The surface morphological evolution of ultrathin SiC buffer layer grown on Si (100) substrate by atmospheric pressure ch
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Xue-Chao Liu,a) Jian-Hua Yang, and Er-Wei Shi Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800, China (Received 13 March 2012; accepted 3 July 2012)
Ultrathin SiC buffer layers have been grown on Si (100) substrates by atmospheric pressure chemical vapor deposition. The evolution of buffer layer morphological properties as a function of carbonization parameters is investigated by atomic force microscopy. Based on the quantitative analysis of the dependences of void density, void depth, void width, and surface roughness on carbonization parameters, a buffer layer growth model is proposed, and the effects of carbonization parameters on buffer layer morphology are clarified. The void density is related to the carbonization temperature, temperature ramp-up rate, and C3H8 concentration by affecting the initial SiC nuclei density. The void size is evolved with processing time and mainly dependent on the carbonization temperature but slightly affected by C3H8 and H2. The buffer layer morphology is deteriorated with increasing H2 flow rate when the C3H8 concentration is fixed.
I. INTRODUCTION
Cubic silicon carbide (3C–SiC) is an attractive wideband gap semiconductor material for high frequency, high temperature, and high power electronic devices due to its excellent physical and chemical properties.1,2 Heteroepitaxial growth of 3C–SiC films on Si substrates by chemical vapor deposition (CVD) is a promising method, which not only can supply large-size low-cost substrate for heteroepitaxial growth of III–V compound semiconductors but also can be integrated with the Si-based devices. Due to the large lattice mismatch (;20%) and difference in thermal expansion coefficient (;8%) between 3C–SiC and Si, a severe strain exists at the interface and in the epitaxial layer. The strain relaxation will result in crystalline defects, such as misfit dislocations, stacking faults, and twins, at the SiC/Si interface and in the SiC epilayers.2,3 These defects have severely restricted the applications of 3C–SiC in electronic devices compared with commercial 4H– and 6H–SiC materials. To partially accommodate the large lattice mismatch, a carbonization process before epitaxial growth has been proved to be a helpful step to obtain high quality 3C–SiC film on Si substrate.4 Carbonization is a chemical reaction process between Si substrate and C-bearing molecules a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.259 J. Mater. Res., Vol. 28, No. 1, Jan 14, 2013
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from the gaseous phase to form an ultrathin 3C–SiC buffer layer. Many people have studied on the buffer layer grown by different techniques with various C-bearing precursors, in terms of morphology, growth kinetics, chemical nature, crystalline structure, and several growth models have been proposed.1,5–14 For the buffer layer morphology, people mainly concentrated on the void, which is the most common interfacial defect associated with heteroepitaxial growth of 3
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