Optical Microscanners and Microspectrometers using Thermal Bimorph Actuators / Edition 1

Optical Microscanners and Microspectrometers using Thermal Bimorph Actuators / Edition 1

by Gerhard Lammel, Philippe Renaud, Sandra Schweizer
     
 

ISBN-10: 0792376552

ISBN-13: 9780792376552

Pub. Date: 01/31/2002

Publisher: Springer US

Optical Microscanners and Microspectrometers using Thermal Bimorph Actuators shows how to design and fabricate optical microsystems using innovative technologies and and original architectures. A barcode scanner, laser projection mirror and a microspectrometer are explained in detail, starting from the system conception, discussing simulations, choice of cleanroom

Overview

Optical Microscanners and Microspectrometers using Thermal Bimorph Actuators shows how to design and fabricate optical microsystems using innovative technologies and and original architectures. A barcode scanner, laser projection mirror and a microspectrometer are explained in detail, starting from the system conception, discussing simulations, choice of cleanroom technologies, design, fabrication, device test, packaging all the way to the system assembly.

An advanced microscanning device capable of one- and two-dimensional scanning can be integrated in a compact barcode scanning system composed of a laser diode and adapted optics. The original design of the microscanner combines efficiently the miniaturized thermal mechanical actuator and the reflecting mirror, providing a one-dimensional scanning or an unique combination of two movements, depending on the geometry. The simplicity of the device makes it a competitive component.

The authors rethink the design of a miniaturized optical device and find a compact solution for a microspectrometer, based on a tunable filter and a single pixel detector. A porous silicon technology combines efficiently the optical filter function with a thermal mechanical actuator on chip. The methodology for design and process calibration are discussed in detail. The device is the core component of an infrared gas spectrometer.

Product Details

ISBN-13:
9780792376552
Publisher:
Springer US
Publication date:
01/31/2002
Series:
Microsystems Series, #14
Edition description:
2002
Pages:
268
Product dimensions:
9.21(w) x 6.14(h) x 0.69(d)

Table of Contents

Prefacexi
1Introduction1
1.1Motivation1
1.2Mems2
1.3Moems3
1.3.1Display technologies3
1.3.2Printers and industrial machining9
1.3.3Imaging scanners9
1.3.4Telecommunication10
1.3.5Adaptive or corrective optics12
1.3.6Spectroscopy applications13
1.3.7Medical applications15
1.4Moems actuation principles16
1.4.1Electrostatic actuation17
1.4.2Piezoelectric actuation22
1.4.3Magnetic actuation23
1.4.4Thermal actuation24
2Basics for a thermally actuated micromirror27
2.1Microactuator specifications27
2.2Principle of the presented microscanner28
2.3The thermal bimorph actuator28
2.3.1Thermal expansion29
2.3.2Stress in bimorph cantilevers and initial rest position29
2.3.3Thermal bimorph actuator design41
2.4Static temperature distribution in the microscanner46
2.4.1Analytical model46
2.4.2Determination of constants51
2.4.3Influence of the different constants on the temperature distribution55
2.4.4Summary58
2.5Response time of the bimorph beam59
2.5.1Thermal cut-off59
2.5.2Measurements of the cut-off frequency of the bimorph actuator60
2.5.3Conclusion61
2.5.4Dynamic temperature distribution in the bimorph beam62
2.6General conclusions64
3Microscanner technology67
3.1Fabrication process67
3.2Process improvements70
3.2.1Dry mirror release70
3.2.2Mirror stiffness and flatness improvement70
3.2.3Mirror reflectivity76
3.3Conclusions76
4One-dimensional microscanner77
4.1Test Set-up77
4.2Static characterization of Chromium based actuators78
4.2.1Single device characterization78
4.2.2Comparing angular deflection among various devices80
4.2.3Resistance variation of Cr layer with temperature84
4.3Static characterization of Nickel based actuators86
4.3.1Angle vs. temperature86
4.3.2Resistance vs. temperature86
4.3.3Angle vs. power87
4.3.4Summary88
4.4Dynamic characterization88
4.4.1Fundamental resonance frequency calculation89
4.4.2Experimental comparison of the resonance frequency94
4.4.3Influence of damping97
4.4.4Thermal cut-off98
4.4.5Dynamic microscanner performances98
4.4.6Lateral suspension mirror100
4.4.7Dynamics of the tunable optical filter with Ni based actuator102
4.4.8Summary104
4.51D scanner applications105
4.5.1Barcode reader105
4.5.2Micromechanical detector for molecular beams109
4.6Conclusions111
5Two-dimensional microscanner113
5.1Principle113
5.2Design and modelling of the raster natural frequency113
5.2.1Analytical model113
5.2.2Simulations119
5.3Dynamic measurements120
5.3.12D-microscanner type 1120
5.3.22D-microscanner type 2122
5.3.3Summary123
5.4Microprojector application123
5.4.1Scanner requirements123
5.4.2Pixel resolution124
5.4.3Static and dynamic mirror deformations126
5.4.4Experimental results127
5.5Conclusions133
6Advanced Optical Filters of Porous Silicon135
6.1Principle135
6.2History of porous silicon136
6.3Fabrication of porous silicon136
6.3.1Single etch cell137
6.3.2Double etch cell138
6.4Parameters determining the structure of porous silicon139
6.4.1Why porous silicon is porous139
6.4.2Substrate doping140
6.4.3Illumination141
6.4.4Electrolyte concentration141
6.4.5Current densities142
6.5Electropolishing144
6.6Porous silicon as sacrificial layer145
6.7Calculation of optical interference filters145
6.7.1Principle145
6.7.2General theory for simulation of optical multilayer filters146
6.7.3Bragg band reflectors148
6.7.4Fabry-Perot bandpass filters150
6.7.5Multi band reflectors151
6.7.6Edge filters152
6.7.7Angular dependence153
6.8Fabrication of optical filter of porous silicon153
6.8.1Effective media theory153
6.8.2Lateral homogeneity156
6.8.3Depth homogeneity156
6.8.4Oxidation and aging161
6.9Summary163
7Micromachining using porous Silicon165
7.1Goals for the technology165
7.2Metal masks166
7.3Nitride masks167
7.4Free-standing porous silicon films167
7.5Mask removal169
7.6Thermal actuator design169
7.6.1Calculation of optimum layer thicknesses173
7.6.2Calculation of beam length180
7.6.3Electrical heater resistance180
7.7Mechanical filter plate suspension181
7.7.1Shape and size of filter plate181
7.7.2Ways of suspension181
7.8Homogeneity of the optical filter184
7.8.1Frontside mask only185
7.8.2Frontside and backside mask186
7.8.3Experimental comparison187
7.8.4Electropolished well189
7.9Process flow190
7.10Summary193
8Tunable Optical Filter and IR Gas Spectroscopy195
8.1Overview of devices195
8.2Optical characterization198
8.2.1Visible light198
8.2.2Infrared light200
8.3Chip separation and packaging202
8.3.1Cleaving202
8.3.2Bonding on PCB204
8.3.3Encapsulation204
8.3.4Protection by a fusible link205
8.4System integration for gas sensing205
8.4.1Principle of infrared gas absorption spectroscopy205
8.4.2Set-up208
8.4.3Experimental results208
8.5Summary210
9Conclusions and outlook211
9.1Conclusions211
9.1.1Micromirror211
9.1.2Tunable optical filter213
9.2Outlook215
Appendices217
A.1Complement to the curvature calculation due to residual stress217
A.2Complement to the static temperature distribution calculation221
A.3Large deflections225
References229
Symbols and Abbreviations255
Glossary of terms263
Acknowledgments267

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