Nv. Nguyen et al., Effects of high-temperature annealing on the dielectric function of Ta2O5 films observed by spectroscopic ellipsometry, APPL PHYS L, 77(19), 2000, pp. 3012-3014
Postdeposition annealing of high-k dielectric Ta2O5 films to eliminate cont
aminations can adversely cause the films to crystallize, which can be detri
mental to their complementary metal-oxide-semiconductor device performances
. In this letter, we will show that spectroscopic ellipsometry can be used
to quickly and nondestructively detect such crystallization by identifying
the two relatively sharp absorption peaks at 4.7 and 5.2 eV in the complex
dielectric function of the films. Such peaks are absent in amorphous Ta2O5
films. In general, these sharp structures in the dielectric function are ex
pected from the presence of long-range order in materials, which produces s
ingularities in their interband density of states. Using this approach, we
will show that Ta2O5 films become crystalline when annealed at or above 750
degreesC and remain amorphous below 700 degreesC. (C) 2000 American Instit
ute of Physics. [S0003-6951(00)05445-0].