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ULSI SEMICONDUCTOR TECHNOLOGY ATLAS ULSI SEMICONDUCTOR TECHNOLOGY ATLAS Chih-Hang Tung George T. T. Sheng Chih-Yuan Lu A JOHN WILEY & SONS, INC., PUBLICATION Copyright2003byJohnWiley&Sons,Inc.Allrightsreserved. PublishedbyJohnWiley&Sons,Inc.,Hoboken,NewJersey. PublishedsimultaneouslyinCanada. Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,ortransmittedinanyformor byanymeans,electronic,mechanical,photocopying,recording,scanning,orotherwise,exceptas permittedunderSection107or108ofthe1976UnitedStatesCopyrightAct,withouteithertheprior writtenpermissionofthePublisher,orauthorizationthroughpaymentoftheappropriateper-copyfeeto theCopyrightClearanceCenter,Inc.,222RosewoodDrive,Danvers,MA01923,978-750-8400,fax 978-750-4470,oronthewebatwww.copyright.com.RequeststothePublisherforpermissionshouldbe addressedtothePermissionsDepartment,JohnWiley&Sons,Inc.,111RiverStreet,Hoboken,NJ07030, (201)748-6011,fax(201)748-6008,e-mail:[email protected]. 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LibraryofCongressCataloging-in-PublicationData: Tung,Chih-Hang,1963- ULSIsemiconductortechnologyatlas/Chih-HangTung,GeorgeT.T.Sheng,Chih-YuanLu. p.cm. Includesbibliographicalreferencesandindex. ISBN0-471-45772-8(cloth) 1.Integratedcircuits—Ultralargescaleintegration—Atlases.2.Electronmicroscopy.I. Sheng,GeorgeT.T.II.Lu,Chih-Yuan,1950-III.Title. TK7874.76.T862003 621.39(cid:1)5—dc21 2003049661 PrintedintheUnitedStatesofAmerica. 10987654321 To my family Li-Chen, Yi, Erh, and my parents Chih–HangTung To Dr. Richard Wagner George T.T. Sheng To my family Fen-Fen, Jim, Charlin, my dear parents and brother Nicky Chih-YuanLu Contents FOREWORD ix PREFACE xi PART I 1 1 Microelectronics and Microscopy 3 2 ULSI Process Technology 36 3 Applications of TEM for Construction Analysis 61 4 TEM Sample Preparation Techniques 90 PART II 141 5 Ion Implantation and Substrate Defects 143 6 Dielectrics and Isolation 179 7 Silicides, Polycide, and Salicide 256 8 Metallization and Interconnects 287 PART III 343 9 ULSI Devices I: DRAM Cell with Planar Capacitor 345 10 ULSI Devices II: DRAM Cell with Stacked Capacitor 365 11 ULSI Devices III: DRAM Cell with Trench Capacitor 399 12 ULSI Devices IV: SRAM 445 PART IV 475 13 TEM in Failure Analysis 477 14 Novel Devices and Materials 526 vii viii CONTENTS 15 TEM in Under Bump Metallization (UBM) and Advanced Electronics Packaging Technologies 558 16 High-Resolution TEM in Microelectronics 609 INDEX 647 FOREWORD ULSI technology goes hand in hand with developments in our capability to observe and analyze device structures. Metrology and analysis engineers are our eyes and ears to the microscopic world that process engineers have created. In the past, without theseeyesandears,wehadmarchedcrippledinpitch-blackdarkness;wetumbledand often fell. George T. T. Sheng is a pioneer in using TEM for semiconductor device analysis and has been involved in TEM studies for over 30 years. He has co-authored a book Transmission Electron Microscopy of Si VLSI Circuits and Structures published in 1983 by John Wiley and Sons. The book was acclaimed as it demonstrated to the semiconductor world how TEM could help industry as well as academe. Over the last 20 years, there has been no book published of similar content and format. Twenty years is effectively an eon for the semiconductor industry as we are all aware of the rapid changes in this area. George has teamed up with his long-time colleague, Dr. Chih-Yuan Lu, and his apprentice, Chih-Hang Tung, and they have come out with an up-to-date compilation of their TEM work in this book. Thedifferencesbetweenthetwobooksdemonstratevividlythesignificantadvance- ments in ULSI technology spanning this 20-year history. The differences also demon- stratetheprogressiveroleofTEMinthesemiconductorindustry.Amongthemanynew areas covered in this book are gate oxide metrology, breakdown mechanism studies, and under-bump metallization microstructural analysis. The book embraces the latest TEM advancements as well as the development of TEM sample preparation technology. Thefuture importance ofTEM inthe semiconductor industry is re-assuredbythe publication of this book. UMC Chair Professor S. M. SZE National Chiao Tung University Hsinchu, Taiwan ix PREFACE Characterizationandanalysisofcontemporarymicroelectronicsdevices,processes,and materials using transmission electron microscopy (TEM) are the focus of this book. Thebookiswrittenforengineersandforgraduateandpostgraduatestudentswhowish to know more about ULSI (ultra large scale integration circuits) process problems and the handling and solution of real process issues. Prior knowledge of ULSI process and semiconductor devices is not essential. The book is divided into four parts: Part I coversthefundamentals.Itbeginswithanintroductiontothevariousmicroscopesand analyticaltoolsusuallyfoundinsemiconductorlaboratories(Chapter 1).ULSIprocess fundamentals (Chapter 2) and device construction analysis (Chapter 3) are discussed next, followed by a detailed presentation of the most important step in TEM analysis: sample preparation (Chapter 4). Part II focuses on a few important device structures in the current ultra (or very) large scale integration (ULSI/VLSI) processes. Included in the discussion are ion implantation and substrate defects (Chapter 5), dielectrics and isolation (Chapter 6), silicides (Chapter 7), and interconnects (Chapter 8). Part III then proceeds to some of the most challenging topics in the contemporary process technologies: DRAM and SRAM (Chapters 9–12). Part IV provides a window on developments in device failure analysis (Chapter 13), advanced packaging and under bump metallization (UBM) technologies (Chapter 15), and nonconventional devices and materials, among these MEMS, SOI, SiGe, and III–V compound semiconductors (Chapters 14 and 16). While every effort has been made to cover as many aspects of microelectronics technologies as we would like to, the scope and examples presented in this book are still limited by our experience and areas of interest. To this end, our areas of interest have become our limitations. Throughout the book ULSI processes are illustrated by ampleexamplesandmicrographs.AswebelievethatintheULSIprocesstechnologies and in electron microscopy there exist a number of excellent textbooks, we have no intention to add another. What we do is to combine both and add many images for the acuteobserversamongourreaders,aswefeel,like Aristotle, thatone cannotthink without images. Images trigger an active intellectual experience. A deliberate perusal of the elements in a picture may in some instances generate curiosity and in other instances the ingenuity displayed by the scientist: “I looked, and this is what I saw. I looked, and this is what I thought. This is how I think it works.” (H. Bobin, The Scientific Images: From Caveto Computer, Abrams, New York, 1992.) Semiconductordeviceandprocesscharacterizationinvolvescross-disciplinarywork. Tremendous effort went into the thousands of samples we analyze and present in this book. Thetask simply couldnot havebeenachievedbyjust the threeof us. We would therefore like to acknowledge our colleagues for their contributions: Our special thanks go to Prof. Simon Sze (AT&T Bell Labs, NDL and NCTU, Taiwan), Prof. King-Ning Tu (IBM and UCLA, USA), Prof. Kin Leong Pey (NTU, xi xii PREFACE Singapore), and Dr. Ron Anderson (IBM, USA) for their technical advice. Our colleagues who helped in various experimental work include Wei-Kun Hung, Show-Ing Hsu, Ting Chou, Chin-Ting Chian, Ray-Chuan Chew, Su-Mei Chen, Chu-Mei Chang (ERSO/ITRI and Vanguard International Semiconductor Corp. Taiwan), and Timothy Yeow, Kun Pan, Geok Peng Gou, Qin Deng, LeiJun Tang and An Yan Du (IME, Sin- gapore). We would like to mention some of our colleagues who read the manuscript andmadesuggestions:Cheng-KouCheng(ERSO,VISC,andIME),Dr.N.Balasubra- manian,Dr.KantaBeraLakshmi,Dr.Chao-YongLi,Poi-SiongTeo(IME,Singapore), Dr. Sam Pan, Dr. Wenchi Ting, Dr. Joseph Ku (MXIC, Taiwan), Dr. Yong-Fen Hsieh, (UMC and MA Tech, Taiwan) Dr. Horng-Chih Lin, Dr. Wen-Fa Wu, Dr. Ming-Shih Tsai,Dr.Tien-ShengChao,andDr.Chao-HsinChien(NDL,Taiwan).Wewouldliketo acknowledge the management and administration support we received from Dr. David C. T. Hsing, Liang-Hsin Chang, and Cheng-TaiChang (ERSO/ITRI,Taiwan), Dr. Bill Chen,Dr.KhenSangTan,and Dr.John L. F.Wang (IME,Singapore),Miin Wu, Tom Yiu, and Y. S. Tan (MXIC, Taiwan). Finally, we would like to acknowledge the assistance of companies during various stages of our endeavors: AT&T Bell Labs (USA), Electronics Research and Ser- vice Organization of Industrial Technology Research Institute (ERSO/ITRI, Taiwan), Institute of Microelectronics (IME, Singapore), Vanguard International Semiconductor Corp. (VISC, Taiwan), Gatan Inc. (USA), FEI Company (USA), Chartered Semicon- ductorManufacturingCorp.(Singapore),MacronixInternationalLtd.(MXIC,Taiwan), and Ardentec Corp. (Taiwan). C. H. TUNG GEORGE T. T. SHENG C. Y. LU PART I 1