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Improved Salicide Process With Multilayer Silicide Formation

IP.com Disclosure Number: IPCOM000044610D
Original Publication Date: 1984-Dec-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 2 page(s) / 88K

Publishing Venue

IBM

Related People

Choi, KW: AUTHOR [+2]

Abstract

The use of diffusion interaction when depositing Ti films over exposed silicon junctions within silicon integrated circuits (ICs) results in the formation of TiSi2 over the exposed gate polysilicon and bare doped Si junctions, without reaction over the field oxide (Fig. 1). The non-reacted metal is subsequently selectively removed using a hot peroxide etching solution (Fig. 2). TiSi2 is most favored because of its low resistivity and the Ti provides a more uniform and reproducible reaction with the silicon. The WSi2, though yielding a higher resistivity than TiSi2, is more stable relative to basic peroxide solution solubility, and less reactive, as deposited, to SiO2 in the field oxide or sidewall oxide spacers on the polysilicon gate line.

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Improved Salicide Process With Multilayer Silicide Formation

The use of diffusion interaction when depositing Ti films over exposed silicon junctions within silicon integrated circuits (ICs) results in the formation of TiSi2 over the exposed gate polysilicon and bare doped Si junctions, without reaction over the field oxide (Fig. 1). The non-reacted metal is subsequently selectively removed using a hot peroxide etching solution (Fig. 2). TiSi2 is most favored because of its low resistivity and the Ti provides a more uniform and reproducible reaction with the silicon. The WSi2, though yielding a higher resistivity than TiSi2, is more stable relative to basic peroxide solution solubility, and less reactive, as deposited, to SiO2 in the field oxide or sidewall oxide spacers on the polysilicon gate line. Sequential deposition of the Ti and W is accomplished using one of the following alternates: 1) Sequential deposition of the Ti followed by
W. The Ti should preferably be within a thickness range of 50 to 100 nm, for Si- doped junctions up to 0.3 mm deep, so as to provide the major current-carrying contribution. The W should have a thickness up to 25nm, so as to protect the diffusion reacted TiSi2 from partial dissolution within the basic peroxide etching solution (Fig. 3A). The diffusion heat treatment should be within a temperature range of 850 C to 900 C (Fig. 3B). The sequential deposition can be carried out by electron beam evaporation, multitarget sputtering and chemical vapor deposition (CVD), using W...