Thermal degeneration of Mo and Pt silicon Schottky diodes

Abstract

In order to gain thermal stability and process compatibility, Mo and Pt silicon Schottky diodes have been annealed in an hydrogen atmosphere. A clear degeneration of the rectifying characteristics has been observed upon 450°C for Mo and 650°C for Pt. Although metal or defect diffusion could not be detected by transient capacitance measurements, the annealed devices did show anomalously high currents at low bias and at low temperatures. This excess current can be tentatively explained in terms of resonant tunnelling via deep centers near the interface metal-semiconductor induced by the annealing. The difference in the critical temperature for degeneration has its origin in the different behaviour of both barrier metals with silicon. While, in the case of platinum it seems that the silicide formation takes place at temperatures below 650°C with a subsequent diffusion of platinum or silicon vacancies into the silicon, in the case of molybdenum, the defect or metallic difusion apparently occurs before the silicide formation.