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Improved TiSi2 Films for VLSI Technology

IP.com Disclosure Number: IPCOM000120193D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 1 page(s) / 51K

Publishing Venue

IBM

Related People

dHeurle: AUTHOR [+2]

Abstract

Because of its low resistivity TiSi2 is widely used in VLSI technology either for interconnections or contacts to silicon. In this latter respect increased miniaturization calls for very shallow junctions and correspondingly thin layers of silicide. Unfortunately, thin layers of almost anything, but especially of TiSi2, tend to lose their continuity and low resistance when exposed to the high temperatures required by device processing. It should be clear that the instability that is of concern here has nothing to do with the chemical stability of TiSi2 as a compound but rather its morphological stability, the ability to retain its shape regardless of processing conditions.

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Improved TiSi2 Films for VLSI Technology

      Because of its low resistivity TiSi2 is widely used in VLSI
technology either for interconnections or contacts to silicon. In
this latter respect increased miniaturization calls for very shallow
junctions and correspondingly thin layers of silicide.
Unfortunately, thin layers of almost anything, but especially of
TiSi2, tend to lose their continuity and low resistance when exposed
to the high temperatures required by device processing.  It should be
clear that the instability that is of concern here has nothing to do
with the chemical stability of TiSi2 as a compound but rather its
morphological stability, the ability to retain its shape regardless
of processing conditions.

      The cause of these instabilities is to be found in nature's
attempt to minimize the surface energy of a system by changing its
shape. Any alloying element that segregates by adsorption to the
surface of a material should increase its morphological stability
precisely because it lowers its specific surface energy.  Surface
segregation implies an addition with (1) an atomic size and/or
valency different from that/those of the host elements. Moreover, it
must have (2) sufficient mobility to be able to move to the surface,
at sufficiently low temperatures to be effective. In TiSi2 that means
that it should be able to act as a substitute element on the silicon
sublattice.  On the other hand, (3) its valency should not be too
different from that...