Advanced Power MOSFET Concepts: Advanced Power MOSFET Concepts.part1.rar

Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Ideal Power Switching Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Ideal and Typical Power MOSFET Characteristics . . . . . . . . . . . . . . . . . . . 3
1.3 Typical Power MOSFET Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.4 Ideal Drift Region for Unipolar Power Devices . . . . . . . . . . . . . . . . . . . . . . 6
1.5 Charge-Coupled Structures: Ideal Specific On-Resistance . . . . . . . . . . . 8
1.6 Revised Breakdown Models for Silicon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.7 Typical Power MOSFET Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1.7.1 DC-DC Sync-Buck Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1.7.2 Variable-Frequency Motor Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
1.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2 D-MOSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.1 The D-MOSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.2 Power D-MOSFET On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.2.1 Channel Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.2.2 Accumulation Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.2.3 JFET Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.2.4 Drift Region Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.2.5 N+ Substrate Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.2.6 Drain and Source Contact Resistance . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.2.7 Total On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.3 Blocking Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.3.1 Impact of Edge Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.3.2 Impact of Graded Doping Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.4 Output Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
2.4.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
2.5 Device Capacitances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
2.5.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
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2.6 Gate Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
2.6.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
2.7 Device Figures of Merit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
2.8 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
3 U-MOSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.1 The U-MOSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.2 Power U-MOSFET On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
3.2.1 Channel Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
3.2.2 Accumulation Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
3.2.3 Drift Region Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
3.2.4 Total On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
3.3 Blocking Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
3.3.1 Impact of Edge Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
3.3.2 Impact of Graded Doping Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
3.4 Output Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
3.4.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
3.5 Device Capacitances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
3.5.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
3.6 Gate Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
3.6.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
3.7 Device Figures of Merit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
3.8 Thick Trench Bottom Oxide Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
3.8.1 On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
3.8.2 Reverse Transfer Capacitance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
3.8.3 Gate Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
3.8.4 Device Figures-of-Merit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
3.9 High Voltage Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
3.9.1 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
3.10 Inductive Load Turn-Off Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 106
3.10.1 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
3.11 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
4 SC-MOSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
4.1 The SC-MOSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
4.2 Power SC-MOSFET On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
4.2.1 Channel Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
4.2.2 Accumulation Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
4.2.3 JFET Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
4.2.4 Drift Region Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
4.2.5 Total On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
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4.3 Blocking Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
4.3.1 Impact of Edge Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
4.4 Output Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
4.4.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
4.5 Device Capacitances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
4.5.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
4.6 Gate Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
4.6.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
4.7 Device Figures of Merit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
4.8 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
5 CC-MOSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
5.1 The CC-MOSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
5.2 Charge-Coupling Physics and Blocking Voltage . . . . . . . . . . . . . . . . . . 162
5.2.1 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
5.3 Power CC-MOSFET On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
5.3.1 Channel Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
5.3.2 Accumulation Resistance for Current Spreading Region . . . . 188
5.3.3 Drift Region Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
5.3.4 Total On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
5.4 Output Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
5.4.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
5.5 Device Capacitances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
5.5.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
5.6 Gate Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
5.6.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
5.7 Device Figures of Merit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
5.8 Edge Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
5.8.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
5.9 High Voltage Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
5.9.1 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
5.10 Process Sensitivity Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
5.11 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
6 GD-MOSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
6.1 The GD-MOSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
6.2 Charge-Coupling Physics and Blocking Voltage . . . . . . . . . . . . . . . . . . 244
6.2.1 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
6.3 Power GD-MOSFET On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
6.3.1 Channel Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
6.3.2 Accumulation Resistance for Current Spreading Region . . . . 266
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6.3.3 Drift Region Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266
6.3.4 Total On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
6.4 Output Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271
6.4.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272
6.5 Device Capacitances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
6.5.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
6.6 Gate Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278
6.6.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280
6.7 Device Figures of Merit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
6.8 Edge Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285
6.9 High Voltage Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285
6.9.1 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286
6.10 Process Sensitivity Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
6.11 Inductive Load Turn-Off Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 310
6.11.1 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
6.12 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
7 SJ-MOSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
7.1 The SJ–MOSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
7.2 Charge–Coupling Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
7.2.1 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
7.3 Power SJ-MOSFET On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
7.3.1 Channel Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350
7.3.2 Accumulation Resistance for Current Spreading Region . . . . 351
7.3.3 Drift Region Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351
7.3.4 Total On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353
7.4 Output Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357
7.4.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357
7.5 Device Capacitances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357
7.5.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
7.6 Gate Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
7.6.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
7.7 Device Figures of Merit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371
7.8 Edge Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
7.8.1 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374
7.9 High Voltage Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378
7.9.1 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378
7.10 Process Sensitivity Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381
7.11 Inductive Load Turn-Off Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 385
7.11.1 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389
7.12 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396
xiv Contents
8 Integral Diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399
8.1 Power MOSFET Body Diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400
8.2 Computer Power Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400
8.2.1 Power U–MOSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402
8.2.2 Power CC–MOSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407
8.2.3 Power JBSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412
8.3 Motor Control Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424
8.3.1 Power U–MOSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425
8.3.2 Power JBSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 430
8.3.3 Power GD–MOSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437
8.3.4 Power GD–JBSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443
8.3.5 Power SJ–MOSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461
8.3.6 Power SJ–JBSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467
8.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472
8.4.1 Low–Voltage Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 473
8.4.2 High–Voltage Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476
9 SiC Planar MOSFET Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477
9.1 Shielded Planar Inversion-Mode MOSFET Structure . . . . . . . . . . . . . . 478
9.1.1 Blocking Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479
9.1.2 Threshold Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484
9.1.3 On–State Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486
9.1.4 Capacitances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493
9.1.5 Gate Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 496
9.1.6 Device Figures of Merit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498
9.1.7 Inductive Load Turn-Off Characteristics . . . . . . . . . . . . . . . . . . . . . 499
9.1.8 Body-Diode Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 503
9.2 Shielded Planar ACCUFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504
9.2.1 Blocking Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 505
9.2.2 Threshold Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510
9.2.3 On–State Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512
9.2.4 Capacitances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517
9.2.5 Gate Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 519
9.2.6 Device Figures of Merit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 522
9.2.7 Inductive Load Turn-Off Characteristics . . . . . . . . . . . . . . . . . . . . . 523
9.2.8 Body–Diode Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527
9.3 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 533
10 Synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 535
10.1 Computer Power Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 536
10.1.1 Inadvertent Turn–On Suppression . . . . . . . . . . . . . . . . . . . . . . . . 537
10.1.2 Device Active Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539
Contents xv
10.1.3 Switching Power Losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540
10.1.4 Input Capacitance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540
10.1.5 Device Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540
10.2 High Voltage Motor Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543
10.3 Device Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549
10.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552
About the Author . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 557

Preface
With increased awareness of the adverse impact on the environment resulting from
carbon emissions into the atmosphere, there is a growing demand for improving the
efficiency of power electronic systems. Power semiconductor devices are recognized
as a key component of all power electronic systems. It is estimated that at
least 50 percent of the electricity used in the world is controlled by power devices.
With the wide spread use of electronics in the consumer, industrial, medical, and
transportation sectors, power devices have a major impact on the economy because
they determine the cost and efficiency of systems. After the initial replacement of
vacuum tubes by solid state devices in the 1950s, semiconductor power devices
have taken a dominant role with silicon serving as the base material. These developments
have been referred to as the Second Electronic Revolution.
In the 1970s, the power MOSFET product was first introduced by International
Rectifier Corporation. Although initially hailed as a replacement for all bipolar
power devices due to its high input impedance and fast switching speed, the silicon
power MOSFET has successfully cornered the market for low voltage (<100 V)
and high switching speed (>100 kHz) applications but failed to make serious
inroads in the high voltage arena. This is because the on-state resistance of silicon
power MOSFETs increases very rapidly with increase in the breakdown voltage.
The resulting high conduction loss, even when using larger more expensive die,
degrades the overall system efficiency.
The large on-state voltage drop for high voltage silicon power MOSFETs and the
large drive current needed for silicon power bipolar transistors encouraged the
development of the insulated gate bipolar transistor (IGBT) [1]. First commercialized
in the early 1980s, the IGBT has become the dominant device used in all
medium and high power electronic systems in the consumer, industrial, transportation,
and military systems, and even found applications in the medical sector. The
US Department of Energy has estimated that the implementation of IGBT-based
variable speed drives for controlling motors is producing an energy savings of over
2 quadrillion btus per year, which is equivalent to 70 Giga-Watts of power. This
energy savings eliminates the need for generating electricity from 70 coal-fired
vii
power-plants resulting in reducing carbon dioxide emissions by over one-Trillion
pounds each year.
With on-going investments in renewable energy sources such as wind and solar
power that utilize power semiconductor device in inverters, it is anticipated that
there will be an increasing need for technologists trained in the discipline of
designing and manufacturing power semiconductor devices. My recently published
textbook [2] provides a comprehensive analysis of the basic power rectifier and
transistor structures. This textbook has been complemented with a monograph on
“Advanced Power Rectifier Concepts” to familiarize students and engineering
professionals with structures that exhibit improved performance attributes.
This monograph introduces the reader to advanced power MOSFET concepts
that enable improvement of performance of these transistor structures. For the
convenience of readers, analysis of the basic transistor structures, with the same
voltage ratings as the novel device structures, have been included in the monograph
to enable comparison of the performance. As in the case of the textbook, analytical
expressions that describe the behavior of the advanced power MOSFET structures
have been rigorously derived using the fundamental semiconductor Poisson’s,
continuity, and conduction equations in this monograph. The electrical characteristics
of all the power MOSFETs discussed in this book can be computed using
these analytical solutions as shown by typical examples provided in each section. In
order to corroborate the validity of these analytical formulations, I have included
the results of two-dimensional numerical simulations in each section of the book.
The simulation results are also used to further elucidate the physics and point out
two-dimensional effects whenever relevant. Due to increasing interest in the utilization
of wide band-gap semiconductors for power devices, the book includes the
analysis of silicon carbide structures.
In the first chapter, a broad introduction to potential applications for power
devices is provided. The electrical characteristics for ideal power MOSFETs are
then defined and compared with those for typical devices. The second and third
chapters provide analyses of the planar DMOSFET structure and the trench-gate
UMOSFET structure with 30-V blocking capability, which can be used as a benchmark
for understanding the improvements achieved using the advanced device
concepts. The analysis includes the on-resistance, the input capacitance, the gate
charge, and the output characteristics.
The next four chapters are devoted to various advanced power MOSFET structures
that allow improvement in the performance of devices with 30-V blocking
capability. The fourth chapter discusses on the “Shielded Channel Planar Power
MOSFET” structure, which allows a significant reduction in the gate charge while
achieving a specific on-resistance close to that of the UMOSFET structure. The
fifth chapter discusses the power CC-MOSFET structure, which utilizes the twodimensional
charge coupling effect to reduce the specific on-resistance by an order
of magnitude. This structure is favorable for use as a synchronous rectifier in the
sync-buck circuit topology used in voltage regulator modules for providing power
to microprocessors in computers.
viii Preface
The next two chapters are devoted to high-voltage silicon device structures that
utilize the charge-coupling concept to reduce the resistance of the drift region. In
chapter six, the charge-coupling phenomenon is accomplished by using a graded
doping profile in conjunction with an electrode embedded in an oxide coated trench
to create the power GD-MOSFET structure. In chapter seven, the charge-coupling
phenomenon is accomplished with adjacent p-type and n-type layers in the drift
region to create the power SJ-MOSFET structure.
Chapter eight provides a detailed discussion of the body-diode within the various
silicon power MOSFET structures. The body-diode can be used in place of the flyback
rectifier utilized in the H-bride circuit commonly used for motor control
applications. It is demonstrated in this chapter that the judicious utilization of a
Schottky contact within the power MOSFET cell structure can greatly improve the
reverse recovery behavior of the body-diode.
Improvement in the performance of high voltage power MOSFET structures can
also be achieved by replacing silicon with silicon carbide as the base material [3].
The much larger breakdown field strength for 4H-SiC allows increasing the doping
concentration in the drift region by a factor of 200-times while shrinking the
thickness of the drift region by one-order of magnitude. However, the silicon
power MOSFET structure must be modified to shield the gate oxide from the
much larger electric fields prevalent in silicon carbide to avoid rupture. In addition,
the base region must be shielded to avoid reach-through breakdown. The onresistance
of these devices becomes limited by the channel resistance.
The final chapter provides a comparison of all the power MOSFET structures
discussed in this book. The devices are first compared for the 30-V rating suitable
for VRM applications and then with the 600-V rating suitable for motor control
applications. In addition, the performance of all the devices is compared over a
wide range of blocking voltages to provide a broader view.
I am hopeful that this monograph will be useful for researchers in academia and
to product designers in the industry. It can also be used for the teaching of courses
on solid state devices as a supplement to my textbook [2].
December, 2009 B. Jayant Baliga
Raleigh, NC

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