Apparatus for studying ultrasmall contacts

On-chip IC dimensions have been scaled down without a corresponding decrease in the size of off-chip interconnects, including pressure contacts. As the number of I/O lines increases, pressure contacts need to operate at low forces. The use of scanning tunneling microscope/atomic force microscope (STM/AFM) technology (treating an STM tip-sample junction either as a model for an ultrasmall contact per se, or a microscopic element of a larger contact) is investigated. A combined AFM/STM has been built to allow electrical characterization of contacts under a range of forces and tip and substrate materials. The contact force can be varied from 10/sup -6/ to 10/sup -9/ N, and contact dimensions (as determined by SEM) are approximately 100-nm in diameter. Initial results demonstrate that the reversibility of a contact depends on the hardness of the contact materials.<>