Stress changes in chemical vapor deposition tungsten silicide (polycide) film measured by x-ray diffraction

• Published in: Journal of vacuum science & technology. A, Vacuum, surfaces, and films Vol. 20; no. 3; pp. 754 - 761
• Main Authors: Pelleg, Joshua, Elish, E.
• Format: Journal Article
• Language: English
• Published: 01-05-2002
• Subjects: WSi2
• ISSN: 0734-2101; 1520-8559
• DOI: 10.1116/1.1467663

Stresses in chemical vapor deposited polycide tungsten silicide
(
poly-Si/WSi
2
)
were evaluated at each stage of the fabrication. The individual layers of the
Si/SiO
2
/
poly-Si/WSi
2
/
poly-Si
multilayered structure were deposited sequentially on separate wafers and subjected to x-ray diffraction analysis in the as deposited and annealed conditions to determine the changes in strain occurring in
WSi
2
.
Samples cut from wafers containing all the layers were either heat treated at 1193 K for 30 min or capped with a 25 nm thermal oxide and the strain in the
WSi
2
film was also analyzed by x-ray diffraction. The change in strain of the
WSi
2
layer, following each step of the fabrication process, was evaluated by the lattice parameter variation of the c axis. The stress is affected by the layers of the multilayered film. An as deposited poly-Si layer on top of
WSi
2
reduces its stress, since it introduces a compressive component. The stress in
WSi
2
is further reduced upon annealing. Poly-Si also maintains a Si supply at the
poly-Si/SiO
2
interface thus eliminating Si out-diffusion during heat treatment in an oxygen containing ambient. Capping the system by a thin oxide layer modifies the stress pattern of the
WSi
2
which becomes compressive.