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Total-Dose Response and Negative-Bias Temperature Instability (NBTI)

D. M. Fleetwood Professor and Chair, EECS Dept. Vanderbilt University Nashville, TN 37235 USA dan.fleetwood@vanderbilt.edu (615) 322-2498 A collaboration between VU EECS and Physics. Total-Dose Response and Negative-Bias Temperature Instability (NBTI).

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Total-Dose Response and Negative-Bias Temperature Instability (NBTI)

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  1. D. M. Fleetwood Professor and Chair, EECS Dept. Vanderbilt University Nashville, TN 37235 USA dan.fleetwood@vanderbilt.edu (615) 322-2498 A collaboration between VU EECS and Physics Total-Dose Response and Negative-Bias Temperature Instability(NBTI)

  2. Assistant Professors Recently Hired in EE • William Robinson • PhD, Georgia Tech, 2003 • computer architecture/VLSI design • mixed-signal integration for focal plane processing • integrated sensor technology • system-on-a-chip multimedia processing william.h.robinson@vanderbilt.edu • Sharon Weiss • PhD, Institute of Optics, Univ. Rochester, 2005 • optical properties of nanostructures • porous silicon; photonic bandgap structures • optical characterization techniques • surface characterization methods sweiss@optics.rochester.edu

  3. Total Dose Oxide and interface traps Leakage in thin SiO2 SOI/double gate High K NBTI Experimental data Theory based on DFT calculations Outline

  4. Traditional MOS Basic Mechanisms After F. B. McLean and T. R. Oldham, HDL Report HDL-TR-2129 (1987)

  5. O H Si O O H+ H2 H Si Si Progress in physical models of interface-trap charge via DFT calculations + SiH + H+→ H2 + D+ S. N. Rashkeev et al., Phys. Rev. Lett. 87, 165506-1 to 165506-4 (2001)

  6. Threshold voltage shifts less important in modern gate oxides Doped Poly-Si Gate SiO2 Device Si After N. S. Saks et al, IEEE Trans. Nucl. Sci. 33, 1185 (1986)

  7. Ultrathin SiO2: the main issue is leakage! RILC M. Ceschia et al., IEEE Trans. Nucl. Sci. 45, 2375 (1998) J. Suñé et al., Semicond. Sci. Technol., 15, 2000.

  8. Improved performance and radiation response possible for FD SOI devices operated in double-gate mode • Front-back coupling • Volume inversion B. Jun et al., IEEE Trans. Nucl. Sci. 51, 3767-3772 (2004).

  9. Alternative Dielectrics to SiO2More defects: greater charge trapping than thermal SiO2 Alumina (EOT 8 nm) EOT 4.5 nm J. A. Felix et al., IEEE Trans. Nucl. Sci. 49, 3191 (2002) J. A. Felix et al., IEEE Trans. Nucl. Sci. 50, 1910 (2003)

  10. Temperature dependence: SiO2 & HfO2 SiO2----Ea (for Not)=0.27  0.03eV HfO2---Ea (for Not)=0.35  0.04eV ---- Ea (for Nit)=0.31  0.04eV ---Ea (for Nit)=0.22  0.03eV Why so low ?? (APL 2005) – summarized here Effects of rad (NSREC 2005) X. J. Zhou et al., Appl. Phys. Lett. 84, 4394 (2004)

  11. For hydrogen … Reactions: A → B DE : Reaction Energy Ea: Reaction Barrier Barriers ↔ Activation Energy Ea B DE A Theory: Methodology • First-principles (density-functional) calculations • Pseudopotentials, plane-wave basis, supercells L. Tsetseris, X. J. Zhou, D. M. Fleetwood, R. D. Schrimpf, and S. T. Pantelides, “Physical mechanisms of negative-bias temperature instability,” Appl. Phys. Lett. 86, 142103-1 to 142103-3 (2005).

  12. = H = Si = O Interface traps: Si dangling bond (D) Hydrogen Passivates-Depassivates: Si-H + H ↔ D + H2 [Or: Si-H + H+↔ D+ + H2 *] D + H ↔ Si-H * S. N. Rashkeev, D. M. Fleetwood, R. D. Schrimpf, and S. T. Pantelides, “Defect Generation by Hydrogen at the Si-SiO2 Interface,” Phys. Rev. Lett. 87, 165506-1 to 165506-4 (2001).

  13. No holes B A B With holes 1.9 eV 1.6 eV A Simple Si-H Dissociation

  14. = H = Si = O REACTION (depassivation) DE ~ 0.5 eV Ea ~ 1 eV

  15. = H = Si = O Si SiO2 MIGRATION H+ in SiO2: fD ~ 0.8 eV H2 in SiO2: fD ~ 0.45 eV Si-H + H+↔ D + H2: H2 diffusion controlling factor

  16. REACTION-DIFFUSION MODEL (Jeppson & Svensson (1977), Ogawa & Shiono (1995)) Defect (ND) + A  Interface trap (Nit) + B Reaction in quasi-equilibrium: Nit(t) CX(t) ~ G/S ND Asymptotic Limit: Nit(t) ~ (DX t)1/4 (G/S ND)1/2

  17. NBTI ACTIVATION ENERGY Ea = ½ DE + ¼ fD DE = 0.5 eV, fD = 0.45 eV So, EaNBTI ~ 0.35 eV L. Tsetseris, X. J. Zhou, D. M. Fleetwood, R. D. Schrimpf, and S. T. Pantelides, “Physical mechanisms of negative-bias temperature instability,” Appl. Phys. Lett. 86, 142103-1 to 142103-3 (2005).

  18. B No holes B DE ≈ 0.6eV Ea≈ 1.2eV A A With holes B DE ≈ 0.2eV Ea≈ 0.35eV A SOURCE (of Hydrogen) for pMOS Dissociation of P-H complexes Confirm experiments (Herring & Johnson, 1992, and others)

  19. = H = Si = O Si SiO2 OXIDE TRAPPED CHARGE H+ in SiO2: fD ~ 0.8 eV H+ from Si to SiO2: DE~ 0.2 eV Ea = ½ DE + ¼ fD Ea ~ 0.3 eV

  20. Future Work • Radiation + NBTI • High-K dielectrics: experiment and theory • Metal gates • Strained substrates & SOI • Aging and temperature response • Much to do!!

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