AVS 51st International Symposium
    Electronic Materials and Processing Monday Sessions
       Session DI-MoA

Paper DI-MoA8
Electronic Properties and Band Alignments of Hf-based Gate Dielectrics on Silicon

Monday, November 15, 2004, 4:20 pm, Room 304B

Session: High-k Dielectrics: Electronic Properties
Presenter: R. Puthenkovilakam, University of California, Los Angeles
Authors: R. Puthenkovilakam, University of California, Los Angeles
J.P. Chang, University of California, Los Angeles
Correspondent: Click to Email
Ultra thin HfO@sub 2@ or HfO@sub x@N@sub y@ thin films are being considered for possibly replacing SiO@sub 2@ gate oxide in silicon based metal-oxide-semiconductor (MOS) transistors. In this work we investigated the electronic structure and band alignments at the HfO@sub 2@(or HfO@sub x@N@sub y@)/Si interfaces which dictate the device performance of transistors in the sub-90nm devices. We used tetragonal structure to model HfO@sub 2@ and nitrogen incorporation was achieved by replacing selective oxygen atoms with nitrogen. The electronic structure of HfO@sub 2@/Si interface showed dangling bond states at the interface due to the reduced coordination of Hf caused by the intrinsic bond constraints at the HfO@sub 2@/Si interface. However, our calculations indicate that these dangling bonds could be passivated by hydrogen or oxygen, which can appropriately change the coordination numbers at the interface, thereby removing the dangling bond states. We also considered the interface of HfSiO@sub 4@/Si and found that there are no dangling bond states at this particular interface, making HfSiO@sub 4@ a promising interfacial layer to improve the interface quality. Band offsets at the HfO@sub 2@/Si interfaces were theoretically calculated and showed that the conduction band offsets ranged from 1.5-1.9 eV depending upon the interface stoichiometry. Band offsets were experimentally determined by measuring the core level to valence band maximum binding energy differences using XPS and were in excellent agreement with the theoretical results. Incorporation of nitrogen into the HfO@sub 2@ network resulted in notable changes in the valence band structure of the material and the corresponding band alignments with silicon and is found to depend on the nitrogen concentration in the bulk of HfO@sub 2@ as well as at the interface.