The present disclosure describes a method for forming a silicon-based, carbon-rich, low-k ILD layer with a carbon concentration between about 15 atomic % and about 20 atomic %. For example, the method includes depositing a dielectric layer, over a substrate, with a dielectric material having a dielectric constant below 3.9 and a carbon atomic concentration between about 15% and about 20%; exposing the dielectric layer to a thermal process configured to outgas the dielectric material; etching the dielectric layer to form openings; and filling the openings with a conductive material to form conductive structures.