Atomic layer growth of SiO₂ on Si(100) using SiCl₄ and H₂O in a binary reaction sequence

The atomic layer control of SiO₂ growth can be accomplished using binary reaction sequence chemistry. To achieve this atomic layer growth, the binary reaction SiCl₄ + 2H₂O → SiO₂ + 4 HCl can be divided into separate half-reactions: (A) SiOH^*+SiCl₄→SiOSiCl^*₃+HCl, SiCl^*+H₂O→SiOH^*+HCl,. where the asterisks designate the surface species. Under the appropriate conditions, each half-reaction is complete and self-limiting and repetitive ABAB... cycles should produce layer-by-layer-controlled SiO₂ deposition. The atomic layer growth of SiO₂ thin films on Si(100) was achieved at temperatures from 600-680 K with reactant pressures from 1-50 Torr. These experiments were performed in a small high pressure chamber situated in an ultrahigh vacuum (UHV) apparatus. This design couples high pressure conditions for film growth with an UHV environment for surface analysis using laser-induced thermal desorption (LITD), temperature-programmed desorption (TPD) and Auger electron spectroscopy (AES). The controlled growth of a stoichiometric and chlorine-free SiO₂ film on Si(100) was demonstrated using these techniques. SiO₂ growth rates of approximately 0.73 ML of oxygen (1.1 Å of SiO₂) per AB cycle were obtained at 600-680 K. Additional vibrational spectroscopic studies performed in a second vacuum chamber utilized transmission Fourier transform infrared (FTIR) experiments on high surface area, oxidized porous silicon to monitor the surface species during the binary reaction sequence chemistry. These FTIR measurements observed the SiCl stretching vibration at 625 cm^-1 and the SioH vibration at 3740 cm^-1 and confirmed that each half-reaction was complete and self-limiting. These studies illustrate the feasibility of atomic-layer-controlled SiO₂ growth and have determined the reactant pressures and substrate temperatures required for the SiO₂ binary reaction sequence chemistry.