Organic Thin Film Transistor
description
Transcript of Organic Thin Film Transistor
ICML Hanyang University
Polymeric Materials for Information & Communication
Organic Thin Film Transistor
Edited by Song Ho, Kim
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1. What is the OTFT?
2. Structure of OTFT
3. Application of OTFT
4. Mechanism Operation
5. Pentacene TFT
- Proposed Research
- Fabrication of Pentacene TFT
Characteristics & Analysis
6. OTFT Materials
Contents
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• First Organic Transistor - 1986• Using organic molecules (Polymers) rather than
silicon for their active material. • Semiconductor
• Advantages– Less Complex & Lower-cost Fabrication
• Solution Processing Photolithographic patterning• lower temperature manufacturing (60-120° C) • Print-able Organic Transistors
– Mechanical flexibility• compatibility with plastic substances: foldable & light
weight– Strong Optical Absorption and Efficient Emission
What is the OTFT(organic thin-film transistor)?
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Structure of OTFT (1)
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Structure of OTFT (2)
Various Structures of Organic Thin-Film Transistor
Bottom-Contact Top-ContactTop-Gate
Bottom-Gate
Source Drain
DielectricSemiconductor
Gate/Substrate
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• Very Similar to MOSFETs
• 3-Terminal Device– Voltage Controled Switch
Structure of OTFT (3)
•Differences –Carrier Transport
•Discrete Energy Levels•Hopping
–Organic Active Layer–Depletion Devices
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Organic Thin Film Transistor
OLED Device
Liquid Crystal Device
E-ink
Antenna
MaterialsIntegration Technology
OLED Display
Plastic TFT LCD
E-paper, E-book
Contactless Smart Card
Wearable Computer
Application of Organic TFT (1)
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FlexibleOLED
FlexibleLCD
OrganicMemory
ImageSensor
BioSensor
OrganicLaser
Smart CardRFID Tag
E-paper
OTFT
ICTechnology
OpticalTechnology
BioTechnologyApparel
Technology
SensorTechnology
Memory device
Technology
LCDTechnology
OLEDTechnology
E-PaperTechnology
ElectricalFabric
Application of Organic TFT (2)
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_
_
gate
gate dielectric
pentacenesource drain
glass substrate
bias on gate
hole accumulation in pentacene
negative
hole flows to drain
positive
depletion
Mechanism of Operation
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• substrate - corning 7059 glass • gate metal - Nickel • gate dielectric - SiO2
• source/drain metal - Palladium All deposition was performed by
Ion beam sputteringPenn. state Univ.
Pentacene TFT
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1. Fabricate Pentacene TFT - gate insulating layer with high dielectric constant - reproducible patterning of pentacene film - source/drain metal with large work function - arrays of pentacene TFT
2. Measurement & Analysis - Vg- Id curve - mobility, threshold voltage, subthreshold slope
3. Evaluation
Proposed Research
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drain
pentacene active layer
• substrate - glass (Corning 7059)
• gate metal - Al, Ni, Cr
• gate dielectric - SiO2, V2O5, Al2O3
• source/drain metal - Au
• active layer - pentacene
• passivation layer
substrate
gatesource
gate dielectric
passivation layer
drain
Schematic Figure of Pentacene TFT
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• Interfacial effect of metal/gate dielectric
- contact resistance, diffusion, dielectric properties
• Adhesion of material
- film lifting, process unstableness
• Making smooth film
- the small surface roughness leads to molecular ordering
• Photolithographic condition for pentacene patterning
- thickness of resist, expose time, develop time
- resist/pentacene interface effect
Process Factors
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Gate sputter, evaporation
wet etching
Gate sputter, evaporation
wet etching
Gate dielectric sputter
dry etching (RIE)
Gate dielectric sputter
dry etching (RIE)
Source/drain sputter, evaporation
wet etching, lift-off
Source/drain sputter, evaporation
wet etching, lift-off
Pentacene ICBD, evaporation
wet & dry etching
Pentacene ICBD, evaporation
wet & dry etching
Passivation CVD
dry etching (RIE)
Passivation CVD
dry etching (RIE)
Fabrication Flow Chart
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Requirement • fabricated at low temperature ( < 300°C) • smooth surface roughness • have a high capacitance with low leakage current • good phase stability
• reproducibility
SiO2, V2O5, Al2O3
Gate Dielectric Layer
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C-VC-V
I-VI-V
AFMAFM
Electrical
characteristicsElectrical
characteristics
RoughnessRoughness
Interfacial
effectInterfacial
effectRBSRBS
I-VI-VAu deposition on gate dielectric
and annealing
Au deposition on gate dielectric
and annealing
Deposition by
Reactive sputtering
Analysis of Gate Dielectric Layer
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-5 0 5 10 15
0.0
2.0x10-7
4.0x10-7
6.0x10-7
8.0x10-7
1.0x10-6
R.T
200µµ 2hr
200µµ 3hr
300µµ
400µµ
SiO2
Cap
acit
ance
(
F/c
m2)
Voltage (V)
C-V Analysis of V2O5 Dielectric Material
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• Evaporation • ICBD (Ion Cluster Beam Deposition)
expected to evaluate pentacene properties
Deposition technique
Simple structure
estimate pentacene properties
Deposition of Pentacene Film
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Photolithographical method - using photosensitized PVA as negative photoresist - UV expose & develop in water - etching unwanted pentacene layer in oxygen plasma
- baking to remove water in pentacene layer
dielectric layerpentacenephotosensitized PVA
Patterning of Pentacene Film
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• Field effect mobility(fe ) and the threshold voltage(Vth) were
obtained in the saturation region using the relation
• Positive threshold voltage arise from an initial accumulation layer
at the pentacene/dielectric interface
- positive gate voltage is required to turn the device fully-off
• Large on/off current ratio can be obtained with small gate voltage
swing
Operation Characteristics
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substrate
gate
pentacene active layer
source
gate dielectric
drain
• pentacene layer is normally conducting
no overlap gate-source, gate-drain
large drain current to flow at zero gate bias
devices are turned off by applying positive gate bias
transistor operating in depletion mode
• 3 mask steps
• no overlap gate-source, gate-drain
Different Structure of Pentacene TFT
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Number Name133 Pentacene
Benzo[b]naphthacene 2,3:6,7-Dibenzanthracene beta,beta'-Dibenzanthracene 2,3,6,7-Dibenzoanthracene lin-Dinaphthanthracene lin-Naphthanthrene
CAS: 135-48-8 M W: 278 L / B: 2.226Width: 7.447 Length: 16.577 Thickness: 3.885
Structure of Pentacene
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Organic Semi-Conductors of Processing Type
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p-Type Materials of OTFT
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Structure and mobility of fused aromatic Compounds
p-Type Materials
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Oligo-thiophenes and Oligo-phenylenes
p-Type Materials
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Thiophenylenes and their mobilities
p-Type Materials
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Polythiophene materials for FET
Conjugated polymers for FET
p-Type Materials
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Hall mobility change of Poly(2-alkylthiophene)s by arrangement and stereo chemistry
Hall Mobility Change of Polythiophenes
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n-Type Materials of OTFT
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Electron Mobilities of n-Type Materials
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Tetracarboxylic anhydrides
Quinodimethane compounds
Phthalocyanines
n-Type Materials
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Fluorinated n-type materials
n-Type Materials
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Physical Properties of Organic Dielectric
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Trends of OTFT Materials(Domestic)
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Trends of OTFT Materials(Abroad)
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Low conductivity and low carrier mobility of Organic semi-conductor
Structure of General FETLow Current and low operating speed
Improvement of physical propertiesSearching of New materials
Improvement ofDevice Structure
New mechanism
High puritycrystallinity
Phase Transition FET
SIT
Problem and Solution of OTFT
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Reference
1) 고분자 과학과 기술 제 17 권 1 호 2006 년 2 월 ‘유기반도체 재료’ 하승규 , 권오식2) 고분자 과학과 기술 제 14 권 5 호 2003 년 10 월 ‘ 유기트랜지스터 재료 연구개발 동향’ 권순기 , 김윤희 , 김형선 , 안준환3) 고분자 과학과 기술 제 15 권 6 호 2004 년 12 월 ‘ 고분자박막트랜지스터 개발동향’ 김보성 , 이용욱 , 홍문표 , 정규하 4) 화학세계 04/06 50 ‘ 단분자 OLED 재료 및 OTFT 재료의 개발동향’ 권순기3) 고분자 과학과 기술 제 14 권 1 호 2003 년 2 월 ‘유기’ 하승규 , 권오식5) University of the South Sewanee, Tennessee September 2002, Eugene Donev
‘Designing and Implementing Organic Thin-Film Transistors (OTFTs)’
6) Adv. Mater. 2000, 12, No. 7 p.481 , Groenendaal,* Friedrich Jonas, Dieter Freitag,
Harald Pielartzik, and John R. Reynolds
‘Poly(3,4-ethylenedioxythiophene) and Its Derivatives: Past, Present, and Future’
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Reference
7) Ali Ali Afzali Afzali, Christos Christos D. D. Dimitrakopoulos Dimitrakopoulos
IBM Research Division T. J. Watson Research Center T. J. Watson Research Center
Yorktown Heights, NY ‘Synthesis and Application of Pentacene Precursor in OTFT’
8) Chang Feng Yu ,Ching Fu Hsu, Yao Peng Chen, and Yu Hua Ma Department of Information
and Communication Engineering Chaoyang University of Technology
‘Dependence of field-effect mobility on the gate field for Pentancene OTFTs’
9) http://chem3.snu.ac.kr/ ~shlee/OTFT.htm
10) http://www.postech.ac.kr/ ce/lamp/research-4.html
11) http://www.organicid.com/structure.html