Low resistivity tungsten film and method of manufacture

A method of forming a tungsten stack and filling a trench on a substrate, the method comprising:

• placing the substrate on a substrate support in a physical vapor deposition chamber, not applying a bias voltage to the substrate support, and forming a tungsten liner layer on the trench comprising dielectric material, two sidewalls and a bottom, the tungsten liner layer covering the two sidewalls and the bottom and formed using a physical vapor deposition process using Kr as a process gas;
• and
• forming a tungsten film directly on the tungsten liner layer to form the tungsten stack having a stack resistivity, the tungsten film formed using a chemical vapor deposition process and filling the trench, wherein formation of the tungsten film does not include forming a nucleation layer on the tungsten liner layer, wherein the trench has a width less than 65 nm,
• wherein not applying the bias voltage to the substrate support controls the grain size of the tungsten liner layer to greater than 200 Ångstroms and improves the stack resistivity.