Control of Interfacial Reaction of HfO2/Ge Structure by Insertion of Ta Oxide Layer

Kuniaki HASHIMOTO  Akio OHTA  Hideki MURAKAMI  Seiichiro HIGASHI  Seiichi MIYAZAKI  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E96-C   No.5   pp.674-679
Publication Date: 2013/05/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E96.C.674
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Fundamentals and Applications of Advanced Semiconductor Devices)
Category: 
Keyword: 
Ge-channel,  high-k dielectrics,  interfacial control layer,  X-ray photoelectron spectroscopy,  energy band alignment,  

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Summary: 
As means to control interface reactions between HfO2 and Ge(100), chemical vapor deposition (CVD) of ultrathin Ta-rich oxide using Tri (tert-butoxy) (tert-butylimido) tantalum (Ta-TTT) on chemically-cleaned Ge(100) has been conducted prior to atomic-layer controlled CVD of HfO2 using tetrakis (ethylmethylamino) hafnium (TEMA-Hf) and O3. The XPS analysis of chemical bonding features of the samples after the post deposition N2 annealing at 300 confirms the formation of TaGexOy and the suppression of the interfacial GeO2 layer growth. The energy band structure of HfO2/TaGexOy/Ge was determined by the combination of the energy bandgaps of HfO2 and TaGexOy measured from energy loss signals of O 1s photoelectrons and from optical absorption spectra and the valence band offsets at each interface measured from valence band spectra. From the capacitance-voltage (C-V) curves of Pt-gate MIS capacitors with different HfO2 thicknesses, the thickness reduction of TaGexOy with a relative dielectric constant of 9 is a key to obtain an equivalent SiO2 thickness (EOT) below 0.7 nm.