Methods and apparatus for tungsten gap fill

A method for forming tungsten gap fill in a feature, comprising:

• treating a first metal gate layer on a substrate having a portion of the first metal gate layer exposed through the feature consisting essentially of CCTBA soak process;
• followed by
• depositing a tungsten liner layer directly atop the treated first metal gate layer in the feature using a physical vapor deposition (PVD) process to produce a PVD tungsten liner layer;
• and followed by:
• depositing a tungsten fill layer into the feature and atop the PVD tungsten liner layer using a chemical vapor deposition (CVD) process;
• wherein the CCTBA soak process consists of a single treatment of providing CCTBA in argon carrier gas at a flow rate of about 200 to 600 sccm, at a substrate temperature of about 175 to 225 degrees Celsius, a chamber pressure of about 1 to 50 Torr, and at a CCTBA concentration of about 1 to 10 atomic percent in the argon carrier gas, for about 5 to 30 seconds;
• and
• wherein the treating of the first metal gate layer is sufficient to modify a microstructure of the PVD tungsten liner layer to have a lower resistivity compared to a PVD W liner layer deposited upon an untreated first metal gate layer.