II. Chemical Vapor Deposition

II. Chemical Vapor Deposition

< Schematic diagram of MOCVD system >

 Ti-buffer layer 의 특성

 왜 Ti 를 adhesion layer 로 사용하는가 ?

 Ti-buffer layer 를 이용한 그래핀 전사시 wrinkle-free graphene Fabrication

 Ti-buffer layer 를 이용한 무 전사 및 저온 (100^oC 이하) 에서 그래핀 성장이 가능한가 ?

 그래핀을 이용한 진정한 N-doped and Boron-doped graphene TFT 는 가능한가 ?

 다양한 전자소자의 Flexibility and Stretchability 는 어느 정도인가 ?

2-5: CVD 응용예 : 그래핀의 무 전사 및 저온 성장

Principle of Nano Cluster Deposition (NCD)

@ At Showerhead Temperature of 200-300^oC

@ Source Vapor : Decompose, Reaction, and crystallized nano-cluster formation

@ The crystallized thin films at low temperature are deposited

@ Flexible substrates are possible From Conventional CVD

Oxide Thin Films Grown at Low Temperature by NCD

Jeon et al. Nanotechnology 19 (2008) 435305, US Patent registered.

Pammi et al. Scripta Materialia 61 (2009) 867

Bi₃NbO₇ Films at 50^oC ITO Films at 60^oC Previous Results by NCD

Sources

Bi(mmp)₃, Nb(NtAm)(NMe₂)₃ Substrate

Ni / Si substrate Concentration

0.05mol/L(hexane) Deposition temperature < 300^oC

System pressure 1 Torr

Vaporizer temperature 140 ^oC

Shower head temperature 250 ^oC

Precursor flow rate 0.05 ml / min Deposition time 1 hour

Deposition conditions

Measurement of electrical properties

Top electrode Thickness : 100nm Size : 100 x 100 (㎛) P-type Si

Bottom electrode : Ni(100nm) Deposited layer

Pt Pt

Deposition of Pt top electrode after photo lithography

Decomposition temperature : < 200^oC

Bi(mmp)₃ Nb(NtAm)(NMe₂)₃

Experimental Process of Bi₃NbO₇ Thin Films

SEM images at various deposition temperatures

T_dep. : No heating T_dep. : 100℃ T_dep. : 150℃

T_dep. : 200℃ T_dep. : 250℃ T_dep. : 300℃

Input ratio [ Bismuth(mol) / Niobium(mol) ] = 2

SEM Surface Image of BNO Thin Films grown at Various Temperatures

AFM images at various deposition temperatures

0 50 100 150 200 250 300 350 0

1 2 3 4 5

Deposition temperature (^oC)

rms roughness(nm)

T_dep. : 100℃

T_dep. : 200℃ T_dep. : 300℃

T_dep. : No heating

um

um um um

um um

um um

Å Å

Å Å

Input ratio [ Bismuth(mol) / Niobium(mol) ] = 2

RMS Roughness of the BNO Thin Films grown at Various Temp.

Particle size

= (0.9 x λ)/(FWHM x cos θ)

= 4.2 nm Scherrer formula:

30 40 50 60

0 20 40 60 80 100 120

2 Theta(degree)

Intensity(arb. units)

24 26 28 30 32 20

40 60

2 Theta(degree)

Intensity(arb. units)

Bi series

Si

Ni 30kV 60mA

3^o/min 40kV 100mA

1^o/min

XRD Patterns of BNO Thin Films grown at RT

BNO Ni

Si

100nm

Deposition temperature = No heating

Input ratio [ Bismuth(mol) / Niobium(mol) ] = 2

10nm

TEM Cross-Sectional and HRTEM Image

170 165 160 155 150 0

10000 20000 30000 40000 50000 60000 70000

Bulk Bi:Nb=2:1

Intensity (Arb. Units)

Binding Energy (eV)

220 215 210 205 200 195 190 10000

12000 14000 16000 18000 20000

Bulk Bi:Nb=2:1

Intensity (Arb. Units)

Binding Energy (eV)

540 535 530 525 520

20000 30000 40000 50000

Bulk Bi:Nb=2:1

Intensity (Arb. Units)

Binding Energy (eV)

Bi 4f Nb 3d

O 1s

4f_5/2

4f_7/2

3d_3/2 3d_5/2

1s

Si Ni BNO

NbLa

O Ka

BiMg NbLg BiMa

BiMz NbL

BiLl BiLa

BiLb

BiLb BiLg NbKa NbKb 2.00 6.00 10.00 14.00 18.00

50nm

Input ratio [ Bismuth(mol) / Niobium(mol) ] = 2 @ No heating

XPS spectra and EDS in BNO thin film

Deposition on trench structure

BNO PETEOS

51.0nm

84.4nm

200nm

1㎛ No heating

BNO _55.0nm

212.0nm

200nm

1㎛

53.0nm

80^oC

BNO

51.0nm

55.0nm

200nm

1㎛ 100^oC

BNO _43.2nm

47.1nm

200nm

1㎛ 150^oC

Step-Coverage of BNO Thin Films by NCD at Various Temperatures

Dielectric and leakage properties at various deposition temperatures

50 100 150 200 250 300 0

10 20 30 40 50 60 70 80 90 100

Deposition Temperature (^oC)

Dielectric constant

0.0 0.1 0.2 0.3 0.4 0.5

Dissipation factor

Deposition temp. for PCB : < 200℃

 Dielectric constant : 32~47

 Dissipation factor : 0.03~0.06

 Breakdown strength : 500~700kV/cm Deposition temperature

limit for PCB

-1000 -500 0 500 1000 10^-10

10^-8 10^-6 10^-4 10^-2 10⁰ 10² 10⁴ 10⁶

Applied Electric Field (kV/cm)

50^oC 150^oC 200^oC 250^oC 300^oC

Leakage Current Density (A/cm2 )

Dielectric and Leakage Properties of BNO Thin Films by NCD

ITO films Crystallized at ~ 60 ^oC

The crystallized ITO nano-

clusters with diameters ranging from 10-15 nm were embedded in the films.

Films deposited with out substrate heating (~ 60

oC) The selective area diffraction pattern (SADP) in Fig. (c) shows that the nano-clusters were clearly crystallized, and the films

deposited

at 60 ^oC were identified as an ITO phase based on the XPS spectra of each element.

SEM images of ITO Vs Deposition Temperature

240^OC

200^OC

220^OC 260^OC

180^OC

AFM images of ITO Vs Deposition temperature

260^OC 240^OC 220^OC

200^OC 180^OC

XRD Pattern & Grain Size of ITO thin films at Dep.

Temperature

Electrical Properties ITO - Deposition Temperature

Optical Properties of ITO - Deposition Temperature