ESD Basics E-Book

Steven H. Voldman

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 341

Veröffentlichungsjahr: 2012

Beschreibung

Electrostatic discharge (ESD) continues to impact semiconductor manufacturing, semiconductor components and systems, as technologies scale from micro- to nano electronics. This book introduces the fundamentals of ESD, electrical overstress (EOS), electromagnetic interference (EMI), electromagnetic compatibility (EMC), and latchup, as well as provides a coherent overview of the semiconductor manufacturing environment and the final system assembly. It provides an illuminating look into the integration of ESD protection networks followed by examples in specific technologies, circuits, and chips.

The text is unique in covering semiconductor chip manufacturing issues, ESD semiconductor chip design, and system problems confronted today as well as the future of ESD phenomena and nano-technology.

Look inside for extensive coverage on:

• The fundamentals of electrostatics, triboelectric charging, and how they relate to present day manufacturing environments of micro-electronics to nano-technology
• Semiconductor manufacturing handling and auditing processing to avoid ESD failures
• ESD, EOS, EMI, EMC, and latchup semiconductor component and system level testing to demonstrate product resilience from human body model (HBM), transmission line pulse (TLP), charged device model (CDM), human metal model (HMM), cable discharge events (CDE), to system level IEC 61000-4-2 tests
• ESD on-chip design and process manufacturing practices and solutions to improve ESD semiconductor chip solutions, also practical off-chip ESD protection and system level solutions to provide more robust systems
• System level concerns in servers, laptops, disk drives, cell phones, digital cameras, hand held devices, automobiles, and space applications
• Examples of ESD design for state-of-the-art technologies, including CMOS, BiCMOS, SOI, bipolar technology, high voltage CMOS (HVCMOS), RF CMOS, smart power, magnetic recording technology, micro-machines (MEMs) to nano-structures

ESD Basics: From Semiconductor Manufacturing to Product Use complements the author’s series of books on ESD protection. For those new to the field, it is an essential reference and a useful insight into the issues that confront modern technology as we enter the Nano-electronic Era.

Leseprobe

Contents

Cover

ESD Series

Title Page

Copyright

Dedication

About the Author

Preface

Acknowledgments

Chapter 1: Fundamentals of Electrostatics

1.1 Introduction

1.2 Electrostatics

1.3 Triboelectric Charging – How does it Happen?

1.4 Conductors, Semiconductors, and Insulators

1.5 Static Dissipative Materials

1.6 ESD and Materials

1.7 Electrification and Coulomb's Law

1.8 Electromagnetism and Electrodynamics

1.9 Electrical Breakdown

1.10 Electroquasistatics and Magnetoquasistatics

1.11 Electrodynamics and Maxwell's Equations

1.12 Electrostatic Discharge (ESD)

1.13 Electromagnetic Compatibility (EMC)

1.14 Electromagnetic Interference (EMI)

1.15 Summary and Closing Comments

References

Chapter 2: Fundamentals of Manufacturing and Electrostatics

2.1 Materials, Tooling, Human Factors, and Electrostatic Discharge

2.2 Manufacturing Environment and Tooling

2.3 Manufacturing Equipment and ESD Manufacturing Problems

2.4 Manufacturing Materials

2.5 Measurement and Test Equipment

2.6 Grounding and Bonding Systems

2.7 Worksurfaces

2.8 Wrist Straps

2.9 Constant Monitors

2.10 Footwear

2.11 Floors

2.12 Personnel Grounding with Garments

2.13 Air Ionization

2.14 Seating

2.15 Carts

2.16 Packaging and Shipping

2.17 ESD Identification

2.18 ESD Program Management – Twelve Steps to Building an ESD Strategy

2.19 ESD Program Auditing

2.20 ESD On-Chip Protection

2.21 Summary and Closing Comments

References

Chapter 3: ESD, EOS, EMI, EMC and Latchup

3.1 ESD, EOS, EMI, EMC and Latchup

3.2 ESD Models

3.3 Electrical Overstress (EOS)

3.4 EMI

3.5 EMC

3.6 Latchup

3.7 Summary and Closing Comments

References

Chapter 4: System Level ESD

4.1 System Level Testing

4.2 When Systems and Chips Interact

4.3 ESD and System Level Failures

4.4 Electronic Systems

4.5 System Level Problems Today

4.6 Automobiles, ESD, EOS, and EMI

4.7 Aerospace Applications

4.8 ESD and System Level Test Models

4.9 IEC 61000-4-2

4.10 Human Metal Model (HMM)

4.11 Charged Board Model (CBM)

4.12 Cable Discharge Event (CDE)

4.13 Summary and Closing Comments

References

Chapter 5: Component Level Issues – Problems and Solutions

5.1 ESD Chip Protection – The Problem and the Cure

5.2 ESD Chip Level Design Solutions – Basics of Design Synthesis

5.3 ESD Chip Floor Planning – Basics of Design Layout and Synthesis

5.4 ESD Analog Circuit Design

5.5 ESD Radio Frequency (RF) Design

5.6 Summary and Closing Comments

References

Chapter 6: ESD in Systems – Problems and Solutions

6.1 ESD System Solutions from Largest to Smallest

6.2 Aerospace Solutions

6.3 Oil Tanker Solutions

6.4 Automobile Solutions

6.5 Computers – Servers

6.6 Mother Boards and Cards

6.7 System Level “On Board” ESD Protection

6.8 System Level Transient Solutions

6.9 Package-Level Mechanical ESD Solutions – Mechanical “Crowbars”

6.10 Disk Drive ESD Solutions

6.11 Semiconductor Chip Level Solutions – Floor Planning, Layout, and Architecture

6.12 Semiconductor Chip Solutions – Electrical Power Grid Design

6.13 ESD and EMC – When Chips Bring Down Systems

6.14 System Level and Component Level ESD Testing and System Level Response

6.15 EMC and ESD Scanning

6.16 Summary and Closing Comments

References

Chapter 7: Electrostatic Discharge (ESD) in the Future

7.1 What is in the Future for ESD?

7.2 Factories and Manufacturing

7.3 Photo-Masks and Reticles

7.4 Magnetic Recording Technology

7.5 Micro-Electromechanical (MEM) Devices

7.6 Micro-Motors

7.7 Micro-Electromechanical (MEM) RF Switches

7.8 Micro-electromechanical (MEM) Mirrors

7.9 Transistors

7.10 Silicon Nanowires

7.11 Carbon Nanotubes

7.12 Future Systems and System Designs

7.13 Summary and Closing Comments

References

Glossary

ESD Standards

ESD Association

Department of Defense

Military Standards

Index

ESD Series

By Steven H. Voldman

ESD Basics: From Semiconductor Manufacturing to Product UseISBN: 9780470979716September 2012

ESD: Design and SynthesisISBN: 9780470685716March 2011

ESD: Failure Mechanisms and ModelsISBN: 9780470511374July 2009

LatchupISBN: 9780470016428December 2007

ESD: RF Technology and CircuitsISBN: 9780470847558September 2006

ESD: Circuits and DevicesISBN: 9780470847541November 2005

ESD: Physics and DevicesISBN: 9780470847534September 2004

Upcoming titles:

ESD: Test and Characterization

Electrical Overstress (EOS): Devices, Circuits, and Systems

The ESD Handbook

This edition first published 2012

© 2012 John Wiley & Sons, Ltd

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Library of Congress Cataloging-in-Publication Data

Voldman, Steven H.

ESD basics : from semiconductor manufacturing to product use / Steven Voldman.

p. cm.

Includes bibliographical references and index.

ISBN 978-0-470-97971-6 (hardback)

1. Electronic apparatus and appliances–Design and construction. 2. Electric discharges. 3. Electronic apparatus and appliances–Protection. 4. Microelectronics. 5. Static eliminators. 6. Electrostatics. I. Title.

TK7836.V65 2012

621.3815–dc23

2012018125

A catalogue record for this book is available from the British Library.

Print ISBN: 9780470979716

To My ParentsCarl and Blossom Voldman

About the Author

Dr Steven H. Voldman is the first IEEE Fellow in the field of electrostatic discharge (ESD) for “Contributions in ESD protection in CMOS, Silicon On Insulator and Silicon Germanium Technology.” He received his B.S. in Engineering Science from University of Buffalo (1979); a first M.S. EE (1981) from Massachusetts Institute of Technology (MIT); a second degree EE Degree (Engineer Degree) from MIT; a MS Engineering Physics (1986) and a PhD in Electrical Engineering (EE) (1991) from University of Vermont under IBM's Resident Study Fellow program.

He was a member of the IBM development for 25 years working on semiconductor device physics, device design, and reliability (e.g., soft error rate (SER), hot electrons, leakage mechanisms, latchup and electrostatic discharge (ESD)). Steve Voldman has been involved in latchup technology development for 27 years. He worked on both technology and with product development in Bipolar SRAM, CMOS DRAM, CMOS logic, Silicon on Insulator (SOI), BiCMOS, Silicon Germanium (SiGe), RF CMOS, RF SOI, smart power, and image processing technologies. In 2008, he was a member of the Qimonda DRAM development team, working on 70, 58 and 48 nm CMOS technology. In 2008, he initiated a limited liability corporation (LLC), and he worked at headquarters in Hsinchu, Taiwan for Taiwan Semiconductor Manufacturing Corportion (TSMC) as part of the 45 nm ESD and latchup development team. He was a Senior Principal Engineer working for the Intersil Corporation on ESD and latchup development from 2009 to 2011. Since 2011, he is presently independent under Dr Steven H. Voldman LLC providing consulting, teaching, and patent litigation expert witness support.

Dr Voldman was chairman of the SEMATECH ESD Working Group from 1995 to 2000. In his SEMATECH Working Group, the effort focused on ESD technology benchmarking, the first transmission line pulse (TLP) standard development team, strategic planning, and JEDEC-ESD Association standards harmonization of the human body model (HBM) standard. From 2000 to 2010, as Chairman of the ESD Association Work Group on TLP and very-fast TLP (VF-TLP), his team was responsible for initiating the first standard practice and standards for TLP and VF-TLP. Steve Voldman has been a member of the ESD Association Board of Directors, and Education Committee. He initiated the “ESD on Campus” program which was established to bring ESD lectures and interaction to university faculty and students internationally; the ESD on Campus program has reached over 40 universities in the United States, Singapore, Taiwan, Malaysia, Philippines, Thailand, India, and China.

Dr Voldman teaches short courses and tutorials on ESD, latchup, and invention in the United States, China, Singapore, Malaysia, Taiwan, Sri Lanka, and Israel. He is a recipient of over 240 issued US patents, in the area of ESD and CMOS latchup. He has served as an expert witness in patent litigation cases associated with ESD and latchup.

Dr Voldman has also written articles for Scientific American and is an author of the first book series on ESD and latchup: ESD: Physics and Devices, ESD: Circuits and Devices, ESD: RFTechnology and Circuits, Latchup, ESD: Failure Mechanisms and Models, and ESD: Design and Synthesis as well as a contributor to the books Silicon Germanium: Technology, Modeling and Design and Nanoelectronics: Nanowires, Molecular Electronics, and Nano-devices. In addition, the International Chinese editions of book ESD: Circuits and Devices and the text ESD: RFTechnology and Circuit is also released.

Preface

This text, ESD Basics: From Semiconductor Manufacturing to Product Use was initiated on the need to produce a text that addresses fundamentals of electrostatic discharge from the manufacturing environment to today's products. As the manufacturing world evolves, semiconductor networks scale, and systems are changing, the needs and requirements for reliability and ESD protection are changing. A text is required that connects basic ESD phenomena to today's real world environment.

Whereas significant texts are available today to teach experts on ESD on-chip design, there is a need for non-experts, non-technical and layman to understand the problems facing the world today. Today, real world ESD and EMI issues surround us; from exploding gas tanks, electrostatic discharge problems in automobiles, cable-induced latchup of computer servers, to automotive noise related issues. Hence, there is a need for non-experts to understand the issues that revolve around us, and what do we do to avoid them.

This text has multiple goals.

The first goal of the text is to teach the basics of electrostatics, and tribo-electric charging and relate them to the electrostatic discharge processes in semiconductor manufacturing, handling and assembly. While teaching some fundamentals, I added some history as well.

The second goal of the text is to teach the electrostatic discharge (ESD), tribo-charging, electrical overstress (EOS), and latchup subject matter. The text opens the door on the issues of electromagnetic interference (EMI) and electromagnetic compatibility (EMC).

The third goal is to relate these processes to modern day chips, and systems in today's world. Hopefully, the examples of problems today will make it more relevant, entertaining and a little fun as well.

The fourth goal is to demonstrate how to protect semiconductor chips with on-chip protection networks.

The fifth goal is to expose the reader to ESD testing of both semiconductor chips and systems.

The sixth goal is to discuss where the future lies with ESD phenomena, standards, testing and future products.

The seventh goal is to provide a glimpse into the future with new nano-structures and nano-systems, and the anticipated electrostatic and electromagnetic issues aheadǃ

This text, ESD: From Semiconductor Manufacturing to Product Use will contain the following:

Chapter 1 introduces the reader to an overview of the language and fundamentals associated with electrostatics. In Chapter 1, a brief discussion of electrostatics, and tribo-electrical phenomena is weaved into the individuals, dates, and history: Thales of Miletus, Gray, Dufay, Franklin, Toepler, Faraday, Cavendish, Coulomb, to Maxwell – just to mention a few. The chapter then quickly fast-forwards to today's issues of electrostatic discharge (ESD), electrical overstress (EOS), latchup, electromagnetic interference (EMI), and electromagnetic compatibility (EMC) in components and systems.Chapter 2 discusses electrostatic discharge control in manufacturing environments. In this chapter, the objective is to provide the reader with a taste of the issues, test methods, standards, and control programs in manufacturing to provide an ESD protected area.In Chapter 3, the subject switches to focus on a deeper look at electrostatic discharge (ESD), electrical overstress (EOS), electromagnetic interference (EMI) and electromagnetic compatibility (EMC). Each of these fields has a vast number of publications, literature, and books. In the introduction, I have provided some of the language, terms, and testing standards.In Chapter 4, system level concerns associated with ESD, EOS, latchup, EMI, and EMC have been discussed relevant to today's application and the future. A brief discussion of electrostatic issues in servers, laptops, hand-held devices, cell phones, disk drives, digital cameras, autos, and space applications was reviewed to educate the reader in the vast number of issues in today's electronic environment. System level ESD tests, such as IEC 61000-4-2, HMM, CDE, and CBM are discussed.Chapter 5 focuses on semiconductor component solutions. The focus of the chapter is on “on-chip” ESD protection networks. ESD protection in digital, analog, and RF applications are discussed. In this chapter, ESD circuits schematics, layout, and semiconductor chip floor planning are also discussed.Chapter 6 focuses on system level solutions. System level solutions being practiced today are shown for ESD, EMI, and EMC. New concepts such as system level EMC scanning techniques are discussed.Chapter 7 discusses ESD protection for today's and tomorrow's nanostructure technology. As the dimensional scaling of devices approaches the nano-meter dimensions, all devices will have to address the implications of static charge, electrostatic discharge (ESD), electromagnetic interference (EMI), and electrical overstress (EOS). This will be true in photo-masks, magnetic recording devices, semiconductor devices, nano-wires to nano-tubes. This concluding chapter takes a look at micro-motors, micro-mirrors, RF MEM switches, and many novel devices.

This introductory text will hopefully pique your interest in the field of electrostatic discharge (ESD), electrical overstress (EOS), electromagnetic interference (EMI), and electromagnetic compatibility (EMC) – and teach how it relates to today's world. To establish a stronger knowledge of ESD protection, it is advisable to read the other texts ESD: Physics and Devices, ESD: Circuits and Technology, ESD: RF Circuits and Technology, ESD: Failure Mechanisms and Models, ESD: Design and Synthesis, and Latchup.

Enjoy the text, and enjoy the subject of ESD, EOS, latchup, EMI, and EMC phenomena.

Baruch HaShem (B”H)

Dr Steven H. VoldmanIEEE Fellow

Acknowledgments

I would like to thank the years of support from the SEMATECH, the ESD Association, the IEEE, and the JEDEC organizations. I would like to thank the IBM Corporation, Qimonda, Taiwan Semiconductor Manufacturing Corporation (TSMC), and the Intersil Corporation. The work in this text comes from thirty years of working with bipolar memory, DRAM memory, SRAM, NVRAMs, microprocessors, ASICs, mixed voltage, mixed signal, RF to power applications. I was fortunate to work in a wide number of technology teams, and with a wide breadth of customers. I was very fortunate to work in bipolar memory, CMOS DRAM, CMOS logic, ASICs, silicon on insulator (SOI), and Silicon Germanium (SiGe) from 1 μm to 45 nm technologies. I was very fortunate to be a member of talented technology and design teams that were both innovative, intelligent, and inventive. This provided opportunity to provide experimental concepts, and try new ideas in ESD design in applications and products.

I would like to thank the institutions that allowed me to teach and lecture at conferences, symposiums, industry, and universities; this gave me the motivation to develop the texts. I would like to thank faculty at the following universities: M.I.T., Stanford University, University of Central Florida (UCF), Vanderbilt University, University Illinois Urbana-Champaign (UIUC), University of California Riverside (UCR), University of Buffalo, National Chiao Tung University (NCTU), Tsin Hua University, National Technical University of Science and Technology (NTUST), National University of Singapore (NUS), Nanyang Technical University (NTU), Beijing University, Fudan University, Shanghai Jiao Tung University, Zheijang University, Huazhong University of Science and Technology (HUST), Universiti Sains Malaysia (USM), Universiti Putra Malaysia (UPM), Kolej Damansara Utama (KDU), Chulalongkorn University, Mahanakorn University, Kasetsart University, Thammasat University, and Mapua Institute of Technology.

I would like to say thank you for the years of support and the opportunity to provide lectures, invited talks, and tutorials to the Electrical Overstress/Electrostatic Discharge(EOS/ESD) Symposium, the International Reliability Physics Symposium(IRPS), the Taiwan Electrostatic Discharge Conference(T-ESDC), the International Electron Device Meeting(IEDM), the International Conference on Solid-State and Integrated Circuit Technology(ICSICT), the International Physical and Failure Analysis(IPFA), IEEE ASICON, and IEEEIntelligent Signal Processing And Communication Systems(ISPACS) Conference.

I would like to thank my many friends for twenty years in the ESD profession – Prof. Ming Dou Ker, Prof. J.J. Liou, Prof. Albert Wang, Prof. Elyse Rosenbaum, Prof. Jo Chiranut Sa-ngiamsak, Timothy J. Maloney, Charvaka Duvvury, Eugene Worley, Robert Ashton, Yehuda Smooha, Vladislav Vashchenko, Ann Concannon, Albert Wallash, Vessilin Vassilev, Warren Anderson, Marie Denison, Alan Righter, Andrew Olney, Bruce Atwood, Jon Barth, Evan Grund, David Bennett, Tom Meuse, Michael Hopkins, Yoon Huh, Jin Min, Keichi Hasegawa, Nathan Peachey, Kathy Muhonen, Augusto Tazzoli, Gaudenzio Menneghesso, Marise BaFleur, Jeremy Smith, Nisha Ram, Swee K. Lau, Tom Diep, Lifang Lou, Stephen Beebe, Michael Chaine, Pee Ya Tan, Theo Smedes, Markus Mergens, Christian Russ, Harold Gossner, Wolfgang Stadler, Ming Hsiang Song, J.C. Tseng, J.H. Lee, Michael Wu, Erin Liao, Stephen Gaul, Jean-Michel Tschann, Tze Wee Chen, Shu Qing Cao, Slavica Malobabic, David Ellis, Blerina Aliaj, Lin Lin, David Swenson, Donn Bellmore, Ed Chase, Doug Smith, W. Greason, Stephen Halperin, Tom Albano, Ted Dangelmayer, Terry Welsher, John Kinnear, and Ron Gibson.

I would like to thank the ESD Association office for the support in the area of publications, standards developments, and conference activities. I would also like to thank the publisher and staff of John Wiley & Sons, for including this text as part of the ESD book series.

To my children, Aaron Samuel Voldman and Rachel Pesha Voldman, good luck to both of you in the future.

To my wife Annie Brown Voldman – thank you for the support and years of work.

And to my parents, Carl and Blossom Voldman.

Baruch HaShem (B”H)

Dr Steven H. VoldmanIEEE Fellow

Chapter 1

Fundamentals of Electrostatics

1.1 Introduction

We are all familiar with electrostatic discharge (ESD): shuffle your feet across a shag carpet in your favorite sneakers, touch a piece of metal, and zap! For a human being, we let out an “ouch!”; but for micro-electronics to nano-electronics, this can lead to product failures [1].

But, today, and in the future, static charge will remain an important industrial issue for the production of both electronic devices to systems. It is also an issue in fields of munitions, explosives, chemical, and material industries. Any industry where there is a risk of impact to quality, yield, degradation, or physical harm will be concerned with electrostatic discharge (ESD), electrical overstress (EOS), electromagnetic interference (EMI), and electromagnetic compatibility (EMC).

In this book, a short survey of ESD from manufacturing to product use will be shown. The text will discuss fundamentals of electrostatics, manufacturing electrostatic issues, component level issues, system level issues, to design.

So, where did all this all begin?

1.2 Electrostatics

The discovery of electrostatic attraction and electrostatic discharge is one of the world's earliest understandings of scientific thought and analysis. Its first discovery goes back to the early foundation of the problem of the nature of matter, astronomy, mathematics and foundation of Greek philosophy, and pre-dates the nature of matter.

1.2.1 Thales of Miletus and Electrostatic Attraction

Thales of Miletus, born in 624 B.C.E and died in 546 B.C.E, was the founder of the Ionian School (or Milesian School) and one of the Seven Wise Men of Ancient Greece in the Pre-Socratic era. Thales was an astronomer, mathematician, and philosopher. He was an inventor and an engineer. Thales of Miletus established a heritage of searching for knowledge for knowledge sake, development of the scientific method, establishment of practical methods, and the conjecture approach to questions of natural phenomenon. The Milesian School is regarded as establishing the critical method of questioning, debate, explanation, justification and criticism. The students of Thales included Euclid, Pythagoras, and Eudemus [2].

It was Thales of Miletus who was accredited with the discovery of the electrostatic attraction created after the material amber was rubbed. Thales noted after amber was rubbed, straw was attracted to the piece of amber. It was from this event, the Greek word for amber, ελεκτρoν (trans. electron) became associated with the electrical phenomenon.

Knowledge of Thales' ideas was common through writings of his disciples and notary Greek Philosophers. In De Anima 411 a7-8, Aristotle stated “Some think that the soul pervades the whole universe, when perhaps came Thales' view that everything is full of gods.” [3].

Electrostatic phenomenon pre-dated early thoughts of the nature of physical matter. Thales of Miletus's ESD experiments and study of electrostatic attraction was before the atomic schools of matter in Greece and Rome. Electrostatic phenomena and thought began before the Greek atomistic schools of Democritus (420 B.C.E.), and Epicurus (370 B. C.E.), and Roman School of Lucretius (50 B.C.E). Thales was deceased by the time the schools of atomic thought were active. On his tomb read, “Here in a narrow tomb Great Thales lie; Yet his renown for wisdom reached the skies [4].”

Robert A. Millikan, in the Introduction of his 1917 edition of “The Electron” [5] stated,

“Perhaps it is merely a coincidence that the man who first noticed rubbing of amber would induce in it a new and remarkable state now known as the state of electrification was also the man who first gave expression to the conviction that there must be some great unifying principle which links together all phenomena and is capable of making them rationally intelligible; that behind all the apparent variety and change of things there is some primordial element, out of which all things are made and the search for which must be the ultimate aim of all natural science. Yet if this be merely coincidence, at any rate to Thales of Miletus must belong a double honor. For he first correctly conceived and correctly stated, as far back as 600 B.C., the spirit which has actually guided the development of physics in all ages, and he also first described, though in a crude and imperfect way, the very phenomenon the study of which has already linked together several of the erstwhile isolated departments of physics, such as radiant heat, light, magnetism, and electricity, and has very recently brought us nearer to the primordial element than we have ever been before.”

J.H. Jeans, in the 1925 Fifth Edition of The Mathematical Theory of Electricity and Magnetism [6], wrote

“The fact that a piece of amber, on being rubbed, attracted to itself other small bodies, was known to the Greeks, the discovery of this fact being attributed to Thales of Miletus”

“A second fact, namely, that a certain mineral ore (lodestone) possessed the property of attracting iron, is mentioned by Lucretius. These two facts have formed the basis from which the modern science of Electromagnetism has grown.”

1.2.2 Electrostatics and the Triboelectric Series

With the death of Thales of Miletus, little progress proceeded on ESD phenomenon. Although history moved forward, the advancement of tribo-electric charging and electrostatic discharge phenomenon was slow relative to the time that passed. In Europe, mankind saw the Roman Empire, the Golden Age of Islam, the Middle Ages, the Black Death, the Renaissance, the Reformation, and the advancement of nation states. ESD phenomenon was discovered by Thales while China was undergoing the Zhou Dynasty. Asia underwent tremendous change with the Qin, Han, Sui, Tang, and Song, Yuan, and Ming dynastic periods, but there was no advancement of this field of knowledge.

With all this social change, insignificant growth in the understanding of electrostatic phenomenon increased until the eighteenth century. The interest in tribo-charging and electrostatic phenomenon became the luxury of scientists supported by the courts of Europe and laboratories of France and England.

So, how does tribo-charging happen?

When two materials come into contact, the atoms contained within the materials come into close contact. Figure 1.1 shows an example of two atoms of different materials. The nucleus is tightly bound, with neutrons and protons, and is positively charged. Strong interactions hold the neutrons and protons together. According to the Bohr model, the electrons orbit around the nucleus, and are drawn to the nucleus by the electrostatic attraction between the negative electrons and the positive nucleus. In a neutral un-charged atom, the number of protons and electrons are equal in number.

Figure 1.1 Tribo-charging of materials – physical contact

When two materials are in contact, charge transfer occurs through the friction or physical contact. An electron of the outer orbitals can transfer from one material to the second material. Figure 1.2 shows an example after the two materials are separated. In this case, the material that loses the electron becomes positively charged, and the material that gains the electron becomes negatively charged.

Figure 1.2 Tribo-charging of materials – separation

1.2.3 Triboelectric Series and Gilbert

Gilbert, in the seventeenth century, noted that interaction between a glass rod and silk produced the same phenomenon discussed by Thales of Miletus – materials when rubbed with silk became “amberized” [5]. Gilbert began construction of the earliest list of tribo-electrification.

1.2.4 Triboelectric Series and Gray

In the same period, Stephen Gray (1696–1736) thought of the concept of the division of materials according to its nature of removing or sustaining electrification [5]. He defined a class of materials which remove “amberization” as conductors, and the class of materials which allowed a body to retain its electrification as non-conductors, or insulators.

1.2.5 Triboelectric Series and Dufay

This work was followed by French physicist Dufay in 1733 discovering the same effect can be achieved with sealing wax and cat's fur and noted the effect was different from the glass rod [5]. Dufay first noted that there was an attractive and repulsive phenomenon between different materials, naming the opposite processes as “vitreous” and “resinous.”

1.2.6 Triboelectric Series and Franklin

Benjamin Franklin – the first American ESD engineer, in 1747, also identified two processes, which he divided into “positive” and “negative” processes. The “positive” process was the first process, discovered by Gilbert, any physical body was electrified positive if repelled by a glass rod which was rubbed with silk. The “negative” process is any body repelled from sealing wax which was rubbed with cat's fur, extending the work of Dufay.

In this time frame, many electrostatic scientists began recording the relationship of one body to another in the electrification process. Lists of materials of the times were ordered to construct the early tribo-electrification chart [6]

. . . “It is therefore possible to arrange any number of substances in a list such that a substance is charged with positive or negative electricity when rubbed with a second substance, according as the first substance stands above or below the second substance on the list. The following is a list of this kind which includes some of the most important substances:

“Cat's skin, Glass, Ivory, Silk, Rock Crystal, The Hand, Wood, Sulphur, Flannel, Cotton, Shellac, Caouthouc, Resins, Guttapercha, Metals, Guncotton.””

J.H. Jeans D.Sc, LL.D, F.R.S

The Mathematical Theory of Electricity and Magnetism Cambridge, England, 1925

1.2.7 Electrostatics – Symmer and the Human Body Model

In this time frame, some electrostatic scientist and engineers explored phenomenon around them, and were the early root of electrostatic discharge (ESD) phenomenon of garments, and possibly early influences on the “human body model.”

Robert Symmer (1759) would do experimental studies in the dark, exploring the electrical discharge phenomenon of removal of his stockings and the interactions of two different sets of stockings, placing two white stockings in one hand and two black stockings in the other [5].

1.2.8 Electrostatics – Coulomb and Cavendish

Coulomb (while other ESD scientists were still enjoying the ESD phenomenon with their stockings and rubbing things together) developed the Torsion Balance, in 1785, beginning a series of processes to understand the relationship of force, charge and physical distance. The experiments of Coulomb were also performed by Cavendish at an earlier date but not published until 1879 by James Clerk Maxwell [7].

1.2.9 Electrostatics – Faraday and the Ice Pail Experiment

At this time, the relationship of positive and negative electrification was not fully understood. In 1837, Michael Faraday performed the “ice-pail experiment” involving glass rod and silk which showed that “positive and negative electrical charges always appear simultaneously and in exactly equal amounts.”

Faraday, in his lecture Forces of Matter – Lecture V Magnetism-Electricity would provide demonstrations of electrostatic charging phenomenon demonstrating the phenomenon and the relationship of positive and negative charging effects [8]. He would close his lecture on electrical phenomenon with “. . . This, then is sufficient, in the outset to give you an idea of the nature of the force which we call ELECTRICITY. There is no end to the things from which you can evolve this power.”

1.2.10 Electrostatics – Faraday and Maxwell

Even at this time frame, the relationship of matter, electrical charging and electrical force was not well understood. Different models were proposed from single electrical fluid models, and two fluid models to explain the charging process. Electrical phenomenon models were established to explain this phenomenon as related to a stress or strain of the medium, moving the thoughts from an atomistic perspective to a field representation. It was in this time frame that Faraday and James Clerk Maxwell began addressing the understanding of electricity and electrical forces in terms of a field perspective, and electrical charge was viewed as a “state of strain in the ether.” James Clerk Maxwell, in Electricity and Magnetism in 1873, created the modern formulation of electricity and magnetism as we understand it today [7].

1.2.11 Electrostatics – Paschen

In 1889, Paschen began an analysis of breakdown phenomenon in gases trying to explain the relationship between gas pressure and electrode spacing [8]. Breakdown phenomenon in media took a great leap forward influencing electrostatic discharge (ESD) understanding in today's devices. Even today, the Paschen breakdown curve is important for understanding the electrical breakdown in air gaps and nano-structures.

1.2.12 Electrostatics – Stoney and the “Electron”

In 1891, the word “electron” as a natural unit of electricity was suggested by Dr. G. Johnstone Stoney, connecting the ideas of Faraday's Law of Electrolysis [5]. At this time, the understanding of the connection to physical matter was not understood, but was used as a measure or unit. Dr. G. Johnstone Stoney reconnected the idea to the Greek word for amber, connecting the early work of Thales of Miletus to the modern day concept of an electrical unit, later to be proven to be connected to matter and atomic theory.

From this brief history, it can be seen that electrostatic attraction pre-dates the earliest thoughts of the understanding of matter. From 600 B.C.E to even as late as the 1890s the relationship of the discovery of Thales of Miletus was not understood as connected to the transfer of electrons which were made of matter.

1.3 Triboelectric Charging – How does it Happen?

Tribo-electric charging occurs when two bodies of materials come into physical contact, followed by separation of the two bodies. (Table 1.1) As discussed before, the word electron comes from the Greek word for “amber.” The word “tribo” also comes from Greek, meaning “to rub.” Tribo-charging has to do with two items that come into contact, followed by their separation. In the process of tribo-charging, electrons transfer from one material to another. Atoms are made of a nucleus which consists of positively charged protons, and neutrally charged neutrons. Outside of the nucleus, electrons establish standing wave orbitals around the nucleus. Electrons are negatively charged. When there are two dissimilar materials of different electric potentials, electrons can transfer from one material to another. After material separation, the material with the extra electron becomes negatively charged, whereas the material that lost the electron becomes positively charged.

Table 1.1 Triboelectric Series.

Positive (+)MaterialsRabbit FurGlassHuman HairNylonWoolFurSilkAluminumPaperCottonSteelWoodAmberNickelGoldPolyesterSiliconTeflonNegative (−)

So, the material property influences whether the electrons transfer. As discussed by Jeans [6], a chart can be constructed predicting the direction of charge transfer.

“It is therefore possible to arrange any number of substances in a list such that a substance is charged with positive or negative electricity when rubbed with a second substance, according as the first substance stands above or below the second substance on the list . . . ”

1.4 Conductors, Semiconductors, and Insulators

The electrical engineer likes to draw some defining boundary lines between insulators, semiconductors, and metals on the basis of such conductivity,

Arthur Von Hippel “Building from Atoms” Chapter 2The Molecular Designing of Materials and Devices, MIT Press, 1965

The physicist Professor Arthur Von Hippel simplifies the matter of what is an insulator, semiconductor, and metal based on the conductivity of a solid [9]. In layman's terms, an insulator is a material that limits the flow of electrons within the bulk volume or surface of the material, and a conductor is a material that allows free flow of electrons within the bulk or surface of the material. An insulator can have a surface resistance of ρs = 1011 ohms and bulk resistance of ρ = 1011 ohms-cm; whereas conductors can have a surface resistance less than ρs = 104 ohms and bulk resistance less than ρ = 104 ohms-cm. The boundaries between them are not well defined.

From a practical perspective, an insulator does not allow the free flow of electrons on its surface, or through its bulk, where in the case of semiconductors and metals, carriers can flow on and within the materials.

In semiconductor devices, components, and systems, the material properties can be a good thing, or a problem. In the case where a material does not allow the free flow of carriers, charge will build up, and can lead to the establishment of electric fields. High electric fields can lead to electrical breakdown, and electrical overstress. In the case where the material allows the free flow of carriers, high currents can establish. High currents can lead to high discharge currents, electrostatic discharge events, self-heating, thermal breakdown, and melting of components, packaging and systems.

1.5 Static Dissipative Materials

In the field of electrostatic discharge protection, it is advantageous to have materials that are not highly insulating, and also not highly conducting. These materials are referred to as static dissipative materials. Static dissipative materials are the materials which are between the insulators and conductors. Hence, we can define them as materials in the range of ρs = 104 ohms to 1011 ohms surface resistance, and the range of ρ = 104 and 1011 ohms-cm bulk resistance. The advantage of having materials that are neither insulators or conductors is the avoidance of static charge buildup or high currents.

1.6 ESD and Materials

Unfortunately, components and systems are not that simple. Both electrical components and systems contain insulators, semiconductors, and metals. Semiconductor components comprise of insulating dielectrics, semiconductors, and metals.

Insulating dielectrics exist as inter-level dielectrics, thin film oxides, and buried oxide films in the substrate. Insulator films in the MOSFET gate dielectric are very thin films whose thickness is dependent on the technology generation. Inter-level dielectric films exist between the wiring levels in a semiconductor chip whose thickness is in the order of the metal wiring film thickness. Electrical breakdown of the dielectrics is a failure mechanism from electrical overstress (EOS), or electrostatic discharge (ESD) events. Insulators are used in systems for cards, boards, supports, and other components.

Metal films exist in semiconductor components as interconnects between the electronic circuits. Semiconductor components contain wire films consisting of aluminum and copper. Refractory metals, such as titanium, cobalt, tantalum, and tungsten are also used for contacts, vias, silicide films, to cladding for the wiring. In systems, metals are used for the system chassis, and shielding.

Semiconductor materials are used throughout semiconductor components as the base wafer for semiconductor devices. The conductivity varies dramatically through semiconductor devices using dopants, from resistive to conductive regions.

As a result, semiconductor components are a stratified medium of layers that consists of metals, insulators, and static dissipative materials. Hence, controlling the conduction and dissipative nature of a semiconductor component can be quite difficult with regions of high conducting and high insulating properties.

1.7 Electrification and Coulomb's Law

“The force between two small charged bodies is proportional to the product of their charges, and is inversely proportional to the square of their distance apart, the force being one of repulsion or attraction according as the two charges are of the same or of opposite kinds.”

Coulomb, 1785

From Coulomb's law, it is understood that the force between two objects is associated with the product of the charges, and inversely proportional to the square of the distance. Hence the electric field associated with a force on a “test charge” is the charge of the object, and inversely proportional to the square of the distance between.

1.7.1 Electrification by Friction

“Bodies may be electrified many other ways, as well as by friction”

Part I Electrostatics Chapter I: Electrification by FrictionA Treatise on Electricity and MagnetismJames Clerk Maxwell, 1891

Electrification can be caused by rubbing two objects together. It is through friction between the surfaces (e.g., the materials touching) that can lead to the charge transfer and charging. When two materials are rubbed together, friction is assisting in the charge transfer process [7, 10].

1.7.2 Electrification by Induction

“No force, either of attraction or of repulsion, can be observed between an electrified body and a body not electrified. When, in any case, bodies not previously electrified are observed to be acted on by an electrified body, it is because they have become electrified by induction”

Part I Electrostatics Chapter I: Electrification by InductionA Treatise on Electricity and MagnetismJames Clerk Maxwell, 1891

From an ESD perspective, charged materials and charged surfaces generate electric fields. These electric field lines start at the positive charge, and end at the negative charge.

Hence a system or component placed near a charged surface can be polarized where negative charges are formed on the surface. In this process of “induction”, given that the object is electrically connected to a ground potential, polarization will occur. When the ground connection is removed, this object will be charged. Charge will flow either to or from the ground connection. In the “induction process”, given that the ground connection and the electric field is removed, the component or system will remain charged [7, 11].

Induction charging is a concern in semiconductor components which have been charged by external fields, and is not electrically grounded. As will be discussed, this is a concern for the “charged device model.” When it is charged there is no concern; but, when the charge is rapidly discharged to a ground connection, high currents can lead to component damage.

1.7.3 Electrification by Conduction

James Clerk Maxwell noted that electrification can occur by placing a “wire” between a first object and a second, where the current flows from the first object to the second. In that time, Maxwell referred to this as “Electrification by Conduction [7].” Today, this would be regarded as charging a body through a voltage source and an electrical circuit. Hence, there are many ways to “charge” a body.

Today, in the manufacturing environment, electrical components, and systems, these charging processes occur and are part of the “events” that must be monitored, controlled, and eliminated.

1.8 Electromagnetism and Electrodynamics

Electromagnetism has three branches, namely Electrostatics, Magnetostatics, and Electrodynamics. Electrostatics and Magnetostatics are independent of each other and address only states of rest. On the other hand, electrodynamics deals with the motion of electricity and magnetism [6].

1.9 Electrical Breakdown

Although we regard electrostatic discharge (ESD) as an electrostatic phenomena, since charge is moving, and currents are flowing, it is electro quasi-static. Electrostatic discharge can be initiated by an arc from a person to an object. The electrostatic discharge event occurs as a result of the breakdown of the air in the gap between the person and the object. The discharge process is a function of spacing of the gap, the geometry of the gap (e.g., curvature, radius of electrodes), cleanliness of the surface, relative humidity, and speed of approach.

So, what is electrical breakdown?

1.9.1 Electrostatic Discharge and Breakdown