Atomic layer deposition of SiO2 at room temperature using NH3-catalyzed sequential surface reactions

Ultrathin SiO2 films were deposited at 300–338 K with atomic layer control using NH3-catalyzed sequential surface reactions. The SiO2 deposition was achieved by splitting the reaction SiCl4+2H2O→SiO2+4HCl into two separate SiCl4 and H2O half-reactions. Successive application of the half-reactions in an ABAB… sequence produced atomic layer controlled SiO2 growth. The NH3 catalyst dramatically lowered the necessary deposition temperature from >600 to 300 K and reduced the required reactant fluxes from ∼109 to ∼105 L. In situ spectroscopic ellipsometry monitored the SiO2 deposition versus reaction temperature and SiCl4, H2O and NH3 partial pressures. The ellipsometric measurements obtained a maximum SiO2 growth rate of 2.16 Å per AB reaction cycle at 303 K. Atomic force microscopy images of the deposited surface topography indicated smooth SiO2 films with a roughness similar to the starting Si(100) substrate. Catalysis of the sequential surface reactions that yield atomic layer controlled growth may be general and could facilitate the low temperature deposition of other binary materials.