Effect of amorphous Si layer on the reaction of carbon and silicon in the C/Si multilayer by high vacuum annealing

Crystalline silicon carbide can be formed on the crystalline silicon (c-Si) substrates by reaction of amorphous silicon (a-Si) and carbon (C) layers when annealed at high temperature. The a-Si layer position under or sandwiching the C layer will affect reaction temperature between the a-Si and C layers at constant annealing time. Vacuum annealing at 500-900 °C was performed to study the effect of a-Si layer on the reaction between C and Si in the three kinds of structures, i.e. C, C/a-Si and a-Si/C/a-Si deposited on c-Si substrates. There was no interdiffusion between the single-layer C and c-Si substrate when annealed up to 900 °C for 1.5 h. But some interdiffusion occurred between C and a-Si of the two-layer C/a-Si structure when annealed at 900 °C for 1.5 h. Simultaneously, transformation of a-Si to polycrystalline Si was detected. The interdiffusion between C and Si in the three-layer a-Si/C/a-Si was more pronounced than in the two-layer C/a-Si. In the a-Si/C/a-Si structure, the transformation of a-Si to polycrystalline Si was observed at 700 °C and significant interdiffusion occurred at 900 °C as well as crystalline SiC formation in the multilayer. The SiC formation temperature is lower than conventional crystalline SiC which is formed at 1200 °C in chemical vapor deposition process. The two a-Si layers sandwiching the C layer in the three-layer a-Si/C/a-Si structure lead to the formation of the nanocomposite structure of SiC, C and Si phases at 900 °C. A possible interdiffusion and reaction mechanism between C and Si in the C/Si multilayers through the grain boundaries of polycrystalline Si is proposed.