Formation and characterization of SiC/Si heterostructures by MEVVA implantation.

摘要

High dose carbon implantation into Si to form silicon carbide (SiC) was performed using a metal vapor vacuum arc (MEVVA) ion source under various conditions. The phase formation characteristics, nucleation and growth kinetics, microstructures and other properties were systematically studied using Fourier transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), transmission electron microscopy (TEM), Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM), and electron field emission measurements.; A consistent scheme to de-convolute the FTIR spectra of SiC layers into amorphous and crystalline SiC components was devised. Results showed that at a fixed dose, the total amount of SiC formed increased linearly with the implant energy and at a fixed energy, it increased with a fractional power of the implant dose (D0.41). It was also found that there is a critical implant energy at a fixed implant dose and a critical dose at a fixed implant energy, at which the crystalline 3C-SiC fraction increases abruptly. Existence of the critical energy and dose is discussed in terms of the ion beam induced crystallization (IBIC) effect.; The crystalline 3C-SiC fraction in the as-implanted samples was found to depend significantly on the order of the dual-energy implantation as a result of the IBIC effect. The phase formation characteristics and growth kinetics of the SiC layers during annealing were studied by deconvolution of the FTIR spectra. It was found that the total amount of SiC formed increased upon annealing, indicating that in the as-implanted samples, not all the implanted C atoms were bonded to Si atoms. During annealing, besides the transformation reaction of a-SiC to 3C-SiC, there is also the reaction between the unbonded C atoms and the host Si atoms to form 3C-SiC.; It was also shown that the carbon composition depth profile in the as-implanted samples was a Gaussian-like distribution. Albeit the temperature during implantation is as low as 200°C, the implanted layers contain polycrystalline 3C-SiC grains. The grain size increases with increasing implant energy. There was significant carbon redistribution from the peak of the Gaussian-like distribution to the sides during annealing. After annealing at 1200°C, a continuous 3C-SiC layer was formed. Both surface and buried SiC layers can be formed by using low and high implant energy, respectively, at a suitable dose.; The electron field emission properties of SiC/Si heterostructures formed by high dose C implantation into Si at 35keV have been studied for the first time. The surface morphology of the SiC/Si heterostructures and their effect on the field emission properties were systematically studied. For each implant dose in the range from 5 x 1017 to 1.2 x 10 18cm2, there was a corresponding optimum annealing condition such that a remarkably low turn-on field of about of IV/mum could be achieved. The formation of a thin SiC surface layer and the formation of densely distributed small protrusions on the surface are believed to be the two factors responsible for the efficient electron field emission. (Abstract shortened by UMI.)