DIETHYLSILANE DECOMPOSITION ON SILICON SURFACES STUDIED USING TRANSMISSION FTIR SPECTROSCOPY

Fourier transform infrared (FTIR) transmission spectroscopy was used to monitor the decomposition of diethylsilane (DES) [(CH3CH2)2SiH2] on high surface area porous silicon samples. The FTIR spectra revealed that DES dissociatively adsorbs on porous silicon to form SiH and SiCH2CH3 species. The infrared absorbances of the CH2CH3 stretching vibrations at 2955-2879 cm-1 and the SiH stretching vibration at 2088 cm-1 were employed to monitor the decomposition of the SiCH2CH3 surface species. As the silicon surface was annealed to 500-750 K, the SiCH2CH3 species decomposed to produce gas phase ethylene [CH2 = CH2] and additional SiH surface species. These reaction products were consistent with a beta-hydride elimination reaction. Above 700 K, the SiH surface species decreased concurrently with the desorption of H-2 from the porous silicon surface. The uptake of surface species was also monitored at various adsorption temperatures to determine the optimal DES exposure temperatures for silicon deposition. Carbon contamination was minimal at DES adsorption temperatures below 640 K prior to H-2 desorption. Because the DES adsorption process is self-limiting at temperatures below 640 K, DES may be a useful molecular precursor for the atomic layer epitaxy of silicon.