Methods and apparatuses for selectively depositing silicon oxide on surfaces relative to a metal-containing surface such as copper are provided. Methods involve exposing a substrate having hydroxyl-terminated or dielectric surfaces and copper surfaces to a copper-blocking reagent such as an alkyl thiol to selectively adsorb to the copper surface, exposing the substrate to a silicon-containing precursor for depositing silicon oxide, exposing the substrate to a weak oxidant gas and igniting a plasma, or water vapor without plasma, to convert the adsorb silicon-containing precursor to form silicon oxide. Some methods also involve exposing the substrate to a reducing agent to reduce any oxidized copper from exposure to the weak oxidant gas.