Norbert Frühauf Universität Stuttgart · • Spin tools for cleaning, development and wet etching...

Norbert Frühauf

Institut für Großflächige Mikroelektronik

Universität Stuttgart

Technologische

Grundlagen aktueller

Bildschirmtrends

www.igm.uni-stutgart.de

Overview Institute for Large Area Microelectronics

The Laboratory:• Cleanroom area of 480 m2, Cleanroom Class 10 and 100

• In operation since May 1991

• Since 2011: Institute for Large Area Microelectronics

• Current Staff (September 2016: 15) plus ca. 10 students

• Max. Substrate Size: 16“x16“ (406 mm x 406 mm)

Available Equipment:• MRS Stepper and MA6-Mask Aligner (Suess) for Lithography

• UV-Laser Lithography System DWL 400 (HIMT)

• Spin tools for cleaning, development and wet etching (STEAG)

• Inline Sputter machines ZV6000 DC/RF (Leybold)

• KAI1 PECVD machine (BALZERS)

• RIE/PE dry etching reactor KAI Etch (BALZERS)

• Modified Ion Implanter for large substrate sizes (EATON)

• Excimer laser crystallization SAELC (SOPRA)

• Ink jet printer and Glove Box system for organic semiconductors

• Equipment for LC cell fabrication

• TAB (OSAKI) and Flip chip bonder FC6 (SUESS)

• Various measurement equipment


Research and Development Competence

Large Area Microelectronic Systems

A-Si, µc-Si and N-, P-channel, and CMOS LTPS TFTs

Metal Oxide TFTs

Solution/Suspension processed OTFT and CNT-TFTs

CNT Electrodes, Color Filter Technology

Active Matrix LCD, OLED and EPD Displays

Rigid and flexible substrates (Glass, Metal foil, Plastic)

Adaptive Optical Elements

Bonding processes on glass and flexible substrates

Integrated Driver Electronics

FPGA Driver electronic systems

483 µm

16

4 µ

m


Current Trends in Displays (specifically TVs)

● Energy Efficiency (Energy Efficiency Labels)

● Ultra High Definition (4k oder 8k)

● Color Space (REC 2020)

● High Dynamic Range (HDR10, Dolby Vision)

● AMLCD vs. AMOLED


Basics Energy Efficiency Index/CategoriesEU Delegiertenverordnung 1062/2010 Reference System (EEI=1)

Power per Area 4,3224 W/dm2

Max Conversion Efficiency 200 lm/W

Max Lumen per Area 86448 lm/m2

Luminance (Lambertian Characteristic) 13765 Cd/m2

AMLCD Efficiency 0,07

Front of Screen Luminance 964 Cd/m2

A+++ < 0.1 96 Cd/m2

A++ < 0,16 154 Cd/m2

A+ < 0,23 222 Cd/m2

A < 0,3 289 Cd/m2

B < 0,42 405 Cd/m2

C < 0,6 578 Cd/m2

D < 0,8 771 Cd/m2

E < 0,9 868 Cd/m2

F < 1 964 Cd/m2

Energy Efficiency Categories:


Electro-optical Principle of Operation

Transmissive(e.g. LCD)

Polarizer

Polarizer

Electrodes and Orientation Layer

Liquid CrystalMolecules

Electrodes and Orientation Layer

5 µm

M.Schadt

Low Driving Voltages Voltage controlled effect Light modulation Color with Color Filters

High Energy Efficiency Current controlled effect Self emitting All colors available

Ca CathodeElectron Transport and

Emission LayerHole Transport Layer

Hole Injection Layer

Substrate (Transparent)

0,5 µm

Self - Emitting(e.g. OLED)

Ch. Tang

ITO Anode


Colored Active Matrix Liquid Crystal Panel

(Source: Spektrum der Wissenschaft)


2 TFT + 1 C Active Matrix OLED (Brody et al.)

Most simple AMOLED pixel structure Switching-TFT plus storage capacitor Analog TFT as current source → stability and homogeneity critical

VD

D

Sel

VDa

ta

C

S

-5 ,0 E -0 6

-4 ,0 E -0 6

-3 ,0 E -0 6

-2 ,0 E -0 6

-1 ,0 E -0 6

0 ,0 E + 0 0-1 0 -5 0U D S in V

I D in

A

U _ G a te = - 4 VU _ G a te = - 5 VU _ G a te = - 6 VU _ G a te = - 7 V

-5,0E-06

-4,0E-06

-3,0E-06

-2,0E-06

-1,0E-06

0,0E+00

-10 -5 0UDS in V

I D in

A

U_ Gate = -4VU_ Gate = -5VU_ Gate = -6VU_ Gate = -7VOLED


Structure of an AMOLED

Metal 1, Gate(Row Metallisation)

GateoxideDrain Source

Substrate

Bufferoxide

Isolation

Metal 2, D/S-Contacts(Column Metallization)

Top ElectrodeConnection

PlanarizingPassivation

StepCoverage Bottom

Electrode

OLEDStack

TopElectrode

Encapsulation

Gap

TopEmission

BottomEmission University of Stuttgart, 2011

(OLED Coating: Novaled)


Color Creation Principle

LCD Color Filter

Backlight

OLED structured OLED Color Filter


Power Efficiency of Active Matrix LCD

Effect Ideal Real

Light from Backlight: 100% 100%

Polarizer: ideal: 50% 50%real: 40% 40%

Color Filter: typ: 30% 15% 12%

Aperture: typ: 60% 9% 7%

70 % Losses by Color Filter !!!!


Quantum Dot Backlights


Practical Implementations QD Backlights

+ Color space

- Power efficiency


Color Space QD Backlights


Current Developments

Photostructurable QD Layers (e.g. Merck)

Color Filter replaced by color structured QD layers

● 3x Efficiency● In Cell Polarizer needed

Quantum Rods instead of Quantum Dots (e.g. Univ. Ghent)

Polarized Emission

● 2x Efficiency (elimination of Polarizer Losses)

T. Augbert et al., Large Scale and Switchable Polarized Emission From Semiconductor Nanorods Aligned in Polymeric Nanofibers, Eurodisplay 2015, S2.4


Color Space Samsung OLED Tablet

(Source: S. Schimpf, University of Stuttgart)


Efficiency Improvement OLEDs

● Always only Light on Demand

● New Concepts for efficient Light Generation

S. Sato, „Organic LED with low power consumption and long lifetimes, SPIE Newsroom, 10.1117/2.1201608.006688

e.g. Exiplex Triplet Energy Transfer (Semiconductor Energy Laboratory, Japan)


Luminance and Contrast Properties

LCD

Viewing angle dependence Typ. Contrast < 1000:1 Luminance defined by backlight

OLED

No viewing angle dependence Typ. Contrast > 100.000:1 Luminance several hundred Cd/m^2

(Lifetime limited !)


Visual perception and High Dynamic Range

Quelle: Helge SeetzenFa. BrightSide

Logarithmic Luminance in cd/m2

Simultaneous Vision Range

Adaptation Range

Displays


HDR 10 vs. Dolby Vision

HDR 10 Dolby Vision

Bit Depth 10 bits/color 12 bits/color

High Brightness 1000 nits(or ≥ 540 für OLEDs)

4000 nits (Mastering bis 10000 nits)

Low Brightness ≤ 0.05 nit (or ≤ 0,0005 nits for OLEDs)

≤ 0,004 nits(Mastering bis 0,0001 nits)

Min. Contrast 20000:1 (or 108000 for OLEDs)

1000000:1 for full content

(adapted from Mathew Brennesholz, „HDR 10 versus Dolby Vision“, Mobile Display Monitor 12 August 2016)


High Dynamic Range LCD

•Contrast typvically several 100:1

• Much lower considering:

➢ Wider viewing angles➢ Wavelength dependence

• Overall Screen Luminance:

Backlight luminance x Modulator Transmission

• Idea for HDR Display (H. Seetzen, ca. 2003):

Put LCD plus modulated backlight in series to achieve 105 :1


Dynamic/Adaptive Backlight

Courtesy: H. Seetzen

BacklightBacklight LCDLCDImageImage Output imageOutput image


Drive LED

Importance of Glare Spread Function


Receive ImageReceive Image

Drive LED

Divide Image byLED light field to obtain LCD values

Receive Image

Drive LED

Divide Image byLED light field to obtain LCD values

Output Luminanceis the product of LED light field andLCD transmission(Problematic error)

Oops


Importance of Glare Spread Function


Veiling Luminance masks imperfection

But: ➢ Issues if LCD contrast variations !!!!➢ High cost for high resolution backlight for Large Screen Sizes


Alternative Possibility for HDR LCD

(Source: Display Search)

• Two full resolution LCD in series (one bw without Color filter) might be

cheaper than high resolution LED backlight

● Cell without Color Filter and only one polarizer < 15 % of total Sales Cost (today well below 300 Euro for 40 inch)

● Panasonic just announced such a Dual layer LCD with C > 1.000.000:1


Flexible OLED Demonstrators

(Source: Sony, 2010)(Universität Stuttgart, 2011)


Flexible LCD with CNT Electrodes, Universität Stuttgart, 2008

Flexible LCD Demonstrator


Ultra Thin Glass LCD Demonstrator

Thin Glass AMLCD(Worldwide First)

~10mm

75m Substrate

S. Höhla, S. Garner, M. Hohmann, O. Kuhls, X. Li, A. Schindler, N. FrühaufFirst Prize: Active matrix color LCDs on ultra thin glass substratesProceedings of Electronic Displays Conference, Paper 16.2 (2011)


EU/BMBF OLEA+ LiCRa Project Plastic LCD Demonstrator

e-mail

phone +49 (0) 711 685-

fax +49 (0) 711 685-

University of Stuttgart

Thank you!

Prof. Dr.-Ing. Norbert Fruehauf

• 66924

•

Institute for Large Area Microelectronics

[email protected]

Allmandring 3B, D-70569 Stuttgart, Germany

Web: www.igm.uni-stuttgart.de

• 66922

•

Norbert Frühauf Universität Stuttgart · • Spin tools for cleaning, development and wet etching...

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