Browse Prior Art Database

Low-Temperature Method for Silicide Formation

IP.com Disclosure Number: IPCOM000101926D
Original Publication Date: 1990-Sep-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Harper, JME: AUTHOR [+4]

Abstract

Titanium disilicide is used as a contact layer and diffusion barrier layer in advanced semiconductor devices. The normal processing sequence includes an initial annealing of Ti on Si to form the C49 crystalline phase of TiSi2 . This step is performed in nitrogen ambient and allows a subsequent chemical etch to leave silicide only on regions of exposed Si, thus creating a self-aligned "salicide" process. After chemical etching, the silicide must be annealed at over 800oC to transform it to the low resistivity C54 phase. Such a high-temperature anneal may degrade the dopant distribution in a shallow junction, or result in non-uniform silicide thickness.

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Low-Temperature Method for Silicide Formation

       Titanium disilicide is used as a contact layer and
diffusion barrier layer in advanced semiconductor devices.  The
normal processing sequence includes an initial annealing of Ti on Si
to form the C49 crystalline phase of TiSi2 .  This step is performed
in nitrogen ambient and allows a subsequent chemical etch to leave
silicide only on regions of exposed Si, thus creating a self-aligned
"salicide" process.  After chemical etching, the silicide must be
annealed at over 800oC to transform it to the low resistivity C54
phase. Such a high-temperature anneal may degrade the dopant
distribution in a shallow junction, or result in non-uniform silicide
thickness.

      The object of the disclosed process is to eliminate the need
for the high-temperature anneal to the C54 phase, by providing a
lower temperature transformation process to obtain this phase.

      The invention described here is to use low energy (300 eV)
nitrogen ion beam bombardment at 500oC to transform the C49 silicide
to C54.  This transformation has been demonstrated and results in a
lowered sheet resistance characteristic of the C54 phase.
Cross-sectional TEM examination shows the presence of crystalline
regions with a structure consistent with the C54 silicide.

      The process of nitridation by low energy ion beam has
additional advantages, including the formation of a surface layer of
TiN at 500oC.  This also is a much lower tempera...