Introduction• Dual high-k technology has been proposed, in which different
high-k materials are used for p-channel and n-channel FETs.

Electronic structure characterization of La incorporated
Hf-based high-k gate dielectrics by NEXAFS• However, the electronic structure, especially for thecharacteristics of the conduction-band minimum which affectingnFET performance with La-incorporated Hf-based oxides, has
not been fully understood yet.

T. Yamamoto1, 2, S. Ogawa1, M. Kunisu1, J. Tsuji1, K. Kita3, M. Saeki2,Y. Oku2, H. Arimura2, N. Kitano2, T. Hosoi2, T. Shimura2, andH. Watanabe2• Near Edge X-ray Absorption Fine Structure (NEXAFS) is a
powerful technique for investigating electronic structure.

1 Toray Research Center Inc., 3-7 Sonoyama 3-chome, Otsu, Shiga 520-8567, Japan
2 Department of Material and Life Science, Graduate School of Engineering, Osaka• In this study, we investigated electronic structure of HfLaO andHfLaSiO gate dielectrics by means of NEXAFS method.

University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
3 Department of Material Engineering, The University of Tokyo, 7-3-1 Hongo,

Bunkyo-ku, Tokyo 113-8656, Japan
Toray Research Center, Inc.

Calculation: DV-X㱍, Structure model: cubic HfO214O 2pO 2s

12840-10-505Energy (eV)

10(b)

12
Intensity (arb. units)

Intensity (arb. units)

Hf 5d
Hf 6p

total
Hf 6s(a)

15

Hf 5d

total

Type 1
Structure: HfLaO (20nm) / SiO2 (600 nm) / Si Substrate

O 2p

Composition: Hf:La=10:0, 7:3, 5:5, 3:7

10

Deposition Method: Co-Sputter

86Type 242Structure: HfLaO (1 nm) / SiO2 (1 nm) / Si Substrate

0Composition: Hf:La=7:3, 3:7051015

Energy (eV)

Deposition Method: Co-Sputter

The density of state around the conduction-band minimum is formedby hybridization between Hf 5d-state and O 2p orbital.
Toray Research Center, Inc.

Annealing Condition: 600oC in N2
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3O K-edge spectrum of thick HfLaO

O K-edge spectrum of thin HfLaO

Samples: HfLaO (20 nm) /SiO2 (600 nm) /Si Sub. (Hf:La= 10:0, 7:3, 5:5, 3:7)

Samples: HfLaO (1 nm) /SiO2 (1 nm) /Si Sub. (Hf:La= 7:3, 3:7)

5CB Edgeegt2g

6: La feature

Intensity (arb. units)

Intensity (arb. units)

CB Edge54

Hf:La=3:7

3

Hf:La=5:5
2

Hf:La=7:3
Hf:La=10:0

1

0
530

535

540

545

550

Hf:La=3:7
4

annealed

3

as-depositedannealed2

as-deposited
Hf:La=7:3

0555

525

Photon Energy (eV)

530

535

540

545

550

555

Photon Energy (eV)

These distinct changes indicate that La incorporation into
HfO2 results in changes in conduction-band structure.
Toray Research Center, Inc.

4537 eV532 eV

1525

2

Study of HfLaO electronic structure

DOS of cubic-HfO2 by DV-X㱍 calculation
16Toray Research Center, Inc.

1The structural change of Hf-based oxides by interfacial silicate
reaction also causes changes in conduction-band structure.
5Toray Research Center, Inc.

6

Study of HfLaSiO electronic structure

HfLaSiO fabrication process

Type 1La-cap processco-sputter process

Structure: HfLaSiO / Si Substrate
Composition: Hf:La=1:0, 3:1, 1:1
Deposition Method: co-sputter SPIR method
Annealing Condition: 850oC

RTO (SiO2: 1.8 nm)

RTO (SiO2: 1.8 nm)

PVD 0.7 nm Hf-La
alloy (Hf:La=3:1,2:1, 1:1)

PVD 0.5 nm HfType 2

HfSiO formation bySPIR (850oC)

Structure: HfLaSiO / Si Substrate
HfLaSiO formation
annealing (850oC)

Composition: Hf:La=5:3

PVD 0.3 nm La
HfLaSiO formation
annealing (550oC,700oC, 850oC)

Deposition Method: La-cap SPIR method
Annealing Condition: 550oC, 700oC, 850oC
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7

O K-edge spectrum of “co-sputter” HfLaSiO

O K-edge spectrum of “La-cap” HfLaSiO

Samples: Co-sputter HfLaSiO /Si Sub. (Hf:La= 1:0, 3:1, 1:1)

Samples: La-cap HfLaSiO /Si Sub. (Annealed temp. = 550oC, 700oC, 850oC)
4.0

CB Edge

3.0

Intensity (arb. units)

Intensity (arb. units)

4.0

2.0

1.0

Hf:La=1:1
Hf:La=3:1
Hf:La=1:0

0.0
530

535

540

Toray Research Center, Inc.

535

540

545

The La incorporation by SPIR annealing at 550oC again
resulted in increased absorption intensity around 532 eV.
9Mechanism of the changes in spectrum-O-Hf-O-Si-O-10• It was found that the conduction-band edge structure formed byhybridized Hf 5d state with O 2p orbital is modulated by Laincorporation.

Bonding units change• We also found that, whereas the electronic structure of thick
HfLaO films is simply determined by the La concentration, theelectronic feature of thin HfLaO and HfLaSiO films is modified
by interface silicate reaction and/or change in the local bonding
configuration driven by thermal annealing.

-O-La-O-Si-O-O-Hf-O-Hf-O-

Si-Sub.
Layer structure change• As a results, the conduction-band edge of these metal oxides
after annealing is mainly determined by HfO2-like bonding.
These findings provide a guideline for designing electric
properties of La-incorporated Hf-based high-k gate dielectrics.

LaSiO
Hf(La)SiO

Si-Sub.
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Conclusion

Si-Sub.

HfLaSiO
SiO2850oC
700oC
550oC
Ref.

1.0

Photon Energy (eV)The conduction-band edge of the HfLaSiO phasehas shifted lower photon energy.

HfLaSiO
SiO22.0530

Photon Energy (eV)HfSiO
SiO2CB Edge

3.00.0545

811

Toray Research Center, Inc.

12