Thermally stable high effective work function TaCN thin films for metal gate electrode applications
Adelmann, Christoph × Meersschaut, Johan Ragnarsson, Lars-Ake Conard, Thierry Franquet, Alexis Sengoku, Naohisa Okuno, Yasutoshi Favia, Paola Bender, Hugo Zhao, Chao OSullivan, barry Rothschild, Aude Schram, Tom Kittl, Jorge Van Elshocht, Sven De Gendt, Stefan Lehnen, Peer Boissiere, Olivier Lohe, Christoph #
American Institute of Physics
Journal of Applied Physics vol:105 issue:5
TaCN layers were deposited using metal-organic chemical-vapor deposition for applications as metal gate electrodes in p-type metal-oxide-semiconductor (pMOS) devices. The films were formed by thermal decomposition of tertiary-amylimido-tris(dimethylamido)tantalum (TAIMATA (R)) between 400 and 600 degrees C. The composition was dependent on the growth temperature with increasing C and decreasing N content at higher temperature. Films grown below 500 degrees C were nearly amorphous and became weakly polycrystalline with a cubic structure at higher growth temperature. The layer density was similar to 8.1 g/cm(3), about half of the TaCN bulk density. Grazing-incidence x-ray diffraction and transmission electron microscopy showed that the films consist of small polycrystalline grains in an amorphous matrix. The resistivity was found to decrease with increasing growth temperature. Lowest resistivity values were around 1 m Omega cm for films grown at 600 degrees C. The films formed an similar to 4 nm thick insulating surface oxide, which leads to a thickness dependence of the film resistivity. Oxygen was also found to diffuse slowly into the bulk metal, which leads to a resistivity aging effect. The effective work function of the TaCN films was found to be 4.8 eV on HfSiO4 and HfSiON and to shift weakly by high thermal budget annealing toward the Si valence band, reaching 4.9 eV on HfSiO4.