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Use of Sb with Silicides for n Doping of Si

IP.com Disclosure Number: IPCOM000040813D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

d'Heurle, FM: AUTHOR [+4]

Abstract

For various applications, e.g., the making of shallow junctions, or the fabrication of low resistance ohmic contact to n silicon, one wants to diffuse a dopant element from a silicide to silicon. The silicide can be prepared by codeposition (sputtering, CVD, coevaporation) or by direct metal-silicon reaction. The doping of the silicide itself may take place by implantation, reactive sputtering or CVD from a gaseous source SbH3, SbF3, SbO5, or simply by direct exposure to the gaseous source itself. A problem which is encountered with such procedures is that the affinity of the metal in the silicide, e.g., Ti in TiSi2 for the doping element, might be so high that the dopant reacts with the silicide rather than diffuse to the silicon.

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Use of Sb with Silicides for n Doping of Si

For various applications, e.g., the making of shallow junctions, or the fabrication of low resistance ohmic contact to n silicon, one wants to diffuse a dopant element from a silicide to silicon. The silicide can be prepared by codeposition (sputtering, CVD, coevaporation) or by direct metal-silicon reaction. The doping of the silicide itself may take place by implantation, reactive sputtering or CVD from a gaseous source SbH3, SbF3, SbO5, or simply by direct exposure to the gaseous source itself. A problem which is encountered with such procedures is that the affinity of the metal in the silicide, e.g., Ti in TiSi2 for the doping element, might be so high that the dopant reacts with the silicide rather than diffuse to the silicon. An extreme case of such a dopant is B which reacts with Ti or Ta to form borides such as TiB2 or TaB2 . In general, the problem with n dopants P and As is less pronounced than it is with B. Yet P and As have a tendency to segregate in, e.g., TiSi2 rather than move into the silicon. P and As in silicon have a tendency to move into the silicide TiSi2 .

This publication points out that Sb is the ideal n dopant for such applications for two reasons: (a) its affinity for metals, W, Ta, ... Ti, etc. is much less than P and As, and (b) because of its large atomic size its solubility in the silicides should be extremely limited. Elemental Si can dissolve a finite amount of Sb (small yet not zero) bec...