In one implementation, a method of forming an amorphous silicon layer on a substrate in a processing chamber is provided. The method comprises depositing a predetermined thickness of a sacrificial dielectric layer over a substrate. The method further comprises forming patterned features on the substrate by removing portions of the sacrificial dielectric layer to expose an upper surface of the substrate. The method further comprises performing a plasma treatment to the patterned features. The method further comprises depositing an amorphous silicon layer on the patterned features and the exposed upper surface of the substrate. The method further comprises selectively removing the amorphous silicon layer from an upper surface of the patterned features and the upper surface of the substrate using an anisotropic etching process to provide the patterned features filled within sidewall spacers formed from the amorphous silicon layer.