoconductivity measurements.
Abstract: Cubic nanocrystalline silicon carbide (3C-SiC) films have been deposited by using the hot wire chemical vapor deposition (HW-CVD) method at a low substrate temperature and at high deposition rate. Structural, optical and electrical properties of these films have been investigated as a function of H2 dilution ratio. The formation of 3C-SiC films has been confirmed from low angle XRD analysis, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, x-ray photoelectron spectroscopy (XPS) and dark and photoconductivity measurements. The FTIR spectroscopy analysis revealed that the bond densities of Si-H and C-H decrease while that of Si-C increases with increase in the H2 dilution ratio. The total hydrogen content decreases with increase in H2 dilution ratio and was found < 15 at. % over the entire range of H2 dilution ratio studied whereas the band gap show an increasing trend with increase in the H2 dilution ratio.
13 citations
TL;DR: In this article, an intrinsic and doped, hydrogen-less amorphous silicon films are RF magnetron sputter deposited and post-hydrogenated in a remote hydrogen plasma reactor at a temperature of 370°C.
9 citations
References
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TL;DR: In this article, nanocrystalline silicon carbide films were deposited on molybdenum substrates, with substrate temperature ranging from 750-1250°C to 1200°C.
Abstract: Nanocrystalline silicon carbide films were deposited by thermal plasma chemical vapor deposition, with film growth rates on the order of 10μm∕min. Films were deposited on molybdenum substrates, with substrate temperature ranging from 750-1250 °C. The films are composed primarily of β-SiC nanocrystallites. Film mechanical properties were investigated by nanoindentation. As substrate temperature increased the average grain size, the crystalline fraction in the film, and the hardness all increased. For substrate temperatures above 1200 °C the average grain size equaled 10-20 nm, the crystalline fraction equaled 80-85 %, and the film hardness equaled approximately 50 GPa.
99 citations
TL;DR: In this article, a review of the fabrication techniques for the realization of convex corners in silicon bulk micromachining technology is presented, which is restricted to the wet anisotropic etching process.
Abstract: Silicon bulk micromachining using the wet anisotropic etching process is widely employed for the development of commercial products such as an inkjet printer head, a pressure sensor, accelerometers, infrared sensors, etc using (1 0 0) silicon wafers. In wet anisotropic etching, the resultant shape and size of the microstructures are restricted by crystallographic properties of silicon. If structures such as seismic mass in an accelerometer are required to be created, convex corners will emerge in the etching process. Considerable deformation occurs at convex corners resulting in poor control on the shape and size of the microstructure. Various methods/techniques are developed to overcome the problem of undercutting at convex corners in a (1 0 0) silicon wafer. Here, we have reviewed the fabrication techniques for the realization of convex corners in silicon bulk micromachining technology. The review is restricted to the wet anisotropic etching process which is usually performed in potassium hydroxide solution, ethylenediamine pyrocatechol solution, tetramethylammonium hydroxide, etc. The corner compensation method is the most widely used technique for the fabrication of convex corners. Various types of corner compensating design have been proposed by different research groups. The corner compensation method gives nearly sharp corners. Recently developed techniques, which do not use any compensating design, give perfect convex corners. The limitations and advantages of all the techniques have been discussed. (Some figures in this article are in colour only in the electronic version)
98 citations
TL;DR: In this article, a comparative study of SiC etching with thermal oxidation in regard to the crystal orientation, polytype and carrier concentration dependence was conducted. But, the etching process is significantly affected by the etch ambience: the rate is greatly reduced by a nitrogen gas purge, which indicates an essential role of dissolved oxygen in the melt.
Abstract: The etching mechanism of SiC single crystals by molten KOH has been investigated. The etching process is significantly affected by the etching ambience: the etching rate is greatly reduced by a nitrogen gas purge. This result clearly suggests an essential role of dissolved oxygen in the melt. SiC{0001} surfaces show a large surface polarity dependence, where the etching rate of SiC(0001)C is about four times larger than that of SiC(0001)Si. The etching rate of SiC(0001)C exhibits an Arrhenius type temperature dependence with an activation energy of 15–20 kcal/mol. The obtained activation energy and selectivity between the (0001)C and the (0001)Si surfaces are quite similar to those for thermal oxidation, which implies that the surface oxidation process occurs during molten KOH etching of SiC and is the rate-limiting step for the etching. We have conducted a comparative study of molten KOH etching with thermal oxidation in regard to the crystal orientation, polytype and carrier concentration dependence.
92 citations
TL;DR: In this article, amorphous silicon carbide (SiC) thin films have been deposited by RF magnetron sputtering on hat surfaces and into micromachined cavities of Si (100).
Abstract: There is a need for chemically resistant coatings that protect the exposed surface of microfluidics components. Pinhole free films with low stress and a good uniformity on flat and inclined surfaces are required. In this study, amorphous silicon carbide (SiC) thin films have been deposited by RF magnetron sputtering on hat surfaces and into micromachined cavities of Si (100). The variation of RF power, deposition pressure and substrate bias voltage have been studied. Depending on the deposition conditions, the film stress can be adjusted from - 1400 MPa to + 100 MPa. Modifications of the deposition rate and the morphology between normal and inclined (54.7 degrees) planes have been observed. Optimal chemical stability was found with slightly compressive (-100 MPa) SiC thin films. No degradation of the protective layer has been observed after 3 h in KOH at 80 degrees C. (C) 2000 Elsevier Science S.A. All rights reserved.
82 citations
TL;DR: In this article, silicon carbide films between 2.3 and 3.0 μm were deposited on AISI 304 stainless steel (SS), carbon steel (CS) and crystalline silicon from a SiC target in a magnetron sputtering system.
Abstract: Silicon carbide films between 2.3 and 3.0 μm were deposited on AISI 304 stainless steel (SS), carbon steel (CS) and crystalline silicon from a SiC target in a magnetron sputtering system. Good mechanical properties were obtained for the films by carefully controlling the deposition parameters. Results of scratch tests revealed that adhesion of the films is a function of deposition parameters and substrate type. Additionally, an influence of substrate preparation prior to deposition was also observed. Critical loads of 20 N, 8 N and 5 N were obtained in case of Si, SS and CS substrates, respectively. Vickers micro-hardness values were between 10 and 30 GPa, films on SS being harder than films on CS. The behavior of the films as corrosion protection barriers in aggressive environments was evaluated by immersion tests and electrochemical impedance spectroscopy measurements. Films on SS exhibited a better corrosion resistance than those on CS. Their adhesion to the SS was outstanding, even after a long time of immersion in a HCl 0.8 M solution, showing that they are efficient protection barriers. The corrosion process of the substrates starts at micro-pores present in the films so that corrosion pits all over the surface of the samples can be observed.
70 citations