Harnessing Multiscale Nonimaging Optics for Automotive Flash Lidar And
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Harnessing Multiscale Nonimaging Optics for Automotive Flash LiDAR and Heterogenous Semiconductor Integration by Todd Houghton A Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Approved July 2020 by the Graduate Supervisory Committee: Hongbin Yu, Chair Hanqing Jiang Suren Jayasuriya Liang Zhang ARIZONA STATE UNIVERSITY August 2020 ABSTRACT Though a single mode of energy transfer, optical radiation meaningfully interacts with its surrounding environment at over a wide range of physical length scales. For this reason, its reconstruction and measurement are of great importance in remote sensing, as these multi-scale interactions encode a great deal of information about distant objects, surfaces, and physical phenomena. For some remote sensing applications, obtaining a desired quantity of interest does not necessitate the explicit mapping of each point in object space to an image space with lenses or mirrors. Instead, only edge rays or physical boundaries of the sensing instrument are considered, while the spatial intensity distribution of optical energy received from a distant object informs its position, optical characteristics, or physical/chemical state. Admittedly specialized, the principals and consequences of non-imaging optics are nevertheless applicable to heterogeneous semiconductor integration and automotive light detection and ranging (LiDAR), two important emerging technologies. Indeed, a review of relevant engineering literature finds two under-addressed remote sensing challenges. The semiconductor industry lacks an optical strain metrology with displacement resolution smaller than 100 nanometers capable of measuring strain fields between high-density interconnect lines. Meanwhile, little attention is paid to the per- meter sensing characteristics of scene-illuminating flash LiDAR in the context of automotive applications, despite the technology’s much lower cost. It is here that non- imaging optics offers intriguing instrument design and explanations of observed sensor performance at vastly different length scales. i In this thesis, an effective non-contact technique for mapping nanoscale mechanical strain fields and out-of-plane surface warping via laser diffraction is demonstrated, with application as a novel metrology for next-generation semiconductor packages. Additionally, object detection distance of low-cost automotive flash LiDAR, on the order of tens of meters, is understood though principals of optical energy transfer from the surface of a remote object to an extended multi-segment detector. Such information is of consequence when designing an automotive perception system to recognize various roadway objects in low-light scenarios. ii DEDICATION This work is dedicated to my mom, dad, brother, friends, and colleagues, who have supported and believed in me throughout my time at the university. iii ACKNOWLEDGMENTS I would like to gratefully acknowledge the following individuals. Thanks to them, I have achieved more in my academic career than I ever thought possible: Professor Hongbin Yu for his invaluable guidance, knowledge, mentorship, and generous support throughout my graduate career. My committee members: Dr. Hanqing Jiang, Dr. Suren Jayasuriya, and Dr. Liang Zhang for their helpful suggestions and evaluation of my work. Kenneth Mossman of the John M. Cowley Center for High Resolution Electron Microscopy for providing support and training on equipment invaluable to my research. My fellow graduate students and colleagues, Jignesh Vanjaria, John Kevin Cava, Michael Saxon, Haokai Yang, and Mayukh Nandy for their thought-provoking discussions, hard work, and comradery. iv TABLE OF CONTENTS Page LIST OF TABLES ................................................................................................................. vii LIST OF FIGURES .............................................................................................................. viii CHAPTER 1 INTRODUCTION ................................................................................................. 1 2 ADVANCED SEMICONDUCTOR PACKAGING: SCALING, TECHNOLOGIES, AND FUTURE CHALLENGES ......................................... 4 2.1 Semiconductor Scaling and Contemporary Microelectronics in 2020 ...... 4 2.2 Advanced Packaging Technologies and Dense Interconnects ................... 6 2.3 Thermal Considerations in Advanced Packaging .................................... 14 2.4 Advanced Packaging and the Automotive Market .................................. 20 3 NANOSCALE STRAIN SENSING VIA LASER DIFFRACTION ................. 28 3.1 Measuring Strain in Microelectronics Packages ...................................... 28 3.2 Strain Mapping of Package Microstructures via Laser Diffraction ......... 42 3.3 Theoretical Background ............................................................................ 45 3.4 Experimental Methods .............................................................................. 62 3.5 Full-Field Pitch Mapping using Computer Automation .......................... 76 3.6 Results and Discussion .............................................................................. 84 3.7 Conclusion ................................................................................................. 91 4 EMERGING TECHNOLOGIES FOR VEHICLE PERCEPTION ................... 93 4.1 Introduction ............................................................................................... 93 4.2 Cameras and Computer Vision ................................................................. 94 v CHAPTER Page 4.3 Light Detection and Ranging (LiDAR) .................................................. 104 4.4 Millimeter Wave Radar ........................................................................... 115 4.5 Sonar ........................................................................................................ 117 4.6 Sensor Fusion .......................................................................................... 120 4.7 Cost .......................................................................................................... 125 5 ROADWAY OBJECT DETECTION VIA LOW-COST FLASH LIDAR AND CAMERA ............................................................................................................ 128 5.1 Introduction ............................................................................................. 128 5.2 Methods ................................................................................................... 130 5.3 Results and Discussion ............................................................................ 141 5.4 Conclusion ............................................................................................... 147 6 CONCLUSION .................................................................................................. 149 REFERENCES ..................................................................................................................... 124 vi LIST OF TABLES Table Page 1. Changes in Grating Pitch due to Thermal Expansion .......................................... 48 2. Influence of Temperature-Dependent nair on Calculated Grating Pitch ............... 52 3. Expected Values of Δθ1 Computed Using Equation 3.32 .................................... 60 4. Absolute Change in Pixel Position, |Δp|, of The Diffracted Beam’s Center ....... 62 5. Itemized Cost of the Flash LiDAR/Camera Sensor Platform ............................ 132 vii LIST OF FIGURES Figure Page 1. Trends in Semiconductor Performance.................................................................... 5 2. Fan-Out Wafer Level Packaging ............................................................................. 8 3. Interconnect Structures Used in 2.5D Packaging .................................................. 10 4. Silicon Die Stacking Methods ................................................................................ 12 5. Concept Design of a Monolithic 3D Integrated Circuit and 3D NAND .............. 14 6. Typical Die/Package Cooling Schemes and Trends in Thermal Density ............. 16 7. Embedded Liquid Cooling Schemes...................................................................... 19 8. Differences Between Automotive and Consumer Test Requirements ................. 21 9. Cost of Electronic Components as a Percentage of Automotive Costs ................ 22 10. Advanced Packaging Schemes for Image Sensors, Antennas, and LiDAR ......... 25 11. Early Digital Image Correlation (DIC) Setups ...................................................... 30 12. Hardware Configuration for 2D DIC, Some Sample Speckle Patterns ................ 31 13. Decomposition of a Matched Pixel Subset’s Displacement and Shape vector .... 33 14. Displacement Fields of a Solder Ball and Crack Board Measured via DIC ......... 37 15. Generating a Moiré Pattern, Configuration of a Shadow Moiré tool .................. 38 16. Sample Preparation, Working Principal, and Results of Moiré Interferometry ... 40 17. Illustrated Concept of Nano-Scale Strain Detection via Laser Diffraction .......... 44 18. Theory of Mechanical Strain in Diffraction Gratings ........................................... 47 19. Diffractive Orders of Transmission and Reflection Gratings ............................... 51 20. Interference Properties of Huygens Wavelets ....................................................... 53 21. Predicted Fraunhofer Intensity Profile of Diffracted Light ..................................