THE DEPENDENCE OF THE STRESS OF CHEMICAL-VAPOR-DEPOSITED TUNGSTEN FILMS ON DEPOSITION PARAMETERS

By forcing the CVD-W reactor in extreme starvation conditions it is possible to obtain low (tensile or compressive) stress tungsten film even at wafer temperatures as low as 400-degrees-C. By combining different steps it is possible to come to a deposition process which can be used for all (interconnect, contact fill, and via fill) application needs in ULSI metallization systems. Using a sample population in which the stress varies more than one order of magnitude, the origin of the stress in the tungsten film is studied further using a substrate bending method for macrostress determination and x-ray techniques for microstress determination and grain size. Microstress in the grains can be higher than the corresponding macrostress of the film. This suggests the presence of a stress-relief mechanism in the tungsten layer. In addition, the influence of the substrate type (sputtered TiN and TiW) on film stress, grain size, and thin film resistivity is discussed.