An Introduction to Contact Resistance

Description

"Contact resistance is both an old and new topic. It is old because fundamentals of the semiconductor-metal contacts were established in the 1930s even earlier than the study on Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET). The new knowledge is on material and integration aspects for contact resistance reduction. As the MOSFETs become smaller and smaller, device parasitics start to dominate performance since the 2010s. The resistance part in MOSFET RC delay is mainly from external parasitics particularly the contact resistance. In the past decade, 3D MOSFETs, also named FinFETs, became the device structure in leading semiconductor technology. The 3D structure brings a unique opportunity for engineering the contact resistance. In physics, this book introduces MOSFET device electronics and contact physics. In material science, a variety of contact metals and silicides are covered. In electrical characterization, test structures and measurements of contact resistance are discussed in depth. Intechnology, state-of-the-art process techniques, material engineering, and integration for contact resistance reduction are introduced. This book can serve as a reference book for students in electrical engineering and material science major and professionals in semiconductor industry"-- Contents Preface Chapter 1 Introduction to Semiconductor Transistor Resistances Abstract Introduction Basic Device Characteristics MOSFETs Inversion Charge in Channel Charge-Sheet Model Current-Voltage Characteristics Constant Mobility Series Resistance in MOSFETs MOSFET Resistance Partition MOSFET Device Performance: Resistance Perspective Impact of MOSFET Scaling to Device Performance Conclusion References Chapter 2 Physics and Materials of Semiconductor-Metal Contacts Abstract Introduction 2.1. MS Contacts 2.1.1. Schottky Contact At Equilibrium (Applied Bias V = 0) Effect of Biasing 2.1.2. Ohmic Contact 2.2. Material Engineering for Ohmic MS Contact 2.2.1. Metals for MS Contact 2.2.2. Silicides 2.2.3. Challenges and Evolution of Silicides NiSi Encroachment and “NiSi-Fang” Defects Ti Liner Silicide 2.2.4. Transistor S/D Doping for Contact Resistance Conclusion References Chapter 3 Electrical Characterization of Contact Resistance Abstract Introduction 1. TLM for Contact Resistance 1.1. TLM 1.2. MR-CTLM 1.3. LTLM 2. Kelvin FET for Contact Resistance 2.1. Kelvin FET (RcFET) Kevin FET Characterization of Lateral Gate-All-Around (LGAA) FET Kevin FET Characterization of Vertical Gate-All-Around (VGAA) FET Summary References Chapter 4 Contact Resistance Reduction Approaches Abstract 4.1. Techniques for Contact Resistance Reduction in Advanced Technology 4.2. Contact Resistivity Reduction Methods 4.2.1. Contact Area Optimization 4.2.2. Schottky Barrier Height Engineering for ρC Reduction 4.2.3. Contact Interface Optimization with Trench Epitaxy 4.2.4. S/D Dopant Tuning for Contact Resistance Increase In-Situ Doping Concentration of S/D Tuning Dopant Elements Active Doping Concentration Improvement via SPE or LPE Downstream Thermal Process Optimization Conclusion References Chapter 5 Meta-Stable Alloys for Ultra-Low Contact Resistance Abstract 1. Introduction to SPE and LPE 1.1. Solid Phase Epitaxy 1.1.1. Amorphous Substrates 1.1.2. Thermal Heating 1.1.3. Crystalline and Amorphous Si and Ge 1.1.4. Crystal-Amorphous Interface 1.1.5. Intrinsic SPE 1.1.6. Dopant Dependence of SPE 1.1.7. Dopant Activation in SPE 1.1.8. Dopant Diffusion and Segregation in SPE 1.2. Liquid Phase Epitaxy 2. Contact Resistance Reduction by MetaStable Alloys in SPE and LPE Conclusion References Chapter 6 Low-Resistance Contact Integration in CMOS Technology Abstract Integration of Contact Resistivity Reduction technique in FinFET Technology 1. Increase In-Situ Doping for Contact Resistivity Reduction 2. SPE Method with Neutral Element in Ion Implantation 3. SPE Method with Doping Elements in Ion Implantation 4. CMOS Integration of Optimized SPE Methods Summary References Chapter 7 Contact Engineering of Two-Dimensional Transition Metal Dichalcogenides Abstract 7.1. Introduction 7.1.1. 2D Materials 7.1.2. Contact Geometries 7.1.3. Carrier Transport 7.2. Contact Interface 7.2.1. Different Contact Metals 7.2.2. Contact Interface Modification 7.2.3. Contact Gating 7.2.4. Contact Scaling 7.3. Benchmarking 7.4. Prospect References About the Editor Index Blank Page