The Effect Of Sputter Deposition Parameters On Selected Properties Of Titanium-tungsten (TiW) Thin Films

Abstract

Titanium-tungsten (TiW) thin films are used in semiconductor device fabrication as diffusion barriers and fuse structures in programmable logic devices. Patterned fuses require consistent electrical characteristics. This study used a statistically designed experiment (SDE) to investigate and model the effect of TiW sputter deposition parameters on several characteristics of the blanket film and patterned fuses. The SDE input factors are substrate pre-deposition etch time, substrate temperature, deposition pressure, target power, and a post deposition thermal cycle. The responses investigated are biaxial stress, electrical resistivity, reflectivity, thickness uniformity, and the critical current density to blow patterned TiW fuses. Two-factor interactions and quadratic effects are explored. The substrate temperature was found to significantly affect stress, resistivity, and the critical current density. The deposition pressure notably affected stress. The structure zone model concept was employed in explaining the results. SEM, TEM, SIMS, and Auger analyses were also employed to assist in data interpretation. TEM showed that a 400°C deposition produced a more distinct polycrystalline structure with evidence of Ti partitioning observed. TEM diffraction data indicated a b(Ti,W) crystal structure with no evidence of a-Ti. Auger analysis confirmed that the concentrations of oxygen and carbon impurities were minimal and did not significantly affect the variation in the responses monitored. I NTRO DU CTI 0 N Proiect Goal The intent of this study was to characterize the effect of several TiW sputter deposition process parameters on selected properties of the TiW film, and to explain the results from the materials engineering perspective of the structure/property relationship; deposition process conditions influence the film structure obtained, with this structure arfecting the properties and performance of the film. Backaround TiW thin films are used in semiconductor device fabrication as diffusion barriers and fuse structures in programmable logic devices. The addition of 5-10 wt. % titanium provides improved adhesion, barrier, corrosion, and contact resistance properties. The application of sufficient current through a patterned TiW fuse will result in melting, termed "blowing", and the loss of electrical continuity. In this manner generic devices can be programmed for custom