Stress tunable tantalum and tantalum nitride films

摘要

The present disclosure pertains to our discovery that the residual stress residing in a tantalum (Ta) film or a tantalum nitride (TaN_x, where 0x≦1.5) film can be controlled (tuned) by controlling particular process variables during deposition of the film. Process variables of particular interest during film deposition, for sputter applied Ta and TaN_x films, include the following. The power to the sputtering target; the process chamber pressure (i.e. the concentration of various gases and ions present in the chamber); the substrate DC offset bias voltage (typically an increase in the AC applied substrate bias power); and, the temperature of the substrate upon which the film is being deposited. When the Ta or TaN_x film is deposited using IMP sputtering, the power to the ionization coil can be used for stress tuning of the film. Of these variables, the process chamber pressure and the substrate offset bias most significantly affect the tensile and compressive stress components, respectively. The most advantageous tuning of a sputtered film is achieved using Ion Metal Plasma (IMP) as the film deposition method. This sputtering method provides for particular control over the ion bombardment of the depositing film surface. Tantalum (Ta) films deposited using the IMP method typically exhibit a residual stress ranging from about +1×10^+10 dynes/cm² (tensile stress) to about −2×10^+10 dynes/cm² (compressive stress), depending on the process variables described above. Tantalum nitride (TaN_x) films deposited using the IMP method typically can be tuned to exhibit a residual stress within the same range as that specified above with reference to Ta films. We have been able to reduce the residual stress in either the Ta or TaN_x films to range between about 6×10^+9 and about −6×10^+9 dynes/cm² using tuning techniques described herein. ;The Ta and TaN_x films can also be tuned subsequent to deposition using ion bombardment of the film surface and annealing of the deposited film.