Germanium-Based Technologies (eBook)

Front Cover 1
Copyright Page 5
Germanium-Based Technologies 4
Contents 6
Editors 14
Contributors 15
List of Acronyms 18
List of Symbols 22
Introduction 26
1 Introduction 26
2 Historical Perspective and Milestones 26
3 Ge as a Novel ULSI Substrate: Opportunities and Challenges 30
4 Outline of the Book 31
References 34
Chapter 1 Germanium Materials 38
1.1 Introduction 38
1.2 Bulk Wafer Manufacturing 39
1.2.1 Germanium raw materials: supply and production flow sheet 39
1.2.1.1 Supply 39
1.2.1.2 Production flow sheet 41
1.2.2 Germanium crystal growth 43
1.2.2.1 Introduction and specific features of Czochralski Ge crystal growth 43
1.2.2.2 Ge single crystals for IR optics 44
1.2.2.3 HP-Ge crystals for radiation detectors 45
1.2.2.4 Dislocation-free Ge crystals 46
1.2.2.5 Modeling of Ge crystal growth 48
1.2.3 Germanium wafer manufacturing 49
1.2.3.1 Introduction 49
1.2.3.2 Wafer preparation: general remarks 50
1.2.3.3 Wafer preparation: process steps 52
1.2.3.4 Germanium recycling 57
1.3 GOI Substrates 57
1.3.1 Back-grind SOI 58
1.3.2 GOI substrates by layer transfer 60
1.3.2.1 Donor wafers 60
1.3.2.2 GOI realization 60
1.3.2.3 Characterization of GOI substrates 61
1.3.2.4 GOI MOSFETs 63
1.3.2.5 GOI as III-V epitaxy template 63
1.4 General Conclusion 63
References 64
Chapter 2 Grown-in Defects in Germanium 68
2.1 Introduction 68
2.2 Intrinsic Point Defects in Germanium 68
2.2.1 Simulation of intrinsic point defect properties 69
2.2.2 Experimental data on vacancy properties 70
2.2.3 Application of the Voronkov model to germanium 71
2.3 Extrinsic Point Defects 74
2.3.1 Dopants 74
2.3.2 Neutral point defects 74
2.3.3 Carbon 75
2.3.4 Hydrogen 75
2.3.5 Oxygen 77
2.3.6 Nitrogen 77
2.3.7 Silicon 78
2.4 Dislocation Formation During Czochralski Growth 79
2.4.1 Thermal simulation 79
2.4.2 Development of mechanical stresses 79
2.4.3 Mechanical properties of germanium 80
2.4.4 Dislocation nucleation and multiplication during crystal pulling 81
2.4.5 Electrical impact of dislocations in germanium 84
2.5 Point Defect Clustering 86
2.5.1 Experimental observations of vacancy clustering 86
2.5.2 Modeling and simulation of vacancy cluster formation 88
2.6 Conclusions 90
Acknowledgements 90
References 90
Chapter 3 Diffusion and Solubility of Dopants in Germanium 94
3.1 Introduction 94
3.2 Diffusion in Semiconductors 94
3.2.1 Diffusion mechanisms 95
3.2.2 Self-diffusion 96
3.3 Intrinsic Point Defects in Germanium 99
3.3.1 Quenching 99
3.3.2 Irradiation 101
3.4 Self- and Group IV Diffusion in Germanium and Silicon 102
3.4.1 Radioactive tracer experiments 103
3.4.2 Isotope effects and Group IV (Si Sn) diffusion in Ge
3.4.3 Doping and pressure effects 107
3.4.4 Diffusion of Ge in Si 108
3.5 Solubility of Impurities in Germanium 110
3.6 Diffusion of Group III and V Dopants in Germanium 113
3.6.1 Group III acceptor diffusion 114
3.6.1.1 Boron 114
3.6.1.2 Aluminum 115
3.6.1.3 Indium and gallium 116
3.6.2 Group V donor diffusion 116
3.6.2.1 Phosphorus 116
3.6.2.2 Arsenic 117
3.6.2.3 Antimony 118
3.6.3 Electric field effects on dopant diffusion in Ge 118
3.6.4 Summary 119
3.7 General Conclusion 120
References 120
Chapter 4 Oxygen in Germanium 124
4.1 Introduction 124
4.2 Interstitial Oxygen 125
4.2.1 Measurement of oxygen concentration 125
4.2.2 Diffusion and solubility 127
4.2.3 Structure of the vibration spectrum and defect model 129
4.3 TDs and the Oxygen Dimer 134
4.3.1 Electronic states of TDs 135
4.3.2 Vibrational spectrum of TDs 140
4.3.3 Vibrational spectrum of the oxygen dimer 145
4.4 Infrared Absorption of Oxygen Precipitates 149
4.5 The Vacancy-Oxygen Defect 151
4.6 Conclusions 153
References 153
Chapter 5 Metals in Germanium 158
5.1 Introduction 158
5.2 Copper in Germanium 159
5.2.1 Distribution coefficient k[sub(d)] 159
5.2.2 Configurations of atomic Cu in Ge 160
5.2.3 The dissociative copper diffusion mechanism 162
5.2.4 Impact of doping density on Cu diffusion and solubility 165
5.2.5 Dissociative versus kick-out mechanism for copper diffusion in germanium 167
5.2.6 Precipitation of copper in germanium 169
5.2.7 Energy levels and capture cross sections of substitutional copper 171
5.2.8 Energy level for interstitial copper and Cu[sub(s)]-Cu[sub(i)] pairs 176
5.2.9 Impact of copper on carrier lifetime in germanium 178
5.3 Ag, Au and Pt in Germanium 180
5.3.1 Distribution coefficient, solubility and diffusivity 180
5.3.2 Energy levels and capture cross sections 185
5.3.3 Impact on carrier lifetime 189
5.4 Nickel in Germanium 190
5.4.1 Solubility and diffusivity of Ni in Ge 190
5.4.2 Energy levels and capture cross sections of Ni in Ge 191
5.4.3 Impact on carrier lifetime 193
5.5 TMs in Germanium 196
5.5.1 Iron 196
5.5.2 Cobalt 197
5.5.3 Manganese 197
5.5.4 Other TMs 198
5.5.4.1 Chromium 198
5.5.4.2 Zirconium 199
5.5.4.3 Titanium and vanadium 199
5.6 Chemical Trends in the Properties of Metals in Ge 199
5.6.1 Electrical properties 199
5.6.2 Optical properties of metals in germanium 201
5.6.3 Trends in the impact on carrier lifetime in Ge 202
5.7 Conclusions 207
References 207
Chapter 6 Ab-Initio Modeling of Defects in Germanium 214
6.1 Introduction 214
6.2 Quantum Mechanical Methods 215
6.2.1 Clusters and supercells 216
6.3 Kohn–Sham and Occupancy Levels 217
6.4 Formation Energies, Vibrational Modes, Energy levels 218
6.5 Defect Modeling in Ge 219
6.6 Defects in Germanium 220
6.6.1 Vacancies and divacancies in Ge 222
6.6.2 The self-interstitial 225
6.6.3 Nitrogen defects 225
6.6.4 Carbon in germanium 226
6.6.5 Oxygen in germanium 226
6.6.6 Thermal donors 228
6.6.7 Hydrogen in germanium 229
6.7 Electrical Levels of Defects 230
6.8 Summary 232
References 233
Chapter 7 Radiation Performance of Ge Technologies 238
7.1 Introduction 238
7.2 Interaction of Radiation with Solids 239
7.2.1 Damage processes 239
7.2.2 Comparison of electron, gamma ray, neutron and proton damage 242
7.2.3 Ion-implantation damage 244
7.3 Primary Radiation-Induced Defects and their Interactions with Impurities in Crystalline Ge 246
7.3.1 Frenkel-pairs, the lattice vacancy, divacancy and self-interstitial atom in Ge 246
7.3.2 Interaction of the intrinsic points defects with impurities in Ge 248
7.3.3 Ion-implantation-induced damage: multi-vacancy and multi-self-interstitial complexes in Ge 252
7.4 Effects on Devices 254
7.5 Conclusions 256
References 256
Chapter 8 Electrical Performance of Ge Devices 260
8.1 Introduction 260
8.2 Germanium p–n Junctions 261
8.2.1 Theory of a large-area p–n junction 262
8.2.2 Theory of a planar p–n junction 266
8.2.3 Theory of an ideal germanium p–n junction 268
8.2.4 Germanium bulk p–n junction diodes 269
8.2.5 State-of-the-art shallow germanium p–n junctions 271
8.3 Germanium-Based Gate Stacks 273
8.3.1 Equivalent oxide thickness 273
8.3.2 Ge/HfO[sub(2)] gate stacks 274
8.3.3 Passivation by an ultra-thin GeON interlayer 275
8.3.4 Si surface passivation 279
8.3.5 PH[sub(3)] surface passivation 286
8.3.6 Alternative high-k on Ge 287
8.4 Conclusion 288
Acknowledgements 289
References 289
Chapter 9 Device Modeling 294
9.1 Introduction 294
9.2 Modeling Germanium versus Silicon 295
9.3 Band Structure 297
9.3.1 Conduction band of bulk germanium 297
9.3.2 Valence band of bulk germanium 299
9.3.3 Energy dispersion in germanium inversion layers: electrons 302
9.3.4 Energy dispersion in germanium inversion layers: holes 305
9.4 Performance Limit 306
9.4.1 Analytical expression for the ballistic current 306
9.4.2 Results: Ge versus Si MOSFETs 308
9.5 Semi-classical Transport 310
9.5.1 BTE: bulk semiconductor 311
9.5.2 BTE: 2D inversion layers 312
9.5.3 Solution of the BTE: methods based on the moments 312
9.5.4 Solution of the BTE: MC for bulk Ge 313
9.5.5 MC with quantum corrections 315
9.5.6 Multi-subband MC 315
9.6 Conclusions 317
References 318
Chapter 10 Nanoscale Germanium MOS Dielectrics and Junctions 322
10.1 Introduction 322
10.2 Germanium Oxynitride Dielectrics 322
10.2.1 Germanium oxynitride synthesis and properties 323
10.2.2 Basic MOS electrical characterizations 326
10.2.3 Dielectric-substrate interface analyses 329
10.2.4 Dielectric leakage behavior 333
10.2.5 Summary 333
10.3 High-permittivity Metal Oxide Dielectrics 335
10.3.1 High-k dielectrics selection criteria 335
10.3.2 ALD of high-k dielectrics 336
10.3.2.1 ALD of zirconia 337
10.3.2.2 ALD of hafnia 341
10.3.3 UVO of high-k dielectrics 348
10.3.3.1 UVO of zirconia 348
10.3.3.2 Zirconia–germanium interface photoemission spectroscopy 350
10.3.3.3 UVO of hafnia 357
10.3.4 Other high-k deposition techniques 358
10.3.4.1 Metal-organic chemical vapor deposition of hafnia 358
10.3.4.2 PVD of zirconia and hafnia 359
10.3.4.3 Atomic oxygen beam deposition of hafnia 360
10.3.5 Nanoscale dielectrics leakage and scalability 361
10.3.6 Summary 364
10.4 Shallow Junctions in Germanium 364
10.4.1 Ion implantation doping 366
10.4.1.1 p-type junction activation with furnace anneal 366
10.4.1.2 Complementary junction activation with rapid thermal anneal 369
10.4.1.3 n-type junction activation dependences 371
10.4.2 SSD doping 376
10.4.2.1 n-type junction activation and diffusion 376
10.4.2.2 Dopant deactivation within activated junctions 379
10.4.3 Metal germanide contacts 380
10.4.4 Summary 382
10.5 General Conclusion 382
References 383
Chapter 11 Advanced Germanium MOS Devices 390
11.1 Introduction 390
11.2 The Quest for High Mobility MOSFET Channel 390
11.2.1 Challenges to scaling conventional CMOS 391
11.2.2 High mobility channel justification and selection 394
11.3 Relaxed Bulk Channel Germanium MOSFETs 395
11.3.1 P-channel MOSFETs 396
11.3.1.1 Germanium oxynitride gate dielectric 396
11.3.1.2 Zirconium-based gate dielectric 396
11.3.1.3 Hafnia gate dielectric 398
11.3.2 n-channel MOSFETs 399
11.4 Strained Epitaxial Channel Germanium MOSFETs 401
11.4.1 Surface strained epitaxial channel 402
11.4.2 Buried strained epitaxial channel 402
11.5 Germanium-on-Insulator MOSFETs 404
11.6 Schottky Source-Drain Germanium MOSFETs 406
11.7 Germanium Nanowire MOSFETs 409
11.8 Conclusions 410
References 410
Chapter 12 Alternative Ge Applications 414
12.1 Introduction 414
12.2 Attractive Properties for Alternative Applications 414
12.2.1 Growth modes 415
12.2.2 Strain influence on electronic alignment 415
12.2.3 Wave guiding 416
12.2.4 Transport properties 417
12.2.5 Brillouin zone folding 418
12.3 Optoelectronics 418
12.3.1 Integration aspects 418
12.3.2 Detectors for the visible to the NIR 419
12.3.3 Modulators 427
12.3.4 Waveguides 428
12.3.5 Optical emitter 430
12.4 Solar Cells 430
12.4.1 Tandem cells 431
12.4.2 Artificial substrates for group III/V solar cells 433
12.5 QD Applications 434
12.5.1 Stressors 434
12.5.2 Memories 435
12.5.3 Tunneling 435
12.6 Field Effect Transistors (other than MOS) 435
12.6.1 MODFET 435
12.6.2 DotFET 437
12.7 Spintronics 437
12.8 Virtual Substrates 438
12.8.1 Strain adjustment 438
12.8.2 Thin virtual substrates 439
12.9 Conclusion 440
References 440
Chapter 13 Trends and Outlook 444
13.1 Introduction 444
13.2 GOI and Epitaxial Germanium Substrates 445
13.2.1 Ge condensation technique 445
13.2.2 Germanium epitaxial growth on silicon 446
13.3 Alternative Ge-based Device Concepts 451
13.3.1 GaAs and III–V on germanium FETs 451
13.3.2 Germanium nanowire and QD devices 453
13.4 Conclusions 454
References 454
Appendix 460
Index 468
A 468
B 468
C 469
D 469
E 471
F 471
G 471
H 472
I 472
J 473
K 473
L 473
M 473
N 474
O 474
P 474
Q 475
R 475
S 475
T 476
U 476
V 476
W 476
X 476
Z 476
Color Plates 36