Preface ......................................................... X
List of Contributors .......................................... XIX
I. Basic Principles and Theory ................................. 1
1. Phase-Coherent Transport .................................... 3
Thomas Schäpers
1.1. Introduction .......................................... 3
1.2. Characteristic Length Scales .......................... 4
1.2.1. Elastic Mean Free Path ........................ 4
1.2.2. Inelastic Mean Free Path ...................... 5
1.2.3. Phase-Coherence Length ........................ 5
1.2.4. Transport Regimes ............................. 6
1.3. Ballistic Transport ................................... 7
1.3.1. Landauer-Buttiker Formalism ................... 7
1.3.2. Split-Gate Point Contact ...................... 9
1.4. Weak Localization .................................... 13
1.4.1. Basic Principles ............................. 14
1.4.2. Weak Localization in One and Two Dimensions .. 15
1.4.3. Weak Localization in a Magnetic Field ........ 16
1.5. Spin-Effects: Weak Antilocalization .................. 19
1.6. Al'tshuler-Aronov-Spivak Oscillations ................ 21
1.7. The Aharonov-Bohm Effect ............................. 23
1.8. Universal Conductance Fluctuations ................... 27
1.8.1. Basic Principles ............................. 27
1.8.2. Detailed Analysis ............................ 29
1.8.3. Fluctuations in Long Wires ................... 31
1.8.4. Energy and Temperature Dependence ............ 32
1.9. Concluding Remarks ................................... 33
References ................................................. 34
2. Charge Transport and Single-Electron Effects in
Nanoscale Systems .......................................... 37
Joseph M.Thijssen,; Herre S.J. van der Zant
2.1. Introduction: Three-Terminal Devices and
Quantization ......................................... 37
2.2. Description of Transport ............................. 40
2.2.1. Structure of Nanoscale Devices ............... 40
2.2.1.1. The Reservoirs ..................... 40
2.2.1.2. The Leads .......................... 41
2.2.1.3. The Island ......................... 41
2.2.2. Transport .................................... 42
2.2.2.1. Coherent-Incoherent Transport ...... 43
2.2.2.2. Elastic-Inelastic Transport ........ 44
2.2.2.3. Resonant-Off-Resonant Transport .... 44
2.2.2.4. First-Order versus Higher-Order
Processes .......................... 44
2.2.2.5. Direct Tunneling ................... 45
2.3. Resonant Transport ................................... 45
2.4. Constant Interaction Model ........................... 49
2.5. Charge Transport Measurements as a Spectroscopic
Tool ................................................. 53
2.5.1. Electronic Excitations ....................... 55
2.5.2. Including Vibrational States ................. 57
2.6. Second-Order Processes ............................... 59
2.6.1. The Kondo Effect in a Quantum Dot with
an Unpaired Electron ......................... 60
2.6.2. Inelastic Co-Tunneling ....................... 61
References ................................... 63
3. Spin Injection-Extraction Processes in Metallic and
Semiconductor Heterostructures ............................. 65
Alexander M.Bratkovsky
3.1. Introduction ......................................... 65
3.2. Main Spintronic Effects and Devices .................. 67
3.2.1. TMR .......................................... 67
3.2.2. GMR .......................................... 68
3.2.3. (Pseudo)Spin-Torque Domain Wall Switching
in Nanomagnets ............................... 70
3.3. Spin-Orbital Coupling and Electron Interference
Semiconductor Devices ................................ 72
3.3.1. Spin-Hall Effect (SHE) and
Magnetoresistance due to Edge Spin
Accumulation ................................. 74
3.3.2. Interacting Spin Logic Circuits .............. 76
3.4. Tunnel Magnetoresistance ............................. 77
3.4.1. Impurity Suppression of TMR .................. 80
3.4.2. Negative Resonant TMR? ....................... 81
3.4.3. Tunneling in Half-Metallic Ferromagnetic
Junctions .................................... 82
3.4.4. Surface States Assisted TMR .................. 84
3.4.5. Inelastic Effects in TMR ..................... 84
3.5. Spin Injection/Extraction into (from)
Semiconductors ....................................... 86
3.5.1. Spin Tunneling through Modified
(Delta-Doped) Schottky Barrier ............... 89
3.5.2. Conditions for Efficient Spin Injection
and Extraction ............................... 95
3.5.3. High-Frequency Spin-Valve Effect ............. 97
3.5.4. Spin-Injection Devices ....................... 99
3.5.5. Spin Source of Polarized Radiation .......... 101
3.6. Conclusions ......................................... 104
References .......................................... 104
4. Physics of Computational Elements ......................... 109
Victor V.Zhirnov and Ralph K.Cavin
4.1. The Binary Switch as a Basic Information-
Processing Element .................................. 209
4.1.1. Information and Information Processing ...... 109
4.1.2. Properties of an Abstract Binary
Information-Processing System ............... 110
4.2. Binary State Variables .............................. 111
4.2.1. Essential Operations of an Abstract
Binary Switch ............................... 111
4.2.2. The Use of Particles to Represent Binary
Information ................................. 111
4.3. Energy Barriers in Binary Switches .................. 113
4.3.1. Operation of Binary Switches in the
Presence of Thermal Noise ................... 113
4.3.2. Quantum Errors .............................. 114
4.3.3. A Combined Effect of Classical and
Quantum Errors .............................. 116
4.4. Energy Barrier Framework for the Operating
Limits of Binary Switches ........................... 116
4.4.1. Limits on Energy ............................ 116
4.4.2. Limits on Size .............................. 117
4.4.3. Limits on Speed ............................. 118
4.4.4. Energy Dissipation by Computation ........... 119
4.5. Physics of Energy Barriers .......................... 119
4.5.1. Energy Barrier in Charge-Based Binary
Switch ...................................... 120
4.5.2. Energy Barrier in Spin-Based Binary
Switch ...................................... 124
4.5.3. Energy Barriers for Multiple-Spin Systems ... 128
4.5. A. Energy Barriers for the Optical Binary Switch ... 130
4.6. Conclusions ......................................... 131
References .......................................... 132
II. Nanofabrication Methods .................................. 135
5. Charged-Particle Lithography .............................. 137
Lothar Berger, Johannes Kretz, Dirk Beyer, and
Anatol Schwersenz
5.1. Survey .............................................. 137
5.2. Electron Beam Lithography ........................... 141
5.2.1. Introduction ................................ 141
5.2.1.1. Electron Sources .................. 141
5.2.1.2. Electron Optics ................... 142
5.2.1.3. Gaussian Beam Lithography ......... 147
5.2.1.4. Shaped Beam Lithography ........... 148
5.2.1.5. Patterning ........................ 151
5.2.2. Resists ..................................... 153
5.2.3. Applications ................................ 158
5.2.3.1. Photolithography Masks ............ 158
5.2.3.2. Direct-Write Lithography .......... 162
5.2.3.3. Maskless Lithography .............. 164
5.2.3.4. Imprint Templates ................. 170
5.3. Ion Beam Lithography ................................ 172
5.3.1. Introduction ................................ 172
5.3.1.1. Ion Sources ....................... 173
5.3.1.2. Ion Optics ........................ 173
5.3.1.3. Patterning ........................ 173
5.3.2. Applications ................................ 173
5.3.2.1. Direct-Structuring Lithography .... 174
5.3.2.2. Imprint Templates ................. 176
5.4. Conclusions ......................................... 176
References ................................................ 177
6. Extreme Ultraviolet Lithography ........................... 181
Klaus Bergmann, Larissa Juschkin, and Reinhart
Poprawe
6.1. Introduction ........................................ 181
6.1.1. General Aspects ............................. 181
6.1.2. System Architecture ......................... 182
6.2. The Components of EUV Lithography ................... 185
6.2.1. Light Sources ............................... 185
6.2.1.1. Plasmas as EUV Radiators .......... 186
6.2.1.2. Laser-Induced Plasmas ............. 187
6.2.1.3. Gas Discharge Plasmas ............. 188
6.2.1.4. Source Concepts and Current
Status ............................ 189
6.2.2. Collectors and Debris Mitigation ............ 191
6.2.3. Multilayer Optics ........................... 194
6.2.4. Masks ....................................... 198
6.2.5. Resist ...................................... 199
6.3. Outlook ............................................. 203
References ................................................ 204
7. Non-Optical Lithography ................................... 209
Clivia M.Sotomayor Torres andjouni Ahopelto
7.1. Introduction ........................................ 209
7.2. Nanoimprint Lithography ............................. 210
7.2.1. The Nanoimprint Process ..................... 210
7.2.2. Polymers for Nanoimprint Lithography ........ 211
7.2.3. Variations of NIL Methods ................... 215
7.2.3.1. Single-Step NIL ................... 215
7.2.3.2. Step-and-Stamp Imprint
Lithography ....................... 216
7.2.3.3. Step-and-Flash Imprint
Lithography ....................... 216
7.2.3.4. Roll-to-Roll Printing ............. 217
7.2.4. Stamps ...................................... 217
7.2.5. Residual Layer and Critical Dimensions ...... 222
7.2.6. Towards 3-D Nanoimprinting .................. 227
7.2.7. The State of the Art ........................ 230
7.3. Discussion .......................................... 230
7.4. Conclusions ......................................... 234
References ................................................ 235
8. Nanomanipulation with the Atomic Force Microscope ......... 239
Ari Requicha
8.1. Introduction ........................................ 239
8.2. Principles of Operation of the AFM .................. 242
8.2.1. The Instrument and its Modes of Operation ... 242
8.2.2. Spatial Uncertainties ....................... 247
8.3. Nanomanipulation: Principles and Approaches ......... 250
8.3.1. LMR Nanomanipulation by Pushing ............. 250
8.3.2. Other Approaches ............................ 253
8.3.3. Manipulation and Assembly of
Nanostructures .............................. 256
8.4. Manipulation Systems ................................ 260
8.4.1. Interactive Systems ......................... 260
8.4.2. Automated Systems ........................... 261
8.5. Conclusion and Outlook .............................. 265
References ................................................ 267
9. Harnessing Molecular Biology to the Self-Assembly of
Molecular-Scale Electronics ............................... 275
Uri Sivan
9.1. Introduction ........................................ 275
9.2. DNA-Templated Electronics ........................... 278
9.2.1. Scaffolds and Metallization ................. 278
9.2.2. Sequence-Specific Molecular Lithography ..... 281
9.2.3. Self-Assembly of a DNA-Templated Carbon
Nanotube Field-Effect Transistor ............ 284
9.3. Recognition of Electronic Surfaces by Antibodies .... 288
9.4. Molecular Shift-Registers and their Use as
Autonomous DNA Synthesizers [11] .................... 293
9.4.1. Molecular Shift-Registers ................... 293
9.4.2. Error Suppression and Analogy Between
Synthesis and Communication Theory .......... 298
9.5. Future Perspectives ........................... 300
References ................................................ 301
10. Formation of Nanostructures by Self-Assembly ............. 305
Melanie Homberger, Silvia Karthauser, Ulrich Simon,
and Bert Voigtlander
10.1. Introduction ........................................ 305
10.2. Self-Assembly by Epitaxial Growth ................... 306
10.2.1. Physical Principles of Self-Organized
Epitaxial Growth ............................ 306
10.2.1.1. Epitaxial Growth Techniques ....... 306
10.2.1.2. Kinetically Limited Growth in
Homoepitaxy ....................... 307
10.2.1.3. Thermodynamically Stable
Nanostructures .................... 309
10.2.1.4. Nanostructure Formation in
Heteroepitaxial Growth ............ 311
10.2.2. Semiconductor Nanoislands and Nanowires ..... 313
10.2.2.1. Stranski-Krastanov Growth of
Nanoislands ....................... 313
10.2.2.2. Lateral Positioning of
Nanoislands by Growth on
Templates ......................... 314
10.2.2.3. Silicide Nanowires ................ 315
10.2.2.4. Monolayer-Thick Wires at Step
Edges ............................. 315
10.2.3. Hybrid Methods: The Combination of
Lithography and Self-Organized Growth ....... 317
10.2.4. Inorganic Nanostructures as Templates
for Molecular Layers ........................ 318
10.3. Molecular Self-Assembly ............................. 320
10.3.1. Attaching Molecules to Surfaces ............. 321
10.3.1.1. Preparation of Substrates ......... 322
10.3.1.2. Preparation of Self-Assembled
Monolayers ........................ 322
10.3.1.3. Preparation of Mixed Self-
Assembled Monolayers .............. 323
10.3.2. Structure of Self-Assembled Monolayers ...... 324
10.3.2.1. Organothiols on Metals ............ 325
10.3.2.2. Carboxylates on Copper ............ 326
10.3.3. Supramolecular Nanostructures 327
10.3.4. Applications of Self-Assembled Monolayers ... 330
10.3.4.1. Surface Modifications ............. 330
10.3.4.2. Adsorption of Nanocomponents ...... 330
10.3.4.3. Steps to Nanoelectronic Devices ... 331
10.4. Preparation and Self-Assembly of Metal
Nanoparticles ....................................... 334
10.4.1. Preparation of Metal Nanoparticles .......... 334
10.4.2. Assembly of Metal Nanoparticles ............. 337
10.4.2.1. Three-Dimensional Assemblies ...... 337
10.4.2.2. Two-Dimensional Assemblies: The
Formation of Monolayers ........... 339
10.4.2.3. One-Dimensional Assemblies ........ 341
10.5. Conclusions ......................................... 344
References ................................................ 344
III. High-Density Memories .................................... 349
11. Flash-Type Memories ....................................... 351
Thomas Mikolajick
11.1. Introduction ........................................ 351
11.2. Basics of Flash Memories ............................ 353
11.2.1. Programming and Erase Mechanisms ............ 353
11.2.1.1. Hot Carrier Injection ............. 354
11.2.1.2. Fowler-NordheimTunneling .......... 357
11.2.1.3. Array Architecture ................ 358
11.3. Floating-Gate Flash Concepts ........................ 359
11.3.1. The Floating-Gate Transistor ................ 359
11.3.2. NOR Flash ................................... 361
11.3.3. NAND Flash .................................. 363
11.3.4. Reliability Aspects of Floating-Gate
Flash ....................................... 365
11.3.5. Scaling of Floating-Gate Flash .............. 366
11.4. Charge-Trapping Flash ............................... 370
11.4.1. SONOS ....................................... 370
11.4.2. Multi-Bit Charge Trapping ................... 372
11.4.3. Scaling of Charge-Trapping Flash ............ 375
11.5. Nanocrystal Flash Memories .......................... 376
11.6. Summary and Outlook ................................. 378
References ................................................ 379
12. Dynamic Random Access Memory .............................. 383
Fumio Horiguchi
12.1. DRAM Basic Operation ................................ 383
12.2. Advanced DRAM Technology Requirements ............... 384
12.3. Capacitor Technologies .............................. 385
12.4. Array Transistor Technologies ....................... 389
12.5. Capacitorless DRAM (Floating Body Cell) ............. 393
12.6. Summary 395 References .............................. 395
13. Ferroelectric Random Access Memory ........................ 397
Soon Oh Park, Byoung Jae Bae, Dong Chul Yoo,
U-In Chung
13.1. An Introduction to FRAM ............................. 397
13.1.1. 1T1C and 2T2C-Type FRAM ..................... 398
13.1.2. Cell Operation and Sensing Scheme of
Capacitor-Type FRAM
13.2. Ferroelectric Capacitors ............................ 401
13.2.1. Ferroelectric Oxides ........................ 401
13.2.2. Fatigue ..................................... 402
13.2.3. Retention ................................... 403
13.2.3.1. Crystallinity of PZT Film ......... 406
13.2.3.2. The MOCVD Deposition Process ...... 406
13.2.3.3. Perovskite Oxide Electrode ........ 407
13.3. Cell Structures ..................................... 408
13.3.1. CUB Structure ............................... 408
13.3.2. COB Structure ............................... 410
13.4. High-Density FRAM ................................... 410
13.4.1. Area Scaling ................................ 410
13.4.2. Voltage Scaling ............................. 412
13.4.3. 3-D Capacitor Structure ..................... 423
13.4.3.1. Limitation of Planar
Capacitor ......................... 413
13.4.3.2. Demonstration of a 3-D
Capacitor ......................... 413
13.5. Summary and Conclusions ............................. 417
References ................................................ 417
14. Magnetoresistive Random Access Memory ..................... 419
Michael C.Caidis
14.1. Magnetoresistive Random Access Memory (MRAM) ........ 419
14.2. Basic MRAM .......................................... 420
14.3. MTJ MRAM ............................................ 422
14.3.1. Antiferromagnet ............................. 426
14.3.2. Reference Layer ............................. 427
14.3.3. Tunnel Barrier .............................. 427
14.3.4. Free Layer .................................. 428
14.3.5. Substrate ................................... 428
14.3.6. Seed Layer .................................. 428
14.3.7. Cap Layer ................................... 429
14.3.8. Hard Mask ................................... 429
14.4. MRAM Cell Structure and Circuit Design .............. 429
14.4.1. Writing the Bits ............................ 429
14.4.2. Reading the Bits ............................ 433
14.4.3. MRAM Processing Technology and.
Integration ................................. 436
14.4.3.1. Process Steps ..................... 437
14.5. MRAM Reliability .................................... 439
14.5.1. Electromigration ............................ 439
14.5.2. Tunnel Barrier Dielectrics .................. 440
14.5.3. BEOLThermal Budget .......................... 440
14.5.4. Film Adhesion ............................... 441
14.6. The Future of MRAM .................................. 441
References ................................................ 443
15. Phase-Change Memories ..................................... 447
Andrea L.Lacaita and Dirk J.Wouters
15.1. Introduction ........................................ 447
15.1.1. The Non-Volatile Memory Market, Flash
Memory Scaling, and the Need for New
Memories .................................... 447
15.1.2. PCM Memories ................................ 448
15.2. Basic Operation of the Phase-Change Memory Cell ..... 449
15.2.1. Memory Element and Basic Switching
Characteristics ............................. 449
15.2.2. SET and RESET Programming Characteristics ... 452
15.3. Phase-Change Memory Materials ....................... 453
15.3.1. The Chalcogenide Phase-Change Materials:
General Characteristics ..................... 453
15.3.1.1. The Pseudo-Binary GeTe-Sb2Te3
Compositions ...................... 454
15.3.1.2. Compositions Based on the
Sb2Te3o "Eutectic" Compound ....... 454
15.3.1.3. Other Material Compositions ....... 455
15.3.1.4. N- or O-Doped GST ................. 455
15.3.2. Material Structure .......................... 455
15.3.2.1. Long-Range Order: Crystalline
State in GST and Doped Sb-Te ...... 455
15.3.2.2. Short-Range Order in
Crystalline versus Amorphous
State ............................. 455
15.3.3. Specific Properties Relevant to PCM ......... 457
15.4. Physics and Modeling of PCM ......................... 458
15.4.1. Amorphization and Crystallization
Processes ................................... 458
15.4.2. Band-Structure and Transport Model .......... 459
15.4.3. Modeling of the SET and RESET Switching
Phenomena ................................... 462
15.4.4. Transient Behavior .......................... 463
15.5. PCM Integration and Cell Structures ................. 464
15.5.1. PCM Cell Components ......................... 464
15.5.2. Integration Aspects ......................... 466
15.5.3. PCM Cell Optimization ....................... 467
15.5.3.1. Concentrating the Volume of
Joule Heating ..................... 467
15.5.3.2. Improving the Thermal
Resistance ........................ 467
15.6. Reliability ......................................... 469
15.6.1. Introduction ................................ 469
15.6.2. Retention for PCM: Thermal Stability ........ 469
15.6.3. Cycling and Failure Modes ................... 470
15.6.4. Read and Program Disturbs ................... 472
15.7. Scaling of Phase-Change Memories .................... 472
15.7.1. Temperature Profile Distributions ........... 472
15.7.2. Scaling of the Dissipated Power and
Reset Current ............................... 473
15.7.3. Voltage Scaling ............................. 475
I5.7.4. Cell Size Scaling ........................... 476
15.7.5. Scaling and Cell Performance: Figure of
Merit for PCM ............................... 478
15.7.6. Physical Limits of Scaling .................. 478
15.8. Conclusions ......................................... 479
References ................................................ 480
16. Memory Devices Based on Mass Transport in Solid
Electrolytes .............................................. 485
Michael N.Kozicki and Maria Mitkova
16.1. Introduction ........................................ 485
16.2. Solid Electrolytes .................................. 486
16.2.1. Transport in Solid Electrolytes ............. 486
16.2.2. Major Inorganic Solid Electrolytes .......... 488
16.2.3. Chakogenide Glasses as Electrolytes ......... 490
16.2.4. The Nanostructure of Ternary
Electrolytes ................................ 492
16.3. Electrochemistry and Mass Transport ................. 494
16.3.1. Electrochemical Cells for Mass Transport .... 494
16.3.2. Electrodeposit Morphology ................... 497
16.3.3. Growth Rate ................................. 500
16.3.4. Charge, Mass, Volume, and Resistance ........ 501
16.4. Memory Devices ...................................... 504
16.4.1. Device Layout and Operation ................. 504
16.4.2. Device Examples ............................. 506
16.4.3. Technological Challenges and Future
Directions .................................. 511
16.5. Conclusions ......................................... 513
References .................................................... 513
Index ......................................................... 517
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