Sputtering methods for depositing stress tunable tantalum and tantalum nitride films

摘要

The present disclosure pertains to our discovery that residual stress residing in a tantalum film or tantalum nitride film can be controlled (tuned) by controlling particular process variables during film deposition. By tuning individual film stresses within a film stack, it is possible to balance stresses within the stack. Process variables of particular interest include: power to the sputtering target; process chamber pressure (i.e., the concentration of various gases and ions present in the chamber); substrate DC offset bias voltage (typically an increase in the AC applied substrate bias power); power to an ionization source (typically a coil); and temperature of the substrate upon which the film is deposited. The process chamber pressure and the substrate offset bias most significantly affect the film tensile and compressive stress components, respectively. The most advantageous tuning of a sputtered film is achieved using high density plasma sputter deposition, which provides for particular control over the ion bombardment of the depositing film surface. When the tantalum or tantalum nitride film is deposited using high density plasma sputtering, power to the ionization source can be varied for stress tuning of the film. We have been able to reduce the residual stress in tantalum or tantalum nitride films deposited using high density plasma sputtering to between about 6× 10.sup.+9 dynes/cm.sup.2 and about -6×10.sup.+9 dynes/cm.sup.2 using techniques described herein. The tantalum and tantalum nitride films can also be tuned following deposition using ion bombardment of the film surface and annealing of the deposited film.