Contact metallurgy for shallow junction Si devices

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Abstract
A contact metallization is described that allows Al interconnection metallization to be used for shallow junction Si devices. Junction penetration by Al during heat treatment of devices is avoided by using a layer of Pd2Si in the contact window between the Al and the Si. In this manner junctions as shallow as 0.2 μm can be contacted that are able to withstand moderate periods of annealing at 400 °C without degradation. Metallurgical changes occurring in the contact region during heat treatment have been investigated. An intermetallic phase, Al3Pd, is found to form which reduces the Si diffusion from the contact region into the Al and contributes to a uniform Si loss over the whole contact region. Thus the ∼1‐μm‐deep Al penetrations that otherwise occur at spots within the contact region and cause the junction degradation are eliminated. The usefulness of Al interconnection metallization is thereby extended to shallower junction devices.