Ion implantation technique for simulatneous formation of a shallow silicon p-n junction and a shallow silicide-silicon ohmic contact

Abstract

Electron beam evaporation is used to coat a p-type silicon substrate with a thin layer of tungsten and then with alternating layers of silicon and tungsten. Bombardment of the coated substrate with As + ions causes intermixing of the metal and silicon layers, dispersion of contaminant atoms at the interface between the first metal layer and the substrate, and implantation of arsenic atoms in the substrate. Subsequent thermal annealing produces a shallow silicide-silicon ohmic contact and simultaneously activates the implanted arsenic donors to form a shallow pn + junction. This technique has been used for the fabrication of mesa diodes with good junction characteristics. A simplified version, in which only a single tungsten layer is deposited on the substrate, has been used as a self-aligned process in the fabrication of metal/oxide/semiconductor field effect transistors with a polycide gate. In the transistors the silicide contacts to the source and drain regions can be made very close to the gate, reducing both the series resistance of these regions and the overall device size.