Design of a compact AFM scanner Compact, high speed and high
accuracy AFM scanner K. 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
Slide 2
Outline Introduction to Atomic Force Microscopes (AFM) Research
questions Requirements and specifications Concept 1 Concept 2
Detailed Design Conclusion K. J. Kamp Design of a compact AFM
scanner 2
Slide 3
Introduction K. J. Kamp Design of a compact AFM scanner 3
Introduction Research Questions Requirements specifications Concept
1 Concept 2 Detailed Design Conclusion
Slide 4
Introduction The atomic force microscope (AFM) Basic operation
principle Probe tip attached to a cantilever is scanned over a
sample Cantilever deflects due to the atomic forces The cantilever
deflection measures the surface topography K. J. Kamp A compact AFM
scanner 4
Slide 5
Introduction The AFM scanner Lateral scanning Triangular
pattern Constant tip speed K. J. Kamp A compact AFM scanner 5
Slide 6
Introduction The AFM scanner Vertical scanning Feedback loop
Cantilever deflection signal minimal The probe tip tracks the
topography K. J. Kamp A compact AFM scanner 6 DOI wafer AFM
measurement
Slide 7
Introduction K. J. Kamp A compact AFM scanner 7 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
Slide 8
Introduction Concept 1:The tripod scanner K. J. Kamp A compact
AFM scanner 8 Actuator 1 Actuator 2 Actuator 3 u1u1 u2u2 u3u3 y z
Sensor x Top View
Slide 9
Research Questions K. J. Kamp A compact AFM scanner 9
Introduction Research Questions Requirements specifications Concept
1 Concept 2 Detailed Design Conclusion
Slide 10
Research questions 1.How do the specifications of the AFM
system translate to the requirements of the AFM scanner? 2.Does the
first scanner concept meet the requirements? 3.Does the second
scanner concept meet the requirements? 4.Is the second scanner
concept valid as a real world design? K. J. Kamp A compact AFM
scanner 10
Slide 11
Requirements K. J. Kamp A compact AFM scanner 11 Introduction
Research Questions Requirements specifications Concept 1 Concept 2
Detailed Design Conclusion
Slide 12
Requirements K. J. Kamp A compact AFM scanner 12 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
Slide 13
Requirements Measurement uncertainty to roll angle Misalignment
sensors and probe tip: 0,5 mm Scanner will rotate (roll angle) This
causes an Abbe error (measurement uncertainty) K. J. Kamp A compact
AFM scanner 13
Slide 14
Requirements Abbe error Platform roll angle Sensor offset Abbe
error: e abbe = tan() Assumptions: = 0,5 mm e abbe < 1,0 nm <
2 microrad K. J. Kamp A compact AFM scanner 14
Slide 15
Requirements Imaging time to resonance frequencies Lateral
resonance frequency > 10 kHz Triangular wave frequency content
Vertical resonance frequency > 30 kHz Tracking error, scanning
speed K. J. Kamp A compact AFM scanner 15
Slide 16
Concept 1 K. J. Kamp A compact AFM scanner 16 Introduction
Research Questions Requirements specifications Concept 1 Concept 2
Detailed Design Conclusion
Slide 17
Concept 1 Analysis of the tripod concept 1.Kinematicsrelated to
scanner stroke 2.Staticsrelated to scanner roll angles (Abbe error)
3.Dynamicsrelated to scanner resonance frequencies Design of a
compact AFM scanner 17
Slide 18
Concept 1 Kinematics analysis Required stroke: 10 x 10 x 2
microns Relation is found between x, y, z (platform position) u1,
u2, u3 (actuators) K. J. Kamp A compact AFM scanner 18 u1u1 u2u2
u3u3 y z x
Slide 19
Concept 1 Example Ten scan lines 10 x 10 microns Actuator
displacement ~ 6 microns Mechanical amplification 10 / 6 = 1.66 K.
J. Kamp A compact AFM scanner 19
Slide 20
Concept 1 Scanner roll angle Hinges are not perfect Lateral
motion will cause the scanner to roll K. J. Kamp A compact AFM
scanner 20 u1u1 u2u2 u3u3 y z x
Slide 21
Titel van de presentatie 21 Concept 1 2D Statics analytical
model
Slide 22
Concept 1 Main cause of AFM scanner roll Stiffness ratio
between longitudinal and lateral stiffness of a rod K. J. Kamp A
compact AFM scanner 22 Normalized stiffness ratio []
Slide 23
Concept 1 Statics Flexure notch hinges Increase longitudinal to
lateral stiffness ratio Decreases the roll angle K. J. Kamp A
compact AFM scanner 23
Slide 24
Concept 1 Statics FEM analysis 3D FEM model K. J. Kamp A
compact AFM scanner 24
Slide 25
Concept 1 Statics FEM results u 1 = 5 microns x = 5 microns = ~
460 microrad K. J. Kamp A compact AFM scanner 25
Slide 26
Concept 1 Statics FEM results Roll angle is lower = ~ 360
microrad K. J. Kamp A compact AFM scanner 26
Slide 27
Concept 1 Statics FEM results Circular notch hinge Roll angle
even lower = ~ 60 microrad K. J. Kamp A compact AFM scanner 27
Slide 28
Concept 1 Dynamics First four resonances: K. J. Kamp A compact
AFM scanner 28
Slide 29
Concept 1 FEM Modal analysis Eigenmode results K. J. Kamp A
compact AFM scanner 29 Lateral 9,3 kHz Roll 42 kHz Yaw 9,8 kHz
Vertical 48 kHz
Slide 30
Summary Can 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 K. J.
Kamp A compact AFM scanner 30 Concept 1
Slide 31
Concept 2 K. J. Kamp A compact AFM scanner 31 Introduction
Research Questions Requirements specifications Concept 1 Concept 2
Detailed Design Conclusion
Slide 32
Concept 2 Orthogonal scanning concept Lateral motion K. J. Kamp
A compact AFM scanner 32 Side view Top view Actuator Sensor
Actuator Sensor Probe tip
Slide 33
Concept 2 Orthogonal scanning concept Vertical motion K. J.
Kamp A compact AFM scanner 33 Side view Top view Actuator Sensor
Actuator Sensor Probe tip
Slide 34
Concept 2 K. J. Kamp A compact AFM scanner 34 Kinematics
Lateral stroke: mechanical amplification = lever ratio b to a x u
lever a b
Slide 35
Concept 2 K. J. Kamp A compact AFM scanner 35 Statics analysis
Analytical model adapted to the orthogonal concept L2L2 x z uxux
K2K2 K2K2 L K1K1 uzuz uu uu uxux uzuz u lever
Slide 36
Concept 2 K. J. Kamp A compact AFM scanner 36 Analytical model
and FEM analysis Pure lateral input (no lever) u x = 5 microns
Analytical model: = 21,7 microrad FEM result = 22,9 microrad The
roll angle is positive
Slide 37
Concept 2 K. J. Kamp A compact AFM scanner 37 Including the
lever Input u x results in a positive roll angle Input u results in
a negative roll angle uu a b uxux uzuz u lever uxux uu
positivenegative
Slide 38
Concept 2 K. J. Kamp A compact AFM scanner 38 Analytical model
and FEM results The length of the vertical rods is varied: The roll
angle shifts from negative to positive Vertical rod length
Analytical FEM 10 mm-82,1 rad-17,8 rad 6 mm-28,4 rad+19,5 rad 3
mm+123,1 rad+73,2 rad
Slide 39
Concept 2 K. J. Kamp A compact AFM scanner 39 The analytical
model is used to find zero roll angle Vertical rod length [m]
Slide 40
Concept 2 K. J. Kamp A compact AFM scanner 40 Resulting roll
angle Final iteration L 1 = 3,0 mm L 2 = 4,0 mm u lever = 10
microns x = 4,9 microns Roll angle = -0,63 microrad
Slide 41
Concept 2 K. J. Kamp A compact AFM scanner 41 Dynamics FEM
modal results Lateral eigenmodes (x,y): ~12,3 kHz Vertical mode
(z): ~36,5 kHz Lateral: Vertical:
Slide 42
Concept 2 K. J. Kamp A compact AFM scanner 42 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
Slide 43
Detailed design K. J. Kamp A compact AFM scanner 43
Introduction Research Questions Requirements specifications Concept
1 Concept 2 Detailed Design Conclusion
Slide 44
Detailed design Component selection Piezo actuators
Triangulation sensors AFM chip holder K. J. Kamp A compact AFM
scanner 44
Slide 45
Detailed design Piezo actuators PI (Physik Instrumente) 5 x 5 x
9 mm for vertical motion 3 x 3 x 13,5 mm for lateral motion K. J.
Kamp A compact AFM scanner 45 TypeDimensionsNom. displ. P885.115 x
5 x 9 mm~6,5 micron P883.313 x 3 x 13,5 mm~13 micron
Slide 46
Detailed design Triangulation sensors Lion Precision capacitive
sensors K. J. Kamp A compact AFM scanner 46 TypeDimensionsRange
C3R-0,83 x 15 mm25 microns
Slide 47
Detailed design AFM chip holder Bruker DAFMCH probe holder
Piezo holder measures 4 x 5 mm at the base. K. J. Kamp A compact
AFM scanner 47
Slide 48
Detailed design Final design overview Outer dimensions (x,y):
26 x 26 mm K. J. Kamp A compact AFM scanner 48 Probe holder Sensor
Lever Piezo actuator
Slide 49
Detailed design Cross-section view (no piezo actuators) K. J.
Kamp A compact AFM scanner 49
Slide 50
Detailed design K. J. Kamp A compact AFM scanner 50
Slide 51
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 K. J. Kamp A compact
AFM scanner 51
Slide 52
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 lateral 9,8
kHz > 10 kHz Resonances vertical 30,4 kHz > 30 kHz K. J. Kamp
A compact AFM scanner 52
Slide 53
Conclusion K. J. Kamp A compact AFM scanner 53 Introduction
Research Questions Requirements specifications Concept 1 Concept 2
Detailed Design Conclusion
Slide 54
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 K. J. Kamp A compact
AFM scanner 54
Slide 55
Questions? K. J. Kamp A compact AFM scanner 55 Introduction
Research Questions Requirements specifications Concept 1 Concept 2
Detailed Design Questions?
