Papers by Keyword: CVD

Abstract: Hot filament CVD (HFCVD) growth of undoped 4H-SiC epitaxial layers on 100 mm n-type 4^o-off 4H-SiC substrates is presented as an alternate growth method for the first time. High quality crystalline material with a low density of polytype inclusions has been demonstrated and characterized with optical micrographs, SEM imaging, micro-Raman measurements, and high resolution XRD. Typical growth rates are ~3 μm/hour. Double rocking omega scans revealed diffraction peaks with a FWHM of 23 arcsec.

Abstract: Understanding the chemistry in CVD of SiC is important to be able to control, improve and scale up the process to become industrially competitive. A thorough understanding have so far been difficult to achieve due to the complex nature of the process. Through modeling tools, and a systematic approach when constructing the chemical models, new insights to the SiC CVD chemistry can be obtained. Using a general model that is independent on the choice of precursors and reactor configuration, and by coupling modeling results to experimental findings, we here show that SiCl₂ and SiH₂ previously suggested as the main silicon bearing growth species in the chlorinated and standard chemistries, respectively, does not contribute significantly to the SiC growth, and that the main active species are C₂H₂, CH₃, Si, and SiCl.

Abstract: By mapping the source and HCl flow rates dependent growth rates, the evolving trend of a quasi-selective epitaxial growth (quasi-SEG) that growing very thin epilayer on mesa top and ensuring an extremely low risk of voids defect generation was firstly figured out on a 5-μm 4H-SiC trench. Then, basing on the acquired knowledge, a 25-μm 4H-SiC trench with an aspect ratio up to ~10 was completely filled in the quasi-SEG mode.

Abstract: We report on the results of a Design of Experiments (DOE) matrix of growth runs used to tune and improve the uniformity of thickness and doping across both 100 mm and 150 mm SiC epiwafers in our epitaxy reactor. Improvement of uniformity beyond the initial process recipe from the tool vendor is shown. Temperature measurement along an entire wafer platter indicate that there is a gas cold region extending into the growth zone that maybe the root cause of the non-uniformity.

Abstract: We report for the first time the successful heteroepitaxial growth of Si(100) oriented layer on top of a 3C-SiC(001) seed. By using a post-growth modification of the 3C-SiC surface (pulse insertion of precursors during cooling), it led to a change in Si nucleation, favoring squared (100) islands instead of elongated (110) ones. Without this surface modification step, the Si layers grown on 3C-SiC were always polycrystalline with a mixture of (110) and (100) orientations. Using such Si(100) layer grown on top of 3C-SiC(100), a (100) oriented 3C-SiC single crystalline layer was successfully grown on top, fabricating thus for the first time a fully (100) oriented multilayer heterostructure made of Si_(substrate)/SiC/Si/SiC.

Abstract: Epitaxial growth of 4H-SiC on 150 mm wafers has been investigated using experimental results and numerical simulations toward the goal of BPDs reduction and doping uniformity control in the epitaxial layer. We have reported analyses of the temperature distribution dependence of the doping uniformity and BPDs propagations on the 3 x 150 mm multi-wafer CVD epitaxial growth. By optimizing epitaxial growth conditions, we have demonstrated an excellent doping and thickness uniformity and a 99.9% BPD free region, simultaneously.

Abstract: This paper describes the modification of ultralight flexible carbon foam by chemical vapor deposition (CVD) of silicon carbide whiskers (SiC_w). The effect of SiC whiskers on the microstructure and the thermal conductivity of carbon foam were investigated by scanning electron microscopy (SEM) and laser flash diffusivity method in a Netzsch LFA427. The results show that the macro-pores (~30 μm) of the carbon foam were divided by the random distribution of SiC whiskers. The diameter of SiC whiskers decreased with decreasing catalyst concentration which resulted in the improved microstructure with a smaller pore diameter (4~6 μm) and a more homogeneous distribution of the pores. The carbon foam reinforced by SiC_w exhibits better insulation performance than the pristine carbon foam when the temperature exceeds 200°C.

Abstract: Silicon carbide nanowires have been extensively studied because of their unique physical and chemical properties. They can be applied in high temperature, high frequency, high power, and corrosive environments, and have a wide range of applications in electronics, chemical industry, energy and other fields. In this paper, SiC nanowires with high output were synthesized by chemical vapor deposition method using methyltrichlorosilane as raw material. The influences of the catalyst and temperature were studied. SiC nanochains were also obtained by adding Al₂O₃ powder under appropriate temperature controlled strategy. These two kinds of one-dimensional SiC nanomaterials were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS) and transmission electron microscope (TEM) methods.

Abstract: CVD SiC material with many excellent physical and chemical properties was used widely in the field of aerospace as reflector materials. In addition, CVD SiC thin film materials because of its compact structure, high purity can also be used as precision optical components of semiconductor industry. But the CVD process is a complex chemical process and the reaction process is very time consuming. Research of chemical vapor deposition for preparing silicon carbide process mechanism is important significance for the expansion of the application of silicon carbide. In this paper, CVD SiC coatings were fabricated by the pyrolysis of methyltrichlorosilane (MTS) in hydrogen at a low pressure. XRD and EDS were used to characterize the component of intermediate. SEM was used to observe the surface morphology and microstructure of coatings. The results indicated that key problem to be solved is to control the growth rate of SiC for high quality deposition coating, while the growth rate is also affected by process parameters. To obtain the materials to meet the use requirements, the need for control of each parameter in the reaction process.

Abstract: The aim of this study was to find conditions allowing the "natural" formation of a regular and controllable step bunched morphology on a 4H-SiC seed without the need of any SiC deposition. This was performed by melting a bulk piece of Si on a 4°off 4H seed in the temperature range of 1500 - 1600°C, for 15 min. After etching the remaining Si, the 4H surface was found to be successfully highly step bunched with steps very parallel and regular. A mechanism of dissolution-precipitation was proposed, which could occur both on a short (step to step) and long (centre to periphery) range. This process is kinetically limited at low temperature (1500-1550°C) and considered to be close to the equilibrium at 1600°C.