Electron microscopy
 
TiSix (titanium silicide) and its Failure in IC devices
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Titanium silicide (TiSix) is of significant importance in the semiconductor industry in 1.0 - 0.25 µm technology due to its characteristics of low resistivity, good thermal stability and self-alignment with silicon [1]. However, the disadvantage of titanium silicide is the transformation from the high resistivity orthorhombic body-centered (C49) state to the thermodynamically favored orthorhombic face-centered (C54) state at small linewidth.

Table 1291. Properties of TiSi2 materials.

Properties
C54
C49
Thin film resistivity
(μΩ − cm)
12-24
60-70
Melting point (°C)
1540
Thermal expansion (ppm/°C)
12
Sintering temperature (°C)
700-900 (high thermal budget)
500-700
Stable on Si up to (°C)
~900
Reaction with Al at (°C)
450
nm of Si consumed per nm of metal
2.27
2.27
High Si consumption results in problem in scaling junctions: Not scalable to ultrashallow junctions
nm of resulting silicide per nm of metal
2.51
2.51
Si consumption (nm Si/nm Silicide)
0.904
Barrier height to n-Si (eV)
0.58

Titanium silicides, in general, induce higher compressive strain than cobalt silicides.[2] The induced strain can be a source for dislocation nucleation in silicon if the silicidations are carried out at high temperatures.[3]

 

 

 

 

 

 

 

 

 

 

 

 

[1] Steven H. Voldman, ESD: Physics and Devices, 2004.
[2] A. Steegen, I. De Wolf, and K. Maex, “Characterization of the local mechanical stress induced during the Ti and Co/Ti salicidation in sub-0.25 μm technologies,” J. Appl. Phys., vol. 86, pp. 4290–4297, 1999.
[3] A. Steegen, M. Stucchi, A. Lauwers, and K. Maex, “Silicide induced pattern density and orientation dependent transconductance in MOS transistors,” IEEE IEDM Tech. Dig., pp. 497–500, 1997.

 

 

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