Flexible Glass E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Serie: Roll-to-Roll Vacuum Coatings Technology
• Sprache: Englisch

Seitenzahl: 559

Veröffentlichungsjahr: 2017

Beschreibung

Provides the reader how to apply flexible glass applications that are not possible or practical to address with alternative substrate materials. Examples of technology areas include displays, touch sensors, lighting, backplanes, and photovoltaics. Built on more than 10 years of valuable discussions and collaborations focused on truly defining what flexible glass means in the context of the emerging electronic and opto-electronic applications, this book provides a broad overview as well as detailed descriptions that cover flexible glass properties, device fabrication methods, and emerging applications. It provides the basis for identifying new device designs, applications, and manufacturing processes for which flexible glass substrates are uniquely suited and encourages and enables the reader to identify and pursue advanced flexible glass applications that do not exist today and provides a launching point for exciting future directions. The chapters are grouped into three sections. The first focuses on flexible glass and flexible glass reliability and has three chapters with authors from Corning. The second section focuses on flexible glass device fabrication which includes chapters on roll-to-roll processing, vacuum deposition, and printed electronics. These chapters are authored by established experts in their respective fields that have extensive experience in processing flexible glass substrates in toolsets that range from research to pilot scale. The third section focuses on flexible glass device applications and includes chapters on photovoltaics, displays, integrated photonics, and microelectronics integration. These are authored by experts with direct experience in fabricating and characterizing flexible glass devices. The diverse list of authors and their depth of experience in working with a variety of material systems, processes, and device technologies significantly adds valuable context to the overall flexible glass discussion.

Leseprobe

Contents

Cover

Title page

Copyright page

Foreword by Peter L. Bocko

Preface

Part I: Flexible Glass & Flexible Glass Reliability

Chapter 1: Introduction to Flexible Glass Substrates

1.1 Overview of Flexible Glass

1.2 Flexible Glass Properties

1.3 Flexible Glass Web for R2R Processing

1.4 Flexible Glass Laser Cutting

1.5 Summary

References

Chapter 2: The Mechanical Reliability of Thin, Flexible Glass

2.1 Introduction

2.2 The Mechanical Reliability of Glass

2.3 Applied Stress

2.4 The Strength of Thin Glass Sheets

2.5 Summary

References

Chapter 3: Low Modulus, Damage Resistant Glass for Ultra-Thin Applications

3.1 Introduction

3.2 Young’s Modulus and Basic Fracture Mechanics

3.3 Vickers Indentation Cracking Resistance of Calcium Aluminoborosilicate Glasses

3.4 Summary

References

Part II: Flexible Glass Device Fabrication

Chapter 4: Roll-to-Roll Processing of Flexible Glass

4.1 Introduction

4.2 Roll-to-Roll Manufacturing Process Equipment

4.3 R2R Deposition and Patterning of ITO on Thin Flexible Glass and Plastic Films

4.4 Conclusions

4.5 Future

Acknowledgements

References

Chapter 5: Thin-Film Deposition on Flexible Glass by Plasma Processes

5.1 Introduction

5.2 Substrate Requirements for Vacuum Processes

5.3 Types of Vacuum Processes

5.4 Large Area Coatings onto Flexible Glass

5.5 Thermal Pre- and Post-Treatment for Flexible Glass

5.6 Future Trends in Vacuum Processing on Flexible Glass

References

Chapter 6: Printed Electronics Solutions-Based Processes with Flexible Glass

6.1 Introduction

6.2 Printing Processes

6.3 Summary of Different Printing Processes

6.4 Example – Printed OPV Cell on Ultra-Thin Flexible Glass

6.5 Future

References

Part III: Flexible Glass Device Applications

Chapter 7: Flexible Glass in Thin Film Photovoltaics

7.1 Introduction

7.2 General Substrate Requirements for Photovoltaic Applications

7.3 Requirements for CdTe Superstrates

7.4 Standard CdTe Device Stack and Processing

7.5 Flexible CdTe Device Performance

7.6 Flex and Bend Testing of CdTe

7.7 Future Trends/Directions

References

Chapter 8: Ultra-Thin Glass for Displays, Lighting and Touch Sensors

8.1 Introduction and Overview

8.2 Ultra Thin Glass Substrates for Flexible Displays

8.3 Thin film Device Processing on Ultra Thin Glass

8.4 Thin Glass Displays

References

Chapter 9: Guided-Wave Photonics in Flexible Glass

9.1 Flexible Guided-Wave Photonics

9.2 Flexible Polymer Passive Waveguide Photonics

9.3 Flexible Polymer Active Waveguide Photonics

9.4 Flexible Polymer Waveguides for Electro-Optic Applications

9.5 Flexible Glass Optical Substrates

9.6 Ultrafast-Laser Fabrication of Embedded Waveguides

9.7 Embedded Waveguides in Flexible Glass

9.8 Prospective of Thermal Poling in Flexible Glass Waveguides

9.9 Summary and Future

References

Chapter 10: Flexible Glass for Microelectronics Integration

10.1 Introduction

10.2 Integration Technology Description: Why Flexible Glass for Electronics/Sensor Integration (3 Dimensional Integrated Circuits – 3DIC)

10.3 Example of Microelectronics/Sensor Integration

10.4 Fabrication Techniques

10.5 Future Direction

References

Index

End User License Agreement

Guide

Cover

Copyright

Contents

Begin Reading

List of Tables

Chapter 1

Table 1.1

Reference flexible substrate materials used for comparison purposes to 100 µm-thick Willow Glass.

Table 1.2

Flexible glass thermal properties. Attributes from both Willow Glass and 0211 Microsheet are shown to highlight variations due to composition.

Table 1.3

Dielectric constant (D

k

) and loss tangent (D

f

) for Willow Glass and representative polymer films.

Table 1.4

Density of flexible glass and representative flexible substrates.

Chapter 2

Table 2.1

The allowable stress as a function of initial, S, and measured strength in a fatigue environment, a. An n value of 20 is assumed.

Chapter 3

Table 3.1

Cationic radii, packing factors, and dissociation energies of oxides [1–2, 4].

Table 3.2

Calcium aluminoborosilicate glass compositions and properties.

Table 3.3

Vickers indentation cracking threshold results.

Chapter 4

Table 4.1

Bend radius possible for 100 MPa bend stress for different glass thicknesses [10].

Table 4.2

Performance and operating specifications for Azores 6600 R2R photolithography system [25].

Table 4.3

As deposited properties of the ITO thin films at ambient temperature on PEN.

Table 4.4

Comparison of bulk resistivity and figure of merit values for as deposited and 90-minute annealed samples of ITO deposited on PEN. Figure of merit was calculated using the method proposed by Haacke in [43].

Table 4.5

ITO properties deposited on PEN following a 90 minute anneal at 110 °C.

Table 4.6

Summary of XRD data collected for samples as deposited and following 90 minute anneal times on PEN substrates.

Table 4.7

Summary of etch rates for ITO deposited at ambient temperatures. All etching was performed at room temperature, except where stated otherwise.

Table 4.8

Summary of sheet resistance, bulk resistivity, transmission and figure of merit for ITO films deposited on Willow Glass, PEN and PET samples

Chapter 5

Table 5.1

Maximum temperature (in °C) of the substrates during 500 nm TiO

2

deposition [25].

Table 5.2

Properties of 500 nm thick TiO

2

layers deposited onto unheated glass [25].

Table 5.3

Selection of layer materials, precursors and application for Atomic Layer Deposition.

Table 5.4

Properties of ITO films deposited by DC sputtering on 3 mm thick low iron glasses and on 100 µm thick flexible glasses. The transmittance T

vis

. is defined as the integrated brightness in the visible range of the spectrum (380 nm to 780 nm) related to a light source similar to daylight (D 65) corresponding to an angle of 2 degrees by a standard observer. The extinction coefficient k and the refractive index are given for 550 nm wavelength. T_L*, T_a* and T_b* are the color values for the transmittance.

Table 5.5

Mechanical film stresses for the single layers of the AR layer stack and the whole AR layer stack prepared at different modes of powering for the sputtering process of titania:

Table 5.6

Technologies for ultra-fast thermal post annealing:

Chapter 6

Table 6.1

Properties of different printing methods.

Table 6.2

Advantages and disadvantages of different printing methods.

Chapter 7

Table 7.1

Examples of flexible from various thin-film PV technologies and their temperature, moisture, and chemical requirements. The growth architecture typically dictates whether or not a transparent substrate is required. The list of examples for each technology is meant to be illustrative rather than exhaustive.

Table 7.2

Water vapor transmission rates for various materials.

Table 7.3

T

s

and CTE for superstrate materials.

Chapter 8

Table 8.1

Qualitative Comparision of Lighting Technologies [6].

Table 8.2

Thermal Parameters of various substrate materials.

Table 8.3

Required substrate characteristics.

Table 8.4

Comparison of switching times for thin glass and reference liquid crystal cells.

Table 8.5

Comparison of TFT parameters on thin and standard glass [52].

Table 8.6

Characteristics of thin glass AMLCD Demonstrator.

Chapter 9

Table 9.1

Key Properties of Optical Polymers for Waveguide Fabrications [6].

Table 9.2

Comparison between polymer flexible photonics and glass flexible photonics technology

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Scrivener Publishing100 Cummings Center, Suite 541JBeverly, MA 01915-6106

Advances in Roll-to-Roll Vacuum Coatings Technology

Often new technologies, processes or materials suddenly appear that attract some publicity. It is not always easy to find reviews of these advances that allow the reader to compare and contrast the different technologies. This series of books aims at providing a source of information that will enable the reader to obtain an overview of groups of recent advances in technologies, processes or materials.

Series Editor: Charles A. BishopE-mail: [email protected]

Publishers at ScrivenerMartin Scrivener ([email protected])Phillip Carmical ([email protected])

Flexible Glass

Enabling Thin, Lightweight, and Flexible Electronics

Edited by

Sean M. Garner

This edition first published 2017 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA© 2017 Scrivener Publishing LLCFor more information about Scrivener publications please visit www.scrivenerpublishing.com.

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Library of Congress Cataloging-in-Publication DataISBN 978-1-118-94636-7

Foreword by Peter L. Bocko

Technological revolutions are often built upon a foundation of self-delusion and naiveté. That bleak statement requires some explanation. While a scientific revolution can be nucleated by an individual’s insight, the delivery of a breakthrough technology requires a shared vision of the innovation’s benefit followed by broad and protracted collaboration among materials, process, systems, device and application specialists. And if these collaborators realized at the outset the level of resolve and resources ultimately required to deliver a revolutionary technological platform, few would get off the ground.

Fortunately, a revolution in electronics based upon flexible glass has progressed well beyond initial naiveté and subsequent (and periodic) stages of disillusionment. This book is a major milepost in this platform’s development, documenting over a decade of hard won advances in the flexible glass platform through collaboration across relevant component technologies and applications. As an early promoter, champion and sponsor for the applications of flexible glass, I am excited that the building blocks for broad innovation have achieved critical mass, and for the first time are accessible in one place.

Glass has a capability of being drawn under heat and tension into a film of arbitrary thickness while retaining its desirable surface, mechanical and optical properties. This is simple and intuitive. After explaining to a customer engineer the process of drawing molten glass into precise sheet for LCDs, he asked “How do you make it thinner?”. “Pull harder.” I answered. Since glass-sheet manufacture has been automated, processes have been pushed to draw glass to the limits of sufficient thinness to achieve flexibility, motivated by the desire to minimize weight, enhance conformability or to enable in-line processing.

While the forming of precise ultra-thin glass has been established across multiple glass manufacturing platforms over the last 20 years, what has been missing were the constellation of enabling component technologies: packaging, handling, deposition, patterning and device design that can be used to transform flexible glass from the glass maker’s forming tool and adapt it to a functional system. This has resulted in skepticism and resistance of the electronics industry for commitment to large scale development of flexible glass platforms.

Things have changed since then, but I expect that it will still take time and much hard work to drive flexible glass to the high-volume applications that fully leverages its potential. The editor of this work as well as chapter author, my erstwhile colleague from Corning, Dr. Sean Garner, is in large part responsible for promoting flexible glass in the technology community and structuring the collaborations that have brought us to the verge of breakthrough of flexible glass into enabling advanced electronic applications. This book represents a major contribution to the field. The long-incubated flexible glass revolution is upon us.

Peter L. BockoAdjunct Professor of Materials Science & Engineering,Cornell UniversityFormer Chief Technology Officer, Corning GlassTechnologies, Corning Incorporated

Preface

Flexible glass continues to emerge as a significant material component for electronic and opto-electronic applications. Its use goes well beyond earlier capacitor applications. For example, new opportunities in fields of displays, sensors, lighting, backplanes, circuit boards, photonic substrates, and photovoltaics continue to be identified. This is much more than just transitioning the devices that exist currently on thicker rigid glass onto a thinner, flexible substrate. Flexible glass substrates in these applications enable new device designs, manufacturing processes, and performance levels not possible or practical with alternative substrate materials and may include electronic applications such as fully-integrated, large-area, smart surfaces. In addition, these new applications require specifically optimized fabrication processes, manufacturing equipment, and device designs that take advantage of the unique properties of flexible glass.

Although there have been previous discussions of flexible glass substrates and devices at conferences and in published journals, they have focused on very specific aspects or applications. This book, however, provides a much broader overview as well as detailed descriptions that cover flexible glass properties, device fabrication methods, and emerging applications. This book is not meant to provide a comprehensive, detailed description of all attributes and possibilities but rather, it provides the basis for identifying new device designs, applications, and manufacturing processes for which flexible glass substrates are uniquely suited. Information in this book encourages and enables the reader to identify and pursue advanced flexible glass applications that do not exist today and provides a launching point for exciting future directions.

Information in this book is based on over 10 years of valuable discussions and collaborations focused on truly defining what flexible glass means in the context of these emerging electronic and opto-electronic applications. This learning is also built upon decades of previous activities in earlier applications. What started personally for me as an “exploratory investigation” has occupied most of my career as I collaborated on various aspects of flexible glass’ definition, processing, and applications. The chapters included here are from some of my more significant collaborations meant to provide an overall, well-rounded perspective.

The chapters are grouped into three sections. The first focuses on flexible glass and flexible glass reliability and has three chapters with authors from Corning. The second section focuses on flexible glass device fabrication which includes chapters on roll-to-roll processing, vacuum deposition, and printed electronics. These chapters are authored by established experts in their respective fields that have extensive experience in processing flexible glass substrates in toolsets that range from research to pilot scale. The third section focuses on flexible glass device applications and includes chapters on photovoltaics, displays, integrated photonics, and microelectronics integration. These are authored by experts with direct experience in fabricating and characterizing flexible glass devices. The diverse list of authors and their depth of experience in working with a variety of material systems, processes, and device technologies significantly adds valuable context to the overall flexible glass discussion.

The required ecosystem to truly enable flexible glass device fabrication in sheet and roll-to-roll processes is continuing to emerge. Although a significant element, flexible glass is one technology component required to advance new electronic and opto-electronic applications. Complementary materials and manufacturing equipment are required to bring this into reality. It’s exciting to see reported activities transition from early device-research demonstrations to discussions about process scale-up and business opportunities.

I’ve truly enjoyed my wide-ranging discussions and interactions over the last several years on all aspects of flexible glass and flexible electronic topics. This has included significant interactions with universities, national labs, and corporate collaborators on all aspects of flexible glass properties, processing, and applications. This book highlights the foundational work that new opportunities can be built upon. By transitioning into a flexible substrate, ultra-thin glass enables a complete paradigm shift in flexible electronic applications and high-throughput, roll-to-roll manufacturing. As high-quality, flexible glass substrates 100ʹs m2 in size and process equipment specifically optimized for it are now available, an exciting revolutionary advancement in electronic device integration has begun.

Sean GarnerJune 2017

Part IFLEXIBLE GLASS & FLEXIBLE GLASS RELIABILITY

Chapter 1Introduction to Flexible Glass Substrates

Sean M. Garner*, Xinghua Li and Ming-Huang Huang

Corning Research & Development Corporation, Corning, NY, USA

*Corresponding author:[email protected]

Abstract

With the expanding applications and research in flexible electronics, the device substrate choice is becoming increasingly critical to the overall device functionality and performance. Glass continues to be a crucial substrate material for display and photovoltaic devices as well as for emerging applications such as OLED lighting. As the glass thickness is reduced to approximately 200 µm or less, the same enabling benefits such as hermeticity, optical quality, surface roughness, and thermo-mechanical stability continue in the glass substrate, but new mechanical behavior arises. Along with the reduced thickness, the glass weight is significantly reduced and flexibility is dramatically increased. This chapter provides an overall description of flexible glass and how its properties enable new device functionality, manufacturing processes, and applications that are not possible or practical with thicker, rigid glass substrates or alterative flexible substrate materials. Comparisons are made to polymer film and metal foil flexible substrate materials that highlight differences in material properties. Laser crack propagation techniques for cutting flexible glass substrates, with the focus on optimizing edge strength, are also described. This basic description of flexible glass enables the device fabrication processes and applications described in subsequent chapters.

Keywords: Flexible substrate, flexible electronics, glass, roll-to-roll, ultra-slim, encapsulation, laser cutting

1.1 Overview of Flexible Glass

With the reduction in glass thickness, associated mechanical properties are likewise affected. For example, the glass substrate weight is reduced as well as its flexural rigidity. Since the flexural rigidity or resistance to bending is proportional to E * t3 [1], (where, E is the Young’s modulus and t is thickness) the glass dramatically becomes more flexible with decreasing thickness. This thickness reduction also results in a decrease of bend stress, which is described in Chapter 2. It is somewhat arbitrary to define a specific thickness value where glass should begin to be referred to as flexible, but it is convenient to use an approximate thickness where it is practical to use continuous spooling or winding operations in the glass manufacturing process. This is mainly driven by the glass flexibility and bend stress enabling practical spool diameters. For discussion purposes, it is convenient to refer to glass that is ≤200 μm as flexible. As a comparison, glass single-mode optical fiber used in telecommunication applications, such as Corning® SMF-28®, has a diameter of 125 μm [2].

Although flexible glass can be used for a variety of applications, the focus of this book will be on use in electronic or opto-electronic device applications. With its reduced thickness but continued intrinsic material properties, flexible glass in general can be used as both a substrate for device fabrication and as a superstrate where it serves as both a substrate and a window to the environment. In addition, flexible glass is an efficient hermetic encapsulating layer. The thickness reduction enables devices that are not only thin but also light weight and conformal or flexible in nature. This resulting flexibility can be utilized in the application after the device has been singulated and packaged, or it can also enable new device manufacturing methods not previously demonstrated with glass substrates such as roll-to-roll (R2R) processing. The unique combination of intrinsic glass material properties with a flexible form factor enable new device designs, applications, and manufacturing processes not practical previously [3].

Flexible glass is compatible with device manufacturing methods not usually associated with glass substrates. These are described in more detail in Chapters 3–6 and include R2R and printed electronic device fabrication methods. These device fabrication methods are optimized for handling and processing flexible glass substrates but still continue to achieve the resolution, registration, performance, and lifetime of devices typically fabricated on thicker, rigid glass substrates.

Emerging flexible glass device and application examples are described in more detail in Chapters 7–10. Application examples include: solar power devices such as photovoltaics and concentrated solar power [4–24], electronic circuit substrates [25–31], antennas [32], integrated optics [33–34], flexible hybrid electronics [15], sensors including touch sensors [21, 31, 35–38], OLED lighting [39–41], and displays and electronic backplanes [31, 36, 42–57]. Each of these application areas can also be further divided, such as displays into LCD [42], OLED display, and e-paper displays [49, 52–53] for example. Also, combining the ability to fabricate electronic and opto-electronic devices along with capabilities of large area lamination, flexible glass enables progression toward large area smart surfaces with integrated display, lighting, sensor, and communication functionality. These applications go beyond simply taking devices that exist today on rigid glass substrates and making them thinner and lighter, but instead opening up new device functionality and application opportunities. The following sections in this chapter summarize the major flexible glass material properties that affect device design and manufacturing processes, as well as providing comparisons to other substrate materials.

1.2 Flexible Glass Properties

In general, a wide variety of thin, flexible glass substrates have historically been produced for applications that have included glass capacitors [58–63], microscope cover slides [58–60], and satellite solar cell cover sheets [64]. These have had their dimensions (thickness, width, length), forming process, and composition optimized specifically for their application requirements. Corning® 0211 Microsheet [65] is an example of a thin, flexible, alkali-containing borosilicate glass primarily used for non-electronic device applications. Corning 0213 [64] and Corning 0214 [66] are examples of a Ce-doped borosilicate glass with UV absorption optimized for satellite solar cell covers. Additionally, examples of flexible silica substrates [67] and flexible ceramic substrates [10, 68–70] have also been demonstrated targeting applications such as high speed circuit boards [29]. Overall, a wide range of flexible inorganic substrate compositions and forming processes have been historically demonstrated, and these were chosen and further optimized based on application requirements.

Over the past 20 years there has been a specific focus on optimizing flexible glass properties specifically for electronic and flexible electronic applications. These emerging applications have new requirements for the glass attributes, and these flexible glass attributes are a combined result of the specific composition and forming process used. Detailed discussions of the glass attributes resulting from specific glass composition or forming process choices are outside the scope of this book since they are covered in detail elsewhere [59–61, 71]. This chapter provides a short overview of representative flexible glass properties.

Throughout this book, Corning® Willow® Glass is used as an example of a flexible glass substrate. It is an alkaline earth boro-aluminosilicate glass composition compatible with semiconductor device manufacturing processes such as those based on silicon, metal oxide, and organic semiconductor materials. Willow Glass is currently manufactured in a continuous fusion draw process and wound directly onto spools in thicknesses ≤200 µm, widths >1 m, and lengths approximately 300 m. The fusion draw process is a glass forming method developed at Corning in the 1960s for the manufacture of thin sheets of glass with pristine surface quality [72]. The process involves flowing molten glass over the walls of both sides of a ceramic isopipe. The two sides of the glass join at the bottom of the isopipe and are drawn into a thin sheet with uniform thickness, where neither side of the glass sheet has come in contact with anything except air. The main advantages of the fusion draw process are the ability to manufacture homogeneous ultra-thin glass sheets with dramatically improved surface quality compared to other methods of glass sheet manufacture, such as the float process used to make glass windows [73]. Besides Willow Glass, the fusion draw process is used to form rigid glass substrates for active matrix flat panel displays such as OLED and liquid crystal displays. An example of these substrates is Corning® Eagle XG® [74] with thicknesses ranging from 0.3 mm to 1.1 mm. Since it is of similar composition as active matrix display glass substrates and also formed using the fusion process, the intrinsic material and surface properties of Willow Glass are similar. The reduction in thickness, though, enables a revolutionary increase in substrate size orders of magnitude larger than what is currently used in display manufacturing. Substrate surface area typically measured in m2 for rigid glass sheets has now increased to 100’s m2 for spooled glass. The combination of increased substrate size and flexibility enables high throughput manufacturing processes such as R2R as well as very large area device fabrication.