RF/MICROWAVE HYBRIDS Basics, Materials and Processes

Transcription

1 RF/MICROWAVE HYBRIDS Basics, Materials and Processes

2 RF/MICROWAVE HYBRIDS Basics, Materials and Processes by Richard Brown Richard Brown Associates, Inc. Shelton, CT KLUWER ACADEMIC PUBLISHERS NEW YORK, BOSTON, DORDRECHT, LONDON, MOSCOW

3 ebook ISBN: Print ISBN: Kluwer Academic Publishers New York, Boston, Dordrecht, London, Moscow Print 2003 Kluwer Academic Publishers Dordrecht All rights reserved No part of this ebook may be reproduced or transmitted in any form or by any means, electronic, mechanical, recording, or otherwise, without written consent from the Publisher Created in the United States of America Visit Kluwer Online at: and Kluwer's ebookstore at:

4 DEDICATION TO JUDY

5 TABLE OF CONTENTS Preface Acknowledgements xiii xv CHAPTER 1: Hybrids vs MMICs 1 CHAPTER 2: Basic Concepts Introduction 5 Maxwell's Laws 5 Permittivity and Permeability 6 Free Space Wavelength 7 Propagation velocity 8 Decibel Scale (db) 9 Q Measurements 9 Small Signal (S-Parameters) 10 5 CHAPTER 3: Planar Waveguides 3.1 Impedance 3.2 Microstrip Guide Wavelength 3.3 Coplanar 3.4 Stripline CHAPTER 4: Current Flow and Loss Considerations Dielectric losses Tan Anisotropy Conductor losses Guide length losses Attenuation Return Loss VSWR, Voltage Standing Wave Ratio Skin Depth Adhesion layers Surface roughness 49 CHAPTER 5: Substrates 55

6 viii Glass Single crystals Polycrystalline ceramics Fabrication Powder pressing Tape casting Roll compaction Lamination Glazing Substrate characteristics Low temperature cofired (LTCC) Clad Materials Glass transition temperature Material properties Fabrication Mechaical patterning 5.6 Cleaning Safety Wet processes Dry processes CHAPTER 6: Thick Film Screen printing Metal foil screens Lithographically defined thick film Photoengravable thick film Photoimagable thick film 6.4 Additive techniques Metal-organics Direct write Direct bond CHAPTER 7: Thin Film 7.1 Physical vapor deposition Evaporation Filament Electron beam Sputtering DC RF

7 ix Magnetron Reactive CHAPTER 8: Dielectric Deposition 8.1 PELPCVD 8.2 Anodization CHAPTER 9: Polymers 9.1 Material Properties Moisture absorption Mechanical properties Glass transition temperature Planarization 9.2 Deposition Spin coating Spray coating Screen printing Other deposition methods 9.3 Patterning Wet etching Dry etching 9.3 Photosensitive polymers CHAPTER 10 Processing Strategies 141 CHAPTER 11: Photolithography 11.1 Photoresist Spin-on Spraying Roller coating Meniscus coating Electrodeposited Dry Film Dip coating Artwork and masks Exposure Non-colllimated Large flood Short flood Collimated Laser exposure

8 x CHAPTER 12: Electroplating General Inorganic additives Organic additives Waveforms Asymmetric dc Pulse Field density Electroless CHAPTER 13: Etching 13.1 Wet etching 13.2 Dry etching Sputtering Ion beam milling Reactive techniques 13.3 Etching effects on imedance CHAPTER 14 Components 14.1 Passive components Resistors Attenuators Capacitors Parallel plate Interdigitated Inductors 14.2 Transmission line components Reciprocal dividers/combiners Filters CHAPTER 15 Packaging 15.1 Level of Integration 15.2 Interconnects Round wire Strip ribbon Modified TAB Integrated wiring Enclosures

9 xi CHAPTER 16: Thermal expansion Substrate attachment Grounding Vias Platability Time domain reflectometry (TDR) Superconductivity Properties of High-Tc materials Materials considerations Substrate materials Expansion coefficient Buffer (barrier) layers Film formation Patterning Off-axis sputtering Pulsed laser deposition Evaporation Metalorganic Wet etching Dry etching CHAPTER 17: MEMS 269 APPENDIX A: Definition of symbols APPENDIX B: Company directory APPENDIX C: Conversion table APPENDIX D: Graphic evaluation of w/h and SUBJECT INDEX for microstrip

10 PREFACE xiii In 1991 this author published a monograph[l] based on his experience teaching microwave hybrid materials and processing technology at the annual ISHM (now the International Microelectronics and Packaging Society, IMAPS) symposia. Since that time, the course has been presented at that venue and on-site at a number of industrial and government organizations. The course has been continually revised to reflect the many evolutionary changes in materials and processes. Microwave technology has existed for almost 175 years. It was only after the invention of the klystron, just before World War II, that microwave design and manufacture moved from a few visionaries to the growth the industry sees today. Over the last decade alone there have been exploding applications for all types of high frequency electronics in the miltary, automotive, wireless, computer, telecommunications and medical industries. These have placed demands, unimaginable a decade ago, on designs, materials, processes and equipment to meet the ever expanding requirements for increasingly reliable, smaller, faster and lower cost circuits. Microwave electronics is realized by monolithic microwave integrated circuits (MMICs), or hybrid microwave integrated circuits (HMICs). Growth in the computer and wireless industries in particular, has spurred the volume manufacture of both products. Mass fabrication of 300mm silicon (Si) and gallium arsenide (GaAs) wafers is being introduced. Additionally, efforts are ongoing to perfect Si and GaAs, moving toward the creation of defect-free crystals, leading to new levels of performance. Hybrid technologists have responded as well to compliment the MMIC efforts. The past decade has witnessed innovative advances in many areas, leading to a variety of new materials and processes. Among these are new powder technologies for photoengravable and photo-definable thick film inks, allowing the use of thick films at frequencies once reserved for thin films. New generation liquid, dry and electrophoretic resists with improved application and sensitivity have appeared on the market. New organic-based substrate composites, organic encapsulants, via technology, planar and buried passives and technology (low temperature co-fired and multi-chip modules) for advanced packaging and interconnects are being exploited to take advantage of advancements in monolithic technology. This text is directed to acquaint technical managers, engineers and technicians, either with experience, or just enetering the field, with the capabilities and limitations of the materials and processes used for fabricating high frequency circuits. It is essentially introductory in nature. Where possible, equations have been kept simple and to a minimum. Unfortunately, there is little consistency with measurement units and notation. In many of the figures and tables originally published by other authors, I have reproduced their data "as is". As such, the conversion table, Appendix E, may be of some help.

11 xiv This text begins with an introduction to hybrid technology and basic high frequency principles. Following these, the major forms of transmission waveguide are discussed, and then current flow and loss considerations. Substrates, thick and thin film deposition, polymers, artwork, masks, photolithography, subtractive, additive and semi-additive methods, electro- and electroless plating and etching are covered. Passive and transmission line components are then treated within the confines of process requirements. With this background established, the text is directed toward the effects of processing and materials on passive and transmission line-based components. Packaging is discussed with emphasis on inductance considerations. Materials and processes for superconductive components are briefly highlighted. 1. R. Brown, Materials and Processes for Microwave Hybrids, International Microelectronics and Packaging Society, ISHM, Reston, VA., (1991)

12 ACKNOWLEDGEMENTS xv This book is really the product of contributions from many people. It is impossible to recognize the advice and suggestions of everyone. However, many colleagues from industry freely gave their time on a variety of topics. A special thank you is extended to the editorial staff at Kluwer for their Jobian patience. I also want to acknowledge the many vendors who sent catalogues and answered innumerable questions, and I want to express my appreciation to all those who gave me permission to use their material and graphics for this text. As such, certain commercial materials, equipment and processes are identified in the text for illustration. Their use neither implies endorsement nor recommendation by the author. Also no implication is implied or expressed that any of the said materials, equipment or processes are the best available or suitable for the purpose. If anyone has been omitted, it was inadvertent. The author assumes sole responsibility for all errors and omissions.