Selective passivation and selective deposition

A method of selective deposition on a second dielectric surface of a substrate relative to a first metal or metallic surface of the substrate, the method comprising, in order:

• treating the first and second surfaces by exposing the substrate to a silane;
• selectively forming a polymer layer from vapor phase reactants on the first surface relative to the second surface;
• baking the polymer layer;
• etching the polymer layer for a first polymer etch time to form a polymer layer leading edge, wherein at least some of the polymer layer remains on the first surface after etching;
• and
• depositing a dielectric layer on the second surface of the substrate from vapor phase reactants,
• wherein the first polymer etch time is selected to control a position of an edge of the dielectric layer to be deposited relative to a boundary between the underlying first and second surfaces.