Adsorption and decomposition of diethyldiethoxysilane on silicon surfaces: New possibilities for SiO2 deposition

Abstract

Diethyldiethoxysilane is an organosilicate that may offer new possibilities for SiO2 deposition. In this study, the adsorption and decomposition of diethyldiethoxysilane (DEDEOS) was examined on Si(100)2×1 and porous silicon surfaces using laser-induced thermal desorption (LITD), temperature-programmed desorption (TPD), Fourier-transform infrared (FTIR), and Auger electron spectroscopy techniques. The FTIR studies revealed that DEDEOS dissociatively adsorbs on porous silicon and deposits ethyl and ethoxy species. These species are observed to decompose via a β-hydride elimination mechanism at ∼700 K. In agreement with this mechanism, TPD studies on Si(100)2×1 observed ethylene (C2H4) at ∼700 K and H2 desorption at ∼800 K. Additionally, the controlled deposition of SiO2 was achieved on Si(100)2×1 using repetitive cycles of DEDEOS adsorption at 300 K followed by thermal annealing at 820 K for 300 s. After the rapid deposition of an oxygen coverage of θO∼2.4 ML, the oxygen deposition rate decreased and reached a constant deposition rate of ∼0.04 ML oxygen per cycle after ten cycles. The constant reactivity of the growing SiO2 film was attributed to dangling bond reactive sites resulting from β-hydride elimination of the ethyl groups (SiCH2CH3→SiH+CH2=CH2) and subsequent H2 desorption (2SiH→2Si+H2). DEDEOS was also utilized to grow SiO2 films under high-pressure chemical vapor deposition conditions. The rate of SiO2 deposition displayed Arrhenius behavior with an activation barrier of Eact=49±6 kcal/mol. This activation barrier is similar to activation barriers measured earlier for SiO2 growth using tetraethoxysilane (TEOS). The deposition rate of SiO2 by DEDEOS was approximately 60 times slower than the deposition rate by TEOS at 943 K and 0.5 Torr.