Observations on aluminum diffusion and its effect on the specific contact resistance of Al/W/Si ohmic contact

Abstract

This paper describes the observation of aluminum diffusion into the silicon base of Al/W/Si ohmic contacts during aluminum annealing, and its effect on the ohmic property of the contact. The contacts are prepared by plasma-deposition of tungsten, then sequential evaporation of aluminum on n + and p + silicon substrates. The contacts were examined by specific contact resistance measurement, I/V characteristic measurement, Rutherford backscattering spectroscopy (RBS) and X-ray diffraction analysis. RBS showed that, at 500°C annealing, the aluminum diffusion was small, but it became evident after 600°C annealing. However, very low specific contact resistance and good ohmic characteristics were found in the samples annealed at 600°C. Thus we conclude that the aluminum annealing in very large scale integration fabrication does not significantly affect the ohmic characteristics of the Al/W/Si contact.