OLED TechnologyOLED TechnologyDavid Hsieh

Contents•• OLED Development StatusOLED Development Status

Key MilestoneKey MilestoneResolution vs. SizeResolution vs. SizeAM and PM Development DisplayAM and PM Development Display

•• Materials Status : Polymer vs. Small MoleculeMaterials Status : Polymer vs. Small MoleculeEfficiency ProgressEfficiency ProgressLifetime ProgressLifetime Progress

•• Tech. Status of OLED Color patterningTech. Status of OLED Color patterning

•• Pending Issues in OLEDPending Issues in OLEDOutOut--coupling Efficiencycoupling EfficiencyLifetime Differential AgingLifetime Differential AgingLTPS NonLTPS Non--Uniformity for AMOLEDUniformity for AMOLED

•• ConclusionConclusion

OLED Development StatusKey Milestone of OLED Development

1995 1999 2000 2002

Pioneer, PM-95

Pioneer, PM, 4 Area Color-99

5.7”PM-OELDIdemistu-97

Motorola Cellular Phone -00

CDT-Seiko Epson2.5” AMPLED-00

Sanyo-Kodak2.4” AMOLED-99

Sony 13” SVGA AMOLED -01

Samsung 15” XGA AMOLED -01

Kodak Digital Camera-03

Chi-Mei & IBM 20” WXGA a-SiAMOLED -03

OLED Development StatusPM Commercialized Displays

PM Mobile Phone (Small Molecule)

Motorolla(Pioneer)

Samsung(SNMD)

LG(Pioneer)

OLED Development StatusSamsung NEC Mobile Display (SNMD)PM OLED Products☞ Current Product

1.1” 94 × 64 Dots, 256 ColorAnycall (SEC) Sub Display Mass Production from 2002. July

☞ Next Product

96×64+IconArea color

96×9665k color

96×64+Icon256 color

Type 1 Type 2 Type 3

Mobile Mono

PM OLED

Mobile Full ColorPM OLED

Mobile S/M *

AM OLED

FlexiblePolymer

AM OLED

Large S/M * , Polymer

AM OLED

* S/M : Small Molecule

Now & Near-term• Cell phones (sub display)• Auto displays• audio, meters, appliances

Next StepNext Step•• Cell phones (main display)Cell phones (main display)•• PDAsPDAs•• Small video (DVC,DSC)Small video (DVC,DSC)

Final & Long Term• Mobile Applications (Flexible)• Monitors• TVs

~ 2001 ~ 2003 ~ 2004 ~ 2007 ~ 2009

Applications of OLED

Glass Clean & Bake

AZ5214 Bus Metal PR Coat

& Bake

Bus Metal PR Thickness ( 1.7 µm )

Bus Resist Expose (Mask

# 1)

Bus Resist Develop

Bus CD & Inspect

Bus Etch and Inspect

Bus PR Strip, Inspect & CD

Dehydration Bake

ITO PR Coat and Bake

ITO PR Thickness ( 1.7 µm )

ITO Resist Expose

(Mask # 2)

ITO Resist Develop

ITO CD and Inspect

ITO Etch and Inspect

ITO PR Strip, Inspect & CD

Dehydration Bake

AZ5206-E Base PR Coat and

Bake

Base PR Thickness ( 0.6 µm )

Base Resist Expose (Mask

# 3)

Base Resist Develop

Base CD and Inspect

Base Cure-Hot Plate

AZ5214 Pillar PR Coat &

Bake

Pillar PR Thickness

(1.7 – 3.7 µm )

Pillar PR Expose

(Mask # 4)

Pillar PR Post Exposure Bake

Passive Matrix Displays: Process Flow

Continue

380x470 glass\ITO\Cr panels start

Continue Pillar PR Flood Exposure

Pillar PR Develop

Pillar CD and Inspect

Oven Hard Bake

Dehydration Bake

O2/CFx Pretreatment

Hole Transport Layer (8 min)

Green Emission Layer (3 min)

Electron Transport

Layer(2 mins)

Electron Injection Layer (0.83 min)

Cathode (0.83 mins)

Encapsulation Cover Clean

Desiccant Dispense

Seal Epoxy Dispense Lamination UV Cure Post Cure Bake Scribe & Break

to final size.

Probe Test: O/S, Log Jrb, Lum,

CIEAssembly Final Test

Sample: Aging/Fade

TestOutgoing QC

Ship

Passive Matrix Displays: Process Flow (continued)

Process Specifications: Materials

Substrates: Glass\ITO\Mo-Ta• Glass: 380 x 470, 0.7 ± 0.03 mm, no visible defects under 10 K lux• ITO: 20-30 Ohms/square, 750 ± 75 Å, 85% Transmission at 400 to 760 nm, . .Roughness < 50 Å, Max. Peak Height 200 Å.• Bus Metal: < 0.3 Ohms/square, 5000 ± 500 Å.

Resist•Photoresist for Pillars (Cathode Isolation) and Base (Cathode Insulation) needs to be morphologically stable upon baking. Layer thickness should be controllable to 0.5 (base) and 1.5 - 4 µm (pillars).

Thin Films• Organics: Purity > 95% (zone sublimed/purified) • Metals: Purity > 90%

Encapsulation• Epoxy Seal: + 0.5 Water absorption when boiled for two hrs, less than 5.0 g/m2

water permeability for 24 hrs, 40 µg/g outgas trapping 120 0C x 15 mins.

Process Specifications: Photo

Facility: Class 100 Clean Room

ITO: The minimum gap between ITO conductors shall be 12.5 µm, the minimum . leakage resistance between neighboring ITO lines shall be 1 Mohm.

Base:• Thickness: 0.5 to 0.6 µm• 12 (VGA) to 4 µm (mono)• Spin Speed ~ 3000 RPM• Soft Bake ~ 90 0C / 90 secs• Hard Bake ~ 250 0C / 200 secs

Pillar: • Thickness ~ 4 µm• 8 (VGA) to 12 µm (mono)• Spin Speed ~ 3000 RPM• Retrograde Angle ~ 45 / 70 0C• Minimum linewidth at 45 / 70 0C ~ 12 / 8 µm• UV Cure ~ ~ 90 mJ/cm2, 200 to 400 nm / 90 secs @ 110 0C

Process Specifications: Thin Films

Vacuum Levels:•Buffer Chamber 1E-6 Torr•Organic Chamber(s) 5E-7 Torr•Electrode 6E-6 Torr

Deposition Rates/Temperatures: •Organics 2 - 4 Å/sec / 270 - 500 0C•Dopants 0.05 - 0.1 Å/sec / 270 - 500 0C•Electrode 0.1 & 20 Å/sec / 500 - 1000 0C

Thickness Uniformity:•Organics > 100 ± 10%•Electrode > 100 ± 20%

Device Structures:•ITO \ HI \ HTL \ Host: Dopant \ ETL \ EIL \ Cathode, where

• HI : IDE406 or CuPC• HTL : IDE320 or HT2• Green/Red Host: AlQ3, Blue Hosts: KBH or IDE120• Dopants: KBD, or IDE102 (B), C545T (G), DCJTB or P1 (R)• ETL: AlQ3• EIL : LiF or Al:Li, 0.5 to 20 nm• Cathode: Al, 70 to 150 nm

Pillar Process

OLED Materials StatusEfficiency Status of Small Molecule

5~6 @ 300 cd/m20.60, 0.38Red

20~22@ 600 cd/m20.27, 0.63Green5~6 @ 300 cd/m20.65, 0.35

14~15 @ 300 cd/m20.61, 0.38RedPh.

OLED

5~6 @ 200 cd/m20.14, 0.14Blue12~13 @ 600 cd/m20.30, 0.65Green

2~3 @ 300 cd/m20.64, 0.36Fl.OLED

Materials Efficiency [cd/A]Color Index

Blue(0.16, 0.32)

Green(0.30, 0.63)

NTSCsRGB

Red 1 (0.61, 0.38)

Red 2 (0.65, 0.35)

Condition : <1000cd/mCondition : <1000cd/m22 @ 4.5~5.5V@ 4.5~5.5V

OLED Materials StatusLifetime Progress

~10,000 @800 cd/m20.61, 0.36Red

~10,000 @400 cd/m20.14, 0.14Blue

~10,000 @800 cd/m20.65, 0.34Phosphorescence

~10,000 @600 cd/m20.27, 0.63Green--Blue

Fluorescence

Materials

~10,000 @500 cd/m20.63, 0.38Red

Lifetime(t ½, D/C Constant Current)

Color Coordinates (x,y)

~10,000 @500 cd/m20.30, 0.65Green

Required RGB Brightness for White 100 cd/m2 AM OLED Driving (Aperture Ratio 40%)- Red : ~600 cd/m2, Green : ~800 cd/m2, Blue : ~400 cd/m2

Tech. Status of OLED Color Patterning Color Patterning Ways of Small Molecule

B G R

Blue EL+

Color Changing Material Blue,Green, Red EL

Emitting Layer

ColorTechnology

Company Main Stream

Advantages

Challenges

High Efficiency,Good Color

High Resolution,Substrate Size

White EL+

C/F

B G R

Simple Process,High Resolution

Top Emission,Color Purity, Low Efficiency

B G R

Idemitsu Kosan TDK, Sanyo

Simple Process,Relatively High Efficiency

Top Emission,Low Efficiency, CCM Cost

Tech. Status of OLED Color Patterning

Current Status of Thermal EvaporationMax. Handling Glass Size : 400x400mm available (Max. 17 inch Display),

600x720 under DevelopmentResolution : about 120ppi

New TechnologiesExtension of Current Tech. : Linear Source, Moving or Multi-Source TechnologyNew Approach : OVPD, DSP

Uniformity may not be a serious IssueMain Challenge Technology : Shadow Mask Tech.

with Bigger Size Glass Handling (Development of New Shadow Mask Tech.)

Tech. Status of OLED Color Patterning Ink- jet Printing Technology

Advantages : Simple Process, Small Usage of MaterialChallenges :

Performance Degradation after Printing (Ink Formulation Issues)Repeatability of Ink-Jet Printing (Blocking of Head, Volume Variation),Non-Uniformity of LEP Film (Non Homogeneous Edges in Pixels )

ITO

WT

PassivationTR Units

Glass Substrate

Bank

Insulator Layer

Subpixel

Bank Channel

Wall layer defines pixel area

Substrate : Top View

Laser Induced Thermal Imaging Technology (LITI)Advantages : High Resolution, Multi-Layer Stacking Capability,

Possible Small Molecule & Polymer Hybrid OLEDChallenges :

Performance Degradation after Printing (Blending Issues)Uniform Film Roll Coating Sensitive Process to Particle Contamination

LTHCPlastic Film

EML LAYER

HTLITO

LASER BeamLASER Beam

Tech. Status of OLED Color Patterning

Tech. Status of OLED Color Patterning LITI Hybrid OLED

LITI Hybrid 2.2“ AMOLED

CathodeETL EML HTL HILITO

EML patterning

Donor Film EML

Polymer, Spin- coatable SM

Evaporated SM

Spin coating or Evaporation on film

Comparison of Aperture Ratio for Various Color Patterning Tech.

Possible High Aperture Ratio in AMOLED,But It Depends on Color Patterning Methods!

70~80%~60%40~50%Aperture Ratio(Top Emission)

± 2.5㎛± 15㎛± 20㎛Patterning Accuracy

>200ppi~150ppi~130ppiResolution

Polymer (LEP)

Ink-JetPrinting

Small Molecule (SM)

Evaporation(Precision Shadow Mask)

Polymer (LEP)Hybrid (Polymer/SM)Materials

LITIItems

Tech. Status of OLED Color Patterning

Pending Issues in OLED

Glass ITO EML ETL Cathode

Optical Out-Coupling Efficiency Improvement(Loss of Optical Output due to Optical Guiding Effect)(Loss of Optical Output due to Optical Guiding Effect)

Eliminate Internal ReflectionEliminate Internal Reflection

Approaches1D/2D Grating Shaped Glass or High Index Glass(n=1.85, Schott SFL57): ~50% upAerogel/Sol-gel Tech.: ~60% upOrdered Micro-lens Array: ~50% up

1D/2D Grating

Aerogel/sol-gel Micro-lens Array

Shaped Glass

Out-Coupling Efficiency Improvement

0

30

6090

120

150

180

Blue-Nano 1 Blue-Nano 2Blue-Nano 3 Blue-Nano 4Blue-Ref.

50 100 150 200 250250 200 150 100 50

L (Cd)

External Q.E. ImprovementExternal Q.E. ImprovementBest Results: Best Results: Up to 70%(Green) Improvement at the Front LightUp to 70%(Green) Improvement at the Front Light

Pending Issues in OLEDPhotonic Crystal Results

Normal PhotonicNormal Photonic Crystal Crystal Test Coupon Test Coupon Test CouponTest Coupon

G: 78 cd/m2 @100mA G: 134 cd/m2 @100mA

Photonic Crystal Results (Test Coupon)

Pending Issues in OLED

Pending Issues in OLEDLifetime Differential Aging ProblemDifferential Aging Problem

Image Burning Image Burning Improvement of OLED LifetimeImprovement of OLED LifetimeDevelopment of Avoiding Driving Tech.Development of Avoiding Driving Tech.

White Balance Shift : Yellowish ProblemWhite Balance Shift : Yellowish ProblemRequired the Same Lifetime of RGBRequired the Same Lifetime of RGB

Image

Pending Issues in OLEDLTPS non-Uniformity Issues

Vth Variation

Ids

Vgs

ELA NonELA Non--uniformity uniformity Improvement of ELA Beam UniformityImprovement of ELA Beam UniformityCompensation Pixel CircuitCompensation Pixel CircuitNonNon--ELA Crystallization is under the DevelopmentELA Crystallization is under the Development

ELA non-Uniformity (2TR)

Voltage or Current Compensation Pixel Circuit

Aperture Ratio IssuesAperture Ratio IssuesAperture Ratio of AM OLED

Top Emission Provides Higher Top Emission Provides Higher Aperture Ratio

50 100 150 2000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8 2TR bottom emitting 4TR bottom emitting 4TR top emitting

Ape

rture

Rat

io

Resolution (ppi)

Low Aperture Ratio Decreases the OLED Lifetime So Much.

Pending Issues in OLED

Top Emission Scheme is the Best Solution, But it Requires a Clear Encap.

Tech.

1st Generation Deposition Equipment

Pretreatment

HIL

HTL

EML/ETLCathode

CathodeEML/ ETL

Zelda

NEW ZELDA

Inverter HTL/ HTLModule

EML/ ETLModule

CathodeModule

2nd Generation Deposition Equipment

Encapsulation • Basic design concept 1. Sheet to sheet process (same as LCD?)2. Isolate device from humidity and oxygen 3. Absorb the humidity into the cell• Key considerations 1. Inner pressure release – mechanical & dispenser2. Capability of desiccant - How long can it works?3. Mechanism – Physical absorption or Chemical

reaction.4. Minimize the humidity and oxygen penetrates –seal

material and cell gap control5. Dry and oxygen free environment

UV

Pressure

Alignment CCD

Quartz Plate

Press Plate

Mechanical Design of Encapsulation

Substrate

x

yθ

Testing• Basic design concept 1. To differentiate good and defective ones before IC

bonding2. To make sure brightness lifetime(to extend not to

shorten)3. To make sure no defect found after sell to customers• Key considerations 1. Simulated driving single input when test to make

sure correct inspection. 2. Burn-in process design to make the device

brightness decay rate smoother – high temperature needed

3. Reliability test under high temperature and high humidity to simulate the failure mode.

Burn-in ProcessLight On Test

Testing Process

Area Color Series Full color series High color seriesMonochrome

96x3x64 ( A )262k Full color

COFSub display

96x392-AC COG

Sub display

80x48Mono TABSub display

42x3x644K full color

COGSub display

80x484 Area color

TAB Sub display

96x16Mono COGSub display

96x3x64 (A )256 Full color

TABSub display

developing

Done

Planning

96x3x6465k Full color

TABSub display

Sub-Display for Mobile Phone in RiTdisplay

ConclusionOLED Manufacturing is Being Matured for Small Size Mobile Application.

Long Life OLED Performance is very Essential to Meet Lifetime Requirements of Various Application.

Image Burning & White Balance Shift

LTPS non-Uniformity is Still a Problem for AM OLED Design.Low Aperture RatioRequired Vth Compensation Driving Scheme

Significant Improvement of OLED Technologies is Progressing. Phosphorescent OLED, OLED Material ImprovementOptical Out-coupling Improvement, Top Emission OLED

Shadow Mask Color Patterning is Seen as a Key Bottle Neck. Required a New Color Patterning Tech. such as LITI