Ferroelectric-Gate Field Effect Transistor Memories: Device Physics and Applications

Description

This book provides comprehensive coverage of the materials characteristics, process technologies, and device operations for memory field-effect transistors employing inorganic or organic ferroelectric thin films. This transistor-type ferroelectric memory has interesting fundamental device physics and potentially large industrial impact. Among various applications of ferroelectric thin films, the development of nonvolatile ferroelectric random access memory (FeRAM) has been most actively progressed since the late 1980s and reached modest mass production for specific application since 1995. There are two types of memory cells in ferroelectric nonvolatile memories. One is the capacitor-type FeRAM and the other is the field-effect transistor (FET)-type FeRAM. Although the FET-type FeRAM claims the ultimate scalability and nondestructive readout characteristics, the capacitor-type FeRAMs have been the main interest for the major semiconductor memory companies, because the ferroelectric FET has fatal handicaps of cross-talk for random accessibility and short retention time. This book aims to provide the readers with development history, technical issues, fabrication methodologies, and promising applications of FET-type ferroelectric memory devices, presenting a comprehensive review of past, present, and future technologies. The topics discussed will lead to further advances in large-area electronics implemented on glass, plastic or paper substrates as well as in conventional Si electronics. The book is composed of chapters written by leading researchers in ferroelectric materials and related device technologies, including oxide and organic ferroelectric thin films.            Preface Contents Contributors Part I Introduction 1 Features, Principles, and Developments of Ferroelectric-Gate Field-Effect Transistors 1.1 Background of Ferroelectric Memories 1.1.1 Historical Background 1.1.2 Classification of Nonvolatile Ferroelectric Memories 1.2 Degradation and Improvement of Memorized States in MFIS Structures 1.2.1 Degradation of Memorized States 1.2.2 Theoretical Analysis of the Band Profile and Retention Degradation of MFIS Capacitors 1.2.3 Calculated Time Dependences of Band Profile and Capacitance of the MFIS Structure 1.2.4 Effects of Currents Through the Ferroelectric and Insulator Layers on the Retention Characteristics of the MFIS Structure 1.2.5 Methods for Suppressing Leakage Current Through the MFIS Structure 1.2.6 Retention Improvement by Heat and Radical Treatments 1.3 Improvement of Ferroelectric-Gate FETs 1.4 Conclusion References Part II Practical Characteristics of Inorganic Ferroelectric-Gate FETs: Si-Based Ferroelectric-Gate Field Effect Transistors 2 Development of High-Endurance and Long-Retention FeFETs of Pt/CaySr1−yBi2Ta2O9/(HfO2)x(Al2O3)1−x/Si Gate Stacks 2.1 Introduction 2.2 Basic Fabrication Process and Characterization of Pt/SBT/HAO/Si FeFETs 2.2.1 Fabrication Process 2.2.2 Static Memory Window 2.2.3 Retention 2.2.4 Endurance 2.2.5 Writing Speed 2.2.6 Id–Vg and Retention at Elevated Temperatures 2.3 Requirements to the Layers in MFIS 2.3.1 Requirements to the Layers M, F, I 2.3.2 Requirements Especially to the I-and-IL Layers 2.3.3 Requirements to the F Layer 2.4 Preparation of HAO for Pt/SBT/HAO/Si Gate Stack 2.4.1 Single HAO(x) and the MIS Characters at Various Composition Ratios 2.4.2 Comparison of O2 and N2 Ambient in Depositing HAO 2.4.3 Effect of N2 Ambient Pressure Increase in Depositing HAO 2.5 Nitriding and Oxinitriding Si of MFIS FeFET 2.5.1 Direct Nitriding Si for Large Memory Window of FeFET 2.5.2 Oxinitriding Si for Improving the Si Interface of FeFET 2.6 Using CSBT Instead of SBT in FeFET 2.7 Summary References 3 Downsizing of High-Endurance and Long-Retention Pt/CaySr1−yBi2Ta2O9/(HfO2)x(Al2O3)1−x/Si FeFETs 3.1 Introduction 3.2 Downsizing Process of CSBT-Based FeFETs 3.2.1 2 μm ≤ L