Helium Ion Microscopy (eBook)

Preface 6
Contents 10
Contributors 18
Acronyms 21
Fundamentals 24
1 The Helium Ion Microscope 25
Abstract 25
1.1 Introduction 25
1.2 The GFIS Gun 26
1.3 Cryogenic Cooling 28
1.4 Vacuum System 30
1.5 Gas Delivery System 32
1.6 The Ion Optical Column 33
1.7 Beam Induced Damage 43
1.8 Detectors and Signal Chain 46
1.9 Vibrational Considerations 50
1.10 Conclusion 51
References 51
2 Single Atom Gas Field Ion Sources for Scanning Ion Microscopy 53
2.1 Introduction 53
2.2 FIM Details 59
2.2.1 Anatomy of Gas-Assisted Etching 60
2.2.2 Precursor Tip 65
2.2.3 SAT Shaping 66
2.2.4 SAT Reproducibility 67
2.2.5 Air Exposure, Thermal Stability, and Faceting 69
2.2.6 Iridium and Other Nanotip Materials 73
2.3 Performance of SATs 75
2.3.1 Best Imaging Voltage 75
2.3.2 Temperature Dependence 76
2.3.3 Shape Dependence 78
2.3.4 Current Stability 79
2.4 Conclusions 81
References 81
3 Structural Changes in 2D Materials Due to Scattering of Light Ions 84
3.1 Introduction 84
3.2 The Scattering Process 85
3.2.1 Elastic Scattering 85
3.2.2 A Note on Inelastic Scattering 87
3.3 Target Evolution Under Ion Impacts 87
3.3.1 After the Binary Collision 87
3.3.2 Molecular Dynamics Simulations of Ion Impacts on 2D Materials 91
3.3.3 Influence of Multiple Impacts 97
3.3.4 A Brief Note on the Substrate 98
3.4 Results 98
3.4.1 Graphene 98
3.4.2 Experimental Results 103
3.4.3 Other 2D Materials 104
3.5 Summary 106
References 107
4 Monte Carlo Simulations of Focused Ion Beam Induced Processing 110
4.1 Introduction 110
4.2 An Example of Monte Carlo Simulation: EnvizION Simulator 112
4.2.1 Material Database 114
4.2.2 Ion Beam Profile 114
4.2.3 Nuclear Energy Loss 114
4.2.4 Electronic Energy Loss and Stopping Cross-Section 116
4.2.5 Ion and Recoil Trajectories 117
4.2.6 Secondary Electrons 118
4.2.7 Precursor Gas Handling 119
4.2.8 Deposition and Etching 120
4.2.9 Sputtering Algorithms 121
4.3 Monte Carlo Simulations of Physical Sputtering 123
4.3.1 Sputtering of Aluminum and Tungsten 126
4.3.2 Sputtering of Copper 130
4.4 EUV Mask Repair 134
4.5 Resolution Limiting and Sputtering Limiting Effects 136
4.6 Summary 138
References 138
5 Secondary Electron Generation in the Helium Ion Microscope: Basics and Imaging 140
Abstract 140
5.1 Introduction 140
5.2 The Processes of Secondary Electron Generation in the Helium Ion Microscope 141
5.3 SE Energy Distribution in HIM 144
5.4 Imaging with SE 149
5.4.1 Topographic Yield 149
5.4.2 SE2/SE1 Ratio 150
5.4.3 SE3 151
5.4.4 Material Characterization by SE Contrast Measurements with Energy Filtering 154
5.5 Imaging Utilizing a High SE Yield in HIM: Ion-to-SE Conversion 158
5.5.1 Scanning Transmission Ion Microscopy (STIM) with SE Detector 158
5.5.2 Reflection Ion Microscopy 159
5.6 Summary 164
References 165
Microscopy 168
6 Introduction to Imaging Techniques in the HIM 169
6.1 Introduction 169
6.2 Imaging Signals and Contrast Mechanisms 170
6.2.1 Secondary Electrons 170
6.2.2 Backscattered Ions 177
6.2.3 Transmitted and Reflected Ions 179
6.2.4 Photons 181
6.3 HIM Imaging Techniques 182
6.3.1 High Resolution Imaging 182
6.3.2 Charge Neutralization 185
6.3.3 Imaging with a Large Depth of Field 186
6.4 Conclusions 190
References 190
7 HIM of Biological Samples 193
7.1 Introduction 193
7.2 Large Depth of Field Bioimaging 194
7.3 Summary 204
References 205
8 HIM Applications in Combustion Science: Imaging of Catalyst Surfaces and Nascent Soot 206
Abstract 206
8.1 Introduction 207
8.2 Organic Nanoparticles: Nascent Soot Analysis 207
8.2.1 Introduction: Soot 207
8.2.2 Soot Sampling 209
8.2.3 Imaging of Soot 209
8.2.4 Analysis of Soot from Ethylene Flames 210
8.2.5 Imaging of Soot from Different C4 Fuels 213
8.2.6 Summary: Imaging of Nascent Soot 214
8.3 CVD-Grown Films of Transition Metal Oxides 214
8.3.1 Introduction 214
8.3.2 Binary Mixtures of TMOs 217
8.3.3 Summary: Imaging PSE-CVD Grown Films 218
8.4 Summary and Conclusions 221
Acknowledgments 221
References 221
9 Channeling and Backscatter Imaging 223
9.1 Introduction 223
9.2 Directional Effects in Ion Solid Interaction 224
9.2.1 Ion Channeling 224
9.2.2 Directional Effects in Secondary Electron Emission 225
9.3 Mapping of Crystal Orientation in the Ion Microscope 228
9.4 Imaging with Ions 233
9.4.1 Backscattered Helium Versus Electrons for Image Generation 233
9.4.2 Subsurface Imaging 234
9.5 Dechanneling Contrast 235
9.5.1 Dechanneling by Thin Films 235
9.5.2 Dechanneling by Lattice Distortions 236
9.6 Summary 240
References 240
10 Helium Ion Microscopy of Carbon Nanomembranes 243
Abstract 243
10.1 Introduction 243
10.2 A Comparison Between HIM and SEM 245
10.3 CNMs on Solid Supports 247
10.4 HIM Imaging of Free-Standing CNMs (Porous Supports and TEM Grids) 248
10.5 Visualization of Large Area CNMs 254
10.6 Imaging of Hybrid and Composite Systems 255
10.7 Imaging of Perforated CNMs 256
10.8 Lithography with Nanomembranes 260
10.9 Summary 261
Acknowledgments 261
References 261
11 Helium Ion Microscopy for Two-Dimensional Materials 263
Abstract 263
11.1 Graphene Characterization 264
11.1.1 Lateral Dimension 265
11.1.2 Thickness and Work Function 267
11.1.3 Surface Contamination 269
11.1.4 Charge Compensation Effect on Graphene Imaging 271
11.1.5 Influence of Beam-Induced Contamination 273
11.2 HIM Modification of Two-Dimensional Materials 274
11.2.1 Controllable Defect Creation in 2D Materials 274
11.2.2 Nano-Patterning of 2D Materials Using HIM 276
References 279
Analysis 281
12 Backscattering Spectrometry in the Helium Ion Microscope: Imaging Elemental Compositions on the nm Scale 282
12.1 Introduction 282
12.2 Principles of Rutherford Backscattering Spectrometry 284
12.3 Challenges in Performing Rutherford Backscattering Spectrometry in the Helium Ion Microscope 287
12.3.1 Screening Effects and Cross Sections 288
12.3.2 Dual, Plural and Multiple Scattering 289
12.3.3 Charge Fraction 292
12.3.4 Sputtering 293
12.4 Experimental Approaches 296
12.4.1 Solid State Detectors 297
12.4.2 Electrostatic Analyzers 298
12.4.3 Time of Flight Spectrometry 300
12.5 Pulsed Primary Beam ToF-BS 302
12.5.1 Experimental Setup 302
12.5.2 Backscattering Spectra and Simulation 304
12.5.3 Imaging in ToF-BS Mode 307
12.5.4 Time of Flight Secondary Ion Mass Spectrometry 309
12.6 Summary 309
References 310
13 SIMS on the Helium Ion Microscope: A Powerful Tool for High-Resolution High-Sensitivity Nano-Analytics 313
Abstract 313
13.1 Secondary Ion Mass Spectrometry 313
13.1.1 Introduction 313
13.1.2 Underlying Fundamentals 314
13.1.2.1 Sputtering Processes 314
13.1.2.2 Ionisation of Sputtered Matter 317
13.1.2.3 Matrix Effect and Quantification 319
13.1.3 Instrumentation 320
13.1.4 SIMS Applications 321
13.2 Fundamental Aspects of SIMS Performed Under He+ and Ne+ Bombardment 323
13.2.1 Dimensions of Collision Cascades 323
13.2.2 Sensitivity 324
13.2.3 Detection Limit Versus Pixel/Voxel Size 327
13.3 Instrumentation for SIMS Performed on the HIM 329
13.3.1 Instrumental Constraints 329
13.3.2 Prototype Instrument for SIMS Performed on the HIM 330
13.4 SIMS Applications on the HIM 333
13.4.1 Mass Spectra 333
13.4.2 Depth Profiling 334
13.4.3 Imaging 335
13.4.4 Correlative Microscopy 336
13.5 Conclusions 338
Acknowledgments 338
References 339
14 Ionoluminescence 340
14.1 Introduction 340
14.2 Ionoluminescence in HIM 342
14.2.1 Semiconductors 342
14.2.2 Alkali Halides 347
14.2.3 Other Minerals 351
14.2.4 Immunofluorescence 354
14.3 IL Patterning 357
14.4 Interaction Volume Measurements Using IL 359
14.5 Summary 361
References 362
Modification 367
15 Direct–Write Milling and Deposition with Noble Gases 368
Abstract 368
15.1 Nanostructuring with Focused Noble Gas Ion Beams 368
15.2 FIB Milling with Noble Gas Ions 369
15.2.1 Bulk Material 369
15.2.1.1 Sputtering Resolution and Yield: He FIB 373
15.2.1.2 Sputter Resolution and Yield: Xe and Ne FIB 375
15.2.1.3 Limitations and Unwanted Artifacts 377
15.2.1.4 Examples of Applications 379
15.2.2 Membranes 381
15.2.2.1 Thick Membranes 382
15.2.2.2 Thin Membranes 382
15.3 Gas Assisted Deposition with Noble Gas Ions 385
15.3.1 Deposition Regimes: Reaction Limited Versus Mass-Transport Limited 387
15.3.1.1 Beam Scan Parameters and Scan Strategies 390
15.3.2 Adsorbate Dissociation: ESA, SE, and Thermal Spikes 391
15.3.3 Lateral Resolution 395
15.3.3.1 Low Aspect Ratio Structures 396
15.3.3.2 High Aspect Ratio Structures 397
15.3.4 Deposit Composition and Internal Structure 400
15.4 Gas Enhanced Etching with Noble Gas Ions 400
15.5 Summary 401
Acknowledgements 401
References 401
16 Resist Assisted Patterning 407
Abstract 407
16.1 Introduction to Lithography 407
16.2 Helium Ion Beam-Resist Interaction 409
16.2.1 Primary Beam Scattering (Forward Scattering) 412
16.2.2 Secondary Electron (SE) Generation 413
16.2.3 Backscattering of the Primary Beam 415
16.3 HIL Experimental Results on EBL Resists 415
16.3.1 Contrast and Sensitivity 416
16.3.2 Resolution 417
16.3.3 Point-Spread Function (PSF) 418
16.4 HIL Applications 419
16.4.1 Pre-screening of EUV Resists 419
16.4.2 Fabrication of Nanoimprint Templates 420
16.5 HIL Dose Optimization Modelling 421
16.6 HIL Versus Milling 422
16.7 Conclusions and Outlook 423
Acknowledgments 424
References 424
17 Focused Helium and Neon Ion Beam Modification of High-TC Superconductors and Magnetic Materials 427
Abstract 427
17.1 Introduction 428
17.2 Introduction to Ion Beam Modification of Superconductors 429
17.2.1 Josephson Junctions 429
17.2.2 Ion Irradiation in High-TC Superconductors 431
17.3 Ion Irradiated Josephson Junctions 435
17.3.1 Masked Ion Irradiated Josephson Junctions 435
17.3.2 GFIS Direct-Write Josephson Junctions 436
17.3.3 GFIS Direct Write Superconducting Quantum Interference Devices 441
17.3.4 Nanowire Josephson Junctions 442
17.3.5 Concluding Remarks on GFIS Fabricated High-TC Josephson Junctions 444
17.4 Nanoscale Manipulation of Magnetization Using GFIS 444
17.4.1 The Effect of Ion-Irradiation on Certain B2 Alloy Thin Film 446
17.4.2 Application of Nanofocussed Ne+ Beam to B2 Alloy Thin Films 450
17.4.3 Future Scope of GFIS-Assisted Magnetic Writing 453
17.5 Conclusions 453
References 454
18 Helium Ion Microscope Fabrication of Solid-State Nanopore Devices for Biomolecule Analysis 458
Abstract 458
18.1 Introduction 458
18.2 HIM Milling of SS-Nanopores 460
18.2.1 Nanopore Formation 461
18.2.2 DNA Translocation 463
18.2.3 Nanopore Arrays 464
18.2.4 Applications of HIM Drilled Nanopores 465
18.3 Manipulation of Device Thickness 467
18.3.1 Membrane Thinning 467
18.3.2 HIM Control of SS-Nanopore Device Dimensions 469
18.3.3 Applications of HIM-Thinned SS-Nanopores 471
18.4 Manipulating Intrinsic Membrane Fluorescence 472
18.4.1 HIM Photoluminescence Reduction 473
18.4.2 Application of HIM Photoluminescence Reduction 474
18.5 Conclusions and Outlook 475
References 477
19 Applications of GFIS in Semiconductors 482
Abstract 482
19.1 Introduction 482
19.2 GFIS Nanomachining Characteristics 483
19.2.1 Charged Particle Interaction with Materials 483
19.2.2 Charged Particle Interaction in Bulk Versus Membrane Substrates 485
19.2.3 Ion Beam Probe Current Distribution 488
19.3 Applications of GFIS in Semiconductors 490
19.3.1 Helium Applications 491
19.3.1.1 Helium Ion Microscopy 491
19.3.1.2 Voltage Contrast Imaging 493
19.3.1.3 Doping Contrast Imaging 495
19.3.1.4 Mask Repair 495
19.3.2 Neon Applications 497
19.3.2.1 Circuit Edit 497
19.3.2.2 Circuit Timing Invasiveness 499
19.3.2.3 Fault Isolation 500
19.3.2.4 TEM Lamella Preparation 501
19.4 GFIS Damage Mitigation 502
19.5 Future of GFIS Applications in Semiconductors 506
Acknowledgments 506
References 507
Appendix A The ALIS Story 510
Index 529