Design of a compact afm scanner
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Design of a compact AFM scanner. Compact, high speed and high accuracy AFM scannerK. J. Kamp June 26, 2013 Committee: Prof . Ir. R.H. Munnig Schmidt Dr. Ir. S. Kuiper Dr. Ir. J. L. Herder Dr. Ir. J. F. L. Goosen. Outline. Introduction to Atomic Force Microscopes (AFM)

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Design of a compact afm scanner

Design of a compact AFM scanner

Compact, high speed and high accuracy AFM scannerK. J. KampJune 26, 2013

Committee:

Prof. Ir. R.H. MunnigSchmidt

Dr. Ir. S. Kuiper

Dr.Ir. J. L. Herder

Dr. Ir. J. F. L. Goosen


Outline

K. J. KampDesign of a compact AFM scanner

Outline

  • Introduction to Atomic Force Microscopes (AFM)

  • Research questions

  • Requirements and specifications

  • Concept 1

  • Concept 2

  • Detailed Design

  • Conclusion


Introduction

K. J. KampDesign of a compact AFM scanner

  • Introduction

  • Research Questions

  • Requirements specifications

  • Concept 1

  • Concept 2

  • Detailed Design

  • Conclusion

Introduction


Introduction1

K. J. KampA compact AFM scanner

Introduction

The atomic force microscope (AFM)

  • Basic operation principle

    • Probe tip attached to a cantileveris scanned over a sample

    • Cantilever deflects due to the atomic forces

    • The cantilever deflectionmeasures the surface topography


Introduction2

K. J. KampA compact AFM scanner

Introduction

The AFM scannerLateral scanning

  • Triangularpattern

  • Constant tip speed

x

z

y


Introduction3

K. J. KampA compact AFM scanner

Introduction

The AFM scannerVertical scanning

  • Feedback loop

  • Cantilever deflection signal minimal

  • The probe tip tracks the topography

DOI wafer AFM measurement


Introduction4

K. J. KampA compact AFM scanner

Introduction

AFM system specifications

  • Surface area (x,y)<15mm x 15mm

  • Measurement range (x,y,z)>10 x 10 x 2 microns

  • Imaging time < 1 s

  • Measurement uncertainty < 1 nm


Introduction5

K. J. KampA compact AFM scanner

Top View

Introduction

z

y

Concept 1:The tripod scanner

x

Sensor

Sensor

Actuator 3

u3

Actuator 1

Actuator 2

u2

u1

Sensor


Research questions

K. J. KampA compact AFM scanner

  • Introduction

  • Research Questions

  • Requirements specifications

  • Concept 1

  • Concept 2

  • Detailed Design

  • Conclusion

Research Questions


Research questions1

K. J. KampA compact AFM scanner

Research questions

  • How do the specifications of the AFM system translate to the requirements of the AFM scanner?

  • Does the first scanner concept meet the requirements?

  • Does the second scanner concept meet the requirements?

  • Is the second scanner concept valid as a real world design?


Requirements

K. J. KampA compact AFM scanner

  • Introduction

  • Research Questions

  • Requirements specifications

  • Concept 1

  • Concept 2

  • Detailed Design

  • Conclusion

Requirements


Requirements1

K. J. KampA compact AFM scanner

Requirements

Research question 1:How do the specifications of the AFM system translate to the requirements of the AFM scanner?

  • Measurement uncertainty < 1 nm Translate to scanner roll angles

  • Imaging time < 1 s Translate to scanner resonance frequencies


Requirements2

K. J. KampA compact AFM scanner

Requirements

Measurement uncertainty to roll angle

  • Misalignment sensors and probe tip: 0,5 mm

  • Scanner will rotate (roll angle)

    → This causes an Abbeerror (measurement uncertainty)


Requirements3

K. J. KampA compact AFM scanner

Requirements

Abbe error

  • Platform roll angle φ

  • Sensor offset δ

  • Abbe error: eabbe = δ tan(φ)Assumptions:

    δ = 0,5 mmeabbe < 1,0 nm φ < 2 microrad


Requirements4

K. J. KampA compact AFM scanner

Requirements

Imaging time to resonance frequencies

  • Lateral resonance frequency > 10 kHz

    Triangular wave frequency content

  • Vertical resonance frequency > 30 kHzTracking error, scanning speed

x

z

y


Concept 1

K. J. KampA compact AFM scanner

  • Introduction

  • Research Questions

  • Requirements specifications

  • Concept 1

  • Concept 2

  • Detailed Design

  • Conclusion

Concept 1


Concept 11

Design of a compact AFM scanner

Concept 1

Analysis of the tripod concept

Kinematicsrelated to scanner stroke

Staticsrelated to scanner roll angles (Abbe error)

Dynamicsrelated to scanner resonance frequencies


Concept 12

K. J. KampA compact AFM scanner

Concept 1

z

y

Kinematics analysis

Required stroke: 10 x 10 x 2 microns

  • Relation is found between

    x, y, z (platform position)

    u1, u2, u3 (actuators)

x

u3

u1

u2


Concept 13

K. J. KampA compact AFM scanner

Concept 1

Example

  • Ten scan lines 10 x 10 microns

  • Actuatordisplacement~ 6 microns

  • Mechanical amplification 10 / 6 = 1.66


Concept 14

K. J. KampA compact AFM scanner

Concept 1

z

y

Scanner roll angle

  • Hinges are not perfect

  • Lateral motion will cause the scanner to roll

x

u3

u1

u2


Concept 15

Titel van de presentatie

Concept 1

2D Statics analytical model


Concept 16

K. J. KampA compact AFM scanner

Concept 1

Main cause of AFM scanner roll

  • Stiffness ratio between longitudinal and lateral stiffness of a rod

Normalized stiffness ratio []


Concept 17

K. J. KampA compact AFM scanner

Concept 1

Statics

  • Flexure notch hinges

    • Increase longitudinal to lateral stiffness ratio

    • Decreases the roll angle


Concept 18

K. J. KampA compact AFM scanner

Concept 1

Statics FEM analysis

  • 3D FEM model


Concept 19

K. J. KampA compact AFM scanner

Concept 1

Statics FEM results

  • u1 = 5 microns

  • x = 5 microns

  • φ = ~ 460 microrad


Concept 110

K. J. KampA compact AFM scanner

Concept 1

Statics FEM results

  • Roll angle is lower

  • φ = ~ 360 microrad


Concept 111

K. J. KampA compact AFM scanner

Concept 1

Statics FEM results

  • Circular notch hinge

  • Roll angle even lower

  • φ=~ 60 microrad


Concept 112

K. J. KampA compact AFM scanner

Concept 1

Dynamics

  • First four resonances:


Concept 113

K. J. KampA compact AFM scanner

Concept 1

FEM Modal analysis

  • Eigenmode results

Yaw9,8 kHz

Lateral9,3 kHz

Roll42 kHz

Vertical 48 kHz


Design of a compact afm scanner

K. J. KampA compact AFM scanner

Concept 1

SummaryCan the requirements be met?

  • Trade-off low roll angle vs. high resonance frequencies

  • Low roll angles require a high stiffness ratio (low lateral stiffness)

  • High resonance frequencies require high stiffness overall

    Conclusion: The individual requirements can not all be met.Concept 1 is not feasible


Concept 2

K. J. KampA compact AFM scanner

  • Introduction

  • Research Questions

  • Requirements specifications

  • Concept 1

  • Concept 2

  • Detailed Design

  • Conclusion

Concept 2


Concept 21

K. J. KampA compact AFM scanner

Concept 2

  • Orthogonal scanning conceptLateral motion

Side view

Top view

Probe tip

Sensor

Sensor

Actuator

Actuator


Concept 22

K. J. KampA compact AFM scanner

Concept 2

  • Orthogonal scanning conceptVertical motion

Side view

Top view

Probe tip

Sensor

Sensor

Actuator

Actuator


Concept 23

K. J. KampA compact AFM scanner

x

Concept 2

Kinematics

Lateral stroke:mechanical amplification = lever ratio b to a

ulever

b

a


Concept 24

z

K. J. KampA compact AFM scanner

φ

x

L

ux

Concept 2

uz

K1

ux

uz

Statics analysis

Analytical model adapted to the orthogonal concept

L2

K2

K2

ulever


Concept 25

K. J. KampA compact AFM scanner

Concept 2

Analytical model and FEM analysis

  • Pure lateral input (no lever)ux = 5 microns

  • Analytical model: φ = 21,7 microrad

  • FEM resultφ = 22,9 microradThe roll angle φ is positive


Concept 26

K. J. KampA compact AFM scanner

ux

uz

Concept 2

b

a

Including the lever

  • Input uxresults in a positive roll angle

  • Input uφresults in a negative roll angle

ulever

positive

negative

ux


Concept 27

K. J. KampA compact AFM scanner

Concept 2

  • Analytical model and FEM results

  • The length of the vertical rods is varied:

  • The roll angle shifts from negative to positive


Concept 28

K. J. KampA compact AFM scanner

Concept 2

  • The analytical model is used to find zero roll angle

Vertical rod length [m]


Concept 29

K. J. KampA compact AFM scanner

Concept 2

Resulting roll angle

Final iteration

L1 = 3,0 mmL2 = 4,0 mm

ulever= 10 microns

x = 4,9 microns

Roll angleφ = -0,63 microrad


Concept 210

K. J. KampA compact AFM scanner

Concept 2

Lateral:

Dynamics

FEM modal results

Lateral eigenmodes(x,y):~12,3 kHzVertical mode (z):

~36,5 kHz

Vertical:


Concept 211

K. J. KampA compact AFM scanner

Concept 2

Summary

  • The orthogonal scanner concept meets all the requirements

  • The stroke of 10 x 10 x 2 microns can be achieved

  • The roll angle is ~ 0,64 microrad

  • The resonance frequencies are 12,3 kHz lateral

    43,4 kHz vertical


Detailed design

K. J. KampA compact AFM scanner

  • Introduction

  • Research Questions

  • Requirements specifications

  • Concept 1

  • Concept 2

  • Detailed Design

  • Conclusion

Detailed design


Detailed design1

K. J. KampA compact AFM scanner

Detailed design

Component selection

  • Piezo actuators

  • Triangulation sensors

  • AFM chip holder


Detailed design2

K. J. KampA compact AFM scanner

Detailed design

Piezo actuators

  • PI (PhysikInstrumente)

  • 5 x 5 x 9 mm for vertical motion

  • 3 x 3 x 13,5 mm for lateral motion


Detailed design3

K. J. KampA compact AFM scanner

Detailed design

Triangulation sensors

  • Lion Precision capacitive sensors


Detailed design4

K. J. KampA compact AFM scanner

Detailed design

AFM chip holderBrukerDAFMCH probe holder

Piezo holder measures 4 x 5 mm at the base.


Detailed design5

K. J. KampA compact AFM scanner

Detailed design

Probe holder

Final design overview

  • Outer dimensions (x,y): 26 x 26 mm

Lever

Sensor

Piezo actuator


Detailed design6

K. J. KampA compact AFM scanner

Detailed design

Cross-section view (no piezo actuators)


Detailed design7

K. J. KampA compact AFM scanner

Detailed design


Detailed design8

K. J. KampA compact AFM scanner

Detailed design

Summary

Specifications

  • Dimensions (x,y) 26 x 26 mm

  • Stroke(microns) 16 x 16 x 6,5

  • Roll angle 5,4 microrad

  • Resonances lateral 9,8 kHz

  • Resonances vertical 30,4 kHz


Detailed design9

K. J. KampA compact AFM scanner

Detailed design

Summary

Specifications Requirements

  • Dimensions (x,y) 26 x 26 mm 15 x 15 mm

  • Stroke(microns) 16 x 16 x 6,5 10 x 10 x 2

  • Roll angle 5,4 microrad< 2 microrad

  • Resonances lateral9,8 kHz > 10 kHz

  • Resonances vertical 30,4 kHz > 30 kHz


Conclusion

K. J. KampA compact AFM scanner

  • Introduction

  • Research Questions

  • Requirements specifications

  • Concept 1

  • Concept 2

  • Detailed Design

  • Conclusion

Conclusion


Conclusion1

K. J. KampA compact AFM scanner

Conclusion

  • The requirements have been set up for the AFM scanner

  • The first concept is not feasible

  • The second concept meets all the requirements and is feasible

  • The detailed design is limited by the selected components:

    1.The required size can not be achieved

    2.The required roll angle is exceeded by a factor 2


Questions

K. J. KampA compact AFM scanner

  • Introduction

  • Research Questions

  • Requirements specifications

  • Concept 1

  • Concept 2

  • Detailed Design

  • Questions?

Questions?


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