1. Sputter Film

2. Gate Al

3. S/D Al, Mo

4. Cu

5.

1

Metal

Gate

Glass (Adhesion)

Etching

TCO (IZO or ITO)

Process

Cr

MoW

Cr/AlNd

Al/Mo

Ti/Al/TiN

MoTi/Cu

Ti/Cu

Gate .

1) Gate

2

Substra te

Al Film

Gra in Boundary

Substra te

Al Hillock

Annealing

2) Pure Al and Hillock

Driving Force : compressive stress

Kinetics : Al diffusion stress relaxation

Hillock compressive stress

Coefficient of Thermal Expansion (10-6K-1) CTE

Al 23.9 Glass 4.5

Mo 4.8 IZO 6.95

Cu 16.5 ITO 8.1

Ti 8.6 SiO2 0.5

a-Si 0.5 Si3N4 0.8

Aluminum Hillock Mechanism

3

Glass Al CVD 3 Al Hillock

Capping Al Hillock .

: (*1E+10Nm-2)

Mo Cr Cu Ag Al Ta Ti AlNx MoNx TiNx AlOx

33 15.7 12.3 7.9 7.1 18.2 11 33 45 60 35

Substrate Substrate

Capping

Al Grain

Hillock Hillock

Capping

* Nitride(or Oxide) N(or O)

*

3) Al/Mo Hillock

4

Gate

S/D MoAlMo

Pixel IZO

Al/Mo (2500/500) AlNd/Mo (2500/500) Al only (2500)

G/D Short

TFT Al/Mo AlNd/Mo .

AlNd Pure Al

Al/Mo Gate : TFT

5

AlNd

7

Hillock formation

1. Sputter Film

2. Gate Al

3. S/D Al, Mo

4. Cu

5.

Metal

SD

n+a-Si (Ohmic Contact)

TCO (IZO or ITO)

Etching

Step Open

Cr

Mo

Cr/AlNd

Mo/Al/Mo

Ti/Al

MoTi/Cu

Ti/Cu

SD .

1) S/D

9

Metal (eV) Metal (eV) Electron Affinity (eV)

Al 4.28 Ag 4.26 Si 4.01

Cu 4.7 Au 5.1 Ge 4.13

Mo 4.6 Ni 5.15 GaAs 4.07

Ti 4.33 Pd 5.12

Cr 4.5 W 4.55

Energy Barrier ,

Energy Barrier Work Function (, ) .

(Mg 3eV Pt 6eV )

Metal m, s ,

m > s : Schottky Contact, m < s : Ohmic Contact

Schottky Contact n+ a-Si Contact .

Metal Metal Semiconductor Semiconductor m > s Schottky contact m > s Schottky contact

2) Metal-Semiconductor Contact

10

(cm)

()

(ppm/)

Si ()

Stable on Si up to()

Al 3.1 660 23.9 ~250

( junction spike) 250

Cu 2.3 1083 17 100 100

Mo 11.5 2610 5 400 ~ 700 400

Ti 86.5 1668 8.5 400 ~ 1000 400

Cr 21 1907 4.9 400 ~ 450 400

Aluminum, Copper SD Barrier Metal

11

S/D Mo Crack (FIB)

Mo 3500 at 0.2Pa Mo 3500 at 0.4Pa

Low Resistance 16.0k

100K

High Resistance 34.4k

80K

AlNd/Mo

SD Mo

Active G-SiN

AlNd/Mo

SD Mo

Active G-SiN

13

1. Sputter Film

2. Gate Al

3. S/D Al, Mo

4. Cu

5.

14

1) Cu

1. ,

Al 3.1ucm, Cu 2.3ucm :

Gate Al 3000, SD Al 4000 Gate Cu 2000, SD Cu 2700

2. ( total 5 4 )

Gate Al/Mo SD Mo/Al/Mo Gate Ti/Cu SD Ti/Cu

Pixel IZO

G-SiN

P-SiN

a-Si/n+

Al/Mo Ti/Cu

Ti/Cu MAM Pixel IZO

G-SiN

a-Si/n+

P-SiN

Glass Glass

15

16

Difficulties in Cu Film Process

1. Sputter Film

2. Gate Al

3. S/D Al, Mo

4. Cu

5. (TCO)

20

TCO (ITO InSnO3)

Display Applications Pixel electrode in Displays

Touch screen

21

*TCO (Transparent Conductive Oxide)

-Resistivity 90%

InO3 + Sn dopant One excess electron from Oxygen atom becomes free electron metal like Conductivity

a-ITO

Etch amorphous ( , ), Etch .

c-ITO ( , )

,

PI Cure . (210 15)

Ar + H2O ( H2) Gas Sputtering a-ITO

H+ OH- In-O-In-O-In

22

Metal

Pixel

(Etching) free

Gate-TCO, SD-TCO Contact

( 1E+04)

Depo Rate

IZO

ITO

a-ITO

AZO, GZO

Pixel .

1) Pixel

23

Sputtered TCO

()

ITO (In-Sn-O)

180~200 Cubic Bixbyite 90% (550nm ) 95% (550nm )

400~ 500 (As Depo)

Amorphous

IZO (In-Zn-O)

300~340 Amorphous

90% (550nm ) 85% (550nm )

2)

() ()

Cr 21.0 (12.9) 1875 CrOx/Cr, CrOxNy/Cr

Mo 11.5 (5.4) 2610 MoOx/Mo

Ni 50 (7.8) 1453 DC Sputter -> Ni alloy (NiW or NiCu)

3) Black Matrix

ITO (60,000X)

24

In2O3, ITO

ITO

ITO Film Hall ( = 1/nq)

(

cm

)

()

26

O2 ITO Film SEM (60,000)

(O2 Etch Rate )

O2 : 0.4 sccm O2 : 1.2 sccm O2 : 2.0 sccm

O2 ITO (SEM)

1237

ITO Vertical SEM

Glass

ITO

28

ITO IZO (200,2hr) RS

ITO RS . IZO RS .

29

Amorphous ITO

amorphous ITO (As Deposited)

230, 1,

32

Chemical Vapor Deposition (CVD)

1) Thermal CVD 2) Plasma-Enhanced CVD (PECVD) 3) ECR-CVD 4) Photo-CVD 5) Metal-Organic CVD (MOCVD)

33

[1.4.2] Thin Film Semiconductor and Insulators

CVD Process

PECVD (Plasma Enhanced Chemical Vapor Deposition)

: Plasma + + (300~350C)

LCD CVD Main

: , Process

34

a-Si PECVD Process

Plasma . ~350C

CVD

Plasma Energy, Gas mix, Gas Flow, Pressure Parameter

, Control

: High Cost of equipment, Uniformity Control

35

CVD Process (A Simple Model)

Main Gas Flow Region

Reactant gas, Carrier gas, By-product

Gas Phase Reaction

Transport to Surface

Surface Diffusion

Redesorption of Film Precursor

Transfer of by-products to main flow

Desorption of Volatile Surface

Reaction Products

Adsorption of Film Precursor Nucleation & Island Growth Step Growth

- Diffusion of gaseous reactants to the surface

- Adsorption of the reacting species on to surface sites

- Surface chemical reaction between the reactants

- Desorption of the reaction by-products

- Diffusion of the by-products away from the surface

36

RF power

Substrates Temperature

Chamber Pressure

Gas Flow Rate

Distance btw. Glass/Electrode

Process Parameters

a-Si : SiH4 + H2

n+ a-Si : SiH4 + H2 + PH3

SiNx : SiH4 + NH3 + H2

SiOx : SiH4 + N2O

(SiH4, NH3, N2, H2)

Process Gas In

Gas Out

Substrate

Plasma

H2 e-

SiH* SiH2* H+

NH3* SiNx

RF-Power

13.56MHz

Process Gas mix

Heater

PECVD in TFT Process

37

[1.7]

(Photolithography)

38

(Cleaning)

(Deposition)

(Photolithography)

(Etching)

(Test)

TFT Fab Flow

39

TFT Fab

41

(Cleaning)

Organic, Ionic contamination

Particle

Ion Na+

Brush scrubbing/Water jet/ Ultrasonic -- particle

dilute HF

Dry

UV/ Ozone/ Plasma cleaning

CLEAN

Rinse

UV

Excimer UV

O3

DI

Air Knife

chemical physical

(TMAH)

(HF)

BRUSH

Water Jet

Ultra

Sonic

(US/MS)

Particle

DI water

Step

Sub

Photo

Depo

DI

HF

TMAH

Brush

Photolithography

PR coating Align Exposure Develop Cleaning Photo mask Transfer

()

PR Coating

Align & Exposure

Develop

Hard-Bake

Inspection

Soft-Bake

Spin Coating

Pre-Bake

ADI

thin film

glass

Photo resist

glass

exposure

glass

light

mask

glass

glass

developer

film etching

Alignment mark

Etch

O.K. 43

M

Spin

Roll coater Spin coater Slit coater

44

Photo ?

Photo Resist

.

Pattern Mask

Pattern

.

Photo Photo

Photo resist

Positive PR ( -)

Negative PR ( )

UV

g-line (436nm) i- line (364nm)

Photo mask

Developer()

- Proximity aligner

- Stepper (lens projection type)

- Scanner (mirror projection projection)

Etching

- wet etching - dry etching