June 13 2006 MURI Review1 Total Dose Response of HfO 2 /Dy 2 O 3 on Ge and Hf 0.6 Si 0.2 ON 0.2 on Si…

June 13 2006 MURI Review 1

Total Dose Response of HfO2/Dy2O3 on Ge and Hf0.6Si0.2

ON0.2 on Si MOS Capacitors

D. K. Chen, R. D. Schrimpf, D. M. Fleetwood, K. F. Galloway, A. Canals Department of Electrical Engineering and Computer Science,

S. T. Pantelides, Department of Physics Vanderbilt University, Nashville, TN

A. Dimoulas, A. Sotiropoulos, and Y. Panayiotatos

Institute of Materials Science, NCSR DEMOKRITOS

Athens, Greece

G. Lucovsky, S. LeeDept of Physics and Material Science,

North Carolina State University Bongim Jun

Dept of Electrical Engineering,Georgia Institute of Technology


• Limitations of ultrathin SiO2 gate dielectric microelectronic devices: high gate leakage current, reduced current drive, and reliability concerns

• Leakage current unmanageable for tox less than ~ 1.2 nm

• Germanium MOS devices

• Higher electron and hole mobility leads to higher drive current

• Unstable native oxide

• Dysprosium oxide on Ge

• HfO2 (K~25) and HfxSiyONz (K~15)

Motivation

M.L. Green, JAP 2001 (90) 5

1.2 nm

1.9 nm


• HfO2/Dy2O3

• No measurable change in C-V characteristics after TID

• Large hysteresis and leakage current

• Hf0.6Si0.2ON0.2

• Significant electron trapping after TID

• Conclusions and future plans

Outline


10nm or 5nm HfO2

1nm Dy2O3

Pt gate

n-type Ge

10nm or 5nm HfO2

1nm Dy2O3

Pt gate

n-type Ge

E0

5.65 eV

4.0 eV2.5 eV

1.5 eV

2.74 eV

0.8 eV

Ec

Ev

EF

HfO2 Dy2O3Pt Ge

EFM

E0

5.65 eV

4.0 eV2.5 eV

1.5 eV

2.74 eV

0.8 eV

Ec

Ev

EF

HfO2 Dy2O3Pt Ge

EFM

HfO2/Dy2O3 on Ge

Eg ~ 5.7 eV (HfO2)


• Hysteresis ~ 800 mV for 10 nm HfO2, ~ 150 mV for 5 nm HfO2.

• No measurable change in C-V characteristics after total dose irradiation to 30 Mrad(SiO2) for 10 nm HfO2 and 10 Mrad(SiO2) for 5 nm HfO2

• Equal electron and hole trapping in HfO2 and/or large leakage currents neutralize radiation-induced oxide traps

C-V Characteristics

EOT= 1.9 nm EOT= 1.1 nm


• Leakage current density @ 1 MV/cm: 30 nA/cm2 (EOT=1.9nm) and 35 nA/cm2 (EOT=1.1nm)

• Large leakage current reflects the interface quality of dysprosium oxide/germanium

Gate Current Densities

EOT= 1.1 nmEOT= 1.9 nm


• HfO2/Dy2O3

• No measurable change in C-V characteristics after TID

• Large hysteresis and leakage current

• Hf0.6Si0.2ON0.2

• Significant electron trapping after TID

• Conclusions

• Future plan

Outline


Hf0.6Si0.2ON0.2 on Si

Hf0.6Si0.2ON0.215 nm(EOT = 4 nm)

Al gate

n-type Si

Hf0.6Si0.2ON0.215 nm(EOT = 4 nm)

Al gate

n-type Si

2.4 eV

3.7 eV

7.2 eV

HfxSiyONz Si


C-V Characteristics

• Hysteresis ~ 15 mV

• Jg ~ 2 nA/cm2 @ VG = 0.4 V


Charge trapping in Hf0.6Si0.2ON0.2 on Si

• Correlation between crystallization and ∆VTH

• Trap density increases with crystallization

• Crystallization increases with increasing thickness

Dit ~ 2 x 1011 cm-2 eV-1 pre-irradiation ∆NOT = 6.27 x 1012 cm2 after 500 krad

Predominantly electron traps

G. Pant, APL 2006 (88) 032901


Plan for future experiments

• Obtain new HfO2/Dy2O3 films of various thicknesses – check hysteresis, leakage, rad response

• Determine the structure and composition of the Hf0.6Si

0.2ON0.2 films – irradiate under negative and zero bias to obtain additional trapping information

• Perform Bias Temperature Instability (BTI) tests to further investigate properties of Hf0.6Si0.2ON0.2 films


• HfO2/Dy2O3 on Ge

• Gate leakage current and/or equal electron hole charge trapping cause neutralization of radiation-induced oxide trap charges

• High border trap densities reflect the physical nature of interface of HfO2/Dy2O3 and Ge

• Future work will concentrate on films with low leakage and hysteresis

• Hf0.6Si0.2ON0.2 on Si

• Low hysteresis

• Significant electron trapping due to film composition

Conclusions

June 13 2006 MURI Review1 Total Dose Response of HfO 2 /Dy 2 O 3 on Ge and Hf 0.6 Si 0.2 ON 0.2 on Si…

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