stabilizing cubic hfo 22 doped ydoped y oo using...

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


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


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)


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


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


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)


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


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


2.5% Y2O3 Annealed2.5% Y2O3 Annealed


2.5% Yttrium Oxide / Hafnium Oxide Annealed Sample

Silicon Substrate

Silicon Dioxide

Hafnia / Yttria film

Epoxy


2.5% Y2O3 Annealed - Diffraction2.5% Y2O3 Annealed - Diffraction


2.5% Yttrium Oxide / Hafnium Oxide Annealed Sample


•Cubic structure•Concentric Circular pattern– Film

•Cubic Hafnium Oxide


20% Y2O3 Annealed20% Y2O3 Annealed


20% Yttrium Oxide / Hafnium Oxide Annealed Sample

Epoxy

Hafnia / Yttria film

Silicon Dioxide

Silicon Substrate


20% Y2O3 Annealed - Diffraction20% Y2O3 Annealed - Diffraction


20% Yttrium Oxide / Hafnium Oxide Annealed Sample


•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


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

+=


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


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?


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


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