Junctionless Field-Effect Transistors

Preface xi

1 Introduction to Field-Effect Transistors 1

1.1 Transistor Action 2

1.2 Metal-Oxide-Semiconductor Field-Effect Transistors 4

1.3 MOSFET Circuits: The Need for Complementary MOS 9

1.4 The Need for CMOS Scaling 11

1.5 Moore's Law 13

1.6 Koomey's Law 13

1.7 Challenges in Scaling the MOSFET 13

1.8 Conclusion 23

References 23

2 Emerging FET Architectures 27

2.1 Tunnel FETs 28

2.2 Impact Ionization MOSFET 34

2.3 Bipolar I-MOS 39

2.4 Negative Capacitance FETs 41

2.5 Two-Dimensional FETs 46

2.6 Nanowire FETs 49

2.7 Nanotube FETs 51

2.8 Conclusion 57

References 58

3 Fundamentals of Junctionless Field-Effect Transistors 67

3.1 Device Structure 69

3.2 Operation 70

3.3 Design Parameters 80

3.4 Parameters that Affect the Performance 82

3.5 Beyond Silicon JLFETS: Other Materials 100

3.6 Challenges 103

3.7 Conclusion 110

References 111

4 Device Architectures to Mitigate Challenges in Junctionless Field-Effect Transistors 125

4.1 Junctionless Accumulation-Mode Field-Effect Transistors 126

4.2 Realizing Efficient Volume Depletion 129

4.3 SOI JLFET with a High- Box 131

4.4 Bulk Planar JLFET 137

4.5 JLFET with a Nonuniform Doping 140

4.6 JLFET with a Step Doping Profile 144

4.7 Multigate JLFET 149

4.8 JLFET with a High- Spacer 153

4.9 JLFET with a Dual Material Gate 157

4.10 Conclusion 162

References 162

5 Gate-Induced Drain Leakage in Junctionless Field-Effect Transistors 173

5.1 Hole Accumulation 174

5.2 Parasitic BJT Action 176

5.3 Impact of BTBT-Induced Parasitic BJT Action on Scaling 177

5.4 Impact of Silicon Film Thickness on GIDL 179

5.5 Impact of Doping on GIDL 187

5.6 Impact of Spacer Design on GIDL 189

5.7 Nature of GIDL in Different NWFET Configurations 190

5.8 Device Architectures to Mitigate GIDL 199

5.9 Conclusion 248

References 249

6 Impact Ionization in Junctionless Field-Effect Transistors 255

6.1 Impact Ionization 256

6.2 Floating Body Effects in Silicon-on-Insulator MOSFETs 256

6.3 Nature of Impact Ionization in JLFETs 260

6.4 Zero Gate Oxide Thickness Coefficient 263

6.5 Single Transistor Latch-Up in JLFETs 266

6.6 Impact of Body Bias on Impact Ionization in JLFETs 267

6.7 Subband Gap Impact Ionization in DGJLFETS with Asymmetric Operation 268

6.8 Impact of Gate Misalignment on Impact Ionization in DGJLFETs 270

6.9 Spacer Design Guideline from Impact Ionization Perspective 272

6.10 Hysteresis and Snapback in JLFETs 273

6.11 Impact of Heavy-Ion Irradiation on JLFETs 275

6.12 Conclusions 276

References 276

7 Junctionless Devices Without Any Chemical Doping 281

7.1 Charge Plasma Doping 282

7.2 Charge Plasma Based p-n Diode 283

7.3 Junctionless I-MOS FET 288

7.4 Junctionless Tunnel FETs 290

7.5 JLTFET on a Highly Doped Silicon Film 294

7.6 Bipolar Enhanced JLTFET 294

7.7 Junctionless FETS Without Any Chemical Doping 297

7.8 Challenges for CPJLFETs 302

7.9 Electrostatic Doping Based FETs 312

7.10 Conclusions 319

References 319

8 Modeling Junctionless Field-Effect Transistors 327

8.1 Introduction to FET Modeling 328

8.2 Surface Potential Modeling of JLFETs 330

8.3 Charge-Based Modeling Approach 351

8.4 Drain Current Modeling Approach 355

8.5 Modeling Short-Channel JLFETs 365

8.6 Modeling Quantum Confinement 372

8.7 Conclusion 379

References 379

9 Simulation of JLFETS Using Sentaurus TCAD 385

9.1 Introduction to TCAD 386

9.2 Tool Flow 387

9.3 Sample Input Deck for Long-Channel JLFETS 391

9.4 Model Calibration 407

9.5 Model Calibration for Short-Channel JLFETs 409

9.6 Model Calibration for NWFETS 422

References 436

10 Conclusion and Perspectives 439

10.1 JLFETS As a Label-Free Biosensor 441

10.2 JLFETS As Capacitorless DRAM 443

10.3 Nanowire Junctionless NAND Flash Memory 444

10.4 Junctionless Polysilicon TFTS with a Hybrid Channel 447

10.5 JLFETS for 3D Integrated Circuits 449

10.6 Summary 450

References 451

Index 457