Comparison of high-order silanes and island formation phenomena during SiGe epitaxy at 500 °C

High-order silane precursors, including trisilane, are candidates for the low-temperature epitaxy process owing to the low energy of Si–Si bond. Higher order silanes are regarded as being more reactive than lower order ones. We compared the SiGe epitaxial growth behaviors of high-order silane precursors on Si substrates in an ultra-high vacuum chemical vapor deposition chamber without a carrier gas. SiGe epitaxial layers with a thickness of 25 nm or more were grown using disilane, trisilane, or tetrasilane precursor at 500 °C. Interestingly, trisilane exhibited more severe island formation than tetrasilane, which has higher reactivity than trisilane, even at lower partial pressure. These islands were not eliminated by lowering pressure but could be suppressed by higher Ge content owing to enhanced surface diffusion.