Instrumentation For the Study of Tantalum Diffusion Barriers Between Silicon Substrates and Copper Films
Currently, the material of choice for interconnects on silicon devices is aluminum. This is because of its ease of processing and low contact resistance. But because of aluminum's tendency to electromigration and junction spiking, it is not suitable for future reduction of silicon devices. Copper is better suited for sub-micron sized interconnects because of its lower electromigration and lower electrical resistance as compared to aluminum. However, copper has a tendency to readily diffuse into silicon; therefore, a diffusion barrier between silicon and copper is needed. Currently tantalum and tantalum nitride are two materials that have been successfully used as diffusion barriers, but a detailed study of the physical properties that affect their diffusion blocking abilities is lacking. It is currently believed that grain boundary density, crystalline structure, and film purity are some of the factors involved in the material's ability to be a successful diffusion barrier. The purpose of this work is to produce the necessary instrumentation to control the growth of both the diffusion barrier film and the copper film onto a silicon substrate, and to characterize the films. The films will be grown in an ultra high vacuum by electron beam evaporation. And the characterization of the films will be accomplished by spectrographic and electrical resistivity means.
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