Foreword ...................................................... vii
Preface ........................................................ xi
List of Abbreviations ........................................ xiii
1 Overview of CMOS Technology .................................. 1
1.1 Introduction ............................................ 1
1.2 MOS Transistor: A Quick Introduction to Classical
Models .................................................. 3
1.2.1 Current-Voltage Characteristics .................. 3
1.2.2 Threshold Voltage ................................ 6
1.3 Short-Channel Effects and Short-Channel Modifications ... 9
1.3.1 Effect on I-V Characteristics ................... 10
1.3.2 Subthreshold Conduction ......................... 11
1.3.3 Short-Channel Effects ........................... 13
1.3.3 Threshold Voltage Roll-Off ...................... 15
1.3.4 Drain-Induced Barrier Lowering (DIBL) ........... 15
1.3.5 Gate Leakage Current ............................ 17
1.3.5.1 Direct-Tunneling ....................... 18
1.3.5.2 Fowler-Nordheim Tunneling .............. 19
1.3.5.3 Poole-Frenkel Emission and Trap-
Assisted Tunneling ..................... 20
1.4 Features and Uniqueness of MOS Transistor .............. 22
1.5 MOS in Deca-Nanometer .................................. 24
1.6 Technology Trends and Options .......................... 30
1.6.1 Technology Trends ............................... 30
1.6.2 Technology Options .............................. 31
1.6.2.1 Device Structures ...................... 32
1.6.2.2 Channel Engineering .................... 34
1.6.2.3 Source and Drain Engineering ........... 37
1.6.2.4 Gate Stack Engineering ................. 38
1.6.3 More than Moore ................................. 41
1.7 Summary ................................................ 43
References .................................................. 44
2 High-k Dielectrics .......................................... 51
2.1 High-k Candidates ...................................... 51
2.2 Electronic Structure of Transition Metals and Rare
Earth Metals ........................................... 54
2.2.1 Electronegativity ............................... 54
2.2.2 Bond Radius ..................................... 56
2.3 Material Properties of Elemental Transition Metal
and Rare Metal Oxides .................................. 57
2.3.1 Atomic and Electronic Structures ................ 57
2.3.2 Electronic Structure of Some High-k Oxides ...... 62
2.3.2.1 Electronic Structure of Aluminum
Oxide .................................. 62
2.3.2.2 Electronic Structure of Crystalline
Hafnium Oxide .......................... 64
2.3.2.3 Electronic Structure of Crystalline
Zirconium Oxide ........................ 67
2.3.2.4 Electronic Structure of Rare Earth
Metal Oxides ........................... 68
2.4 Bandgap and Band Offset Energies ....................... 74
2.5 Bond Ionicity and Dielectric Constant .................. 77
2.6 Carrier Effective Masses ............................... 79
2.7 Thermal Stability ...................................... 81
2.7.1 Crystallization ................................. 81
2.7.2 Decomposition and Si Out-Diffusion .............. 83
2.8 Disorders and Defects .................................. 86
2.8.1 Intrinsic Oxygen Vacancies ...................... 88
2.8.2 Oxygen Interstitials ............................ 94
2.8.3 Grain Boundary States ........................... 96
2.8.4 Extrinsic Defects ............................... 97
2.8.5 High-k/Si Interface Traps ...................... 103
2.9 Summary ............................................... 104
References ................................................. 105
3 Complex Forms of High-k Oxides ............................. 113
3.1 Introduction .......................................... 113
3.2 Silicates and Aluminates Pseudo-Binary Alloys ......... 114
3.3 Stoichiometric Binary Alloys .......................... 118
3.4 Doping ................................................ 120
3.5 Thermal Stability and Phase Separation ................ 128
3.6 Summary ............................................... 130
References ................................................. 134
4 Dielectric Interfaces ...................................... 139
4.1 Introduction .......................................... 139
4.2 High-k/Silicon Interface .............................. 140
4.2.1 Interfacial Bonding ............................ 140
4.2.2 Bond Strain, Relaxation, and Phase Diagrams .... 148
4.2.3 Band Offsets ................................... 152
4.3 High-k/Metal Interface ................................ 154
4.3.1 Need of Metal Gate ............................. 154
4.3.2 Band Offset Energies ........................... 156
4.3.3 Interface Stability ............................ 157
4.4 Summary ............................................... 161
References ................................................. 161
5 Impacts on Device Operation ................................ 167
5.1 Introduction .......................................... 167
5.2 Gate Leakage Current .................................. 167
5.2.1 Current Conduction Mechanisms .................. 168
5.2.2 Parameters Governing the Charge Transport ...... 171
5.3 Threshold Voltage Control and Fermi-Level Pinning ..... 173
5.4 Channel Mobility ...................................... 180
5.5 Subthreshold Characteristics .......................... 182
5.6 Dielectric Breakdown .................................. 186
5.7 Hot-Carrier Effects ................................... 189
5.8 Temperature Instabilities ............................. 193
5.9 Summary ............................................... 196
References ................................................. 196
6 Fabrication Issues ......................................... 203
6.1 Process Integration ................................... 203
6.2 Atomic Layer Deposition ............................... 207
6.3 Metal Organic Chemical Vapor Deposition ............... 211
6.4 Physical Vapor Deposition ............................. 212
6.5 Etching ............................................... 213
6.6 Summary ............................................... 215
References ................................................. 215
7 Conclusions ................................................ 221
Appendix A: Fundamental Physical Constants and Unit
Conversions ................................................... 225
Appendix B: Properties of Si and SiO2 ......................... 227
Index ......................................................... 229
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