pantelides_muri_2007

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ATOMIC-SCALE THEORY OF RADIATION-INDUCED PHENOMENA Sokrates T. Pantelides Department of Physics and Astronomy, Vanderbilt University, Nashville, TN and Oak Ridge National Laboratory, Oak Ridge, TN The theory team: Matt Beck, Leonidas Tsetseris, George Hadjisavvas, Sasha Batyrev, Ryan Hatcher, Blair Tuttle AFOSR/MURI REVIEW 2007 In collaboration with the rest of the MURI team

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THEORY OBJECTIVES DISPLACEMENT DAMAGE Defects, charging electrons ALTERNATE DIELECTRICS Interface structure, interface defects, NBTI,… CARRIER MOBILITIES LEAKAGE CURRENTS FROM ATOMIC-SCALE PHYSICS TO ENGINEERING MODELS

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Atomic-scale physics: DENSITY FUNCTIONAL THEORY PSEUDOPOTENTIALS, SUPERCELLS TOTAL ENERGY, FORCES ON ATOMS o Stable defect configurations o Bulk, interface o Reaction energies, activation barriers EVOLUTION OF SYSTEM electrons in instantaneous ground state vs electrons allowed to evolve freely BULK – INTERFACE CHARGING

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THEORY OBJECTIVES DISPLACEMENT DAMAGE Defects, charging electrons ALTERNATE DIELECTRICS Interface structure, interface defects, NBTI,… CARRIER MOBILITIES LEAKAGE CURRENTS FROM ATOMIC-SCALE PHYSICS TO ENGINEERING MODELS TALK BY A. MARINOPOULOS

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Van Benthem & Pennycook, ORNL

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Si-SON-HfO2 Vanderbilt team POST-IRRADIATION SWITCH-BIAS ANNEALING

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THEORY OBJECTIVES DISPLACEMENT DAMAGE Defects, charging electrons ALTERNATE DIELECTRICS Interface structure, interface defects, NBTI,… CARRIER MOBILITIES LEAKAGE CURRENTS FROM ATOMIC-SCALE PHYSICS TO ENGINEERING MODELS TALK BY A. MARINOPOULOS TALK BY M. BECK

A Displacement Single Event : 

A Displacement Single Event How does energy translate to electrical activity?

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Red (hot) atoms: KE > 0.22 eV Black atoms: displaced > 0.2 Å 25 eV kick Snapshot after 100 fs

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THEORY OBJECTIVES DISPLACEMENT DAMAGE Defects, charging electrons ALTERNATE DIELECTRICS Interface structure, interface defects, NBTI,… CARRIER MOBILITIES LEAKAGE CURRENTS FROM ATOMIC-SCALE PHYSICS TO ENGINEERING MODELS TALK BY A. MARINOPOULOS TALK BY M. BECK TALK BY I. BATYREV

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PSG PSG Al Al Al 7*1017 cm-3 3*1017 cm-3 6*1015 cm-3 3*1015 cm-3 SiO2 SiO2 100 % H2 C B E -10 10 µm µm 0.5 1.0 1.5

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THEORY OBJECTIVES DISPLACEMENT DAMAGE Defects, charging electrons ALTERNATE DIELECTRICS Interface structure, interface defects, NBTI,… CARRIER MOBILITIES LEAKAGE CURRENTS FROM ATOMIC-SCALE PHYSICS TO ENGINEERING MODELS TALK BY A. MARINOPOULOS TALK BY M. BECK TALK BY I. BATYREV PLUS SOMETHING SPECIAL

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Universal mobility NOT ANY MORE

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Strained n-type Si p type Si p type Si oxide “metal” Strained-Si Bulk MOSFET K. Rim, J. L. Hoyt, and J. F. Gibbons (2000) Fischetti et al. 2002: fit data with unusually low interface roughness

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ALL MOBILITY CALCULATIONS SUPPRESS ATOMIC-SCALE DETAIL Si SiO2 V(z) ~30-100= EFFECTIVE-MASS THEORY BULK ENERGY BANDS INFINITE POTENTIAL BARRIER FREE PARAMETERS

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ATOMIC-SCALE SIMULATIONS SOI MOSFET

Scattering Potential : 

Scattering Potential Videal Vdefect DV = Vdefect - Videal

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ATOMIC-SCALE ROUGHNESS

Mobility Enhancement : 

Mobility Enhancement Data from bulk MOSFETs or SOI MOSFETs with t>5 nm

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Image by Pennycook et al. WHAT CONTROLS THE ABRUPTNESS OF THE Si-SiO2 INTERFACE?

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(~3.5 eV)

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Si SiO2 Diffusion activation energies EA = 1.2 eV EA = 2.0 eV

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Thermal oxidation: a random “deposition” process? Analogy with film growth: where O2 lands, it sticks

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“Reorganization” at the Si-SiO2 interface Gain in energy ~ 1-2 eV ? smoother interface Lateral diffusion barrier ~2.1 – 2.3 eV

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“Fractal Concepts in Surface Growth”, Barabasi and Stanley Random deposition with relaxation

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Still, why do you need 800ºC to get a smooth interface? O diffusion in Si Ea = 2.3 eV But, binding of O to interface E ~ 1.0 eV “Desorption enhanced lateral diffusion” Ea ~3.3 eV ! That’s the 800ºC !

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“Reorganization” at the Si-SiO2 interface Gain in energy ~ 1-2 eV ? smoother interface Lateral diffusion barrier ~2.1 – 2.3 eV Desorption-enahnced lateral diffusion barrier ~3.3 eV