MEMS Mechanical Sensors - Stephen Beeby Part 1 potx

[...]... (10 0) orientation Poisson’s ratio, (10 0) orientation –3 Density (gcm ) Lattice constant (Å) –6 1 Thermal expansion coefficient (10 K ) 1 1 Thermal conductivity (Wm K ) 1 1 Specific heat (Jg K ) Melting point (°C) Energy gap (eV) Dielectric constant 7 1 Dielectric strength (10 Vm ) 2 1 1 Electron mobility (cm V s ) 2 1 1 Hole mobility (cm V s ) 7 850 16 0 0.28 2.33 5.435 2.6 15 7 0.7 1, 410 1. 12... Melting temperature ( C) SiO2 Quartz 70 0.33 2.7 0 .17 24 Al2O3 (96%) 303 0. 21 3.8 9 6 73 0 .17 2.3 8.4 0.55 10 7 0 .16 2.6 9 0.55 0.2 2.37 0.25 0. 014 0. 015 1, 500 660 2,000 1, 700 1, 600 19 0 0.22 2.3 7 2.3 Stainless Steel 200 0.3 8 3.0 16 1. 48 1, 414 Al circular wafers with typical diameters of 10 0 mm (4 inches), 15 0 mm (6 inches), 200 mm (8 inches), or 300 mm (12 inches) in a variety of thicknesses Amorphous... Figure 1. 1 pressure) 10 10 0 1, 000 Gap separation x gas pressure (microns*atm) 10 ,000 A plot of breakdown voltage against electrode separation (in air at 1 atmosphere of 1. 5 For Whom Is This Book Intended? Table 1. 1 5 Properties of Silicon and Selected Other Materials Property Si {11 1} Young’s modulus (GPa) Poisson’s ratio 3 Density (g/cm ) Yield strength (GPa) Thermal coefficient of expansion (10 /K)... Brignell, J E., and N M White, Intelligent Sensor Systems, Bristol, England: IOP Publishing, 19 94 Judy, J W., “Microelectromechanical Systems (MEMS) : Fabrication, Design and Applications,” Smart Materials and Structures, Vol 10 , 20 01, pp 11 15 11 34 CHAPTER 2 Materials and Fabrication Techniques 2 .1 Introduction MEMS devices and structures are fabricated using conventional integrated circuit process techniques,... is either n- or p-type The doping is done with impurities to give a resistivity of between 0.0 01 and 10 ,000 Ωcm For mainstream integrated circuit processing wafers are typically of the order of 10 to 30 Ωcm corresponding to an impurity level of ∼3 × 10 14 cm–3 for n-type and ∼9 × 10 14 cm–3 for p-type Table 2 .1 shows some of the properties of crystalline silicon It should be remembered that some of the... electrical and mechanical engineering disciplines, and those who work in the field of sensors and actuators will have the joy of participating in one of the truly interdisciplinary fields in the whole of science References [1] [2] [3] [4] Nexus MST market analysis, http://www.nexus -mems. com Feynman, R P., “There’s Plenty of Room at the Bottom,” Journal of Microelectromechanical Systems, Vol 1, No 1, 19 92, pp... lattice point The crystal structure is shown in Figure 2 .1 The crystal planes and directions are designated by Miller indices, as shown in Figure 2.2 Any of the major coordinate axes of the cube can be designated as a direction, and planes perpendicular to these are designated as {10 0} planes The {11 1} planes are planes perpendicular to the directions, which are parallel to the diagonals of... claimed in 19 60) to the first person who could make an electric motor 1/ 64 in3 (about 0.4 mm3) These size limits turned out to be slightly too large and the motor was actually made using conventional mechanical engineering methods that did not require any new technological developments 1. 2 What Are MEMS? MEMS means different things to different people The acronym MEMS stands for microelectromechanical... manufacturers is usually either {10 0} or {11 1} orientation, although other orientations can be obtained from specialist suppliers This orientation identifies the plane of the top surface of the wafer The wafers are cut at one edge to form a primary flat in a {11 0} plane A secondary flat is also cut on another edge to identify the wafer orientation and doping type, which is either n- or p-type The doping is done... techniques that have been part of the MEMS toolkit for many years This chapter deals mainly with these core techniques, but also with those process techniques borrowed from integrated circuit manufacturing 2.2 Materials 2.2 .1 2.2 .1. 1 Substrates Silicon Just as silicon has dominated the integrated circuit industry, so too is it predominant in MEMS There are a number of reasons for this: (1) pure, cheap, and . 10 7 5.6.4 Magnetic 10 9 5.7 Smart Sensors 10 9 References 11 2 CHAPTER 6 Pressure Sensors 11 3 6 .1 Introduction 11 3 6.2 Physics of Pressure Sensing 11 4 6.2 .1 Pressure Sensor Specifications 11 7 6.2.2 Dynamic. (10 –6 K 1 ) 2.6 Thermal conductivity (Wm 1 K 1 ) 15 7 Specific heat (Jg 1 K 1 ) 0.7 Melting point (°C) 1, 410 Energy gap (eV) 1. 12 Dielectric constant 11 .9 Dielectric strength (10 7 Vm 1 )3 Electron. Sensing 12 0 vi Contents 6.2.3 Pressure Sensor Types 12 1 6.3 Traditional Pressure Sensors 12 1 6.3 .1 Manometer 12 1 6.3.2 Aneroid Barometers 12 2 6.3.3 Bourdon Tube 12 2 6.3.4 Vacuum Sensors 12 3 6.4