Fig. 1-1 Phase diagram for CO

35

Fig. 1-1 Phase diagram for CO2.

Fig. 1-2 Density-pressure-temperature surface for pure CO2.

36

Table 1-1 Critical temperature and pressure for some common fluids.

Table 1-2 Comparison of physical properties of CO2.

37

Fig. 2-1 The supercritical fluid system.

High-pressure Syringe Pump B (Co-solvent)

Co-solvent Syringe CO2 Syringe

ReactionChamber

Manual Valve

Manual ValveHigh-pressure Syringe Pump A (CO2)

Valve B Valve A

Reaction Chamber

H2O Vapor

150℃

( b ) H2O-Vapor Treatment Process



ReactionChamber

Manual Valve


Valve B Valve A



ReactionChamber

Manual Valve


Valve B Valve A

Reaction ChamberReaction ChamberReaction Chamber

H2O VaporH2O Vapor

150℃

( b ) H2O-Vapor Treatment Process



ReactionChamber

Manual Valve


Valve B Valve A

Reaction ChamberMixture :90% SCCO210% Propyl Alcohol & H2O

SCC

O2 &

C

3 H7 O

H &

H2 OSCCO2

C3 H

7 OH

&

H2 O

150℃

( a ) SCCO2 Treatment Process



ReactionChamber

Manual Valve


Valve B Valve A



ReactionChamber

Manual Valve


Valve B Valve A

Reaction ChamberReaction ChamberReaction ChamberMixture :90% SCCO210% Propyl Alcohol & H2O

Mixture :90% SCCO210% Propyl Alcohol & H2O

SCC

O2 &

C

3 H7 O

H &

H2 O

SCC

O2 &

C

3 H7 O

H &

H2 OSCCO2

C3 H

7 OH

&

H2 O SCCO2SCCO2SCCO2

C3 H

7 OH

&

H2 O

150℃

( a ) SCCO2 Treatment Process

38

Fig. 2-2 The experiment processes of thin HfO2 film with various treatments.

Si wafer

HfO2, deposited by DC magnetron sputtering at room temperature under Ar/O2 ambient

1. Baking-only treatment: only baked on a hot plate at 150 °C for 2 hrs.2. H2O vapor treatment: immersed into a pure H2O vapor ambience at 150 °C for 2 hrs.3. 1500~3000psi-SCCO2 treatment: was placed in the supercritical fluid system at 150°C for 2 hrs.

Defect passivation process:

Analysis of Material:

Analysis of Electrical characteristics:1. current density-electric field (J-E) characteristics.2. capacitor-voltage (C-V) characteristics.3. breakdown voltage4. gate bias stress

Al metal, deposited by thermally evaporating

1. Fourier transformation infrared spectroscopy (FTIR).2. Thermal desorption spectroscopy (TDS).3. X-ray Photoelectron Spectroscopy (XPS).4. Auger Depth Profile (AES).5. Transmission Electron Microscopy (TEM).

Si wafer

HfO2, deposited by DC magnetron sputtering at room temperature under Ar/O2 ambient

1. Baking-only treatment: only baked on a hot plate at 150 °C for 2 hrs.2. H2O vapor treatment: immersed into a pure H2O vapor ambience at 150 °C for 2 hrs.3. 1500~3000psi-SCCO2 treatment: was placed in the supercritical fluid system at 150°C for 2 hrs.


Analysis of Material:

Analysis of Electrical characteristics:1. current density-electric field (J-E) characteristics.2. capacitor-voltage (C-V) characteristics.3. breakdown voltage4. gate bias stress


1. Fourier transformation infrared spectroscopy (FTIR).2. Thermal desorption spectroscopy (TDS).3. X-ray Photoelectron Spectroscopy (XPS).4. Auger Depth Profile (AES).5. Transmission Electron Microscopy (TEM).

39

Wavenumber (cm-1)

400 600 800 1000 1200 1400 1600 1800 2000

Inte

nsity

(ar

b. u

nits

)

Baking-only treatmentH2O vaper treatment3000 psi-SCCO2 treatment

509cm-1；HfO2

690cm-1；HfO2

1070cm-1；SiO2

Wavenumber (cm-1)

400 600 800 1000 1200 1400 1600 1800 2000

Inte

nsity

(ar

b. u

nits

)

Baking-only treatmentH2O vaper treatment3000 psi-SCCO2 treatment

509cm-1；HfO2

690cm-1；HfO2

1070cm-1；SiO2

Wavenumber (cm-1)

400 600 800 1000 1200 1400 1600 1800 2000

Inte

nsity

(arb

. uni

ts)

1500psi SCCO22000psi SCCO22500psi SCCO23000psi SCCO2

509cm-1；HfO2

690cm-1；HfO2

1070cm-1；SiO2

Wavenumber (cm-1)

400 600 800 1000 1200 1400 1600 1800 2000

Inte

nsity

(arb

. uni

ts)

1500psi SCCO22000psi SCCO22500psi SCCO23000psi SCCO2

509cm-1；HfO2

690cm-1；HfO2

1070cm-1；SiO2

( a )

( b ) Fig. 2-3 The FTIR spectra of HfO2 films (a) after various

post-treatments, including Baking-only, H2O vapor and

3000psi-SCCO2 treatment, (b) after SCCO2 treatment under

different pressure.

40

Fig. 2-4 The transporting mechanism for SCCO2 fluids taking H2O

molecule into HfO2 film.

Hf dangling bond

Driving into HfO2 film by SCCO2 fluids

Reaction with Hf dangling bond

CO2 molecule

propyl alcohol molecule

H2O molecule

Hf molecule

Oxygen molecule

attract H2O partattract CO2 part

HO – C – C – C –H

H

H

H

H H

H

Hf dangling bond

Driving into HfO2 film by SCCO2 fluids

Reaction with Hf dangling bond

CO2 molecule


H2O molecule

Hf molecule

Oxygen molecule


HO – C – C – C –H

H

H

H

H H

H

41

m/e = 18 (H2O)

Temperature (0C)200 400 600 800

Inte

nsity

(arb

. uni

ts)

Baking-onlyH2O vapor3000psi-SCCO2

(b)

m/e = 32 (O2)

Temperature (0C)200 400 600 800

Inte

nsity

(arb

. uni

ts)

Baking-onlyH2O vapor3000psi-SCCO2

(a)

Fig. 2-5 The thermal desorption spectroscopy (TDS) measurement, (a)

m/e (mass-to-charge ratio) = 32 peak that is attributed to O2,

(b) m/e = 18 peak that is attributed to H2O.

42

Baking-only treatment

Bonding energy (eV)

121416182022

Inte

nsity

Experiment curveFitting curveHf 4f7/2 in HfO2

Hf 4f5/2 in HfO2

Hf 4f5/2

Hf 4f7/2

( a )

H2O-vapor treatment

Bonding energy (eV)

121416182022

Inte

nsity


Hf 4f5/2 in HfO2

Hf 4f5/2

Hf 4f7/2

( b )

3000 psi-SCCO2 treatment

Bonding energy (eV)

121416182022

Inte

nsity


Hf 4f5/2 in HfO2

Hf 4f5/2

Hf 4f7/2

( c )


Bonding energy (eV)

121416182022

Inte

nsity


Hf 4f5/2 in HfO2

Hf 4f5/2

Hf 4f7/2

( a )


Bonding energy (eV)

121416182022

Inte

nsity


Hf 4f5/2 in HfO2

Hf 4f5/2

Hf 4f7/2


Bonding energy (eV)

121416182022

Inte

nsity


Hf 4f5/2 in HfO2

Hf 4f5/2

Hf 4f7/2

( a )

H2O-vapor treatment

Bonding energy (eV)

121416182022

Inte

nsity


Hf 4f5/2 in HfO2

Hf 4f5/2

Hf 4f7/2

( b )

H2O-vapor treatment

Bonding energy (eV)

121416182022

Inte

nsity


Hf 4f5/2 in HfO2

Hf 4f5/2

Hf 4f7/2

H2O-vapor treatment

Bonding energy (eV)

121416182022

Inte

nsity


Hf 4f5/2 in HfO2

Hf 4f5/2

Hf 4f7/2

( b )


Bonding energy (eV)

121416182022

Inte

nsity


Hf 4f5/2 in HfO2

Hf 4f5/2

Hf 4f7/2

( c )


Bonding energy (eV)

121416182022

Inte

nsity


Hf 4f5/2 in HfO2

Hf 4f5/2

Hf 4f7/2


Bonding energy (eV)

121416182022

Inte

nsity


Hf 4f5/2 in HfO2

Hf 4f5/2

Hf 4f7/2

( c )

Fig. 2-6 The X-ray photoemission spectra of HfO2 films Hf 4f after

various post-treatments, including (a) Baking-only, (b) H2O

vapor and (c) 3000psi-SCCO2 treatment.

43

H2O vapor treatment

Bonding energy (eV)

526528530532534536538540

Inte

nsity

Experiment curveFitting curveHf-OSi-O

Si-O

Hf-O


Bonding energy (eV)

526528530532534536538540

Inte

nsity


Si-O

Hf-O


Bonding energy (eV)

526528530532534536538540

Inte

nsity


Si-OHf-O

( a )

( b )

( c )

H2O vapor treatment

Bonding energy (eV)

526528530532534536538540

Inte

nsity


Si-O

Hf-O

H2O vapor treatment

Bonding energy (eV)

526528530532534536538540

Inte

nsity


Si-O

Hf-O


Bonding energy (eV)

526528530532534536538540

Inte

nsity


Si-O

Hf-O


Bonding energy (eV)

526528530532534536538540

Inte

nsity


Si-O

Hf-O


Bonding energy (eV)

526528530532534536538540

Inte

nsity


Si-OHf-O


Bonding energy (eV)

526528530532534536538540

Inte

nsity


Si-OHf-O

( a )

( b )

( c )

Fig. 2-7 The X-ray photoemission spectra of HfO2 films O 1s after

various post-treatments, including (a) Baking-only, (b) H2O

vapor and (c) 3000psi-SCCO2 treatment.

44

0 50 100 150 200 250 300 350 4000.0

0.5

1.0

1.5

2.0

2.5

3.0

MC

ount

s/eV

/Sec

Time (Seconds)

Hf MN2 Si KL1 C KL1 O KL1

3000psi-SCCO2

0 50 100 150 200 250 300 350 4000.0

0.5

1.0

1.5

2.0

2.5

3.0

MC

ount

s/eV

/Sec

Time (Seconds)


H2O Vapor

0 50 100 150 200 250 300 350 4000.0

0.5

1.0

1.5

2.0

2.5

3.0

MC

ount

s/eV

/Sec

Time (Seconds)


Baking-only

( a )

( b )

( c )

0 50 100 150 200 250 300 350 4000.0

0.5

1.0

1.5

2.0

2.5

3.0

MC

ount

s/eV

/Sec

Time (Seconds)


3000psi-SCCO2

0 50 100 150 200 250 300 350 4000.0

0.5

1.0

1.5

2.0

2.5

3.0

MC

ount

s/eV

/Sec

Time (Seconds)


3000psi-SCCO2

0 50 100 150 200 250 300 350 4000.0

0.5

1.0

1.5

2.0

2.5

3.0

MC

ount

s/eV

/Sec

Time (Seconds)


H2O Vapor

0 50 100 150 200 250 300 350 4000.0

0.5

1.0

1.5

2.0

2.5

3.0

MC

ount

s/eV

/Sec

Time (Seconds)


H2O Vapor

0 50 100 150 200 250 300 350 4000.0

0.5

1.0

1.5

2.0

2.5

3.0

MC

ount

s/eV

/Sec

Time (Seconds)


Baking-only

0 50 100 150 200 250 300 350 4000.0

0.5

1.0

1.5

2.0

2.5

3.0

MC

ount

s/eV

/Sec

Time (Seconds)


Baking-only

( a )

( b )

( c )

Fig. 2-8 Auger electron spectroscopy: (a) 3000psi-SCCO2 treatment (b)

H2O vapor treatment and (c) Baking-only treatment.

45

Fig. 2-9 The TEM images show the MIS (Al/HfO2/Si-Substrate)

structure after various post-treatments: (a) Baking-only

treatment (b) H2O vapor treatment and (c) 3000psi-SCCO2

treatment.

5 nm( a ) Baking-only

( b ) H2O vapor

( c ) 3000 psi-SCCO2

Si

HfO2, ~70 Å

Si

HfO2, ~66 Å

Si

HfO2, ~70 Å

SiOX, < 5 Å

SiOX, < 5 Å

SiOX, ~ 5 Å

5 nm

5 nm

5 nm5 nm( a ) Baking-only

( b ) H2O vapor

( c ) 3000 psi-SCCO2

Si

HfO2, ~70 Å

Si

HfO2, ~66 Å

Si

HfO2, ~70 Å

SiOX, < 5 Å

SiOX, < 5 Å

SiOX, ~ 5 Å

5 nm5 nm

5 nm5 nm

46

Electric field (MV/cm)0.0 0.5 1.0 1.5 2.0 2.5 3.0

J (A

mp.

/cm

2 )

10-9

10-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100 Baking-only treatmentH2O vapor treatment3000psi-SCCO2 treatment

Al HfO2 Silicon

e-

“+” bias common

Fowler-Nordheim tunneling

Schottky-Richardson emission

Frenkel-Poole emission

Al HfO2 Silicon

e-

“+” bias common

Fowler-Nordheim tunneling

Schottky-Richardson emission

Frenkel-Poole emission

Fig. 2-10 Conduction mechanism for Al/HfO2/Si MIS structure.

Fig. 2-11 The leakage current densities of HfO2 films after different

treatments. (The negative bias is applied on gate electrode)

47

E1/2 (MV/cm)1/20.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

ln(J

)

-18.5

-18.0

-17.5

-17.0

-16.5

-16.0

AlHfO2 Si

e- SiOx

common

“-” bias

(b)E1/2 (MV/cm)1/2

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

ln(J

)

-18.5

-18.0

-17.5

-17.0

-16.5

-16.0

AlHfO2 Si

e- SiOx

common

“-” biasAl

HfO2 Si

e- SiOx

common

“-” bias

(b)

Fig. 2-12 (a) Curve of ln (J/E) versus reciprocal of electric field (1/E)

for the baking-only treated HfO2 film, and a schematic

energy band diagram accounting for trap-assisted tunneling

shown in the inset. (b) Leakage current density versus the

square root of electric field (E1/2) plot for the 3000

psi-SCCO2 treated HfO2 film. The inset shows the energy

band diagram of Schottky-type conduction mechanism.

1/E (cm/MV)0 1 2 3 4 5

ln(J

/E2 )

-40

-38

-36

-34

-32

-30Eapplied > 0.7 MV/cm.

(a)

Al

HfO2Si

e-

“-” bias

common

SiOx

Al

HfO2Si

e-

“-” bias

common

SiOx

48


J (A

mp.

/cm

2 )

10-8

10-7

10-6

10-5

10-4

10-3

10-21500 psi-SCCO2 treatment2000 psi-SCCO2 treatment 2500 psi-SCCO2 treatment3000 psi-SCCO2 treatment

E1/2 (MV/cm)1/2

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

ln(J

/E)

-32

-30

-28

-26

-24

-22

-20 1500psi-SCCO2

2000psi-SCCO2

2500psi-SCCO2

3000psi-SCCO2

Al

HfO2 Si

“-” bias

common

SiOx

e-

E1/2 (MV/cm)1/2

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

ln(J

/E)

-32

-30

-28

-26

-24

-22

-20 1500psi-SCCO2

2000psi-SCCO2

2500psi-SCCO2

3000psi-SCCO2

Al

HfO2 Si

“-” bias

common

SiOx

e-

E1/2 (MV/cm)1/2

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

ln(J

/E)

-32

-30

-28

-26

-24

-22

-20 1500psi-SCCO2

2000psi-SCCO2

2500psi-SCCO2

3000psi-SCCO2

Al

HfO2 Si

“-” bias

common

SiOx

e-e-

( a )

( b )

Fig. 2-13 (a) The leakage current densities of HfO2 films after SCCO2

treatments under different pressures (The negative bias is

applied on gate electrode). (b) The plot of ln (J/E) versus E1/2,

which is according to Poole-Frenkel emission, and inset is

the energy band diagram of Poole-Frenkel emission.

49


J (A

mp.

/cm

2 )

10-9

10-8

10-7

10-6

10-5

10-4

10-3

10-2

Baking-only treatmentH2O vapor treatment3000 psi-SCCO2 treatment

AlHfO2 Si

“+” biascommon

SiOx

hole

e-

hole


J (A

mp.

/cm

2 )

10-9

10-8

10-7

10-6

10-5

10-4

10-3

10-2

Baking-only treatmentH2O vapor treatment3000 psi-SCCO2 treatment

AlHfO2 Si

“+” biascommon

SiOx

hole

e-

hole

AlHfO2 Si

“+” biascommon

SiOx

hole

e-

hole

VGS (Volt.)-6 -4 -2 0 2 4 6

Cap

acita

nce

(F)

0

1e-9

2e-9

3e-9

4e-9

5e-9

6e-9Baking-only, reverseBaking-only, forwardH2O vapor, reverseH2O vapor, forward3000 psi-SCCO2, reverse3000 psi-SCCO2, forwardΔV

1 MHz

Reverse

Forward

Fig. 2-14 The leakage current densities of HfO2 films after different

treatments (The positive bias is applied on gate electrode).

Inset plots the energy band diagram of leakage current.

Fig. 2-15 The capacitance-voltage characteristics of HfO2 films after

different treatment, measuring at 1M Hz with gate bias swing

from negative voltage to positive voltage (forward) and from

positive voltage to negative voltage (reverse).

50

Fig. 2-16 The mechanism of extracting of fixed charge with SCCO2 fluids.

-Removing negative charge by SCCO2 fluids

+Removing positive charge by SCCO2 fluids+

-

Dipole, which could attract negative/positive charge

Oxygen molecule

Hydrogen molecule

+-

Dipole, which could attract negative/positive charge

Oxygen molecule

Hydrogen molecule

CO2 molecule

H2O molecule


HO – C – C – C –H

H

H

H

H H

H


CO2 molecule

H2O molecule


HO – C – C – C –H

H

H

H

H H

H


51

Gate SiCdielectric

Cdepletion

Cit

Gate SiCdielectric Cdepletion

(a) (b)

Gate SiCdielectric

Cdepletion

Cit



(a) (b)

1M & 100K Hz (Forward)

VGS (Volt.)-6 -4 -2 0 2 4 6

Cap

acita

nce

(F)

0

1e-9

2e-9

3e-9

4e-9

5e-9

6e-9Baking-only, 1M HzBaking-only, 100K HzH2O vapor, 1M HzH2O vapor, 100K Hz3000 psi-SCCO2, 1M Hz3000 psi-SCCO2, 100K Hz

Fig. 2-17 The equivalent capacitance models of MOS structure (a)

without Cit, (b) with Cit.

Fig. 2-18 The capacitance-voltage characteristics of HfO2 films after

different treatment, measuring at 1M Hz and 100k Hz with

forward gate bias swing.

52

Vgs (volt.)0 20 40 60 80 100

J (A

mp.

/cm

2 )

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14 Baking-onlyH2O Vapor3000 psi-SCCO2

(b)

Vgs (volt.)-25 -20 -15 -10 -5 0

J (A

mp.

/cm

2 )

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14 Baking-onlyH2O Vapor3000 psi-SCCO2

(a)

Fig. 2-19 The breakdown characteristic curves of HfO2 films after

various treatments (a) at positive and (b) at negative gate

bias region, individually.

53

Stress voltage VGS = 5 Volt. ； E = 5 MV/cm

Time (sec.)0 200 400 600 800 1000

I/I0

1e-2

1e-1

1e+0

1e+1

1e+2

1e+3

1e+4

1e+5

1e+6

1e+7 Baking-only, I0 = 1.3 x 10-5 (A/cm2)H2O vapor, I0 = 1.2 x 10-5 (A/cm2)3000 psi-SCCO2, I0 = 6.2 x 10-7 (A/cm2)

18.0117.6617.50Hf 4f5/2

16.3716.0315.88Hf 4f7/2

Hf 4f

3000psi-SCCO2H2O-vaporBaking-only

Bonding energy

18.0117.6617.50Hf 4f5/2

16.3716.0315.88Hf 4f7/2

Hf 4f


Bonding energy

Fig. 2-20 The variation of leakage current of different-treated HfO2

films as a function of stress time at a high electric field = 5

MV/cm.

Table 2-1 Summary of binding energies for ultra thin HfO2 films Hf 4f

after various post-treatments, including Baking-only, H2O

vapor and 3000psi-SCCO2 treatment.

54

531.83531.64531.50Si-O

530.47530.18530.08Hf-OO 1S


Bonding energy

531.83531.64531.50Si-O

530.47530.18530.08Hf-OO 1S


Bonding energy

Table 2-2 Summary of binding energies for ultra thin HfO2 films O 1s

after various post-treatments, including Baking-only, H2O

vapor and 3000psi-SCCO2 treatment.

Table 2-3 The extracted parameters from C-V curves of HfO2 films

after different treatment, measuring at 1M Hz with gate bias

swing from negative voltage to positive voltage (forward).

The Vfb means the flat-band voltage, and defined as C/Cmax

= 80%. The change of flat-band voltage of different- treated

HfO2 films under forward swing is label as ∆V.

~ 00.10.9ΔV (volt.)0.1- 1.6- 3.2V0.5 (volt.), C/Cmax = 50%

29.424.820.4Dielectric const.

SCCO2-3000psiH2O vaporBaking-only

~ 00.10.9ΔV (volt.)0.1- 1.6- 3.2V0.5 (volt.), C/Cmax = 50%

29.424.820.4Dielectric const.

SCCO2-3000psiH2O vaporBaking-only

55

Fig. 3-1 The experiment processes of thin SiNX film with various treatments.

1. Baking-only treatment: only baked on a hot plate at 150 °C for 2 hrs.2. H2O vapor treatment: immersed into a pure H2O vapor ambience at 150 °C for 2 hrs.3. 3000psi-SCCO2 treatment: was placed in the supercritical fluid system at 150°C for 2 hrs.

Si wafer

SiNx ( 50nm ), deposited by PECVD at 300 0C


Analysis of Electrical characteristics:1. Current density-electric field (J-E) characteristics.2. Capacitor-voltage (C-V) characteristics.3. Breakdown voltage


Fourier transformation infrared spectroscopy (FTIR).

1. Baking-only treatment: only baked on a hot plate at 150 °C for 2 hrs.2. H2O vapor treatment: immersed into a pure H2O vapor ambience at 150 °C for 2 hrs.3. 3000psi-SCCO2 treatment: was placed in the supercritical fluid system at 150°C for 2 hrs.

Si wafer

SiNx ( 50nm ), deposited by PECVD at 300 0C


Analysis of Electrical characteristics:1. Current density-electric field (J-E) characteristics.2. Capacitor-voltage (C-V) characteristics.3. Breakdown voltage


Fourier transformation infrared spectroscopy (FTIR).

56

Wavenumber (cm-1)1000 2000 3000 4000

Abs

orba

nce

Baking-onlyH2O Vapor3000psi-SCCO2

850cm-1；Si-N

2180 cm-1；Si-H stretch3340 cm-1；N-H stretch

Wavenumber (cm-1)1000 2000 3000 4000

Abs

orba

nce

Baking-onlyH2O Vapor3000psi-SCCO2

850cm-1；Si-N

2180 cm-1；Si-H stretch3340 cm-1；N-H stretch

VGS (volt.)-10 -5 0 5 10

J (A

mp.

/cm

2 )

10-9

10-8

10-7

10-6Baking-onlyH2O vapor3000psi-SCCO2

Fig. 3-2 The FTIR spectra of SiNX films after various post-treatments,

including Baking-only, H2O vapor and 3000psi-SCCO2

treatment.

Fig. 3-3 The leakage current densities of SiNX films after different

treatments.

57

VGS (volt.)-100 -50 0 50 100

J (A

mp.

/cm

2 )

0

5

10

15

20Baking-onlyH2O vapor3000psi-SCCO2

Vgs (Volt.)-4 -2 0 2 4

Cap

acita

nce

(F)

0

2e-10

4e-10

6e-10Baking-only, forwardBaking-only, reverseH2O vapor, forwardH2O vapor, reverse3000psi-SCCO2, forward3000psi-SCCO2, reverse

1 MHz

Forward

Reverse

Vgs (Volt.)-4 -2 0 2 4

Cap

acita

nce

(F)

0

2e-10

4e-10

6e-10Baking-only, forwardBaking-only, reverseH2O vapor, forwardH2O vapor, reverse3000psi-SCCO2, forward3000psi-SCCO2, reverse

1 MHz

Forward

Reverse

Fig. 3-4 The breakdown characteristic curves of SiNX films after

various treatments.

Fig. 3-5 The capacitance-voltage characteristics of SiNX films after

different treatment, measuring at 1M Hz with gate bias swing

from negative voltage to positive voltage (forward) and from

positive voltage to negative voltage (reverse).

58

Fig. 3-6 The structure of a-Si:H TFTs.

Fig. 3-7 The experiment processes of a-Si:H TFTs with various treatments.

Glass

Cr

Al

a-Si ~1500Å

Gate~1500Å

SiNx ~ 3000Å

n+ a-Si~500ÅSource / Drain~3000Å

Front channel

Back channel

1. Baking-only treatment: only baked on a hot plate at 150 °C for 2 hrs.

2. 1500~3000psi-SCCO2 treatment: was placed in the supercritical fluid system at 150°C for 2 hrs.

Analysis of Electrical characteristics:1. The transfer and output characteristics of a-Si:H TFTs.

2. The transfer characteristics of TFT devices were measured at different temperatures (from 30 °C to 75 °C).


Glass

Cr

Al

a-Si ~1500Å

Gate~1500Å

SiNx ~ 3000Å


Glass

Cr

Al

a-Si ~1500Å

Gate~1500Å

SiNx ~ 3000Å


59

V DS = 0.1 volt.

V GS (volt.)-10 -5 0 5 10

NI D

S (A

mp.

)

10 -15

10-14

10-13

10-12

10-11

10-10

10-9

10-8

10-7

Before SCCO 2 treatm entAfter SCCO 2 treatm ent

0.271.22Vt (volt.)

0.821.05S.S

(volt./dec.)

0.320.30Mobility(cm2V-1s-1)

After treatment

Before treatment

0.271.22Vt (volt.)

0.821.05S.S

(volt./dec.)

0.320.30Mobility(cm2V-1s-1)

After treatment

Before treatment

(4)

(3) (2)

(1)

W / L= 20/10μm

VDS ( Volt.)0 5 10 15 20 25

I DS (

10-6

Am

p.)

0.0

0.2

0.4

0.6

0.8

Before SCCO2 treatmentAfter SCCO2 treatment

VGS = 10 V

VGS = 5 V

Fig. 3-8 The transfer characteristics of identical a-Si:H TFTs before and

after the SCCO2 treatment. The gate bias region (1), (2), (3),

(4) express sequentially above- threshold, forward

sub-threshold, reverse sub-threshold and Pool-Frenkel

emission region [47].

Fig. 3-9 The output characteristics of a-Si:H TFTs before and after SCCO2

treatment.

60

VGS (volt.)-10 -5 0 5 10

NID

(Am

p.)

10-15

10-14

10-13

10-12

10-11

10-10

10-9

10-8

10-7

300C400C500C600C

1/T0.0030 0.0031 0.0032 0.0033 0.0034

ln(N

I DS)

-28

-26

-24

-22

-20

-18

-16

VGS

VDS = 0.1 volt.

VGS (volt.)-4 -2 0 2 4

E act. =

EC -

E F (ev

)

0.0

0.2

0.4

0.6

0.8

1.0

1.2Before SCCO2 treatmentAfter SCCO2 treatment

Off-stateOn-state

EC

EV

EFEact. = EC - EF

Fig. 3-10 The transfer characteristics of SCCO2-treated TFT at

different temperature, in linear operation region with VDS =

0.1 V. Inset is the plot of ln(IDS) versus reciprocal of

temperature (1/T).

Fig. 3-11 The plot of activation energy versus gate bias, before and

after SCCO2 treatment. The inset shows the definition of

activation energy (Eact.).

61

Fig. 3-12 The density of states in mobility gap of a-Si:H film. (a) a-Si:H

TFT with no SCCO2 treatment before and after the hot

baking on a hot plate at 150 °C for 120 min, which taken as

the control sample. (b) a-Si:H TFT device before and after

SCCO2 treatment.

Ea = Ec - EF (eV)0.2 0.4 0.6 0.8 1.0

Den

sity

of s

tate

s (c

m-3

eV-1

)

1016

1017

1018

1019

Before baking-onlytreatmentAfter baking-onlytreatment

Ea = Ec - EF (eV)0.2 0.4 0.6 0.8 1.0

Before SCCO2 treatmentAfter SCCO2 treatment

(a) (b)

Tail-states

Deep-states

Tail-states

Deep-states

62

Fig. 4-1 The experiment processes of Memories with various treatments.

63

20 nm


20 nm20 nm20 nm


20 nm

3000psi-SCCO2 treatment

20 nm20 nm20 nm


VGS (Volt.)

-6 -4 -2 0 2 4 6

J (A

mp.

/ cm

2 )

1e-11

1e-10

1e-9

1e-8

1e-7

1e-6

1e-5

1e-4

1e-3

Baking-only treatment3000 psi-SCCO2 treatment

( a ) ( b )

Fig. 4-2 The TEM images show the Non-volatile Memories structure

after various post-treatments: (a) Baking-only treatment (b)

3000psi-SCCO2 treatment.

Fig. 4-3 The leakage current densities of Non-volatile Memories after

different treatments.

64

VGS (Volt.)-5 -4 -3 -2 -1 0 1

Cap

cita

nce

(F)

0.0

2.0e-10

4.0e-10

6.0e-10

8.0e-10

1.0e-9

1.2e-9

-1V to -3V-3V to -1V0V to -4V-4V to 0V1V to -5V-5V to 1V


Forward

Reverse

VGS (Volt.)-5 -4 -3 -2 -1 0 1

Cap

cita

nce

(F)

0.0

2.0e-10

4.0e-10

6.0e-10

8.0e-10

1.0e-9

1.2e-9



Forward

Reverse


VGS (Volt.)-5 -4 -3 -2 -1 0 1

Cap

cita

nce

(F)

0.0

2.0e-10

4.0e-10

6.0e-10

8.0e-10

1.0e-9

1.2e-9


Forward

Reverse


VGS (Volt.)-5 -4 -3 -2 -1 0 1

Cap

cita

nce

(F)

0.0

2.0e-10

4.0e-10

6.0e-10

8.0e-10

1.0e-9

1.2e-9


Forward

Reverse

( a )

( b )

Fig. 4-4 The capacitance-voltage hysteresis characteristics of

Non-volatile Memories after different treatment: (a)

Baking-only treatment (b) 3000psi-SCCO2 treatment.

.

65

Retention Time (sec)1 10 100 1000 10000

Vth

(V)

-2.40

-2.35

-2.30

-2.25

-2.20

-2.15

-2.10

Program +5VErase -5V

Retention Time (sec)1 10 100 1000 10000

Vth

(V)

-2.3

-2.2

-2.1

-2.0

-1.9

-1.8

-1.7

Program +5VErase -5V

( a )

( b ) Fig. 4-5 The retention characteristics of Non-volatile Memories after

different treatment: (a) Baking-only treatment (b)

3000psi-SCCO2 treatment.



66

Table 4-1 Summary of electrical Characteristics for Non-volatile

Memories after various post-treatments, including

Baking-only and 3000psi-SCCO2 treatment.

9.32E+04< 5Retention 20% Time ( Sec )

-12.5Decay Rate 1~1000 ( mV/dec )

P(+5V) / E(-5V)P(+5V) / E(-5V)Program / Erase ( V )

3000psi-SCCO2 treatmentBaking-only treatment

9.32E+04< 5Retention 20% Time ( Sec )

-12.5Decay Rate 1~1000 ( mV/dec )

P(+5V) / E(-5V)P(+5V) / E(-5V)Program / Erase ( V )

3000psi-SCCO2 treatmentBaking-only treatment

Documents

Fig. 1-1 Phase diagram for CO