Design of a compact AFM scanner Titel van de presentatie 19-4-2017 14:26 Design of a compact 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

Outline Introduction to Atomic Force Microscopes (AFM) Design of a compact AFM scanner Outline Introduction to Atomic Force Microscopes (AFM) Research questions Requirements and specifications Concept 1 Concept 2 Detailed Design Conclusion

Titel van de presentatie 19-4-2017 14:26 Design of a compact AFM scanner Introduction Research Questions Requirements specifications Concept 1 Concept 2 Detailed Design Conclusion Introduction

Introduction The atomic force microscope (AFM) A compact AFM scanner 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

x z y Introduction The AFM scanner Lateral scanning Triangular pattern A compact AFM scanner Introduction The AFM scanner Lateral scanning Triangular pattern Constant tip speed y x z

Introduction The AFM scanner Vertical scanning Feedback loop A compact AFM scanner Introduction The AFM scanner Vertical scanning Feedback loop Cantilever deflection signal minimal The probe tip tracks the topography DOI wafer AFM measurement

Introduction AFM system specifications A 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

Introduction z y x u3 u2 u1 Top View Concept 1:The tripod scanner A compact AFM scanner Top View Introduction Concept 1:The tripod scanner Actuator 1 Actuator 2 Actuator 3 u1 u2 u3 y z Sensor x

Research Questions Introduction Research Questions A compact AFM scanner Introduction Research Questions Requirements specifications Concept 1 Concept 2 Detailed Design Conclusion Research Questions

A 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 Introduction Research Questions A compact AFM scanner Introduction Research Questions Requirements specifications Concept 1 Concept 2 Detailed Design Conclusion Requirements

A 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

Titel van de presentatie 19-4-2017 14:26 A 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 Abbe error (measurement uncertainty)

Requirements Abbe error Platform roll angle φ Sensor offset δ A compact AFM scanner Requirements Abbe error Platform roll angle φ Sensor offset δ Abbe error: eabbe = δ tan(φ) Assumptions: δ = 0,5 mm eabbe < 1,0 nm φ < 2 microrad

Requirements Imaging time to resonance frequencies A compact AFM scanner Requirements Imaging time to resonance frequencies Lateral resonance frequency > 10 kHz Triangular wave frequency content Vertical resonance frequency > 30 kHz Tracking error, scanning speed y x z

Concept 1 Introduction Research Questions Requirements specifications A compact AFM scanner Introduction Research Questions Requirements specifications Concept 1 Concept 2 Detailed Design Conclusion Concept 1

Concept 1 Analysis of the tripod concept Design of a compact AFM scanner Concept 1 Analysis of the tripod concept Kinematics related to scanner stroke Statics related to scanner roll angles (Abbe error) Dynamics related to scanner resonance frequencies

Concept 1 Kinematics analysis Required stroke: 10 x 10 x 2 microns A compact AFM scanner 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) u1 u2 u3 y z x

Concept 1 Example Ten scan lines 10 x 10 microns A compact AFM scanner Concept 1 Example Ten scan lines 10 x 10 microns Actuator displacement ~ 6 microns Mechanical amplification 10 / 6 = 1.66

Titel van de presentatie 19-4-2017 14:26 A compact AFM scanner Concept 1 Scanner roll angle Hinges are not perfect Lateral motion will cause the scanner to roll u1 u2 u3 y z x

Titel van de presentatie Concept 1 2D Statics analytical model

Titel van de presentatie 19-4-2017 14:26 A 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 1 Statics Flexure notch hinges A compact AFM scanner Concept 1 Statics Flexure notch hinges Increase longitudinal to lateral stiffness ratio Decreases the roll angle

A compact AFM scanner Concept 1 Statics FEM analysis 3D FEM model

Concept 1 Statics FEM results u1 = 5 microns x = 5 microns A compact AFM scanner Concept 1 Statics FEM results u1 = 5 microns x = 5 microns φ = ~ 460 microrad

Concept 1 Statics FEM results Roll angle is lower φ = ~ 360 microrad A compact AFM scanner Concept 1 Statics FEM results Roll angle is lower φ = ~ 360 microrad

Concept 1 Statics FEM results Circular notch hinge A compact AFM scanner Concept 1 Statics FEM results Circular notch hinge Roll angle even lower φ = ~ 60 microrad

A compact AFM scanner Concept 1 Dynamics First four resonances:

Concept 1 FEM Modal analysis Eigenmode results Lateral9,3 kHz A compact AFM scanner Concept 1 FEM Modal analysis Eigenmode results Lateral9,3 kHz Yaw 9,8 kHz Roll 42 kHz Vertical 48 kHz

Concept 1 Summary Can the requirements be met? A compact AFM scanner Concept 1 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

Concept 2 Introduction Research Questions Requirements specifications A compact AFM scanner Introduction Research Questions Requirements specifications Concept 1 Concept 2 Detailed Design Conclusion Concept 2

Concept 2 Side view Top view A compact AFM scanner Concept 2 Orthogonal scanning concept Lateral motion Side view Top view Probe tip Sensor Sensor Actuator Actuator

Concept 2 Side view Top view A compact AFM scanner Concept 2 Orthogonal scanning concept Vertical motion Side view Top view Probe tip Sensor Sensor Actuator Actuator

A compact AFM scanner Concept 2 Kinematics Lateral stroke: mechanical amplification = lever ratio b to a x ulever a b

A compact AFM scanner Concept 2 Statics analysis Analytical model adapted to the orthogonal concept L2 x z φ ux K2 L K1 uz uφ uφ ux uz ulever

Concept 2 Analytical model and FEM analysis A 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 result φ = 22,9 microrad The roll angle φ is positive

Concept 2 ux uφ uφ a b ux uz ulever Including the lever A compact AFM scanner Concept 2 uφ a b ux uz ulever Including the lever Input ux results in a positive roll angle Input uφ results in a negative roll angle positive negative ux uφ

Concept 2 Analytical model and FEM results A 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 Vertical rod length φ Analytical φ FEM 10 mm -82,1 μrad -17,8 μrad 6 mm -28,4 μrad +19,5 μrad 3 mm +123,1 μrad +73,2 μrad

Concept 2 The analytical model is used to find zero roll angle A compact AFM scanner Concept 2 The analytical model is used to find zero roll angle Vertical rod length [m]

Compact AFM 19-4-2017 14:26 A compact AFM scanner Concept 2 Resulting roll angle Final iteration L1 = 3,0 mm L2 = 4,0 mm ulever = 10 microns x = 4,9 microns Roll angle φ = -0,63 microrad

Compact AFM 19-4-2017 14:26 A compact AFM scanner Concept 2 Dynamics FEM modal results Lateral eigenmodes (x,y): ~12,3 kHz Vertical mode (z): ~36,5 kHz Lateral: Vertical:

Compact AFM 19-4-2017 14:26 A 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

Titel van de presentatie 19-4-2017 14:26 A compact AFM scanner Introduction Research Questions Requirements specifications Concept 1 Concept 2 Detailed Design Conclusion Detailed design

Detailed design Component selection Piezo actuators A compact AFM scanner Detailed design Component selection Piezo actuators Triangulation sensors AFM chip holder

Detailed design Piezo actuators PI (Physik Instrumente) A compact AFM scanner 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 Type Dimensions Nom. displ. P885.11 5 x 5 x 9 mm ~6,5 micron P883.31 3 x 3 x 13,5 mm ~13 micron

Detailed design Triangulation sensors A compact AFM scanner Detailed design Triangulation sensors Lion Precision capacitive sensors Type Dimensions Range C3R-0,8 Ø3 x 15 mm 25 microns

Detailed design AFM chip holder Bruker DAFMCH probe holder A compact AFM scanner Detailed design AFM chip holder Bruker DAFMCH probe holder Piezo holder measures 4 x 5 mm at the base.

Detailed design Probe holder Final design overview Lever Sensor A compact AFM scanner Detailed design Probe holder Final design overview Outer dimensions (x,y): 26 x 26 mm Lever Sensor Piezo actuator

Detailed design Cross-section view (no piezo actuators) A compact AFM scanner Detailed design Cross-section view (no piezo actuators)

A compact AFM scanner Detailed design

Detailed design Summary Specifications Dimensions (x,y) 26 x 26 mm A 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 design Summary Specifications Requirements A 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 lateral 9,8 kHz > 10 kHz Resonances vertical 30,4 kHz > 30 kHz

Titel van de presentatie 19-4-2017 14:26 A compact AFM scanner Introduction Research Questions Requirements specifications Concept 1 Concept 2 Detailed Design Conclusion Conclusion

Conclusion The requirements have been set up for the AFM scanner A 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

Titel van de presentatie 19-4-2017 14:26 A compact AFM scanner Introduction Research Questions Requirements specifications Concept 1 Concept 2 Detailed Design Questions? Questions?