Physical vapor deposition of low-stress nitrogen-doped tungsten films

Abstract

Nitrogen-doped tungsten films characterized by low stress (e.g. less than 250 MPa) and excellent adhesion to an underlying dielectric layer are deposited by physical vapor deposition (PVD). The films can be used as hardmask layers in fabrication of 3D memory stacks and can be deposited directly onto a top dielectric layer in a stack of layers. The low stress films are characterized by higher concentration of nitrogen at the interface with the dielectric layer than in the bulk of the film, and have a nitrogen content of between about 5-20% atomic. The films having a thickness of between about 300-900 nm can be deposited in a PVD process chamber by forming a plasma in a process gas comprising a noble gas and nitrogen, where the flow rate of nitrogen is between about 10-17% of the total flow rate of the process gas.