Uncooled Infrared Imaging Arrays and Systems SEMICONDUCTORS AND SEMIMETALS Volume 47 Semiconductors and Semimetals A Treatise Edited by R. K. Willardson Eicke R. Weber CONSULTING PHYSICIST DEPARTMEOFN MTA TERIALSSC IENCE SPOKANEW, ASHINGTON AND MINERALE NGINEERING UNIVERSIOTFY C ALIFORNIA AT BERKELEY In memory of Dr. Albert C. Beer, Founding Co-Editor in 1966 and Editor Emeritus of Semiconductors and Semimetals. Died January 19, 1997, Columbus, OH. Uncooled Infrared Imaging Arrays and Systems SEMICONDUCTORS AND SEMIMETALS Volume 47 Volume Editors PAUL W. KRUSE INFRARED SOLUTIONS, INC MINNEAPOLIS, MINNESOTA DAVID D. SKATRUD DEPARTMENT OF THE ARMY PHYSICS DIVISION ARMY RESEARCH OFFICE RESEARCH TRIANGLE PARK NORTH CAROLINA ACADEMIC PRESS San Diego London Boston New York Sydney Tokyo Toronto @ This book is printed on acid-free paper. COPYRIGH0T 1997 BY ACADEMIC PRESS All rights reserved. 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Copy fees for pre-1997 chapters are as shown on the title pages; if no fee code appears on the title page, the copy fee is the same as for current chapters. 0080-8784197 $25.00 ACADEMIC PRESS 525 B Street, Suite 1900, San Diego, CA 92101-4495, USA 1300 Bovlston Street. Chestnut Hill. Massachusetts 02167. USA http://w&w.apnet.coh ACADEMIC PRESS LIMITED 24-28 Oval Road, London NWI ?DX,U K http://www.hbuk.co.uk/ap/ International Standard Serial Number: 0080-8784 International Standard Book Number: 0-12-752155-0 PRINTED IN THE UNITED STATES OF AMERICA 97 98 99 00 01 BB 9 8 7 6 5 4 3 2 1 Contents LISTO F CONTRIBUTOR.S. . . . . . . . . . . . . . . . . . . . . . . . . . xi PREFACE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii Chapter 1 Historical Overview Rudolph G. Buser and Michuel F. Tompsett I . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i I1. History of Electronic Materials Research for Uncooled Imagers . . . . . . . 6 1. Ferroelectric- Pyroelectric Materials . . . . . . . . . . . . . . . . . . 6 2 . Resistive Materials . . . . . . . . . . . . . . . . . . . . . . . . . 8 111. Uncooled Imaging Arrays Using Silicon Read-Out . . . . . . . . . . . . . 9 I . Ferroelectric-Pyroelectric Arrays . . . . . . . . . . . . . . . . . . . 9 2 . Resistive Bolometric Arrays . . . . . . . . . . . . . . . . . . . . . 11 1V.Future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Chapter 2 Principles of Uncooled Infrared Focal Plane Arrays Paul W. Kruse I . Importance of the Thermal Isolation Structure . . . . . . . . . . . . . . 17 11. Principal Thermal Detection Mechanisms . . . . . . . . . . . . . . . . . 23 1 . Resistive Bolometers . . . . . . . . . . . . . . . . . . . . . . . . . 23 2 . Pyroelectric Detectors and Ferroelectric Bolometers . . . . . . . . . . . 25 3 . Thermoelectric Detectors . . . . . . . . . . . . . . . . . . . . . . . 29 111 . Fundamental Limits . . . . . . . . . . . . . . . . . . . . . . . . . . 31 1. Temperature Fluctuation Noise Limit . . . . . . . . . . . . . . . . . 31 2 . Background Fluctuation Noise Limit . . . . . . . . . . . . . . . . . 33 IV. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 References and Bibliography . . . . . . . . . . . . . . . . . . . . . . 40 V vi CONTENTS Chapter 3 Monolithic Silicon Microbolometer Arrays R . A . Wood I . Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 I1. Responsivity of Microbolometers . . . . . . . . . . . . . . . . . . . . 47 1. Microbolometer Model . . . . . . . . . . . . . . . . . . . . . . . 47 2. Resistance Changes in Microbolometer Materials . . . . . . . . . . . . 51 3. Microbolometer Heat Balance Equation . . . . . . . . . . . . . . . 56 4 . Solutions of the Heat Balance Equation . . . . . . . . . . . . . . . . 51 5 . Heat Balance with No Applied Bias . . . . . . . . . . . . . . . . . 51 6. Heat Balance with Applied Bias . . . . . . . . . . . . . . . . . . . 59 7. Calculations of V-I Curves . . . . . . . . . . . . . . . . . . . . . 61 8. LoadLine . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 9. Low-Frequency Noise in Microbolometer with Applied Bias . . . . . . . 68 10 . Microbolometer Responsivity with Pulsed Bias or Large Radiation Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 11. Numerical Calculation of Microbolometer Performance . . . . . . . . . 71 111. Noise in Bolometers . . . . . . . . . . . . . . . . . . . . . . . . . . 15 1. Bolometer Resistance Noise . . . . . . . . . . . . . . . . . . . . . 15 2. Noise from Bias Resistors . . . . . . . . . . . . . . . . . . . . . . 19 3. Thermal Conductance Noise . . . . . . . . . . . . . . . . . . . . . 80 4. Radiation Noise . . . . . . . . . . . . . . . . . . . . . . . . . . 81 5 . Total Electrical Noise . . . . . . . . . . . . . . . . . . . . . . . . 83 6. Preamplifier Noise . . . . . . . . . . . . . . . . . . . . . . . . . 85 IV . Microbolometer Signal-to-Noise . . . . . . . . . . . . . . . . . . . . . 86 1. Noise Equivalent Power (NEP) . . . . . . . . . . . . . . . . . . . . 86 2. Noise Equivalent Temperature Difference (NETD) . . . . . . . . . . . 86 3 . Detectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 4 . Comparison with the Ideal Bolometer . . . . . . . . . . . . . . . . . 89 5 . Johnson Noise Approximation . . . . . . . . . . . . . . . . . . . . 91 V . Electric Read-Out Circuits for Two-Dimensional Microbolometer Arrays . . . 91 VI . Offset Compensation Schemes . . . . . . . . . . . . . . . . . . . . . . 95 VII . Gain Correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 VIII . Modulation Transfer Function (MTF) . . . . . . . . . . . . . . . . . . 98 IX . Microbolometer Physical Design, Fabrication, and Packaging . . . . . . . . 98 1. One-Level Microbolometers . . . . . . . . . . . . . . . . . . . . . 100 2. Two-Level Microbolometers . . . . . . . . . . . . . . . . . . . . . 102 3. Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 X . Practical Camera Development . . . . . . . . . . . . . . . . . . . . . 116 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 Chapter 4 Hybrid Pyroelectric-Ferroelectric Bolometer Arrays Charles M . Hanson I . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 I1. Principles of Pyroelectric Detectors . . . . . . . . . . . . . . . . . . . 124 1. Pyroelectricity and Ferroelectric Materials . . . . . . . . . . . . . . . 124 2. Modes of Operation . . . . . . . . . . . . . . . . . . . . . . . . . 139 3. Signal and Noise . . . . . . . . . . . . . . . . . . . . . . . . . . 144 111. Practical Considerations and Designs . . . . . . . . . . . . . . . . . . 154 CONTENTS vii 1. Ferroelectric Material Selection . . . . . . . . . . . . . . . . . . . . 154 2. Thermal Isolation . . . . . . . . . . . . . . . . . . . . . . . . . . 156 3. Modulation Transfer Function (MTF) . . . . . . . . . . . . . . . . . 158 4 . Read-out Electronics . . . . . . . . . . . . . . . . . . . . . . . . 159 5 . System Electronics . . . . . . . . . . . . . . . . . . . . . . . . . 161 6. Choppers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 IV. Systems Implementations . . . . . . . . . . . . . . . . . . . . . . . . 169 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 Chapter 5 Monolithic Pyroelectric Bolometer Arrays Dennis L . Polla and Jun R . Choi I . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 I1 . Detector Design Methodology . . . . . . . . . . . . . . . . . . . . . 176 1. Materials Processing . . . . . . . . . . . . . . . . . . . . . . . . 178 2. Materials Characterization . . . . . . . . . . . . . . . . . . . . . . 181 3. Thermal Isolation Structures . . . . . . . . . . . . . . . . . . . . . 183 4. Micromachined Sensor Process Design . . . . . . . . . . . . . . . . . 184 5 . Integrated Circuits . . . . . . . . . . . . . . . . . . . . . . . . . 186 I11 . Process Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 IV . Silicon-Based Integrated Pyroelectric Detector Arrays . . . . . . . . . . . 189 1 . Cell Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 2. Circuit Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 191 3. Silicon-Based PbTiO, Array Performance . . . . . . . . . . . . . . . 195 V . Gallium Arsenide-Based Integrated Pyroelectric Detectors . . . . . . . . . 197 VI . Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 Chapter 6 Thermoelectric Uncooled Infrared Focal Plane Arrays Nobukuzu Teranishi I . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 I1. Thermopile Infrared Detector . . . . . . . . . . . . . . . . . . . . . . 204 1 . Mechanism for Uncooled Infrared Detector . . . . . . . . . . . . . . 204 2. Comparison Among Uncooled Infrared Detector Schemes . . . . . . . . 205 3. The Seebeck Effect . . . . . . . . . . . . . . . . . . . . . . . . . 206 4 . Various Thermopile Infrared Detectors . . . . . . . . . . . . . . . . 209 111. A 128 x 128 Pixel Thermopile Infrared Focal Plane Array . . . . . . . . . 210 1. Polysilicon Thermopile Infrared Detector . . . . . . . . . . . . . . . . 210 2 . Characteristics of a Thermopile lnfrared Detector . . . . . . . . . . . . 211 3. Signal Read-Out Circuit . . . . . . . . . . . . . . . . . . . . . . . 211 4. Charge-Coupled Device Scanner . . . . . . . . . . . . . . . . . . . 213 5.Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214 6 . Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 7 . Future Improvements . . . . . . . . . . . . . . . . . . . . . . . . 217 IV. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218 viii CONTENTS Chapter 7 Pyroelectric Vidicon Michael F. Tompsett ].History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 I1 . Performance Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 223 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 Chapter 8 Tunneling Infrared Sensors T. W Kenny 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 I1. Sensor Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 1. Sensor Thermal Model . . . . . . . . . . . . . . . . . . . . . . . 229 2 . Sensor Mechanical and Electrical Model . . . . . . . . . . . . . . . . 232 3. Noise Model and Considerations . . . . . . . . . . . . . . . . . . . 236 111 . Tunneling Transducer Background . . . . . . . . . . . . . . . . . . . . 239 1. Comparison of Tunneling and Capacitive Transducers . . . . . . . . . . 241 2. Tunneling Transducer Design Considerations . . . . . . . . . . . . . . 243 1V. Tunneling Infrared Sensor Design and Fabrication . . . . . . . . . . . . . 245 V . Tunneling Transducer Operation . . . . . . . . . . . . . . . . . . . . 253 VI . Infrared Sensor Operation and Testing . . . . . . . . . . . . . . . . . . 259 VII. Future Prospects for the Tunneling Infrared Sensor . . . . . . . . . . . . 264 VIII . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 Chapter 9 Application of Quartz Microresonators to Uncooled Infrared Imaging Arrays . John R . Vig. Raymond L . Filler and Yoonkee Kim I . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 I1. Quartz Microresonators as Infrared Sensors . . . . . . . . . . . . . . . . 271 111. Quartz Thermometers and Their Temperature Coefficients . . . . . . . . . 212 IV. Oscillator Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273 V . Frequency Measurement . . . . . . . . . . . . . . . . . . . . . . . . 274 VI . Thermal Isolation . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 VII . Infrared Absorption of Microresonators . . . . . . . . . . . . . . . . . 277 VIII . Predicted Performance of Microresonator Arrays . . . . . . . . . . . . . 279 IX . Producibility and Other Challenges . . . . . . . . . . . . . . . . . . . 281 X . Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . 283 Appendix. Performance Calculations . . . . . . . . . . . . . . . . . . . 284 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294 Chapter 10 Application of Uncooled Monolithic Thermoelectric Linear Arrays to Imaging Radiometers Paul W. Kruse I . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297 I1. Identification of Incipient Failure of Railcar Wheels . . . . . . . . . . . . 298 CONTENTS ix 1 . Technical Description of the Model IR 1000 Imaging Radiometer . . . . . 298 2 . Performance of the Model 1R 1000 lmaging Radiometer . . . . . . . . . 300 3. Initial Application . . . . . . . . . . . . . . . . . . . . . . . . . . 304 4.Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309 111. Imaging Radiometer for Predictive and Preventive Maintenance . . . . . . . 309 1 . Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310 2 . Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312 3. Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317 4.Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318 INDEX 319 CONTENOTFS V OLUMESI N THISS ERIES 327