AVS 52nd International Symposium
    Electronic Materials and Processing Monday Sessions
       Session EM-MoA

Paper EM-MoA10
Atomic Layer Chemical Vapor Deposition and Characterization of Hf-silicate, Hf-silicate/Al2O3, and Hf-silicate/SiO2 Gate Dielectrics

Monday, October 31, 2005, 5:00 pm, Room 309

Session: High-k Dielectric Growth and Processing
Presenter: J. Kim, POSTECH, Korea
Authors: J. Kim, POSTECH, Korea
K. Yong, POSTECH, Korea
Correspondent: Click to Email
Silicate or aluminate including hafnium components is considered to be the most promising alternative gate dielectrics, due to good thermal stability in direct contact with silicon. Hf-silicate (HfSi@sub x@O@sub y@) films were grown by ALCVD using the precursor combination of tetrakis-diethylamido-hafnium [Hf(NEt@sub 2@)@sub 4@] and tetra-n-buthyl orthosilicate [Si(O@super n@Bu)@sub 4@]. A highly conformal, uniform Hf-silicate films of a few nm was observed by high resolution-TEM. The Hf/(Hf+Si) was average 0.38 for the bulk film, indicating a Si-rich composition. However, the formation of Hf-silicide (Hf-Si@sub x@) at Hf-silicate/Si interfaces was induced by the reaction of metallic Hf atoms with Si substrate atoms. As a gate oxide becomes thinner, the interfaces have shown to play a key role in device performance. In order to improve the interface properties, the Al@sub 2@O@sub 3@ and chemical SiO@sub 2@ layers were introduced to fabricate the Hf-silicate/Al@sub 2@O@sub 3@ and Hf-silicate/SiO@sub 2@ stacks, respectively. Al@sub 2@O@sub 3@ films were deposited by ALCVD at 200 @super o@C using Al(CH@sub 3@)@sub 3@ and H@sub 2@O. The chemical SiO@sub 2@ of ~1.5 nm was formed by phirana (H@sub 2@SO@sub 4@/H@sub 2@O@sub 2@=4:1) cleaning process. The Hf-silicate/Al@sub 2@O@sub 3@ bilayer showed amorphous characteristics, while Hf-silicate films showed a micro-crystalline structure. The Hf-Six formation was significantly decreased in the case of Hf-silicate/Al@sub 2@O@sub 3@ and Hf-silicate/SiO@sub 2@ bilayer. Compared with Hf-silicate, Hf-silicate/Al@sub 2@O@sub 3@ exhibited a lower leakage current density of 8.9 x 10@super -8@ A/cm@super 2@ at a gate bias of -1 V for an equivalent oxide thickness of 5.2 nm. Hf-silicate/Si and stacked Hf-silicate/SiO@sub 2@/Si were furnace annealed at 650, 750, and 850 @super o@C in the N@sub 2@O/Ar and N@sub 2@O/O@sub 2@ atmosphere. The phase transition (crystallization) was confirmed by XRD, FT-IR and Raman-IR results.