Shallow-junction diode formation by implantation of arsenic and boron through titanium-silicide films and rapid thermal annealing

Abstract

The performance of diodes fabricated on n-type and p-type Si substrates by implanting As or B through a low-resistivity titanium-silicide layer is discussed. The effects of varying the implant dose, energy, and postimplant thermal treatment were investigated. After implantation, a rapid thermal anneal was found to remove most of the implant damage and activate the dopants, which resulted in n/sup +/-p and p/sup +/-n junctions under a low-resistivity silicide layer. The n/sup +/-p junctions were as shallow as 1000 AA with reverse leakage currents as low as 5.5 mu A/cm/sup 2/. A conventional furnace anneal resulted in a further reduction of this leakage. Shallow p/sup +/-n junctions could not be formed with boron implantation because of the large projected range of boron ions at the lowest available energy. Ti silicide films thinner than 600 AA exhibited a sharp rise in sheet resistivity after a furnace anneal, whereas thicker films exhibited more stable behavior. This is attributed to coalescence of the films. High-temperature furnace annealing diffused some of the dopants into the silicide film, reducing the surface concentrations at the TiSi/sub 2/-Si interface.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>