1. THE NATIONAL INSTITUTE OF ENGINEERING
Department OF MECHANICAL ENGINEERING
CENTRE FOR NANO-TECHNOLOGY
MYSURU, KARNATAKA, india
PROJECT REPORT ON Source/Drain Schottky Barrier Height(SBH) reduction by Metal-Insulator-Semiconductor(M-I-S) structure using TiO2 and HfO2 ultrathin dielectric insertion and barrier inhomogenity studies via Gaussian distribution model for Field Effect Transistor application PRESENTED BY INTERNAL GUIDE EXTERNAL GUIDE HARISHA C P Dr. SIDDHARTH JOSHI Dr. MING-HAN LIAO 4NI17INT ASSOCIATE PROFESSOR PROFESSOR IV SEMESTER, M.TECH CENTER FOR NANOTECHNOLOGY DEPT. OF MECHANICAL ENGG. NIE, MYSURU, INDIA NIE, MYSURU, INDIA NTU, TAIWAN (ROC)

2. Contents INTRODUCTION LITERATURE SURVEY OBJECTIVE AND METHODOLOGY
ATOMIC LAYER DEPOSITION AND PRECURSORS
THEORY BEHIND M-S CONTACTS
THEORETICAL AND EXPERIEMNTAL DETAILS
ELECTRICAL PROPERTIES
SHOTTKY BARRIER HEIGHT EXTRACTION MODELS
TEMPERATURE DEPENDANT I-V
EXPERIMENTAL ANALYSIS
POLARIZATION STUDIES ON BILAYER SAMPLES
FUTURE WORK
CONCLUSION
REFERENCES
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

3. Introduction
Fermi Level Pinning (FLP) at Metal-Semiconductor is a major problem which results in high Schottky barrier for electrons.
FLP origin is attributed to the Metal Induced Gap States (MIGS) or bond polarization in addition to the physical non idealities of the interface such as dangling bonds.
This Schottky barrier can be modulated by inserting a ultrathin dielectric between metal and semiconductor.
This dielectric layer between metal and semiconductor helps to depin the Fermi Level.
The present work is to experimentally demonstrate how an intermediate TiO2 and HfO2 affects the carrier transport mechanism and SBH.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

4. Introduction ECB ϕb EFM EVB EG (b) P-Type Semiconductor
(a) N-Type Semiconductor ϕb
EFM EG
ECB
EVB
Figure 1: Band diagrams for (a) n-type and (b) p-type metal-semiconductor junction at zero bias (equilibrium).
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

5. Introduction ϕb EFM (b) M-I-S Contact with high-K dielectric
(a) Traditional M-S Contact ϕb
EFM
Large FLP
MIGS
Polarization dipoles
Metal
Semiconductor
Less FLP
High-K dielectric
Thermionic barrier
Tunnel barrier
MIGS reduced
Figure 2: (a) The origin of FLP in the M-S junction (b) M-I-S contact system characterized by Fermi level depinning and lower Φb.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

6. Fig 3: Contact resistance Vs insulator thickness
Introduction
Fig 3: Contact resistance Vs insulator thickness
Hu, Saraswat, and Wong Appl. Phys. Lett. 99, (2011)
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

7. Literature Survey
1. The influence of Fermi level pinning/depinning on the Schottky barrier height and contact resistance in Ge/CoFeB and Ge/MgO/CoFeB structures. Lee et al. Appl. Phys. Lett. 96, (2010) 2. Metal/III-V effective barrier height tuning using atomic layer deposition of high-κ/high-κ bilayer interfaces. Hu, Saraswat, and Wong Appl. Phys. Lett. 99, (2011) 3. Mechanism of Schottky barrier height modulation by thin dielectric insertion on n-type germanium. B.-Y. Tsui and M.-H. Kao Appl. Phys. Lett. 103, (2013) 4. Alleviation of Fermi-level pinning effect on metal/germanium interface by insertion of an ultrathin aluminum oxide. Zhou et al. Appl. Phys. Lett. 93, (2008) 5. The comprehensive study and the reduction of contact resistivity on the n-InGaAs M-I-S contact system with different inserted insulators. M.-H.Liao and C.Lien AIP Advances5,057117(2015) 6. Fermi level depinning and contact resistivity reduction using a reduced titania interlayer in n-silicon metal-insulator-semiconductor ohmic contacts. Agrawal et al. Appl. Phys. Lett. 104, (2014)
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

8. Literature Survey
7. Experimental demonstration on the ultra-low source/drain resistance by metal-insulator-semiconductor contact structure in In0.53Ga0.47As field effect transistors. M.-H. Liao and P.-K. Chen AIP Advances 3, (2013) 8. Experimental demonstration for the implant-free In0.53Ga0.47As quantum well metal-insulator-semiconductor field-effect transistors with ultra-low source/drain resistance. M.-H. Liao and L. C. Chang Appl. Phys. Lett. 103, (2013) 9. Contact resistivities of metal-insulator-semiconductor contacts and metalsemiconductor contacts. Yu et al. Appl. Phys. Lett. 108, (2016) 10. Reduced Contact Resistance Between Metal and n-Ge by Insertion of ZnO with Argon Plasma Treatment. Zhang et al. Nanoscale Research Letters (2018) 11. Effective Schottky Barrier Height Lowering of Metal/n-Ge with a TiO2/ GeO2 Interlayer Stack. Gwang-Sik Kim, Sun-Woo Kim, Seung-Hwan Kim, June Park, Yujin Seo, Byung Jin Cho, Changhwan Shin, Joon Hyung Shim, and Hyun-Yong Yu; ACS Appl. Mater. Interfaces 2016, 8, 35419−35425
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

9. Literature Survey
12. Schottky barrier height reduction for metal/n-InP by inserting ultra-thin atomic layer deposited high-k dielectrics.
Zheng et al. Appl. Phys. Lett. 103, (2013)
13. Analysis of the Inhomogeneous Barrier in In/p-Si Schottky Contact and Modified Richardson Plot.
J.M. DHIMMAR, H.N. DESAI, B.P. MODI J. NANO- ELECTRON. PHYS. 8, (2016)
14. Temperature dependent electrical characterisation of Pt/HfO2/n-GaN metal-insulatorsemiconductor (MIS) Schottky diodes.
Shettyetal. AIPAdvances5,097103(2015)
15. Schottky barrier height extraction from forward current-voltage characteristics of nonideal diodes with high series resistance.
K. Ahmed and T. Chiang Appl. Phys. Lett. 102, (2013)
16. Effect of atomically controlled interfaces on Fermi-level pinning at metal/Ge interfaces.
Yamane et al. Appl. Phys. Lett. 96, (2010)
17. Temperature Dependency of Schottky Barrier Parameters of Ti Schottky Contacts to Si-on-Insulator.
I. Jyothi et al; Materials Transactions, Vol. 54, No. 9 (2013) pp to 1660 ©2013 The Japan Institute of Metals and Materials
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

10. Literature Survey
18. Mean Barrier Height and Richardson Constant for Pd/ZnO Thin Film-Based Schottky Diodes Grown on n-Si Substrates by Thermal Evaporation Method.
Divya Somvanshi and Satyabrata Jit; IEEE ELECTRON DEVICE LETTERS, VOL. 34, NO. 10, OCTOBER 2013
19. Schottky Barrier Height Engineering for Electrical Contacts of Multilayered MoS2 Transistors with Reduction of Metal-Induced Gap States.
Gwang-Sik Kim, Seung-Hwan Kim, June Park, Kyu Hyun Han, Jiyoung Kim, and Hyun-Yong Yu; ACS Nano 2018, 12, 6292−6300
20. The Richardson constant and barrier inhomogeneity at Au/Si3N4/n-Si (MIS) Schottky diodes.
A Tataro˘glu and F Z P¨ur; Phys. Scr. 88 (2013)
21. A text book on “Semiconductor Physical Electronics” by Sheng S. Li
22. A text book on “Physics of Semiconductor Devices” by S. M. Sze and Kwok K. Ng
23. A text book on “Semiconductor Physics and Devices” by Donald A. Neamen
24. A text book on “Semiconductor device fundamentals” by Robert F. Pierret
25. A text book on “Semiconductor Devices: Theory and Application” by James M. Fiore
26. A text book on “Understanding Semiconductor Devices” by Sima Dimitrijev
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

11. Objective and Methodology
M-I-S Contact Structure
Semiconductor
Ultrathin Dielectric
Thin Metal
Tunneling
Ohmic Contact
Figure 4: Schematic diagram of M-I-S diode and tunneling through insulator
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

12. Objective and Methodology
SBH reduction mechanisms by thin dielectric layer
To reduce MIGS by blocking electron wave function from metal to semiconductor (MIGS model)
Dipole formed at Metal/Semiconductor interface would cause potential drop to alleviate SBH (Dipole model)
Fixed charges in dielectric layer would also cause extra potential drop (Fixed charge model)
Figure 5: Mechanisms of SBH reduction.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

13. Objective and Methodology
By Egun
By Sputtering
By ALD
Semiconductor (n-type and p-type)
TiO2 and HfO2 (3nm, 2nm and 1nm) and bilayer
Pt (100nm)
Ohmic Contact
Semiconductor (n-type and p-type)
TiO2 and HfO2 (3nm, 2nm and 1nm) and bilayer
Al (100nm)
Ohmic Contact
Figure 6: Schematic diagram of M-I-S diode in this work
Contact Area : cm2 using shadow mask
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

14. Objective and Methodology
Wafer details
Sl. No.
Details
N-Type
P-Type 1
Dopant
Phosphorous
Boron 2
Doping Concentration
1 ͂ 2X1016 /cm3
2 ͂ 6X1014/cm3 3
Resistivity
1-10 Ω-cm
11-14 Ω-cm 4
Crystal Orientation
<100>
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

15. Objective and Methodology
Wafer cleaning procedure
Acetone
Alcohol
DI Water
DHF (50:1)
DI Water
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

16. Atomic Layer Deposition & Precursors
Study on TiO2 deposition by ALD
Precursor 1:Tetrakis(dimethylamino)titanium (TDMAT)
Precursor 2: H2O
Chamber Temperature : 250⁰C
Base pressure : 7E-3 torr
Working Pressure : 4.3 torr
Precursor temperature: 65 ⁰C
Precursor line temperature: 90 ⁰C
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

17. Atomic Layer Deposition & Precursors
Study on HfO2 deposition by ALD
Precursor 1: Tetrakis(ethylmethylamino)hafnium(IV) (TEMAH)
Precursor 2: H2O
Chamber Temperature : 300⁰C
Base pressure : 4E-2 torr
Working Pressure : 2.0 torr
Precursor temperature: 60 ⁰C
Precursor line temperature: 120 ⁰C
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

18. Atomic Layer Deposition & Precursors
Sl. No.
Technical parameters
TiO2
HfO2 1
Band gap
3.5eV
5.8eV 2
Electron affinity
4.15+/-0.25eV
2.5+/-0.25eV 3
Conduction band offset
1.4 4
Dielectric constant 80 25
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

19. Theory behind M-S contacts
Electrical nature of Ideal MS contacts
Where,
ՓM = Metal Work function
ՓS = Semiconductor Work function
Source: Semiconductor Device fundamentals by Robert F. Pierret
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

20. Theory behind M-S contacts
According to the Schottky–Mott relation: SBH can be calculated as follows :
For an ideal Schottky contact to an n-type semiconductor :
For an ideal Schottky contact on p-type semiconductor :
Where,
ՓB= Schottky Barrier Height ՓM = Metal Work function
Eg = Semiconductor band gap χ = Electron affinity of semiconductor
Source: Semiconductor Device fundamentals by Robert F. Pierret
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

21. Theory behind M-S contacts
For an ideal Schottky contact on n-type semiconductor :
1) Using Pt as electrode :
ՓB= ՓM- χ = = 1.6eV
1) Using Al as electrode :
ՓB= ՓM- χ = = 0.23eV
Source: Work function values are from Journal of Applied Physics, Vol. 48, No. 11, November 1977
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

22. Theory behind M-S contacts
For an ideal Schottky contact on p-type semiconductor :
1) Using Pt as electrode :
ՓB= Eg+ χ- ՓM= = -0.5eV
1) Using Al as electrode :
ՓB= Eg+ χ- ՓM= = 0.87eV
Source: Work function values are from Journal of Applied Physics, Vol. 48, No. 11, November 1977
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

23. Theoretical and Experimental details
Semiconductor
Metal
Theoretical SBH
Theoretical contact type
Our experimental observation based on I-V
n-Si Pt
1.6 eV
Schottky/Rectifying Al
0.23 eV
Semi-Ohmic/non-rectifying
p-Si
-0.5 eV
Ohmic/non-rectifying
0.87 eV
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

24. Experimental details Semiconductor Metal Single Layer HfO2
Single Layer TiO2
Bi-layer HfO2/TiO2
Bi-layer TiO2/HfO2
n-Si Pt
3nm, 2nm and 1nm
1nm each Al
p-Si
M-S structure
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

25. Electrical Properties
M-S and M-I-S structures comparison on n-Si
Increase in reverse current
Reduction of SBH
Enhances the TE
More carriers emitted from metal to SC.
Semiconductor (n-type Si)
TiO2 (3nm, 2nm and 1nm) and bilayer
Pt (100nm)
Ohmic Contact
Conclusion : Indication of Schottky to Ohmic conversion.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

26. Electrical Properties
M-S and M-I-S structures comparison on n-Si
Increase in reverse current
Reduction of SBH
Enhances the TE
More carriers emitted from metal to SC.
Semiconductor (n-type Si)
HfO2 (3nm, 2nm and 1nm) and bilayer
Pt (100nm)
Ohmic Contact
Conclusion : Indication of Schottky to Ohmic conversion.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

27. Electrical Properties
M-S and M-I-S structures comparison on n-Si
Reverse current remains unchanged.
Carriers can tunnel through the interfacial dielectric layer.
Semiconductor (n-type Si)
TiO2 (3nm, 2nm and 1nm) and bilayer
Al (100nm)
Ohmic Contact
Conclusion : Ohmic nature retained.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

28. Electrical Properties
M-S and M-I-S structures comparison on n-Si
Small reduction in reverse current
Large tunnel barrier effect.
Semiconductor (n-type Si)
HfO2 (3nm, 2nm and 1nm) and bilayer
Al (100nm)
Ohmic Contact
Conclusion : Ohmic nature retained.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

29. Electrical Properties
M-S and M-I-S structures comparison on p-Si
Small increase in both forward and reverse current
Carriers can tunnel through the interfacial layer along with Thermionic emission
Semiconductor (p-type Si)
TiO2 (3nm, 2nm and 1nm) and bilayer
Pt (100nm)
Ohmic Contact
Conclusion : A small improvement in Ohmic nature.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

30. Electrical Properties
M-S and M-I-S structures comparison on p-Si
Considerable increase in both forward and reverse current
Carriers can tunnel through the interfacial layer along with Thermionic emission
Semiconductor (p-type Si)
HfO2 (3nm, 2nm and 1nm) and bilayer
Pt (100nm)
Ohmic Contact
Conclusion : A considerable improvement in Ohmic nature.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

31. Electrical Properties
M-S and M-I-S structures comparison on p-Si
Decrease in forward current with TiO2 insertion and bilayer insertion
Semiconductor (p-type Si)
TiO2 (3nm, 2nm and 1nm) and bilayer
Al (100nm)
Ohmic Contact
Conclusion : Indication of Schottky to Ohmic conversion???
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

32. Electrical Properties
M-S and M-I-S structures comparison on p-Si
Decrease in forward current with HfO2 insertion and bilayer insertion
Semiconductor (p-type Si)
HfO2 (3nm, 2nm and 1nm) and bilayer
Al(100nm)
Ohmic Contact
Conclusion : Indication of Schottky to Ohmic conversion???
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

33. SBH Extraction (J-V Model)
The J-V relation for a Schottky diode under the forward bias (qV>3kT) is given by
Where,
J0 =saturation current density
n = ideality factor
V=forward bias voltage
T=Temperature
q= Electron charge
k= Boltzmann constant
ՓB0= Apparent SBH at zero bias
A*= Richardson constant A* for p-Si=32A/cm2K2 and for n-Si=112A/cm2K2
Step 1: ln(J) Vs V plot
Step 2: Slope=q/nkT and intercept at V=0 is J0 (forward bias)
Using this value in the above equation, ՓB can be deduced.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

34. SBH Extraction (Thermionic Emission Model)
To take care of the uncertainty of the Richardson constant and the effective diode area, we consider I-V-T method under reverse bias,
Step 1: produce ln(J0/T2) Vs 1000/T (Richardson plot) (Reverse bias)
Step 2 : Slope=-qՓB/k and intercept on the ordinate gives A* ( effective Richardson constant)
The J-V relation of a Schottky diode with a thin interfacial insulator in between the metal and semiconductor is given by
Where is the tunneling probability, which can be considered as a modification to the effective Richardson constant A*.
(For M-S contact)
(For M-I-S contact)
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

35. SBH Extraction (Gauss Distribution Model)
This model takes the surface inhomogeneities into account by assuming that the Schottky barrier exhibits a Gaussian distribution profile over the contact area.
The Gaussian distribution of barrier heights can be expressed by the following equation:
A linear fit on the plot of Փap versus q/2kT gives,
y-axis intercept gives us the value of zero bias barrier height Փb0.
The slope of the line gives the value of standard deviation σ2.
Finally inhomogeneities in the barrier height are accounted for in the modified Richardson’s plot as per the below equation.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

36. Temperature dependant I-V(I-V-T)
Pt/n-Si (M-S) Contact
This case is very important as it is a Schottky contact
SBH based on room temperature I-V=0.71eV
Note : Schottky nature at room temperature.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

37. Richardson plot and SBH extraction(TE model)
Pt/n-Si (M-S) Contact
Conventional Richardson plot
y = x
SBH, ՓB = 0.53eV Richardson Constant A*= 6.35X10-3Acm-2K-2
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

38. Richardson plot and SBH extraction(GD model)
Pt/n-Si (M-S) Contact
Temperature T (K)
Barrier Height ՓB (eV)
298
0.6239
318
0.6649
338
0.6973
358
0.8247
378
0.8896
We observe that SBH increases from 0.62eV to 0.88eV as the temperature is increased from 298K to 378K.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

39. Richardson plot and SBH extraction(GD model)
Pt/n-Si (M-S) Contact
Zero bias SBH, ՓB0=1.882 eV
Standard deviation, σs2= 0.066V
y = x
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

40. Richardson plot and SBH extraction(GD model)
Pt/n-Si (M-S) Contact
Modified Richardson plot
y = x
SBH, ՓB = 1.80eV Richardson Constant A*= 5.29Acm-2K-2
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

41. Temperature dependant I-V(I-V-T)
Pt/HfO2(3nm)/n-Si (M-I-S) Contact
SBH based on room temperature I-V=0.59eV
Note : Schottky nature at room temperature.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

42. Richardson plot and SBH extraction(TE model)
Pt/HfO2(3nm)/n-Si (M-I-S) Contact
Conventional Richardson plot
y = x
SBH, ՓB = 0.425eV Richardson Constant A*= 1.83X10-5Acm-2K-2
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

43. Richardson plot and SBH extraction(GD model)
Pt/HfO2(3nm)/n-Si (M-I-S) Contact
Temperature T (K)
Barrier Height ՓB (eV)
298
0.6565
318
0.7556
338
0.7674
358
0.8123
378
0.8602
We observe that SBH increases from 0.65eV to 0.86eV as the temperature is increased from 298K to 378K.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

44. Richardson plot and SBH extraction(GD model)
Pt/HfO2(3nm)/n-Si (M-I-S) Contact
Zero bias SBH, ՓB0= 1.55eV
Standard deviation, σs2= 0.045V
y = x
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

45. Richardson plot and SBH extraction(GD model)
Pt/HfO2(3nm)/n-Si (M-I-S) Contact
Modified Richardson plot
y = x
SBH, ՓB = 1.53eV Richardson Constant A*= 76.64Acm-2K-2
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

46. Summary of SBH Model Pt/n-Si Pt/HfO2(3nm)/n-Si Schottky-Mott rule
1.6eV -
Room temperature J-V model (Forward bias)
0.71eV
0.59eV
Thermionic Emission model (Reverse bias) (Conventional Richardson plot)
0.53eV
0.42eV
Thermionic Emission with Gauss Distribution model (Forward bias) (Based on apparent SBH)
1.88eV
1.55eV
Gauss Distribution model )(Forward bias) (Modified Richardson plot
1.80eV
1.53eV
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

47. Temperature dependant I-V(I-V-T)
Pt/p-Si (M-S) Contact
SBH based on room temperature I-V=0.56eV
Note : Ohmic nature at room temperature.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

48. Richardson plot and SBH extraction(TE model)
Pt/p-Si (M-S) Contact
y = -0.18x
Conventional Richardson plot
SBH, ՓB = 0.18eV Richardson Constant A*= 1.22X10-7Acm-2K-2
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

49. Richardson plot and SBH extraction(GD model)
Pt/n-Si (M-S) Contact
Temperature T (K)
Barrier Height ՓB (eV)
298
0.5779
318
0.5959
338
0.6140
358
0.7197
378
0.7507
We observe that SBH increases from 0.57eV to 0.75eV as the temperature is increased from 298K to 378K.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

50. Richardson plot and SBH extraction(GD model)
Pt/n-Si (M-S) Contact
Zero bias SBH, ՓB0=1.42eV
Standard deviation, σs2= 0.044V
y = x
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

51. Richardson plot and SBH extraction(GD model)
Pt/n-Si (M-S) Contact
Modified Richardson plot
y = x
SBH, ՓB = 1.23eV Richardson Constant A*= Acm-2K-2
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

52. Polarization studies on bilayer samples
EFM EG
ECB
EVB
Metal n-Si
Metal Insulator n-Si
Metal Insulator1 Insulator2 n-Si
Tunneling current
(a)
(b)
(c)
Figure 7 : Schematic band diagram of a pinned Fermi level and depinning with single and double dielectric layers
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

53. Polarization studies on bilayer samples
Measurement condition
Applied Voltage : 5V
Applied field : 25000kV/cm
Hysteresis period : 100ms
Frequency : 1.00X101 Hz
P max=30.952
P max=3.768
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

54. Polarization studies on bilayer samples
Measurement condition
Applied Voltage : 5V
Applied field : 25000kV/cm
Hysteresis period : 100ms
Frequency : 1.00X101 Hz
P max=4.839
P max=89.864
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANO-TECHNOLOGY, NIE , MYSURU.

55. Future work
Completing I-V-T measurement and extracting SBH for other samples.
XPS studies will be carried out in order to understand the TiO2 and HfO2 stoichiometry and the physics behind the interface.
Polarization studies will be conducted to understand the contribution of dipole density towards MIGS reduction and leakage phenomena will be analyzed in comparison with C-V curves.
The in-situ annealing will be carried out in ALD chamber at various temperatures (if time permits).
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANOTECHNOLOGY, NIE MYSURU

56. DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANOTECHNOLOGY, NIE MYSURU
Conclusion
We found that, the M-I-S structures can have reduced SBH and thus can yield lower contact resistance at source/drain region.
The thickness of the interfacial insulator is found to be a critical factor.
We found to have distorted P-E curves for M-I-S structures due to high leakage current. But, the polarization values are still considerable which is the clear indication of dipole formation at high-k/high-k interface. Which needs further investigation through C-V curves at same frequency levels.
The Gaussian distribution model gives the accurate value on SBH compared to J-V model and TE model.
DEPARTMENT OF MECHANICAL ENGG., CENTRE FOR NANOTECHNOLOGY, NIE MYSURU

57. THANK YOU