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3 () TFT Fab. Process

2

1)

2)

3) 4

4)

5) poly-Si

6)

7) CMOS

8) TFT

3

LCs

LCD Mode Demands to LCs

IPS -High

-Low 1-Good reliability (mura-free)

FFS -High n

-Low 1-Good reliability (mura-free)

LCD Mode Demands to LCs

VA

(MVA, PVA, New-ASV)

-Low 1-High for

Low Vop & High Light Efficiency

+ -

LC Materials for Monitor & TV

4

LCD Mode

Intrinsic Issues Solutions

IPS Vth 1/d, off 1 d2/K22

Fast Response: d Vth 1 ; Limitation exists

-CN LCs

with High Reliability

-New LCs for high

and low 1

VA on Molecular dynamics & 1 off 1 d

2/K33 ; Advantage due to bend deformation

1 > 100 mPa.s with relatively low

-New LCs for high

and low 1(Breakthrough ??)

FFS Vth 1/d, off 1 d2/K22

Fast Response: d Vth 1 ; Advantage exists

-Focus on LCs for low 1with High Reliability

Issues for LCD Modes and Development Status

5

Off On

Substrate

Light Light

Light

IPSIPS

Off On

Substrate

Off On

Substrate

LightLight LightLight

LightLight

IPSIPS

LC Molecule

OFF ON

Light

FFS

Light

Light

Glass

Glass

Electric

Field

Metal

LC Molecule

OFF ON

Light

FFS

Light

Light

Glass

Glass

Electric

Field

Metal

PVA

Wide-Viewing-Angle Technologies used

in Production by Korean companies

6

IPS

CsBus Line

Gate

Bus Line

Source Bus Line

Cgd

TFT

Cs CLC

Cs

Glass

Glass

FFS

Cs Bus Line

Gate Bus Line

Source Bus Line

Cgd

TFT

CsCLCCf

Cs

Glass

Glass

Cf

CpdCpd

One Pixel Structure of FFS

Ctotal =Cgd + Cs + CLC (IPS) Ctotal = Cgd + Cs + Cf + CLC (FFS)

Cst in Light-Transmitted Area !!!

7

Corning 7059 & 1737 glass

Thermal absorption ratio

Relativity of Glass & temperature

Characteristics of glass substrate for TFT-LCD

Corning Corning 1737Corning Eagle

2000

Corning

Annealed

Glass (1737)

NA 35

(NH

Techno

glass)

Density

20oC2.54g/cm3 2.37g/cm3 2.55/cm3

roughness

~ Thermal

expansion

37.8 10-7 / oC

( 0 ~ 300oC )

31.8 10-7 / oC

( 0 ~ 300oC )

38.4 10-7 / oC

( at 300oC )

12 ~ 13 ppm

( at 400oC 2h )

2 ~ 3 ppm

( at 600oC 2h )

8

Protection Sheet

Vertical Prism Sheet

Horizontal Prism Sheet

Diffusion Sheet

Light Guide Plate (LGP)

Reflection Sheet

Lamp&Lamp Cover

Details of Side(Wedge) type

9

Lamp

1. Principle & Structure of CCFL(Cold cathode Fluorescence Lamp)

1. Normal glow discharge2. Rare gas & mercury (a few mg)3. Proccess

- Glow discharge in low vapor pressured Mercury by added high electric field - UV ray (253.7nm) emitted these ultraviolet rays excite the phosphor.

- Excited phosphor atoms return to low energy level, the visible light is emitted. (Its wave length is decided by the phosphor material.)

10

Lamp

2. Characteristic color x, y coordinates - White region- x=0.2980.01, y=0.2950.01

(in case of 14 Lamp)- Color control mixing R G B Phosphor materials

3. Lamp & Lamp Cover - Lamp cover absorbed >60% of light- Only ~30% light entered LGP- Need New design and new materials

for Wedge

for Direct

11

Light Guide Plate (LGP)

1. Flat LGP / Shaped LGP by Mold injection

2. Polymer materials = PMMA

3. General Characteristics of PMMA as a Light Guiding

General Usage LGP Application Remarks

ColorTransparentHalf-Trans

TransparentDepend on process

& Materials

Specific Weight 1.19 1.19 -

Reflect Index 1.49 ~ 1.62 1.49 -

OpticalEnergy Gap

3.8 ~ 4.4 eV 3.8 eV -

OpticalTransmittance

88 ~ 93(0.1, 350~850nm)

93Below the 380nm,Absorption region

Yellowish of LGPOlefin resin

12

3. Lens Film- Structure (Vertical, Horizontal)

- Function : To enhance bright & Light exit angle

- Brightness Enhanced Film (BEF), DBEF, MBEF, etc

- 3M, Exclusive Patent

LGP

Diffusion film

=~70o

13

Further Research for Flat Lamp

1. E (External Fluorescence Lamp)

- http://www.harison.co.jp- EE (external electrode free lamp)- AFL (arrayed fluorescence lamp)- Possible to form Array & Mosaic with 1 inverter

- Sustain voltage is higher than that of CCFL(1000~1400) (~800 or lower)

GndHot

Inverter

http://www.harison.co.jp/

14

Further Research for Flat Lamp

2. Osram Flat Lamp1. Specification

- 15, 7000cd/m2, 48Watt

2. Results- 5700cd/m2, Uniformity of ~70%

3. Electrode structure- Parallel electrode with dendritic tip

4. Drawbacks- Heat/Weight/Inverter size

Inverter Electrode structure

15 Flat Lamp

spacer

16

(Transfer) (output)

17

Glass substrate

a-Si:H

Source DrainGate

Gate Insulator

Glass substrate

DrainSource

Gate

Gate Insulator

a-Si:H

Glass substrate

a-Si:H

Gate Insulator

Gate

DrainSource

Glass substrate

a-Si:H

Gate Insulator

Gate

DrainSource

Etch stopper

1) Coplanar type 2) Stagger type

3) Inverted Stagger type4) Inverted Stagger - ISI type

TFT

18

TFT

19

(SID SHORT COURSE, 2001)

TFT (1)

20


TFT (1)

21

TFT

22

LTPS TFT-LCD AMOLED (1)

23


24

( , TFT Array , 2002)


25


I-V Characteristics of a-Si TFT(1)

26


I-V Characteristics of a-Si TFT(2)

28

( , TFT Array , 2002)

AMOLED

29

OLED

30

OLED

31

OLED

32

HPD-CVD

33

( , TFT Array , 2002)

35

2.2

. Sputter

. CVD

. Photolithography

. Dry etching

. Wet etching

.

. line

38

TFT Panel Process

42

Gate & S / D Bus Line Pixel Electrode

Capacitor Electrode PAD

Align Key Black Matrix Mask

Static Charge Protect

- Resistance : Signal Delay

- Etching : Taper, CD Uniformity, Etch Rate

- Thermal Characteristic : Heat Expansion, Hillock

- : Etchant, , Developer, Stripper

- : Metal Galvanic Cell

- : PAD Corrosion

- Contact : Metal Contact, S/D Contact

- Other : LC

Metal for TFT-LCD Process

TFT-LCD Metal

Required

43

Metal deposition

Metal deposition

PVD CVD

Sputtering Evaporation PECVD

Inert gas

Reactive gas (reactive gas plasma)

Advantage

Multi-sputtering with good controls

In-situ surface cleaning

Disadvantage

Impurity in the sputter gas

Radiation or ion damage

Target material dependence

DC, RF(AC) Sputtering

E-gun or crucible source

Advantage

High purity deposition

High deposition rate

No trapped gases

No radiation damage

Disadvantage

Poor control on deposition rate

Not suitable for compound

Poor Step coverage

Advantage

Excellent step coverage

High throughput

Selective deposition possible

High deposition rate

Disadvantage

Limited to available precursors

Not suitable for compound

Particle generation

Rougher surfaces

Gas entrapment

Toxic hazardous gas

Decomposition procducts

Required

- Step coverage ( CVD >> Sputtering >> Evaporation )

- No damage during deposition (Evaporation >> CVD >> Sputtering)

- No stress, Good adhesion

- Smooth films

- Crystalline films

44

-Sputtering Plasma energy Target Target .

-Sputter Issue Gate S/D .

() ()

Ag 2.0 (1.6) 961 FCC

Cu 2.3 (1.7) 1083 FCC

Al 3.1 (2.7) 660 FCC

Mo 11.5 (5.4) 2610 FCC

Cr 21.0 (12.9) 1875 BCC

Ni 50 (7.8) 1453 BCC

ITO 180~200 - Cubic Bixbyite

. Sputter

45

DC diode discharge

46

0.1

1

10

100

1000

10 15 20 25 30 35 40

Diagonal Size (inch)

Require

d R

esis

tivity

(

cm

)

Gate VGA(GV) Gate XGA(GX) Gate HDTV(GH) Data VGA(DV)

Data XGA(DX) Data HDTV(DH) Al-Nd Mo

Cr -Ta MoTa

Panel Gate, S/D

47

0.0

5.0

10.0

15.0

20.0

50 100 150

Depo

Resistivity (

cm)

Al-Nd alloy PECVD Anneal

-2.0E+09

-1.0E+09

0.0E+00

1.0E+09

2.0E+09

3.0E+09

4.0E+09

0 100 200 300 400 500

Temperature ( )Stress

(dyn

e/

)

Al-Nd pure Al Stress Thermal Hysteresis

Al-Nd

48

15

20

25

30

35

0.3 0.6 0.9

Pressure (Pa)

Resistivity ()

100

150

200

(2.2mTorr)

0

0.4

0.8

1.2

1.6

2

0.1 0.4 0.9

Pressure (Pa)

Stress (E+10 dyne/

)

100

200

300

Cr Resistivity () Stress ()

Cr

49

200

240

280

320

360

400

100 120 140 160 180 200 220

Heater Setting ( )

Resistivity (

)

Heater Setting ITO Film

200

250

300

350

400

0.6 0.8 1 1.2 1.4 1.6 1.8 2

O2 (sccm)

Resistivity (

)

O2

50

(O2 : 0.4sccm) (O2 : 1.2sccm) (O2 : 2.0sccm)

O2 ITO Film SEM (60,000)

O2 ITO Film

51

100 ITO, IZO Anneal Rs ( 1200)

0

5

10

15

20

25

30

35

40

45

50

0.6sccm 1.4sccm 2.2sccm 3.0sccmO

Rs

(/

)

ITO (as depo Rs) ITO (anneal Rs)

IZO (as depo Rs) IZO (anneal Rs)

200 ITO, IZO Anneal Rs ( 1200)

0

5

10

15

20

25

30

35

40

45

50

0.6sccm 1.4sccm 2.2sccm 3.0sccmO

Rs

(/

)

ITO (as depo Rs) ITO (anneal Rs)

IZO (as depo Rs) IZO (anneal Rs)

O2 Anneal IZO, ITO Rs

52

Item Ag Cu Al AlNd

Resistivity

(cm)2.1 2.3 3.1 ~ 4.5

Hillock X O X O

Anti-Corrosion X X

Adhesion to Glass or a-Si

X X O O

Dry Etching X O

Reflectance O X O O

n+a-Si Contact

O O X X

ITO Contact O O X X

Target CoastO

recycleO O X

(O Good, Not So Good, X Bad)

Low resistive metals for the bus lines of TFT-LCD

53

High-Aperture-Ratio TFT-LCD Using a Low Dielectric Material

Gate Data lineSiNx

Organic

insulator

Pixel Electrode

(ITO)

Drain/Source

a-

Si:H

n+

54

TFT on Color Filter Structure

A) Color Filter patterning

B) BCB TFT fabrication

C) BM Patterning

Common Electrode

Top Glass Substrate

ITO (Pixel electrode)

Ni Silicide Passivation

55

-CVD (, , rf power, DC)

.

(1)APCVD(Atmospheric Pressure Chemical Vapor Deposition)

- , gas flow .

(2)LPCVD(Low Pressure Chemical Vapor Deposition)

- .

(3)PECVD(Plasma Enhanced Chemical Vapor Deposition)

- glow , .

. CVD

56

P-5000 PECVD Chamber

57

(1)Electron-Impact Dissociation reaction

dissociation reactive radical . reactiveradical . Plasma surface reaction radical .

e + O2 O + O + e

(2) Electron-Impact Ionization reaction

Electron dissociation .

e + O2 O2+ + 2e ( Ionization )

e + O2 O+ + O + 2e ( Ionization + Dissociation )

e + SF6 SF6- SF5- + F ( Electron Attachment )

(3) Electron-Impact Excitation reaction

Electron radical radical vibration rotational excitation .

e + F F* + e ( Excitation )

PECVD

58

Film GH GL

DEPO RATE (/min) 1800 850

Uniformity (STD, Edge 15mm) 63

Refractive Index 1.889

Stress (dyne/cm2) 1.0E+8 -1.25E+10

WER (/min,500:1HF) 60

N-H Bond (E22/cm3) 1.19 2.77

Si-H Bond (E22/cm3) 0.44 0.05

N-H/Si-H RATIO 2.70 58.7

TOTAL H (E22/cm3) 1.63 2.82

Dielectric Constant 7.3

Gate SiNx

59

Film

DEPO RATE (/ MIN) 960



Stress (dyne/cm2) -3.50E+9

Si-H/Si-H2 Ratio 2.6

H Concentration (Area) 5.7

Resistivity(cm) 33.5

a-Si

60

Film AL AH AL AH

DEPO RATE (/ MIN) 580 1200 580 1320

Uniformity (STD, Edge 15mm) 79 84

Refractive Index 4.20 4.35

Stress (dyne/cm2) -3.9E+9 -4.7E+9 -2.0E+9 -4.0E+9

Si-H/Si-H2 Ratio 10.5 12.3 13.9 8.3

H Concentration (Area) 3.8 4.2 3.3 4.1

Conductivity(DARK, ATM) 8.30E-9 3.60E-8 9.75E-9 4.24E-9

n+ a-Si

61

Film

DEPO RATE (/ MIN) 2070



Stress (dyne/cm2) -5.0e+9

WER(/MIN, 500:1HF) 140

N-H Bond (E22/cm3) 2.16

Si-H Bond (E22/cm3) 0.52

N-H/Si-H Ratio 4.15

Total H (E22/cm3) 2.69

Dielectric Constant 6.8

Passivation SiNx

62

-

. Photolithography

65

Slit & Spin

PR

66

Stepper

67

Aligner

68

Schematic View

Scanning Projection Exposure

69

- Gas Ionize Electron Ion , PLASMA Etch Plasma Etch Dry Etch .

(1)

- .

- .

- .

(2)

- .

- , .

- .

- .(Cu, Pt)

. Dry etching

70

PE(Plasma Etch) MODE

71

RIE(Reactive Ion Etch) MODE

72

( )

1.GLASS DAMAGE .

2.SINx/SI/Ta/MO/ITO/AL/Cr ETCH

3.LOW PRESSURE(100mTorr)

4.HIGH DENSITY THROUGHT

PUT .

:MODEL - LAM

LAM ETCHER

> COOLING: He COOLING

> CLAMPING: ESC (Electrostatic

Chucking )

TCP(Transformer Coupled Plasma)MODE

73

Material Gas plasma

Si CF4, CF4 + O2, CCl2F2

POLY Si CF4, CF4 + O2, CF4N2

Amorphous Si CF4, CF4 + O2,

SiO2 CF4, CF4 + O2, HF

SiN CF4, CF4 + O2, HF

Mo CF4, CF4 + O2

W CF4, CF4 + O2

Au C2Cl2F4

Pt CF4 + O2, C2Cl2F4 + O2

Ti CF4

Al CCl4, CCl4 + Ar, BCl3, Cl2

Cr Cl2, CCl4, CCl4 + Ar, O2

Dry etching etching gas

74

TFT (DRY & WET ETCH )

DRY ETCH WET ETCH

1. . 1. .

2. .

( Gas )

2. .

(Chemical )

3. Clean Process ( ) 3. .

4. 4.

5. Control 5. Control

6. Pattern 6. Pattern

7. Process Parameter

8. Wet Etch .

9. Etching Damage.

75

PE RIE SPUTTER ETCH

ETCH

MECHANISM

PRESSURE > 0.1Torr < 0.1Torr < 0.1Torr

WAFER

LOCATION

GROUNDED

ELECTRODE

POWERED

ELECTRODE

POWERED

ELECTRODE

ETCH

SPECIESFREE RADICAL

RADICAL

REACTION CHEMICALCHEMICAL

PHYSICALPHYSICAL

R PRODUCT R Ion PRODUCT+

Ion PRODUCT+

LOW HIGH HIGH LOW LOW PHYSICAL SPUTTERREACT ION ETCH

PRESSURE POWER ANISOTROPIC ISOTROPIC SELECT IVITY RIEETCH

HIGH LOW LOW HIGH HIGH CHEMICAL PLASMAREACT ION ETCH

Etch Mode Etch

76

Bar Space

Pitch

Pattern Bias

CD Bar

High over etch

PR

PR

Overetch

PR

Etched film

Lateral Etch

dry etching

77

Etching

PR

N+ a-Si

a-Si

G-SiNx

Glass

Active Etch Profile

Active Etch

78

Etching

S/D Cr

N+ a-Si

a-Si

G-SiNx

Gate Metal

Channel

Channel

n+ Channel ETCH

79

Etching Etching

PR PR

Passivation Passivation

Cr G-SiNx

Gate Matel

Contact Hole & Data Pad Etch Gate Pad Etch

Contact Hole Gate Pad

80

Etching

81

Taper Etching Mechanism

82

Photoresist Lifting Taper Etching Mechanism

Al/Mo Taper Etching Mechanism

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