jose corona advisors: lin you and joseph kopanski ......summer 2016 outline Øtheory Ø scanning...
TRANSCRIPT
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COMSOL SIMULATION STUDY OF THE EFFECT OF PROBE TIP SHAPE
ON THE MEASUREMENT OF AN ELECTRICAL FIELD GRADIENT GENERATED BY MICROELECTRONIC
TEST STRUCTURES
Jose CoronaAdvisors: Lin You and Joseph Kopanski
Engineering Physics Division, PMLSummer 2016
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OUTLINE
Ø Theory
Ø Scanning Kelvin Force Microscopy (SKFM)
Ø Motivation
Ø COMSOL Model Builder
Ø Results
Ø Importance of tip shape
Ø Cantilever Effect
Ø Importance of Tip Shape
Ø Clearance Effect
Ø Differential Voltage
Ø Different Size Ratios
Ø Conclusions
Ø Future Work
Ø References
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MOTIVATION
ØPrecise nano-scale measurements
ØUse of Scanning Kelvin Force Microscopy (SKFM)
ØElectric Field Measurements are HIGHLY dependent on the shape of the probe
ØDesign an Electrical Tip Shape Profiler Reference Material
Image from Semiconductor Manufacturing & Design Community
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WORKING PRINCIPLES OF SKFM
ØTapping Mode vs. Mode LiftImage credit: Kaja
(Kaja’s PhD THESIS 2010)
Scanning Kelvin Force Microscope (SKFM)
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15°
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COMSOL MODEL BUILDER
Fig. 5
Domain Probe
Image credit: Kaja
(Kaja’s PhD THESIS 2010)
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COMSOL MODEL BUILDER
Materials
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Air
Copper
Glass
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Electrostatics ØCharge Conservation ØZero ChargeØFloating PotentialØBiasingØGround
COMSOL MODEL BUILDER
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+10V
Ground
Floating Potential
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Meshing
COMSOL MODEL BUILDER
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Parametric Sweep
COMSOL MODEL BUILDER
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∠𝑡𝑖𝑝Clearance
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ØThe Surface Potential dependency on the shape of the tip
ØSharper vs. Blunter tips
Ø5°Ø (-2.52 , 0.140)
Ø(2.66 , -0.149)Ø35°
Ø(-2.52 , 0.101)Ø(2.66 , -0.113)
IMPORTANCE OF TIP SHAPE
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
-5 -4 -3 -2 -1 0 1 2 3 4 5
Surf
ace
Pote
ntia
l [V
]
Position [µm]
Surface Potential of Lateral Scan
5° 20° 35° 12.5° 27.5°
-0.2-0.15-0.1
-0.050
0.050.1
0.150.2
-5 -4 -3 -2 -1 0 1 2 3 4 5
Der
ivat
ive
Surf
ace
Pote
ntia
l [dV
]
Derivative Position [dµm]
Instantaneous Surface Potential at any Given Point
5° 12.5° 20° 27.5° 35°
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FP
+10V
-10V
GRD
Glass
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
-15 -10 -5 0 5 10 15
Surf
ace
Pote
ntia
l [V
]
Position [um]
Cantilever Effect
5deg
25deg
45deg
-0.25
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
-15 -10 -5 0 5 10 15
Surf
ace
Pote
ntia
l [V
]
Position [um]
Cantilever Effect
5deg
25deg
45deg
CANTILEVER EFFECT
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CLEARANCE EFFECTS ON SURFACE POTENTIAL
0
0.1
0.2
0.3
0.4
0.5
0.6
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5
Surf
ace
Pote
ntia
l [V
]
Position [µm]
5º Cone Angle KFM Scan
10nm
43nm
77nm
110nm
144nm
177nm
210nm
244nm
277nm
310nm
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5
Surf
ace
Pote
ntia
l [V
]
Position [µm]
35º Cone Angle KFM Scan
10nm
43nm
77nm
110nm
144nm
177nm
210nm
244nm
277nm
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Glass+10V
GRD
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+10V Glass
GRD
CLEARANCE EFFECTS ON SURFACE POTENTIAL
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Surf
ace
Pote
ntia
l [V
]
Position [µm]
5º Cone Angle KFM Scan
10nm
20nm
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Surf
ace
Pote
ntia
l [V
]
Position [µm]
35º Cone Angle KFM Scan
10nm
20nm
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DIFFERENTIAL VOLTAGE
Ø 5º Cone Angle highest SP and most narrow widthØ Coherent
results as before
Ø Smaller lift height, higher SP
-0.02
-0.015
-0.01
-0.005
0
0.005
-15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Diff
eren
tial V
olta
ge [
dV]
Position [µm]
Determining the Width of the Tip
5°
35°
20°
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
-15 -10 -5 0 5 10 15
Surf
ace
Pote
ntia
l [V
]
Position [µm]
Surface Potential of Rectangular Scan with Conical Tip
5°(10nm)
5°(20nm)
35°(20nm)
35°(10nm)
20°(20nm)
20°(10nm)
(20-10)nm
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DIFFERENT SIZE RATIOS
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Surf
ace
Pote
ntia
l [V
]
Position [µm]
Lateral Scan of 5:1 Eccentric Cone
longside
shortside
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Surf
ace
Pote
ntia
l [V
]
Position [µm]
Lateral Scan of 2:1 Eccentric Cone
10nm longside
10nm shortside
Ø Noticeable gap
Ø Indicates the direction of scan
Long side
Short side
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SUMMARY AND OUTLOOK
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ØExtract: ØBase shapeØTip angleØHeight
ØFuture work: ØCompare
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THANK YOU!
• How AFM Works: Scanning Kelvin Probe Microscopy (SKPM), Web. (http://www.parkafm.com/index.php/medias/nano-academy/how-afm-works#prettyPhoto).
• Khaled Kaja. Development of nano-probe techniques for work function assessment and application to materials for microelectronics. Physics. Universite Joseph-Fourier - Grenoble I, 2010. English. <tel-00515370>
• http://semimd.com/insights-from-leading-edge/2010/10/02/iftle-18-the-3d-ic-forum-at-2010-semicon-taiwan/
References
Any Questions?
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CONCLUSIONS
Ø COMSOL’s ability to simulate SKFM
Ø Effect of Tip on the Surface Potential Measurement
Ø Seen through development of many DUTs
Ø IF SLOPE DETERMINED INSERT HERE
Ø Various lift heights affect Surface Potential
Ø Differential Voltage Produced
Ø V
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GOALS
• 3D COMSOL Simulation of Scanning Kelvin Force Microscopy (SKFM)• SKFM à Electric field measurements
• Determine the field distribution to design Electrical Tip Shape Profiler Reference Material• Cone Angle
• Base
• Height
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THEORY OF SURFACE POTENTIAL
Electric Potential – work per unit charge to move a point charge
Coulomb’s Law – Electric force between charges
Gauss’s Law – Used to determine the Electric field of a Gaussian surface
Image from HyperPhysics
Image from HyperPhysics
Image from HyperPhysics
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elewor.html#c2
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VAN DER WAAL’S FORCES
http://www.eng.usf.edu/~tvestgaa/ThinFilm/
Image by
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http://mathworld.wolfram.com/FullWidthatHalfMaximum.html
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