Piezoresistive Effect of p-Type Single Crystalline 3C-SiC: Silicon Carbide Mechanical Sensors for Harsh Environments (Springer Theses)

This book addresses the piezoresistance in p-type 3C-SiC, which it investigates using experimental characterization and theoretical analysis. The gauge factor, the piezoresistive coefficients in two-terminal and four-terminal resistors, the comparison between single crystalline and nanocrystalline SiC, along with the temperature dependence of the piezoresistive effect in p-type 3C-SiC are also discussed. Silicon carbide (SiC) is an excellent material for electronic devices operating at high temperatures, thanks to its large energy band gap, superior mechanical properties and extreme chemical inertness. Among the numerous poly types of SiC, the cubic single crystal, which is also well known as 3C-SiC, is the most promising platform for microelectromechanical (MEMS) applications, as it can be epitaxially grown on an Si substrate with diameters of up to several hundred millimeters. This feature makes 3C-SiC compatible with the conventional Si-based micro/nano processing and also cuts down the cost of SiC wafers. The investigation into the piezoresistive effect in 3CSiC is of significant interest for the development of mechanical transducers such as pressure sensors and strain sensors used for controlling combustion and deep well drilling. Although a number of studies have focused on the piezoresistive effect in n-type 3C-SiC, 4H-SiC and 6H-SiC, comparatively little attention has been paid to piezoresistance in p-type 3C-SiC. In addition, the book investigates the piezoresistive effect of top-down fabricated SiC nanowires, revealing a high degree of sensitivity in nanowires employing an innovative nano strain-amplifier. The large gauge factors of the p-type 3C-SiC at both room temperature and high temperatures found here indicate that this poly type could be suitable for the development of mechanical sensing devices operating in harsh environments with high temperatures.iv> Supervisor’s Foreword 7 Abstract 9 Acknowledgements 10 Contents 12 Abbreviations 15 Physical Constants 16 Symbols 17 1 Introduction and Literature Review 18 1.1 Research Background of the Piezoresistive Effect in SiC 18 1.2 Silicon Carbide as a Material for MEMS Applications 20 1.2.1 Crystalline Structure and Physical Properties 20 1.2.2 Growth Process of SiC 21 1.2.3 MEMS Fabrication Process 23 1.3 Piezoresistive Effect of Silicon Carbide 27 1.3.1 Definition of the Piezoresistance 27 1.3.2 Piezoresistance of Silicon Carbide 28 1.3.3 Applications of Silicon Carbide Piezoresistive Effect 37 1.4 Summary of the Literature Review and the Aims of This Dissertation 40 1.4.1 Perspective of the Piezoresistive Effect in SiC 40 1.4.2 The Aims of This Research 40 References 41 2 Theory of the Piezoresistive Effect in p-Type 3C-SiC 48 2.1 Energy Band of 3C-SiC 48 2.1.1 Crystallographic and Energy Band Structure of 3C-SiC 48 2.1.2 Principle of the Piezoresistive Effect in p-Type 3C-SiC 52 2.2 The Piezoresistive Coefficients of 3C-SiC 58 2.2.1 Definition of the Piezoresistive Coefficients 58 2.2.2 Piezoresistive Coefficients of Two-Terminal and Four-Terminal Resistors 60 2.2.3 Piezoresistive Coefficients in Arbitrary Cartesian Coordinate 62 References 63 3 3C-SiC Film Growth and Sample Preparation 65 3.1 Growth of Single Crystalline 3C-SiC 65 3.1.1 The LPCVD Process of p-Type 3C-SiC 65 3.1.2 Optical Characterization of the As-Grown 3C-SiC Film 67 3.1.3 Electrical Properties of the As-Grown 3C-SiC Films 69 3.2 Fabrication of 3C-SiC Piezoresistors 71 3.3 Characterization of Ohmic Contact of SiC Resistors ƒ 75 References 77 4 Characterization of the Piezoresistive Effect in p-Type Single Crystalline 3C-SiC 78 4.1 Measurement Method 78 4.2 Measurement Results at Room Temperature 81 4.2.1 The Gauge Factors of Two Terminal p-Type 3C-SiC 81 4.2.2 Piezoresistive Coefficients of Single Crystalline 3C-SiC 87 4.2.3 Thickness Dependence of the Piezoresistive Effect of p-Type 3C-SiC Nano Thin Films 90 4.3 The Piezoresistive Effect in p-Type 3C-SiC at High Temperatures 95 4.3.1 Methodology and Sample Preparation 95 4.3.2 The Piezoresistive Effect of the Suspended 3C-SiC at Room Temperature 96 4.3.3 The Themoresistive Effect of 3C-SiC 98 4.3.4 Joule Heating Effect in Suspended SiC Structures 100 4.3.5 Coupling the Piezo- and Thermo-Resistive Effects in SiC 102 4.4 The Piezoresistive Effect in Four-Terminal SiC Resistors 106 4.4.1 Configuration of SiC Four-Terminal Resistors 106 4.4.2 Shear Piezoresistive Coefficients in Four-Terminal Resistors 108 4.4.3 Orientation Dependence of the Piezoresistive Effect in Four-Terminal Resistors 112 References 112 5 The Piezoresistive Effect in p-Type Nanocrystalline SiC 115 5.1 Growth Process of Nanocrystalline SiC on Si 115 5.2 Characterization of the Gauge Factor in p-Type Nanocrystalline SiC 117 5.3 Discussion 119 References 121 6 The Piezoresistive Effect of Top Down p-Type 3C-SiC Nanowires 123 6.1 Piezoresistance of Non-released SiC Nanowires 123 6.1.1 Fabrication of Top Down SiC Nanowires 123 6.1.2 The Gauge Factor of the Non-released SiC Nanowires 124 6.2 The Piezoresistance of Suspended SiC Nanowire Using Nano-strain Amplifier 126 6.2.1 The Principle of the Nano-strain Amplifier 127 6.2.2 Demonstration of Nano Strain-Amplifier in p-Type 3C-SiC Nanowires 129 References 131 7 Conclusion and Perspectives 132 7.1 Conclusion 132 7.2 Research Perspectives 134 Appendix A Process Flow of the SiC/Si Beam 135 Appendix B Estimation of the Error Between the Simulation and the Actual Results of the Strain in 3C-SiC Resistor 140 Appendix C Estimation of the Piezoresistance in 3C-SiC Using the PZR Coefficients 142 Appendix D Estimation of the GF of 3C-SiC Films with Different Thicknesses 146 Appendix E In Situ Characterization of the Strain Effect on p-Type 3C-SiC at High Temperatures 150 Appendix F Orientation Dependence of the Piezoresistive Effect in p-Type 3C-SiC Four-Terminal Resistors 152 About the Author 155 Front Matter....Pages i-xxi Introduction and Literature Review....Pages 1-30 Theory of the Piezoresistive Effect in p-Type 3C-SiC....Pages 31-47 3C-SiC Film Growth and Sample Preparation....Pages 49-61 Characterization of the Piezoresistive Effect in p-Type Single Crystalline 3C-SiC....Pages 63-99 The Piezoresistive Effect in p-Type Nanocrystalline SiC....Pages 101-108 The Piezoresistive Effect of Top Down p-Type 3C-SiC Nanowires....Pages 109-117 Conclusion and Perspectives....Pages 119-121 Back Matter....Pages 123-146