Chromium as a Diffusion Barrier Between NiSi , Pd2Si , or PtSi and Al

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Abstract
We show that the thermal instability that is observed in Schottky diodes with an Al film on , , or contact to can be removed by proper deposition of a Cr layer, 1000–2000Å thick, between the Al and the underlying silicide layer. The structure can be formed by sequential evaporation of Ni, Pd, or Pt, Cr, and Al, and subsequent thermal annealing to form the contact silicide and sinter the Al contact. Isochronal annealing for 30 min over the temperature range of 350°–500°C shows that the barrier holds electrically at 450°C and fails at 500°C. Forward I‐V measurements are used to determine the barrier height, and elemental profiles are investigated using backscattering spectrometry. The successful utilization of the Cr barrier depends on the deposition conditions. Bilayers of Cr and Al deposited at high rates in another vacuum evaporator consistently reacted more rapidly than those usually observed by us and also reported in the literature. We believe that under usual deposition conditions the impurities incorporated in the films are essential for the successful operation of Cr as a sacrificial barrier.
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