Fabrication of Si–C–N compounds in silicon carbide by ion implantation

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Abstract

The chemical variation and depth profile of silicon carbide implanted with nitrogen and overgrown with epitaxial layer has been studied using X-ray photoelectron spectroscopy (XPS). The results of this study have been supplemented by transmission electron microscopy (TEM) imaging and electron energy loss-spectroscopy (EELS) in an attempt to correlate the chemical and structural information. Our results indicate that the nitrogen implantation into silicon carbide results in the formation of the Si–C–N layer. XPS revealed significant change in the bonding structure and chemical states in the implanted region. XPS results can be interpreted in terms of the silicon nitride and silicon carbonitride nanocrystals formation in the implanted region which is supported by the electron microscopy and spectroscopy results.

Introduction

Si–C–N materials are of considerable interest as high temperature engineering materials combining the properties of silicon carbide and silicon nitride [1]. A number of experimental and theoretical investigations of the electronic and structural properties of the silicon carbonitride films have been carried out using different growth techniques for the Si–C–N film synthesis. Ion implantation provides a practical method of synthesis of Si–C–N compounds and has been successfully employed to produce Si–C–N composite layers in silicon [2], [3]. The combination of carbon and nitrogen implantation in silicon has been investigated to produce a silicon carbonitride layers with tailored stoichiometries [2]. It has been shown that Si–C–N films with carbon concentration above the solubility limit in Si3N4 remained amorphous after annealing at 1250 °C. IR and XPS analysis of the Si–C–N films has suggested the formation of an amorphous network of mixed Si(C, N)4 tetrahedrons.

Ion implantation has only rarely been applied to the fabrication of Si–C–N layers in silicon carbide material. Early examples studied nitrogen implantation in silicon carbide at room temperature [4]. It has been reported that nitrogen implantation into SiC at room temperature associated with the formation of SixCyNz composite. McHargue et al. [5] have shown the possibility of more significant replacement of carbon by nitrogen atoms during nitrogen implantation in silicon carbide at high temperatures. Miyagawa et al. [6] have observed β-Si3N4 crystallites formation in a polycrystalline β-SiC after nitrogen implantation at 1100 °C. The ion implantation with nitrogen ions at room temperature into 70% SiC–C films has also been reported to form SiCyNz compound [7]. In this paper we study the structural, chemical and bonding variations in silicon carbide by implanting nitrogen ions at high dose and high temperature.

Section snippets

Experimental

14N+ ions at 200 keV were implanted into the 4H silicon carbide wafers, using Varian300XP ion implanter. The dose of implantation was 1.4 × 1018 at. cm−2. During implantation the wafers were maintained at temperature of 650 °C. After the implantation, a silicon carbide epitaxial layer (0.65 μm thick) has been deposited on as-implanted layer by CVD method at 1600 °C to produce structure for applications in new integrated devices. The resulted structure is shown in Fig. 1(a).

X-ray photoelectron

TEM imaging

The TEM image shown in Fig. 1(b) demonstrates the structure of the 4H-SiC film implanted at 200 keV with a nitrogen dose of 1.4 × 1018 at. cm−2 (14N+) and substrate temperature of 650 °C followed by the 4H-SiC epitaxial film deposition. The implanted region is clearly visible as a bright region with two dark defective regions. The bright region corresponds to the projected range depth of nitrogen. The dark defective regions exhibit significant diffraction contrast due to the strains related to the

Conclusion

Our results indicate that the nitrogen implantation into silicon carbide results in the formation of the silicon carbonitride layer. The epitaxial overgrowth of the implanted SiCN layer results in high quality single crystal 4H-SiC layer. High resolution imaging of structural defects revealed the formation of Si3N4/Si2CN4 nanocrystalline inclusions and amorphous graphitic component in the implanted layer. XPS revealed significant change in the bonding structure and chemical states in the

Acknowledgements

The authors acknowledge the facilities, scientific and technical assistance of the Australian Microscopy and Microanalysis Research Facility at the Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, a facility funded by The University, State and Commonwealth Governments.

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