Spacer profile engineering using films with continuously increased etch rate from inner to outer surface

Abstract

Interlayer dielectric gap fill processes are enhanced by forming gate spacers with a tapered profile. Embodiments include forming a gate electrode on a substrate, depositing a spacer material over the gate electrode and substrate, the spacer layer having a first surface nearest the gate electrode and substrate, a second surface furthest from the gate electrode and substrate, and a continuously increasing etch rate from the first surface to the second surface, and etching the spacer layer to form a spacer on each side of the gate electrode. Embodiments further include forming the spacer layer by depositing a spacer material and continuously decreasing the density of the spacer material during deposition or depositing a carbon-containing spacer material and causing a gradient of carbon content in the spacer layer.