Decomposition of silicon hydrides following disilane adsorption on porous silicon surfaces

Disilane (Si₂H₆) is used for silicon chemical vapor deposition (CVD) and is a potential precursor for atomic layer epitaxy (ALE) on silicon surfaces. In this study, Fourier transform infrared (FTIR) transmission spectroscopy was employed to examine the adsorption and decomposition of disilane on high surface area porous silicon surfaces. The FTIR spectra revealed that disilane dissociatively adsorbs on porous silicon surfaces at 200 K to form a large fraction of SiH₃ surface species and some SiH₂ and SiH surface species. The SiH_x stretching modes between 2125–2156 cm⁻¹, the SiH₃ degenerate deformation mode at 862 cm⁻¹ and the SiH₂ scissor mode at 907 cm⁻¹ were then employed to monitor the decomposition of the surface hybride species during thermal annealing. Between 200–600 K, the SiH₃ species decreased and were depleted from the silicon surface. Concurrently, the SiH₂ surface species were observed to increase between 200–440 K and subsequently to decrease between 440–620 K. Only monohydride species remained on the porous silicon surface at 620 K. Above 640 K, the SiH surface species decreased concurrently with H₂ desorption. Adsorption studies were also conducted at various isothermal temperatures. These disilane adsorption and decomposition experiments provide important insights to the surface chemistry during silicon CVD and ALE processing.