X ray photoelectron spectroscopy (xps) iit kgp

Semiconductor device characterization using

XPS and UPSCentre of Excellence in Nanoelectronics

Indian Institute of Technology, Bombay

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Introduction Data Processing List according to each Analysis Ultraviolet Photoelectron Spectroscopy XPS Applications in Semiconductor Devices

• MIS Contacts• MOSCAP structures

• MoS2 and MoS2-TiO2 structures

OUTLINE

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Introduction

X-ray Photoelectron Spectroscopy (XPS) is a surface-sensitive spectroscopic technique that is used to measure : elemental composition empirical formula chemical state and electronic state of the elements that

exist within a material

The Versa Probe is PHI’s second generation XPS based Multi-technique system. The unique strength of the system is its ability to image and analyze features as small as 10μm in diameter.

Model: PHI 5000 Versa Probe-II

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Data Processing List according to each Analysis

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OUTLINE

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Ultraviolet Photoelectron Spectroscopy (UPS)

If ultraviolet photons (rather than X-rays) are used, the technique is called Ultraviolet Photoelectron Spectroscopy (UPS).

Other than the photon source, instrumentation is identical to that of XPS.

The optional Ultraviolet photon source provides low energy photons for Valence Band and Fermi edge measurements.

Helium gas can be used to generate single and doubly ionized UV photon sources.

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• Al2O3 thin film• Nickel Silicide

OUTLINE

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XPS Applications in Semiconductor Devices

XPS was used for the study of Metal Insulator Semiconductor (MIS) contacts fabricated on low-doped bulk n-Ge substrates

n-Ge

YbTiO2

Au

• Depth Profile of the structure gives a plot of Atomic Concentration vs. Sputter Time• Presence of TiO2 is detected from the plot

TiO2

Ti2p scan after 35, 37, 39 min sputter times

After 35 min sputter (energy interval on x axis is 0.25 eV)



• Similar spectra seen at 3 different points in the depth profile• Spectral deconvolution shown on next slide

4504554604654704753000

3200

3400

3600

3800

4000

4200

Spectrum Ti(II)2p3/2 (454.41 eV)

Ti(IV) 2p3/2 Ti(II)2p1/2

Ti(III) 2p 1/2 Ti(IV) 2p1/2 (463.13)

Ti(III) 2p3/2 (458.27 eV)

Energy (eV)

Counts

• Different oxidation states of Ti • Presence of Ti(II), Ti(III) and Ti(IV) from this it is

concluded that it has oxygen deficient phase• The intensity of O1s peak at 532eV increases

suggests oxygen vacancies thus, oxygen deficient TiO2 has been formed at the interface.

5285305325345365380

0.2

0.4

0.6

0.8

1

1.2

Binding Energy (eV)

O1s bare TiO2

5285295305315325335345355365375380

0.2

0.4

0.6

0.8

1

1.2

Binding Energy (eV)

O1s interface TiO2

4504524544564584604624644664684700

0.2

0.4

0.6

0.8

1

1.2

Binding Energy (eV)

Ti2p bare TiO2

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Introduction Basic Theory of XPS XPS as a Surface Analysis Technique Data Processing List according to each Analysis Ultraviolet Photoelectron Spectroscopy XPS Applications in Semiconductor Devices



OUTLINE

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Inte

nsi

ty (a.u

.) O1s Al2O

3

526 528 530 532 534 536

O1s HfO2

Binding Energy (eV)

Inte

nsity (

a.u

.)

Inte

nsi

ty (a.u

.)

O1s HfAlO(Al=11.6%)

0

5

10

15

20

25

30

35

HfAlO(Al:Hf=1:2)

HfAlO(Al:Hf=2:1)

HfAlO(Al:Hf=3:3)

% A

l

HfO2

Recipe Used

529.8

530.0

530.2

530.4

530.6

530.8

531.0

HfO2

HfAlO(Al:Hf=1:2)

HfAlO(Al:Hf=3:3)

O1s

pea

k po

sitio

n(eV

) Al2O

3

HfAlO(Al:Hf=2:1)

Figure shows O1s peak position as function of Al%

Al% determination using XPS

XPS Applications in Semiconductor Devices (contd.)

XPS was used for the study of MOSCAP structures fabricated on Ge substrates

HfO2/HfAlO/Al2O3

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Shift in Hf4f peak after PDA of HfO2/GeO2/Ge indicating

formation of GeOHf

Effect of Post Deposition Anneal (PDA) on HfO2

0 5 10 15 200.0

0.2

0.4

0.6

0.8

1.0

Inte

nsity

(A.U

.)

Time (min)

Hf4f without PDA Hf4f with PDA O1s without PDA O1s with PDA Ge3d without PDA Ge3d with PDA

HfO2 Ge

substrate

13 14 15 16 17 18 19 20 21 22 23

0.31eVInte

nsi

ty (a.

u.)

Binding Energy (eV)

Hf4f withPDA Hf4f without PDA

Depth profile of HfO2/GeO2/Ge indicating GeO2 growth and formation of GeOHf,


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Introduction Basic Theory of XPS XPS as a Surface Analysis Technique Data Processing List according to each Analysis Ultraviolet Photoelectron Spectroscopy XPS Applications in Semiconductor Devices



OUTLINE

Mo-3d and S-2p core level shifts to higher binding energy from MoS2 to TiO2–MoS2 confirms charge transfer at the interface.


XPS was used to study MoS2 and TiO2-MoS2 structures

10 5 0 -50

2M

4M

6M

8M

Coun

ts (a

.u.)

Binding Energy(eV)

MoS2

TiO2-MoS

2

12.0 11.6 11.2 10.8

11.9

MoS2

TiO2-MoS

2

11.6

He I-UPS measurements of TiO2–MoS2 and MoS2 show a reduction in work-function (0.3 eV) using TiO2 as an interlayer


UPS was used to study MoS2 and TiO2-MoS2 structures

-2 0 2 4 6 8 10121416182022

0

20

40

60

80

100

Ato

mic

concentr

ation (%

)

Sputter time (min)

Al2p si2p c1s N1s O1s

-2 0 2 4 6 8 10 12 14 16

0

20

40

60

80

100

Ato

mic

perc

enta

ge (%

)

Sputter time (min)

Al2p si2p c1s N1s O1s

Figure 1(a) and 1(b) shows atomic concentration of spray coated Al2O3

film after furnace annealing of 400 o C and 850o C respectiely in O2 ambient

Depth profile of Al2O3 thin film by XPS

XPS Analysis of Al2O3 thin film

Chemical and interface properties of Al2O3 film is studied with the help of X-

ray photoelectron spectroscopy (XPS) depth profile analysis and the results are shown in the figure .

XPS analysis shows presence of SiOx interfacial layer after furnace annealing and the thickness of SiOx interfacial layer increases as the annealing temperature increases. Si and O are interdiffused which indicates presences of SiOx. The Length of inter diffused region is more for high temp anneal.

The carbon and nitrogen content is almost zero throughout the sample. The carbon signal at the surface is attributed to unavoidable inclusion of

carbon from XPS instrument.

The Atomic percentage of chemical components present in the film indicates that the Al2O3 film is almost stoichiometric in nature

NiSi on Si

• NiSi is formed by deposition of Ni on Si and by thermal annealing at the temperature of 500 0C, for 60 sec.

• The formation of NiSi can be realised by the metal diffusion through semiconductor at that elevated temperature

Ni

Si

Nickel silicide

Si

The depth profile of the nickel silicide(NiSi) is shown in the figure.

The sputter rate was used to be 2.5 nm/ cycle

The inset shows the Ni/Si ratio of the thin film. Which indicates that Ni/Si ~ 1 till 27 nm. This observation indicates that the NiSi film is uniform till 27 nm.

The thickness was confirmed by cross-sectional SEM.

Ref:S. Roy, K. Midya, S. P. Duttagupta, and D. Ramakrishnan; Nano-scale NiSi and n-type silicon based Schottky Barrier diode as a near infra-red detector for room temperature operation; J. Appl. Phys. 116, 124507 (2014).

Depth Profile of NiSi/n-Si

Si and O are interdiffused which indicates presences of SiOx. the Length of inter diffused region is more for high temp anneal.

Reduction of Langmuir-Blodgett Graphene Oxide monolayer sheets

• Thickness of as-transferred GO monolayer sheets obtained by AFM height profile was found to be ~1 nm

In the de-convoluted C-1s core level spectra

C-1s core level

Peaks at 284.5 eV and 285.4 eV are, respectively, assigned to sp2-C (graphitic) and the damaged alternant hydrocarbon structure/sp3-C, while the component at 289.7 eV is attributed to the π–π* shake up satellite of the 284.5 eV peak.

The peaks at 286.3 eV, 287.2 eV, and 288.4 eV are, respectively, attributed to oxygen functionalities, namely, C–O, C=O, and COOH

Gulbagh Singh, V. D. Botcha, D. S. Sutar, S.S. Talwar, R.S. Srinivasa and S.S. Major, “Highly reduced graphene oxide monolayer sheets” (Under Review Under Review in Carbon).

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Conclusion

Survey Spectra of XPS helps us to detect the element present on the surface of a material The composition of the detected element can be calculated from the Narrow Spectra Sputtering is used to analyze the composition of Depth Profiles Angle Resolved XPS enables us to analyze the depth profiles at various angles Scanning X-ray Imaging (SXI) for secondary electron, images all conducting and insulating samples UPS can be used for work-function, valence band and Fermi edge measurements

Si and O are interdiffused which indicates presences of SiOx. the Length of inter diffused region is more for high temp anneal.

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Thank You !

Engineering

X ray photoelectron spectroscopy (xps) iit kgp