Selective epitaxial growth of silicon carbide on silicon by low-temperature chemical vapor deposition

Selective epitaxial growth (SEG) of 3C-SiC on SiO{dollar}sb2{dollar} masked Si substrate via low temperature chemical vapor deposition (CVD) using {dollar}rm SiHsb4{dollar}-C{dollar}rmsb2Hsb4{dollar}-{dollar}rm HCl{dollar}-{dollar}rm Hsb2{dollar} system was investigated experimentally and theoretically. Thermodynamic analysis was conducted to determine the deposition conditions necessary for SiC SEG. The ratio of C/Si {dollar}ge{dollar} 1 minimized the probability of silicon codeposition. The SiO{dollar}sb2{dollar} etching efficiency did not differ with the choice of carrier gas (H{dollar}sb2{dollar} or H{dollar}sb2{dollar} + He mixtures); instead, the total gas flow rate and temperature had a much greater effect. A lower carrier gas flow rate and a substrate temperature lower than 1400 K minimized the SiO{dollar}sb2{dollar} etching. The stability of the SiO{dollar}sb2{dollar} mask in H{dollar}sb2{dollar} or H{dollar}sb2{dollar} and He mixtures at a variety of temperatures was experimentally examined and compared to the thermodynamic predictions. Only a modest improvement in the mask durability was observed when H{dollar}sb2{dollar} was partially substituted with He as the carrier gas, leading to the conclusion that the direct reaction between Si and SiO{dollar}sb2{dollar} was the predominate oxide degradation reaction, which is in agreement with the thermodynamic prediction. The effects of the SiO{dollar}sb2{dollar} mask degradation caused by the high deposition temperature and enhanced by the addition of HCl can be minimized either by using a thick SiO{dollar}sb2{dollar} mask or reducing the deposition temperature further. HCl was essential to ensure selectivity and reduce deposition temperature. Epitaxial SiC was achieved at a temperature as low as 1273 K by experimentally optimizing C/Si and Cl/Si ratios for blanket deposition. At this optimum deposition condition, i.e., with H{dollar}sb2{dollar}/Si ratio of 8000, C/Si ratio of 1, and Cl/Si ratio of 50, SiC SEG was achieved with very good crystal quality. Besides HCl, the SiO{dollar}sb2{dollar} mask pattern also impacted the SiC SEG. Smaller pattern size resulted in about 10% higher growth rate and better crystal quality.