Mechanical Microsensors

by Elwenspoek, Miko; Wiegerink, Remco J.

• ISBN13: 9783540675822
• ISBN10: 3540675825
• Format: Hardcover
• Copyright: 2001-01-01
• Publisher: Springer Verlag

Summary

This book provides a comprehensive description of microsensors for mechanical quantities (flow, pressure, force, inertia) fabricated by silicon micromachining. Since the design of such sensors requires interdisciplinary teamwork, the presentation is made accessible to engineers trained in electrical and mechanical engineering, physics and chemistry. The reader is guided through the micromachining fabrication process. A chapter on microsensor packaging completes the discussion of technological problems. The description of the basic physics required for sensor design includes the mechanics of deformation and the piezoresistive transduction to electrical signals. There is also a comprehensive discussion of resonant sensors, the hydrodynamics and heat transfer relevant for flow sensors, and, finally, electronic interfacing and readout circuitry. Numerous up-to-date case studies are presented, together with the working, fabrication and design of the sensors.

Table of Contents

Introduction	1	(4)
MEMS	5	(19)
Miniaturisation and Systems	5	(1)
Examples for MEMS	6	(7)
Bubble Jet	7	(2)
Actuators	9	(1)
Micropumps	10	(3)
Small and Large: Scaling	13	(7)
Electromagnetic Forces	13	(3)
Coulomb Friction	16	(1)
Mechanical Strength	16	(1)
Dynamic Properties	17	(3)
Available Fabrication Technology	20	(4)
Technologies Based on Lithography	20	(1)
Silicon Micromachining	21	(1)
LIGA	22	(1)
Miniaturisation of Conventional Technologies	23	(1)
Introduction into Silicon Micromachining	24	(35)
Photolithography	24	(1)
Thin Film Deposition and Doping	25	(7)
Silicon Dioxide	26	(1)
Chemical Vapour Deposition	27	(2)
Evaporation	29	(2)
Sputterdeposition	31	(1)
Doping	31	(1)
Wet Chemical Etching	32	(8)
Isotropic Etching	32	(2)
Anisotropic Etching	34	(2)
Etch Stop	36	(4)
Waferbonding	40	(5)
Anodic Bonding	41	(2)
Silicon Fusion Bonding	43	(2)
Plasma Etching	45	(10)
Plasma	45	(2)
Anisotropic Plasma Etching Modes	47	(1)
Configurations	48	(5)
Black Silicon Method	53	(2)
Surface Micromachining	55	(4)
Thin Film Stress	56	(1)
Sticking	57	(2)
Mechanics of Membranes and Beams	59	(26)
Dynamics of the Mass Spring System	59	(4)
Strings	63	(2)
Beams	65	(15)
Stress and Strain	65	(1)
Bending Energy	66	(1)
Radius of Curvature	67	(3)
Lagrange Function of a Flexible Beam	70	(1)
Differential Equation for Beams	70	(2)
Boundary Conditions for Beams	72	(1)
Examples	73	(2)
Mechanical Stability	75	(2)
Transversal Vibration of Beams	77	(3)
Diaphragms and Membranes	80	(5)
Circular Diaphragms	80	(2)
Square Membranes	82	(2)
Buckling of Bridges	84	(1)
Principles of Measuring Mechanical Quantities: Transduction of Deformation	85	(12)
Metal Strain Gauges	85	(1)
Semiconductor Strain Gauges	86	(4)
Piezoresistive Effect in Single Crystalline Silicon	87	(1)
Piezoresistive Effect in Polysilicon Thin Films	88	(1)
Transduction from Deformation to Resistance	89	(1)
Capacitive Transducers	90	(7)
Electromechanics	90	(4)
Diaphragm Pressure Sensors	94	(3)
Force and Pressure Sensors	97	(35)
Force Sensors	98	(8)
Load Cells	101	(5)
Pressure Sensors	106	(26)
Piezoresistive Pressure Sensors	107	(5)
Capacitive Pressure Sensors	112	(7)
Force Compensation Pressure Sensors	119	(2)
Resonant Pressure Sensors	121	(5)
Miniature Microphones	126	(4)
Tactile Imaging Arrays	130	(2)
Acceleration and Angular Rate Sensors	132	(21)
Acceleration Sensors	133	(12)
Introduction	133	(1)
Bulk Micromachined Accelerometers	134	(4)
Surface Micromachined Accelerometers	138	(5)
Force Feedback	143	(2)
Angular Rate Sensors	145	(8)
Flow sensors	153	(56)
The Laminar Boundary Layer	153	(15)
The Navier-Stokes Equations	153	(4)
Heat Transport	157	(1)
Hydrodynamic Boundary Layer	158	(5)
Thermal Boundary Layer	163	(3)
Skin Friction and Heat Transfer	166	(2)
Heat Transport in the Limit of Very Small Reynolds Numbers	168	(5)
Thermal Flow Sensors	173	(22)
Anemometer Type Flow Sensors	174	(7)
Two-Wire Anemometers	181	(2)
Calorimetric Type Flow Sensors	183	(5)
Sound Intensity Sensors - The Microflown	188	(6)
Time of Flight Sensors	194	(1)
Skin Friction Sensors	195	(5)
``Dry Fluid Flow'' Sensors	200	(5)
``Wet Fluid Flow'' Sensors	205	(4)
Resonant Sensors	209	(20)
Basic Principles and Physics	209	(13)
Introduction	209	(2)
The Differential Equation of a Prismatic Microbridge	211	(1)
Solving the Homogeneous, Undamped Problem using Laplace Transforms	212	(3)
Solving the Inhomogeneous Problem by Modal Analysis	215	(2)
Response to Axial Loads	217	(2)
Quality Factor	219	(1)
Nonlinear Large-Amplitude Effects	220	(2)
Excitation and Detection Mechanisms	222	(3)
Electrostatic Excitation and Capacitive Detection	223	(1)
Magnetic Excitation and Detection	223	(1)
Piezoelectric Excitation and Detection	223	(1)
Electrothermal Excitation and Piezoresistive Detection	224	(1)
Optothermal Excitation and Optical Detection	224	(1)
Dielectric Excitation and Detection	225	(1)
Examples and Applications	225	(4)
Electronic Interfacing	229	(30)
Piezoresistive Sensors	230	(10)
Wheatstone Bridge Configurations	230	(3)
Amplification of the Bridge Output Voltage	233	(2)
Noise and Offset	235	(1)
Feedback Control Loops	236	(1)
Interfacing with Digital Systems	237	(1)
Analog-to-Digital Conversion	237	(3)
Voltage to Frequency Converters	240	(1)
Capacitive Sensors	240	(8)
Impedance Bridges	241	(4)
Capacitance Controlled Oscillators	245	(3)
Resonant Sensors	248	(11)
Frequency Dependent Behavior of Resonant Sensors	248	(1)
Realizing an Oscillator	249	(2)
One-Port Versus Two-Port Resonators	251	(1)
Oscillator Based on One-Port Electrostatically Driven Beam Resonator	251	(6)
Oscillator Based on Two-Port Electrodynamically Driven H-shaped Resonator	257	(2)
Packaging	259	(15)
Packaging Techniques	260	(9)
Standard Packages	260	(2)
Chip Mounting Methods	262	(1)
Wafer Level Packaging	263	(2)
Interconnection Techniques	265	(2)
Multichip Modules	267	(2)
Encapsulation Processes	269	(1)
Stress Reduction	269	(1)
Pressure Sensors	270	(2)
Inertial Sensors	272	(1)
Thermal Flow Sensors	272	(2)
References	274	(17)
Index	291