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 bina ry reaction sequence chemistry. To achieve this atomic layer growth, t he binary reaction SiCl4 + 2H(2)O --> SiO2 + 4 HCl can be divided into separate half-reactions: (A) Si-OH + SiCl4 --> SiO-Si-Cl-3* + HCl, ( B) Si-Cl + H2O --> Si-OH* + HCl, where the asterisks designate the su rface species. Under the appropriate conditions, each half-reaction is complete and self-limiting and repetitive ABAB... cycles should produ ce layer-by-layer-controlled SiO2 deposition. The atomic layer growth of SiO2 thin films on Si(100) was achieved tit temperatures from 600-6 80 K with reactant pressures from 1-50 Torr. These experiments were pe rformed in a small high pressure chamber situated in an ultrahigh vacu um (UHV) apparatus. This design couples high pressure conditions for f ilm growth with an UHV environment for surface analysis using laser-in duced thermal desorption (LITD), temperature-programmed desorption (TP D) and Auger electron spectroscopy (AES). The controlled growth of a s toichiometric 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 Angstrom of SiO2) per AB cycle were obtained at 600-680 K. Additional vibrational spectroscopic studies performed in a second va cuum chamber utilized transmission Fourier transform infrared (FTIR) e xperiments on high surface area, oxidized porous silicon to monitor th e surface species during the binary reaction sequence chemistry. These FTIR measurements observed the Si-Cl stretching vibration at 625 cm(- 1) and the SiO-H 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 determine d the reactant pressures and substrate temperatures required for the S iO2 binary reaction sequence chemistry.