US Patent 9595451 Highly selective etching methods for etching dielectric materials

Methods for forming high aspect ratio features using an etch process are provided. In one embodiment, a method for etching a dielectric layer to form features in the dielectric layer includes (a) supplying an etching gas mixture during a first mode to etch a portion of a dielectric layer disposed on a substrate while forming a passivation protection in the dielectric layer, wherein the dielectric layer is etched through openings defined in a patterned mask layer disposed on the dielectric layer, (b) supplying an etching gas mixture during a second mode to continue forming the passivation protection in the dielectric layer without etching the dielectric layer, and repeatedly performing (a) and (b) to form features in the dielectric layer until a surface of the substrate is exposed.