Total-Dose Response and Negative-Bias Temperature Instability (NBTI)
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MURI kick-off: 5/10/05 Total-Dose Response and Negative-Bias Temperature Instability (NBTI) D. M. Fleetwood Professor and Chair, EECS Dept. Vanderbilt University Nashville, TN 37235 USA [email protected] (615) 322-2498 A collaboration between VU EECS and Physics
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D. M. Fleetwood Professor and Chair, EECS Dept. Vanderbilt University Nashville, TN 37235 USA [email protected] (615) 322-2498 A collaboration between VU EECS and Physics. Total-Dose Response and Negative-Bias Temperature Instability (NBTI). - PowerPoint PPT Presentation
Transcript of Total-Dose Response and Negative-Bias Temperature Instability (NBTI)
MURI kick-off: 5/10/05
Total-Dose Response and Negative-Bias Temperature Instability (NBTI)
D. M. Fleetwood
Professor and Chair, EECS Dept.
Vanderbilt University
Nashville, TN 37235 USA
(615) 322-2498
A collaboration between VU EECS and Physics
MURI kick-off: 5/10/05
Assistant Professors Recently Hired in EE
William RobinsonPhD, Georgia Tech, 2003
• computer architecture/VLSI design• mixed-signal integration for focal plane
processing• integrated sensor technology
• system-on-a-chip multimedia processing [email protected]
Sharon WeissPhD, Institute of Optics, Univ. Rochester, 2005
• optical properties of nanostructures• porous silicon; photonic bandgap structures
• optical characterization techniques• surface characterization methods
MURI kick-off: 5/10/05
Outline
• Total Dose– Oxide and interface traps
– Leakage in thin SiO2
– SOI/double gate– High K
• NBTI– Experimental data– Theory based on DFT calculations
MURI kick-off: 5/10/05
Traditional MOS Basic Mechanisms
After F. B. McLean and T. R. Oldham, HDL Report HDL-TR-2129 (1987)
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Progress in physical models of interface-trap charge via DFT calculations
H+
H
O
Si
O
SiH H2
Si
O+
SiH + H+ → H2 + D+
S. N. Rashkeev et al., Phys. Rev. Lett. 87, 165506-1 to 165506-4 (2001)
MURI kick-off: 5/10/05
Threshold voltage shifts less important in modern gate oxides
Doped Poly-Si Gate
Device Si
SiO2
After N. S. Saks et al, IEEE Trans. Nucl. Sci. 33, 1185 (1986)
MURI kick-off: 5/10/05
Ultrathin SiO2: the main issue is leakage!
J. Suñé et al., Semicond. Sci. Technol., 15, 2000.
RILC
M. Ceschia et al., IEEE Trans. Nucl. Sci. 45, 2375 (1998)
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Improved performance and radiation response possible for FD SOI devices operated in double-gate mode
B. Jun et al., IEEE Trans. Nucl. Sci. 51, 3767-3772 (2004).
•Front-back coupling•Volume inversion
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Alternative Dielectrics to SiO2
More defects: greater charge trapping than thermal SiO2
J. A. Felix et al., IEEE Trans. Nucl. Sci. 49, 3191 (2002)
Alumina (EOT 8 nm)
EOT 4.5 nm
J. A. Felix et al., IEEE Trans. Nucl. Sci. 50, 1910 (2003)
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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
X. J. Zhou et al., Appl. Phys. Lett. 84, 4394 (2004)
Why so low ?? (APL 2005) – summarized hereEffects of rad (NSREC 2005)
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Theory: MethodologyFirst-principles (density-functional) calculations
Pseudopotentials, plane-wave basis, supercells
A
BEa
E
For hydrogen …
Reactions: A → B
E : Reaction Energy
Ea: Reaction Barrier
Barriers ↔ Activation Energy
L. Tsetseris, X. J. Zhou, D. M. Fleetwood, R. D. Schrimpf, and S. T. Pantelides, “Physical mechanisms of negative-bias temperature instability,” Ap
pl. Phys. Lett. 86, 142103-1 to 142103-3 (2005).
MURI kick-off: 5/10/05
Interface traps: Si dangling bond (D)
Hydrogen
Passivates-Depassivates:
Si-H + H ↔ D + H2
[Or: Si-H + H+ ↔ D+ + H2 *]
D + H ↔ Si-H
= H
= Si
= O
* 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).
MURI kick-off: 5/10/05
Simple Si-H Dissociation
1.9 eV
No holes
With holes
1.6 eV
A
BA
B
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REACTION (depassivation)
= H
= Si
= O
E ~ 0.5 eV Ea ~ 1 eV
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MIGRATION
H+ in SiO2: D ~ 0.8 eV
H2 in SiO2: D ~ 0.45 eV
Si-H + H+ ↔ D + H2:
H2 diffusion controlling factor
Si SiO2
= H
= Si
= O
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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
MURI kick-off: 5/10/05
NBTI ACTIVATION ENERGY
So, EaNBTI ~ 0.35 eV
Ea = ½ E + ¼ D
E = 0.5 eV, D = 0.45 eV
L. Tsetseris, X. J. Zhou, D. M. Fleetwood, R. D. Schrimpf, and S. T. Pantelides, “Physical mechanisms of negative-bias temperature instability,” Ap
pl. Phys. Lett. 86, 142103-1 to 142103-3 (2005).
MURI kick-off: 5/10/05
SOURCE (of Hydrogen) for pMOS
Dissociation of P-H complexes
A
B
E ≈ 0.2 eV
A
B
Ea ≈ 0.35 eV
With holes
E ≈ 0.6 eV
A
B
Ea ≈ 1.2 eV
No holes
Confirm experiments (Herring & Johnson, 1992, and others)
MURI kick-off: 5/10/05
OXIDE TRAPPED CHARGE
H+ in SiO2: D ~ 0.8 eV
H+ from Si to SiO2: ~ 0.2 eV Si SiO2
= H
= Si
= O
Ea = ½ E + ¼ D
Ea ~ 0.3 eV
MURI kick-off: 5/10/05
Future Work
• Radiation + NBTI
• High-K dielectrics: experiment and theory
• Metal gates
• Strained substrates & SOI
• Aging and temperature response
Much to do!!
