AVS 52nd International Symposium
    Thin Films Tuesday Sessions
       Session TF-TuM

Invited Paper TF-TuM7
The Atomic-Layer-Deposited HfO@sub 2@ Gate Dielectric Films; Chemistry of Interface and Electrical Performances

Tuesday, November 1, 2005, 10:20 am, Room 306

Session: Atomic Layer Deposition - Oxides
Presenter: C.S. Hwang, Seoul National University, Korea
Authors: T.J. Park, Seoul National University, Korea
M.J. Cho, Seoul National University, Korea
S.H. Hong, Seoul National University, Korea
M.H. Seo, Seoul National University, Korea
J.H. Kim, Seoul National University, Korea
J.H. Park, Seoul National University, Korea
C.S. Hwang, Seoul National University, Korea
Correspondent: Click to Email
HfO@sub 2@ thin films were deposited on HF-dipped Si wafers at temperatures ranging from 250 to 300°C using an atomic-layer-deposition technique with N-containing Hf[N(CH@sub 3@)@sub 2@]@sub 4@, Hf[N(CH@sub 3@)(C@sub 2@H@sub 5@)]@sub 4@ or Hf[N(CH@sub 3@)(@sub 2@H@sub 5@)]@sub 3@[OC(CH@sub 3@)@sub 3@] and H@sub 2@O or O@sub 3@ as the precursor and oxidant, respectively. A thin interfacial SiN@sub x@ layer was spontaneously formed at the HfO@sub 2@/Si interface during film growth. This interfacial SiN@sub x@ layer played a critical role in improving the thermal stability and interfacial trap (D@sub it@) property. D@sub it@ of < 5 x 10@super 10@ cm@super -2@eV@super -1@ near the mid-gap energy states was obtained from most of the process conditions but it usually suffer from the degradation by high temperature post-deposition annealing (PDA) at temperatures > 800°C. The adoption of O@sub 3@ oxidant reduced carbon impurity concentration and made the film more amorphous compared to the films grown using H@sub 2@O as oxidant. Although ozone was effective in reducing the impurity concentration, the higher concentration slightly deteriorated the dielectric performance. Investigation of the interface states using X-ray photoelectron spectroscopy revealed that the excessive oxygen incorporated during the film growth made the interfacial sub-oxide species (SiO, Si@sub 2@O@sub 3@ and silicate) and SiO@sub 2@ coordinate more with oxygen. This was further confirmed by the MOSFET performance comparison fabricated with HfO@sub 2@ gate dielectrics using different O@sub 3@ concentration. An electron effective mobility of ~ 65% of the MOSFET with SiO@sub 2@ as gate dielectric was obtained from the stoichiometric HfO@sub 2@ gate dielectric film. The effective mobility from the MOSFET with the oxygen excess HfO@sub 2@ film was only ~ 45 %.