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`TCL 1017, Page 3
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`

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`~ IQUID CRYSTAL
`LAT PANEL*
`DISPLAYS
`
`MANUFACTURING
`SCIENCE &
`TECHNOLOGY
`
`WILLIAM C. O’MARA
`
`VAN NOSTRAND REINHOLD
`New York
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`TCL 1017, Page 4
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`

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`Copyright © 1993 by Van Nostrand Reinhold
`
`Library of Congress Catalog Card Number 9243119
`ISBN 0-442-01428-7
`
`All rights reserved. No part of this work covered by the copyright
`hereon may be reproduced or used in any form or by any means---
`graphic, electronic, or mechanical, including photocopying, record-
`ing, taping, or information storage and retrieval systems---without
`the written permission of the publisher.
`
`I(~)P
`
`Van Nostrand Reinhold is a division of International
`Thomson Publishing. ITP logo is a trademark under license.
`
`Printed in the United States of America
`
`Van Nostrand Reinhold
`115 Fifth Avenue
`New York, NY 10003
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`International Thomson Publishing
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`Nelson Canada
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`M1K 5G4, Canada
`
`16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
`
`Library of Congress Cataloging in Publication Data
`
`O’Mara, William C.
`Liquid crystal flat panel displays: manufacturing sciece &
`technology / William C. O’Mara.
`p. cm.
`Includes index
`ISBN 0-442-01428-7
`1. Liquid crystal display. I. Tide
`TK7872.L56046 1993
`621.38---dc20
`
`,
`
`9243119
`CIP
`
`TCL 1017, Page 5
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`

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`LIQUID CRYSTAL FLAT PANEL DISPLAY
`
`Table of Contents
`
`LARGE AREA LIQUID CRYSTAL DISPLAYS ....................................... 1
`1.1 Computer Displays .................................................................................... 3
`1.1.1 Desktop Computers .............................................................................. 3
`1.1.2 Portable Computers .............................................................................. 3
`1.1.3 Engineering Workstations ............ : ....................................................... 7
`1.1.4 Computer Display Summary ................................................................ 7
`1.2 Television Displays ................................................................. : .................. 9
`1.2.1 Portable TVs ......................................................................................... 9
`1.2.2 Projection Displays ............................................................................ 10
`1.2.3 High Definition TV ............................................................................ 11
`1.2.4 Video Camera Viewfinders ................................................................ 11
`1.3 Automotive Applications ........................................................................ 11
`1.4 Other Applications .................................................................................. 12
`1.5 Liquid Crystal Display Technology ....................................................... 13
`1.5.1 Types of Liquid Crystal Display ........................................................ 16
`1.5.2 Passive vs Active Addressing ............................................................ 21
`1.5.3 Workstation ~B/W Display .................................................................. 23
`1.5.4 Polymer Dispersed Displays .............................................................. 24
`1.5.5 Automotive Display ........................................................................... 26
`1.6 Active Matrix Devices ............................................................................. 27
`1.6.1 Two Terminal Devices ............................ : .......................................... 28
`1.6.2 Amorphous Silicon Transistors .......................................................... 31
`1.6.3 Polysilicon Transistors ....................................................................... 35
`1.6.4 Comparison of Device Performance .................................................. 39
`1.6.5 Ferroelectric Polymer ..................................................... " .................... 43
`1.6.6 Printed Transistors .................... : ......................................................... 45
`1.7 Display Manufacturers ........................................................................... 47
`1.7.1 Japan ...................................... ............................................................. 47
`Current Suppliers ..................................................................................... 48
`1.7.2 USA .................................................................................................... 48
`Xerox ....................................................................................................... 48
`Department of Defense Initiatives ........................................................... 48
`
`ooo
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`Iii TCL 1017, Page 6
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`

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`TABLE OF CONTENTS
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`LIQUID CRYSTAL FLAT PANEL DISPLAYS
`
`IBM ...................................... : .................................................................. 48
`Advanced Display Manufacturers ........................................................... 50
`Others .............................................................................................. ¯ ........ 51
`1.7.3 Rest Of World .................................................................................... 51
`Europe ..................................................................................................... 51
`Korea ....................................................................................................... 53
`Other Asian Firms ............ , ...................................................................... 53
`References ...................................................................................................... 54
`
`FIGURES
`1-1 Portable and laptop computers .................................................................... 3
`1-2 Active matrix liquid crystal display screen size in recent years ................. 5
`1-3 Pixel count versus display diagonal size for flat panels ............................. 6
`1-4 No. of pixels & display diagonal for high information content displays .... 7
`1-5 Basic liquid Crystal polymer molecule ...................................................... 14
`1-6 Principle of operation of a twisted nematic liquid crystal display ............ 15
`1-7 Transmission versus voltage curves for TN and STN materials ............... 18
`1-8 Schematic representation of passive and active matrix color LCD’s ....... 22
`1-9 Polymer dispersed liquid crystal projection TV system ........................... 24
`1-10 Structure of the dispersed liquid crystal droplets .................................... 25
`1-11 Projection display using polysilicon thin film transistors ....................... 28
`1-12 Amorphous silicon PIN diode ................................................................. 29
`1-13 MIM diode structure ............................................................................... 30
`1-14 Double pixel design, for MIM diode ....................................................... 30
`1-15 Cross-section view of three TFT configurations .................................... 32
`1-16
`Aluminum gate a-Si TFT ........................................................................ 33
`1-17
`Light leakage in TFT structure ............................................................... 33
`1-18
`Plan view of TFT structure with light shield .......................................... 33
`1-19
`Hitachi TFT array equivalent circuit ................. ~ ..................................... 34
`1-20
`Relative cost of silicon TFT processes ........................ , .......................... 42
`1-21
`Data rate of driver circuits for complex TFT displays ............................ 43
`1-22
`Construction of ferroelectric matrix active device .................................. 44
`1-23
`LCD panel structure with ferroelectric matrix device ............................ 44
`1-24
`Comparison of photolithography and printing for imaging on FPD’s .... 46
`1-25
`Photoresist application by offset printing ............................................... 46
`1-26
`Polysilicon transistors made by offset printing and photolithography ... 47
`
`TABLES
`1-1 Classification of Portable Computers ......................................................... 4
`1-2 Japanese Large Flat Panel Displays ............................................................ 8
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`iv
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`TCL 1017, Page 7
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`

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`TABLE OF COHTEHTS
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`LIQUID CRYSTAL FLAT PANEL DISPLAYS
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`1-3 Japanese LCD TV and VCR Displays ...................................................... 10
`1-4 Calculation of S for various values of Nmax ............................................ 17
`1-5 Requirements for Vertical TN LCD Display ............................................ 19
`1-6 Types of Liquid Crystal Displays ............................................................. 20
`1-7 Processing and Relative Cost of Active and Passive Displays ~ ................ 31
`1-8 TFT Array Process and Specifications ..................................................... 31
`1-9 Resistivity of Metals ................................................................................. 35
`1-10 Comparison of a-Si and poly-Si TFTs .................................................... 37
`1-11 Polysilicon Fabrication Methods and TFT Properties ............................ 38
`1-12 Comparison of TFT, PIN Diode, and MIM Diode Displays .................. 40
`1-13 CMOS poly-Si TFT and a-Si:H TFT Comparison ................................. 4i
`1-14 AMLCD Drive Circuit Types ................................................................. 42
`1-15 Characteristics of Ferroelectric Liquid Crystal Display ......................... 45
`1-16 Liquid Crystal Display Status in Japan ................................................... 49
`1-17 Advanced Display Manufacturers Association Members ....................... 50
`1-18 US Liquid Crystal Display Activity ........................................................ 51
`1-19 European LCD Activity .......................................................................... 52
`1-20 Liquid Crystal Display Status in Korea .................................................. 53
`1-21 LCD Manufacturing in Asia ................................................................... 53
`
`DISPLAY MANUFACTURING PROCESS ............................................... 57
`2.1 Color Filter Manufacturing .................................................................... 58
`2.1.1 Glass Substrate Preparation ................................................................ 58
`Glass Fabrication ..................................................................................... 58
`Cutting, Beveling, Polishing ................................................................... 59
`Annealing ......... " ....................................................................................... 61
`Cleaning ............................................................................ : ..................... 63
`ITO Deposition ........................................................................................ 66
`2.1.2 Color Filter Process ............................................................................ 70
`Black Matrix Definition .......................................................................... 71
`71
`Dye Method .............................................................................................
`Pigment Method ............................ ¯ .......................................................... 71
`Electrodeposition ..................................................................................... 72
`Printing ................................................................................................
`~..73
`Overcoating ........................................................................................ ..~.. 73
`ITO Deposition ................................................................................... ...’.. 73
`2.2 Active Matrix Display Manufacturing ................................................. 74
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`TCL 1017, Page 8
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`TABLE OF COHTEHTS
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`LIQUID CRYSTAL FLAT PANEL DISPLAYS
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`2.2.1 Thin Film Transistor Manufacturing .................................................. 74
`Plasma CVD & Sputtering ...................................................................... 75
`Photolithography ..................................................................................... 77
`Etching .................................................................................................... 78
`Transistor Processes ................................................................................ 79
`2.2.2 In Process Testing .............................................................................. 84
`Optical Inspection ................................................................................... 84
`Electrical Inspection ................................................................................ 85
`Functional Inspection ............................................................................. 85
`2.2.3 Defect Repair ................................. . ..................................................... 85
`2.3 Display Assembly ..................................................................................... 86
`2.3.1 Orientation Film Deposition and Rubbing ......................................... 86
`2.3.2 Seal Printing ....................................................................................... 87
`2.3.3 Spacer Placement and Sealing ............................................................ 90
`2.3.4 Liquid Crystal Injection ..................................................................... 90
`2.3.5 Inspection and Test ............................................................................. 91
`2.3.6 Polarizer Attach .................................................................................. 91
`2.3.7 Die Attach .......................................................................................... 94
`2.3.8 Backlight ............................................................................................ 97
`2.4 DISPLAY MANUFACTURING ............................................................ 98
`2.4.1 STN Display Manufacturing .............................................................. 98
`2.4.2 Color Filter Manufacturing .............................................................. 100
`2.4.3 Equipment for Color Filter Manufacturing ...................................... 101
`2.5 AMLCD Factory ................................................................................... 101
`2.5.1 Throughput and Productivity ........................................................... 101
`2.5.2 Manufacturing Cost and Yield ......................................................... 103
`Yield vs ASP ............................... ~ ......................................................... 103
`Manufacturing Cost Model ................................................................... 105
`Manufacturing Yield Model .................................................................. 106
`AMLCD Factory ................................................................................... 108
`
`FIGURES
`2-1 Schematic outline of the display manufacturing process .......................... 57
`2-2 Fusion process for glass sheet formation ................................................. 58
`2-3 Thermal expansion of Corning 7059 glass .............................................. 62
`2-4 Thermal shrinkage of NA 35 glass: heat treatment time & temperature. 62
`2-5 Cleaning methods evaluated by contact angle measurement ................... 66
`2-6 Sputtering voltage, deposition temperature, and ITO film resistivity ...... 69
`2-7 Plasma-assisted electron beam evaporation equipment ............................ 70
`2-8 Color Filter Formation .............................................................................. 72
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`TCL 1017, Page 9
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`TABLE OF (cid:128)OHTEHTS
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`LIQUID CRYSTAL FLAT PANEL DISPLAYS
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`2-9 Active Device Formation .......................................................................... 76
`2-10 Photoresist adhesion by side etch for various precoating processes ....... 78
`2-11 Cross-section view of three TFT configurations .................................... 79
`2-12 Assembly, Packaging & Test .................................................................. 88
`2-13 Automated flat panel assembly line ........................................................ 89
`2-14 Variations in external pressure & spacer size lead to cell gap variations .... 91
`2-15 Active matrix liquid crystal display cross section .................................. 93
`2-16 Packaging configurations in flat panel displays ...................................... 94
`2-17 Number and pitch of leads for flat panel displays .................................. 95
`2-18 Connection of TAB tape to flat panel leads w/anisotropic conductive paste.. 96
`2-19 Schematic of backlight arrangement with light pipe .............................. 97
`2-20 Factory layout for passive matrix LCD manufacturing .......................... 98
`2-21 Simulated yield curves: defect densities in TFT manufacturing .......... 104
`2-22 Cost components of flat panel display production ................................ 106
`2-23 NEC two story AMLCD fabrication facility layout ............................. 109
`
`TABLES
`2-1 Glass Substrates for Flat Panel Display Manufacturing ........................... 60
`2-2 Glass Substrate Specification for Active Matrix Display ......................... 63
`2-3 Proposed Substrate Standard Sizes for Flat Panel Displays ..................... 64
`2-4 Cleaning Processes for Flat Panel Displays .............................................. 65
`2-5 DI Water Quality and Substrate Particle Count ........................................ 66
`2-6 Types of Color Filters for LCDs ............................................................... 71
`2-7 Color Filter Process Comparison .............................................................. 74
`2-8 Process Flow Chart for Inverted-Staggered Back Channel Etched TFT .. 80
`2-9 Inverted-Staggered Trilayered TFT Process ............................................. 81
`2-10 Process Flow for Normal Staggered TFT ............................................... 82
`2-11 TFT Array Process and Specifications ................................................... 83
`2-12 Defects in LCD TFT Array Manufacturing ............................................ 84
`Causes of Defects in Assembled Flat Panel Displays ............................. 92
`2-13
`Clean room Conditions for STN Process Line ....................................... 99
`2-14
`Production Lines for Large Liquid Crystal Displays in Japan ................ 99
`2-15
`AMLCD Equipment Productivity and Price ......................................... 102
`2-16
`AMLCD Production Equipment Categories ......................................... 102
`2-17
`In-Process Inspection and Repair Equipment List .................... ,. ........... 103
`2-18
`Assembly and Die Attach Equipment ................................................... 104
`2-19
`TFT Array Yield Summary (No Repair) .............................................. 107
`2-20
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`TABLE OF CONTENTS
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`LIQUID CRYSTAL FLAT PANEL DISPLAYS
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`MATERIALS FOR FLAT PANEL DISPLAYS ...................................... 113
`3.1 Glass Substrates ..................................................................................... 113
`3.2 ITO Sputtering .......................................................... ~ ........................... 114
`3.2.1 ITO Powder and Thin Film Properties ............................................. 116
`3.3 Other Sputtering Materials .................................................................. 117
`3.4 Color Filters ........................................................................................... 118
`3.4.1 Dye Method ...................................................................................... 119
`3.4.2 Pigment Dispersion .......................................................................... 121
`3.4.3 Electrodeposition .............................................................................. 124
`3.4.4 Electromist ....................................................................................... 125
`3.4.5 Overcoat ........................................................................................... 126
`3.4.6 Two Color Approach ....................................................................... 126
`3.5 Process Chemicals & Gases .................................................................. 126
`3.6 Photoresists ............................................................................................ 129
`3.7 Photomasks ............................................................................................ 129
`3.8 Orientation Films .................................................................................. 130
`3.8.1 Polyimide Orientation Films ............................................................ 131
`3.9 Spacers ..................................................................................... .~. ............. 135
`3.10 Sealing Materials ................................................................................. 137
`3.11 Liquid Crystals .................................................................................... 138 ’
`3.11.1 Other Liquid Crystal Materials ...................................................... 142
`3.11.2 Polymer Dispersed Displays .......................................................... 144
`3.11.3 Polymer Network Displays ........................................................... 146
`3.12 Polarizers/Compensation Films ......................................................... 146
`3.13 Die Attach/Connector Materials ........................................................ 149
`3.14 Display Backlighting ........................................................................... 152
`References .................................................................................................... 157
`
`FIGURES
`3-1 CIE Chromaticity Diagram for color filters ............................................ 121
`3-2 Resistance to fading of dyed and printed color filters ............................ 121
`3-3 Comparison of spin-coated and printed filter element ............................ 122
`3-4 Transmittance of green pigment material / function of particle size ..... 123
`3-5 Schematic of electrodeposition process for color filters ......................... 125
`3-6 Synthesis and structure of aliphatic soluble polyimide ........................... 132
`3-7 Glass fiber spacer size distribution ......................................................... 137
`3-8 Typical liquid Crystal ............................................................................. 138
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`TABLE OF COHTEHTS
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`LIQUID CRYSTAL FLAT PANEL DISPLAYS
`
`3-9 Nematic phase ........................................................................ : ................ 139
`3-10 Cholesteric phase .................................................................................. 139
`3-11 Smectic phase ........................................................................................ 139
`3-12 Structure & properties of difluorobenzene derivatives ......................... 143
`3-13 Trans-4-n-pentylcyclohexyl (PCH-5) derivatives ................................. 143
`3-14 Structure of polarizer film for LCD ...................................................... 147
`3-15 Polarizer film structures ........................................................................ 147
`3-16 Transmittance vs polarization efficiency .............................................. 148
`3-17 Heat seal connector construction .......................................................... 151
`3-18 Usage ratio of TAB ICs ........................................................................ 151
`3-19 IC bonding methods in chip on glass packaging .................................. 153
`3-20 Construction of WedgeLightTM backlight ........................................... 154
`3-21 Spatial brightness uniformity of Wedgelight TM ................................. 155
`3-22 Flat fluorescent lamp structure .............................................................. 156
`
`TABLES
`3-1 LCD Glass Supplier Matrix in Japan ...................................................... 114
`3-2 ITO Film Properties ................................................................................ 115
`3-3 Characteristics of ITO Targets ................................................................ 115
`3-4 Glass Substrates for Liquid Crystal Displays ......................................... 117
`3-5 Specifications for High Density ITO Target ........................................... 118
`3-6 Properties of Color Filters ....................................................................... 119
`3-7 Test Conditions for Color Filters ............................................................ 119
`3-8 Alternative Methods of Color Filter Formation ...................................... 123
`3-9 Solubility of Cleaning Chemicals ........................................................... 127
`3-10 Particles in Electronic Chemicals ......................................................... 127
`3-11 DI Water Quality ................................................................................... 128
`3-12 Measurement of Cleaning Efficiency ................................................... 128
`3-13 Alignment Film Material Requirements ............................................... 131
`3-14 Comparison of Polyimides for Orientation Film Applications ............. 134
`3-15 Plastic Spacer Size Variation ................................................................ 136
`3-16 Plastic Spacer Thermal Expansion Coefficient ..................................... 137
`3-17 Parameters Specified in Liquid Crystal Formulations .......................... 140
`3-18 Relation Between UV Exposure and Turn On Voltage ........................ 145
`3-19 Polarizing Film Structures .................................................................... 148
`3-20 STN Display Cost ................................................................................. 155
`3-21 Comparison of B acklight Technologies ................................................ 156
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`TABLE O[ ¢OHTEHTS
`LIQUID CRYSTAL FLAT PANEL DISPLAYS
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`MANUFACTURING EQUIPMENT ......................................................... 159
`4.1 Substrate Cleaning ................................................................................ 159
`4.2 Photoresist Application/Baking ........................................................... 160
`4.2.1 Spin Coating ..................................................................................... 160
`4.2.2 Roll Coating ..................................................................................... 160
`4.2.3 Conveyor Ovens ............................................................................... 160
`4.3 Photolithography .................................................................................. ~ 16t)
`4.3.1 Steppers ............................................................................................ 161
`4.3.2 Mirror Projection .............................................................................. 162
`4.4 Etching/Stripping .................................................................................. 164
`4.4.1 Wet Etch Equipment ........................................................................ 164
`4.4.2 Plasma Etching/Ashing .................................................................... 164
`4.5 Thin Film Deposition ............................................................................ 165
`4.5.1 Sputtering ......................................................................................... 165
`4.5.2 Chemical Vapor Deposition ............................................................. 167
`4.5.3 Plasma CVD ..................................................................................... 170
`4.5.4 LPCVD and APCVD ....................................................................... 173
`4.5.5 Thermal Processing .......................................................................... 174
`4.5.6 Ion Implant/Doping .......................................................................... 175
`Phased Linear Scanner .......................................................................... 176
`Ion Flux Doping .................................................................................... 177
`4.6 Test Equipment ..................................................................................... 179
`4.6.1 Visual and Functional Test ............................................................... 179
`4.6.2 Optical Imaging ................................................................................ 180
`Optical Image Processing Equipment ..................................................... 182
`Digital Image Processing Equipment .................................................... 184
`4.6.3 Electrical Evaluation ........................................................................ 184
`Transfer Admittance .............................................................................. 185
`. IBM Test Set ......................................................................................... 186
`4.6.4 Voltage Imaging ............................................................................... 189
`4.7 TFT Repair ............................................................................................ 189
`4.7.1 Laser Cutting .................................................................................... 190
`4.7.2 Laser-Assisted Deposition ................................................................ 191
`4.8 Assembly ................................................................................................ 192
`4.8.1 Polymer Printing .............................................................................. 192
`4.8.2 Assembly/Final Test ......................................................................... 194
`4.8.3 Die/PCB Attach ................................................................................ 198
`References .................................................................................................... 199
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`TCL 1017, Page 13
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`TABLE OF COHTEHTS
`LIQUID CRYSTAL FLAT PANEL DISPLAYS
`
`FIGURES
`4-1 Mirror projection schematic diagram ...................................................... 163
`4-2 Example of PECVD system for thin film deposition ............................. : 170
`4-3 Deposition chamber cutaway schematic ................................................. 171
`4-4 Cross section of PEVD electrode .......................................................... 171
`4-5 Plan view of phased linear scanner showing two substrates ................... 177
`4-6 Cross-section view of linear scanner end station ................................... 177
`4-7 Ion bucket source and deposition chamber schematic ............................ 179
`4-8 Optical pattern filtering for defect imaging .......................................... 182
`4-9 Transfer admittance testing ................................................................... 186
`4-10 Schematic diagram of voltage imaging of a TFT array ........................ 189
`4-11 Laser connect and disconnect alternatives ............................................ 190
`4-12 Laser connect and disconnect using polysilicon ................................... 190
`4-13 Polymer printing schematic .................................................................. 193
`
`TABLES
`4-1 Canon MPA-2000 Specifications ........................................................... 163
`4-2 Nextral NE550 RIE System Specifications ............................................ 165
`4