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UICPhysicsAPS March Meeting 2008
Stabilizing Cubic HfO2 Doped Y2O3 using TEMStabilizing Cubic HfO2 Doped Y2O3 using TEM
Peter Gu, W. Walkosz, R.F. KlieNanoscale Physics Group
University of Illinois at Chicago
•http://www.tedpella.com/grids_html/si-window.jpg
UICPhysicsAPS March Meeting 2008
Moore’s LawMoore’s Law• 1965 by Intel
cofounder, Gordon Moore
• Exponential increase in transistor density
• Limit to trend• SiO2 (2 nm –
breakdown)• Criteria
• Insulating• Thermally Stable• Chemically Stable• High κ materials
•http://www.developers.net/storyImages/062404/inteldemystifying1.jpg
UICPhysicsAPS March Meeting 2008
XRD-dataXRD-data
Image from professor Takoudis’ group
GI-XRD 2.5% Y in HfO2annealed at different temperatures
0
100
200
300
400
500
600
700
800
900
1000
10 20 30 40 50 60 70
2 Theta
Inte
nsity
tetra.-HfO2
cubic-HfO2
monclinic-HfO2
925 C
800 C
600 C
(111)(200) (220) (311)
(101)
(002) (110) (112) (200) (103) (211)
(222)
UICPhysicsAPS March Meeting 2008
XRD-dataXRD-data
GI-XRD 20% Y in HfO2annealed at different temperatures
0
100
200
300
400
500
600
700
800
900
1000
10 20 30 40 50 60 70
2 Theta
Inte
nsity
tetra.-HfO2
cubic-HfO2
monclinic-HfO2
925 C
800 C
600 C
(111) (200) (220) (311) (222)
(101) (002)(110)
(112)(200) (103)(211)
Image from professor Takoudis’ group
UICPhysicsAPS March Meeting 2008
κ vs Yttrium Concentrationκ vs Yttrium Concentration
•Image from professor Takoudis’ group
• % Yttrium concentration measured via XPS
• κ measured via CV• Local Max ~ 20%
Yttrium
UICPhysicsAPS March Meeting 2008
Research PlanResearch Plan• Samples:
• Annealed 2.5% Y2O3 on HfO2• Unannealed 2.5% Y2O3 on HfO2 • Annealed 20% Y2O3 on HfO2
• TEM 3010• Diffraction mode
• Check crystal structure – polymorphs (cubic vs. tetragonal vs. monoclinic) • Check for homogeneity• SiO2 layer thickness• Grain Size
•Journal of Applied Physics 103, 084103 (2008)
UICPhysicsAPS March Meeting 2008
2.5% Y2O3 Un-Annealed2.5% Y2O3 Un-Annealed
Image at 150,000 Magnification
2.5% Yttrium Oxide / Hafnium Oxide Un-Annealed Sample
Silicon Substrate
Silicon Dioxide
Hafnia / Yttria film -layers
Epoxy
UICPhysicsAPS March Meeting 2008
2.5% Y2O3 Un-Annealed - Diffraction2.5% Y2O3 Un-Annealed - Diffraction
Image at 50 cm Camera Length
2.5% Yttrium Oxide / Hafnium Oxide Un-Annealed Sample
•Superimposed Patterns•Spot Pattern – Silicon Substrate (001)
•Cubic structure•Fuzzy circular – Film
•Amorphous
UICPhysicsAPS March Meeting 2008
2.5% Y2O3 Annealed2.5% Y2O3 Annealed
Image at 600,000 Magnification
2.5% Yttrium Oxide / Hafnium Oxide Annealed Sample
Silicon Substrate
Silicon Dioxide
Hafnia / Yttria film
Epoxy
UICPhysicsAPS March Meeting 2008
2.5% Y2O3 Annealed - Diffraction2.5% Y2O3 Annealed - Diffraction
Image at 50 cm Camera Length
2.5% Yttrium Oxide / Hafnium Oxide Annealed Sample
•Superimposed Patterns•Spot Pattern – Silicon Substrate (001)
•Cubic structure•Concentric Circular pattern– Film
•Cubic Hafnium Oxide
UICPhysicsAPS March Meeting 2008
20% Y2O3 Annealed20% Y2O3 Annealed
Image at 500,000 Magnification
20% Yttrium Oxide / Hafnium Oxide Annealed Sample
Epoxy
Hafnia / Yttria film
Silicon Dioxide
Silicon Substrate
UICPhysicsAPS March Meeting 2008
20% Y2O3 Annealed - Diffraction20% Y2O3 Annealed - Diffraction
Image at 50 cm Camera Length
20% Yttrium Oxide / Hafnium Oxide Annealed Sample
•Superimposed Patterns•Spot Pattern – Silicon Substrate (001)
•Cubic structure•Concentric Circular pattern– Film
•Cubic Hafnium Oxide
(0,0,0)Si
(2,0,0)Si
(-2,0,0)Si
(4,0,0)Si
(-4,0,0)Si
(1,1,-1)Si
(-1,1,-1)Si
(-1,-1,1)Si
(1,-1,1)Si
•(3,-1,1)Si
(-3,-1,1)Si
(3,1,-1)Si
(-3,1,-1)Si
(0,2,-2)Si
(0,-2,2)Si
(2,-2,2)Si
(-2,-2,2)Si
(-2,2,-2)Si
(-1,3,-3)Si
(1,-3,3)Si
(-1,-3,3)Si(0,-4,4)Si
(-3,-3,3)Si
(-4,-2,2)Si
(-5,-1,1)Si
(1,1,1)HfO2
(2,0,0)HfO2
(1,1,3)HfO2
UICPhysicsAPS March Meeting 2008
SiO2 Layer AnalysisSiO2 Layer Analysis
• Expected for 30 nm film thickness: • ~3 nm for 20% Y2O3• ~12 nm for 2.5% Y2O3
• Silicon Dioxide Layer Analysis2.5% Y2O3
unannealed(nm)2.5% Y2O3
annealed(nm)20% Y2O3
annealed(nm)average 2.289 3.072 3.175
max 3.845 5.774 4.2min 0.939 1.303 0.765
stdev 0.875 1.332 0.759
2 2
2
+ constant
SiO layer thickness film layer thickness SiO layer thicknessfilm layer thicknessfilm dielectric SiO dielectric constant total dielectric constant
+=
UICPhysicsAPS March Meeting 2008
Grain Size AnalysisGrain Size AnalysisGrain Size Measurements - 20%
annealed sampleGrain Size Measurements - 2.5%
annealed sampleAlong Grain
(nm)Perpendicular to Grain
(nm)Along Grain
(nm)Perpendicular to Grain
(nm)Average
(nm) 4.339 5.510 5.705 5.069Standard
Dev. 0.833 1.217 1.007 1.507
UICPhysicsAPS March Meeting 2008
Summary / ConclusionSummary / Conclusion
• 20% Annealed Sample has a larger dielectric constant than 2.5% Annealed Sample
• No Difference in Structural makeup of interfacial film (Both cubic polymorph)
• No Difference in Silicon Dioxide Layer Thickness
• No Difference in Grain Size• Difference in film shape or thickness?• Difference in Oxygen Concentration?
UICPhysicsAPS March Meeting 2008
AcknowledgementsAcknowledgements
• National Science Foundation• Grant NSF EEC 0755115• NSF CMS 0829903
• Department of Defense• Professor R.F. Klie• Professor C. Takoudis• Professor G. Jursich• PhD G. Yang• PhD Q. Tao• Weronica Walkosz• Ke-Bin Low• K.C. Kragh
UICPhysicsAPS March Meeting 2008
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the use of organic self-assembled monolayers, Appl. Phys. Lett. 71, 891 (1997), DOI:10.1063/1.119679• 12. J.M. Zuo and J.C. Mabon, Web-based Electron Microscopy Application Software: Web-EMAPS,
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