Conference Paper

Fluorinated HfO2 gate dielectrics engineering for CMOS by pre- and post-CF4 plasma passivation

Dept. of Electron. Eng., Chang Gung Univ., Taoyuan
DOI: 10.1109/IEDM.2008.4796706 Conference: Electron Devices Meeting, 2008. IEDM 2008. IEEE International
Source: IEEE Xplore


In this paper, we demonstrate TaN/fluorinated HfO2 CMOS devices, focusing on symmetry and asymmetry fluorine incorporation at top or bottom HfO2 interfaces. 16% permittivity enhancement, 65% and 91% mobility increases for electron and hole, respectively, under high electric field was achieved. Reliability of n- and p-MOSFET was improved 3 orders and 8% for GIDL and hot carrier immunity, respectively. A physical model of shallow and deep trapping level affected by fluorine was proposed to explain the NBTI and PBTI improvements.

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    ABSTRACT: High-k/germanium (Ge) interfaces are significantly improved through a new interface engineering scheme of using both effective pregate surface GeO<sub>2</sub> passivation and postgate dielectric (postgate) treatment incorporating fluorine (F) into a high-k/Ge gate stack. Capacitance-voltage (C-V) characteristics are significantly improved with minimum density of interface states (D<sub>it</sub>) of 2 times 10<sup>11</sup> cm<sup>-2</sup> ldr eV<sup>-1</sup> for Ge MOS capacitors. A hole mobility up to 396 cm<sup>2</sup>/V ldr s is achieved for Ge p-metal-oxide-semiconductor field-effect transistors (pMOSFETs) with equivalent oxide thickness that is ~10 Aring and gate leakage current density that is less than 10<sup>-3</sup> A/cm<sup>2</sup> at V<sub>t</sub> plusmn 1 V. A high drain current of 37.8 muA/mum at V<sub>g</sub> - V<sub>t</sub> = V<sub>d</sub> = -1.2 V is presented for a channel length of 10 mum. The Ge MOSFET interface properties are further investigated using the variable-rise-and-fall-time charge-pumping method. Over three times D<sub>it</sub> reduction in both upper and lower halves of the Ge bandgap is observed with F incorporation, which is consistent with the observation that frequency-dependent flat voltage shift is much less for samples with F incorporation in the C-V characteristics of Ge MOS capacitors.
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