Methods for forming a diamond like carbon layer with desired film density, mechanical strength and optical film properties are provided. In one embodiment, a method of forming a diamond like carbon layer includes generating an electron beam plasma above a surface of a substrate disposed in a processing chamber, and forming a diamond like carbon layer on the surface of the substrate. The diamond like carbon layer is formed by an electron beam plasma process, wherein the diamond like carbon layer serves as a hardmask layer in an etching process in semiconductor applications. The diamond like carbon layer may be formed by bombarding a carbon containing electrode disposed in a processing chamber to generate a secondary electron beam in a gas mixture containing carbon to a surface of a substrate disposed in the processing chamber, and forming a diamond like carbon layer on the surface of the substrate from elements of the gas mixture.