Fritz Haber Institute of the Max Planck Society

- Department of inorganic chemistry -

Chemical Vapor Deposition

18.01.2013

Julian Tornow

Modern Methods in Heterogeneous Catalysis,

FHI Berlin

18.01.2013

Application of Chemical Vapor Deposition

Helmholtz Gemeinschaft

Thin film deposition for multiple applications

Wikipedia

IBM Corporation

Helmholtz Gemeinschaft

CATS communications

ionbond

What is a thin solid film?

Definition by thickness: < 1µm

Definition by properties: dominanted by surface properties

Definition by deposition: molecular bottom up growth (CVD or PVD)

Thin solid silicon film on graphite

(by chemical vapor deposition)

1 µm

5 µm

Thick solid silicon/carbon film

(by tape casting)

Chemical vs. Physical Vapor Deposition

Physical Vapor Deposition (PVD)

Atomar deposition using physical effects (high kinetic energy, condensation on surfaces).

target

plasma

HF

SputteringEvaporation

substrate

material

Advantages:

• codeposition

• low substrate temperature

• all mater can be deposited

substrate

plasma

www.wikipedia.de

sputteringevaporation

www.tf.uni-kiel.de/matwis/amat

Disadvantages:

• limited to 2D-deposition

• low surface selectivity

• low deposition rate

Precursor Gas

Chemical Vapor Deposition (CVD)

Atomar deposition by decomposition of a precursor on the substrate surface.

Chemical vs. Physical Vapor Deposition

www.future-fab.com www.tf.uni-kiel.de/matwis/amat

Advantages

• 3D-deposition

• surface selective deposition

Disadvantages

• high substrate temperature

• precursors not existing for every

element

• no codeposition

Typical CVD reactions

Pyrolysis (thermally activated decomposition)

SiH4 (g)→ Si (c) + 2H2 (g)

SiH2Cl2 (g) → Si (c) + 2HCl (g)

CH4 (g)→ C (graphite, diamond) + 2H2 (g)

Ni(CO)4 (g) → Ni (c) + 4CO (g)

Oxidation

SiH4 (g) + 2O2 (g) → SiO2 (c) + 2H2O (g)

3SiH (g) + 4NH (g) → Si N (c) + 12H (g)3SiH4 (g) + 4NH3 (g) → Si3N4 (c) + 12H2 (g)

Reduction

WF6 (g) + 3H2 (g) → W (c) +6HF (g)

SiHCl3 (g) + H2 (g) → Si (c) + 3HCl (g)

Hydrolysis

2AlCl3 (g) + 3H2O (g) → Al2O3 (c) + 6HCl (g)

Exchange

Ga(CH3)3 (g) + AsH3 (g) → GaAs (c) + 3CH4 (g)

Nucleation

Total interface energy

rArArAG γγγ 222 −+∝∆

SiH4 (g)→ SiH4 (p) → Si (c) + 2H2 (g)

Difficult nucleation if precursor-precursor bonding is stronger than

precursor-substrate-bonding → island growth, inhomogeneous coverage

siiikkI rArArAG γγγ 222 −+∝∆

Volume energy

molsatV V

rk

p

pRTG

3

ln⋅

−=∆

Stable nucleus if IV GG ∆>∆

M. Ohring; Academic Press 1992

Homogeneous and heterogeneous nucleation

Thin film growth modes

Franck van der Merve Stranski-Kastanov Vollmer-Weber

γs

γf

Modification of the subtrate

surface → change of γs and γi

Modification of reaction

Surf. Sci. Rep. 38 (2000) 195

sfi γγγ <+sfi γγγ +≥

γi

γs: substrate free surface

γf: film free surface

γi: substrate/film interface

Modification of reaction

pressure→ change of γf and γs

Temperature dependency of growth rate

Reaction limited regime

Typically Arrhenius behavior

=RT

EAR Aexp

Mass transport limited regime

Diffusion limited transport of

precursor to the reactive surface

Desorption regime

Desorption of deposited material or

alternative reaction pathwaysHitchman, M. et al; London academic press 1993

Constructing a CVD-reactor

Membrane

valves Filter 2

µm

Reaction gas premixing

Quarztube

Check valvesMass Flow

Controller

Graphitrohr

Coil

Inductive reaction furnace (1300 °C)SiH4

100%, or 10%, 1% in H2

Ar

H2

20-100 kHz

10-500 sccm

10-500 sccm

100-5000 sccm

O2

H2

bypass

Schematic flow diagram of a CVD-reactor

Pin: 3 bar

Pirani

0,1 – 1000 mbar

Pressure

controllerExhaust

gas

Exhaust

cleaningVacuum pump

65m3/h

cooling

trapCyclonC3H8

CH4

H2

100-5000 sccm

O2

Cl2

SiCl4

Bubbler

Reaction gas premixing

Mass flow controller (MFC)

Electronic

controller

MFM

Control valve

Gaswww.bronkhorst.de

www.bronkhorst.de

Membrane

valves Filter 2

µm

Reaction gas premixing

Quarztube

Check valvesMass Flow

Controller

Graphitrohr

Coil

Inductive reaction furnace (1300 °C)SiH4

100%, or 10%, 1% in H2

Ar

H2

20-100 kHz

10-500 sccm

10-500 sccm

100-5000 sccm

O2

H2

bypass

Schematic flow diagram of a CVD-reactor

Pin: 3 bar

Pirani

0,1 – 1000 mbar

Pressure

controllerExhaust

gas

Exhaust

cleaningVacuum pump

65m3/h

cooling

trapCyclonC3H8

CH4

H2

100-5000 sccm

O2

Cl2

SiCl4

Bubbler

Liquid precursor transport via bubbler

www.fluidat.com

satbub

satN

N

satNV pp

pQ

p

pQQ

−==

2

2

2

• saturation of carrier gas bubbles with precursor

• saturation within a few mm bubble distance

Mass flow of precursor QV:

→ AlternaGve to bubbler: Evaporator

(heating of tubes might be necessary)

STREM Chemicals

Bronkhorst

J. Vac. Sci. Technol: 19 (2001)329

Membrane

valves Filter 2

µm

Reaction gas premixing

Quarztube

Check valvesMass Flow

Controller

Coil

Inductive reaction furnace (1300 °C)SiH4

100%, or 10%, 1% in H2

Ar

H2

20-100 kHz

10-500 sccm

10-500 sccm

100-5000 sccm

O2

H2

bypass

Schematic flow diagram of a CVD-reactor

Pin: 3 bar

Pirani

0,1 – 1000 mbar

Pressure

controllerExhaust

gas

Exhaust

cleaningVacuum pump

65m3/h

cooling

trapCyclonC3H8

CH4

H2

100-5000 sccm

O2

Cl2

SiCl4

Bubbler

Reactor geometries

And several others…

Hitchman, M. et al; London academic press 1993

Classification of CVD processes

CVD

Thermal

CVD

Plasma

CVD

Photo

CVDCVI

Catalytic

CVDCVD CVD CVDCVI

CVD

APCVD

LPCVD

HTCVD

MTCVD

PECVD

DC CVD

RF CVD

MW CVD

Hot-wire

CNT

Classification of CVD processes

CVD

Thermal

CVD

Plasma

CVD

Photo

CVDCVI

Catalytic

CVDCVD CVD CVDCVI

CVD

APCVD

LPCVD

HTCVD

MTCVD

PECVD

DC CVD

RF CVD

MW CVD

Hot-wire

CNT

APCVD and LPCVD

Atmospheric pressure CVD (APCVD)

• high deposition rates

• reduced film conformity

Low pressure CVD (LPCVD)

• pressure 0.1-10 mbar

• homogeneous film deposition

• large amount of wafer loading (DKn > Dmol)

www.dowcorning.de

www.centrotherm.de

Hot wall vs. cold wall reactor

Hot wall reactor Cold wall reactor

• heating of the whole reactor tube

• good temperature control

• deposition on the tube wall

(esp. for endothermic reactions)

• Method: resistive

• heating only the sample or a susceptor

inside the reactor tube

• inhomogeneous temperature profile

• reaction only at sample (especially for

endothermic reactions)

• Methods: inductive, capacitive, IR,

Microwave

Classification of CVD processes

CVD

Thermal

CVD

Plasma

CVD

Photo

CVDCVI

Catalytic

CVDCVD CVD CVDCVI

CVD

APCVD

LPCVD

HTCVD

MTCVD

PECVD

DC CVD

RF CVD

MW CVD

Hot-wire

CNT

Plasma enhanced CVD

www.spiegel.de

Mixture of molecules, ions, radicals and electrons

www.spiegel.de

• activation of precursor by plasma

• lowering of the substrate temperature

• possible substrate damage

• plasma ignition:

• DC

• RF

• MW

www.wikipedia.de

Plasma enhanced CVD

Classification of CVD processes

CVD

Thermal

CVD

Plasma

CVD

Photo

CVDCVI

Catalytic

CVDCVD CVD CVDCVI

CVD

APCVD

LPCVD

HTCVD

MTCVD

DC CVD

RF CVD

MW CVD

Hot-wire

CNT

Photo CVD

Laser assisted CVD

→ photoactivation of precursor

→ local heaGng of substrate resulGng in

local deposition

Low deposition rate, allows or 3D-structuring

laser.gist.ac.kr

laser.gist.ac.kr

Repair of integrated circuit by Laser CVD

Classification of CVD processes

CVD

Thermal

CVD

Plasma

CVD

Photo

CVDCVI

Catalytic

CVDCVD CVD CVDCVI

CVD

APCVD

LPCVD

HTCVD

MTCVD

PECVD

DC CVD

RF CVD

MW CVD

Hot-wire

CNT

Cracking precursor bonds on hot catalyst.

Thin film deposition

(decrease substarte temperature)Growing Carbon nanotubes

Catalytic CVD

J. Nanosci. Nanotechnol. 10 (2010)3739

Classification of CVD processes

CVD

Thermal

CVD

Plasma

CVD

Photo

CVDCVI

Catalytic

CVDCVD CVD CVDCVI

CVD

APCVD

LPCVD

HTCVD

MTCVD

PECVD

DC CVD

RF CVD

MW CVD

Hot-wire

CNT

Chemical Vapor Infiltration

Deposition on porous substrates

Problem: closing of the pores

Solution I: optimized reaction rate – e.g. the rate of SiCl4 depostion can be

adjusted by the Cl/H-ratio.

Solution II: Intermittent growth by ALD or TPCVD

Problem: Inhomogeneities by temperature- or concentration gradients

Solution: Use of mass transport limited regime (→hohe T),

! Conflit with pore closing!

J. Mater. Chem. 3 (1993) 1307 J. Crystal Growth 31 (1975) 299

Deposition methods

Fixed bed reactor

- Inhomogeneities

- scalable (defined conditions)

- not suitable for powders → usage of porous materials

- simple set-up

Fixed bed vs. fluidized bed reactors

Fluidized bed reactor

- Homogeneous deposition

- non scalable

- not suitable for powders

Werther, J.; Fluidized-Bed Reactors, in Ullman‘s Enzeklopedie 2002,

Membrane

valves Filter 2

µm

Reaction gas premixing

Quarztube

Check valvesMass Flow

Controller

Coil

Inductive reaction furnace (1300 °C)SiH4

100%, or 10%, 1% in H2

Ar

H2

20-100 kHz

10-500 sccm

10-500 sccm

100-5000 sccm

O2

H2

bypass

Schematic flow diagram of a CVD-reactor

Pin: 3 bar

Pirani

0,1 – 1000 mbar

Pressure

controllerExhaust

gas

Exhaust

cleaningVacuum pump

65m3/h

cooling

trapCyclonC3H8

CH4

H2

100-5000 sccm

O2

Cl2

SiCl4

Bubbler

Traps for particles and chemicals

Particle traps

• Filters

• Dust-Trap

• Cyclones

Filtering particles and corrosive chemicals to protect the pump.

Chemical traps

• Absorption solids (e.g. zeolites)

• cooling traps (temperature controled)

Cooling trap for temperatures from 77-273K

Membrane

valves Filter 2

µm

Reaction gas premixing

Quarztube

Check valvesMass Flow

Controller

Coil

Inductive reaction furnace (1300 °C)SiH4

100%, or 10%, 1% in H2

Ar

H2

20-100 kHz

10-500 sccm

10-500 sccm

100-5000 sccm

O2

H2

bypass

Schematic flow diagram of a CVD-reactor

Pin: 3 bar

Baratron

0,1 – 1000 mbar

Pressure

controllerExhaust

gas

Exhaust

cleaningVacuum pump

65m3/h

cooling

trapCyclonC3H8

CH4

H2

100-5000 sccm

O2

Cl2

SiCl4

Bubbler

Vacuum system

Vacuum pump

Scroll pump or rotary vane pump

reactor QaQz

Qeff p

p

QS a=Pumping speed:

p

Steady state:

0=−⋅=−= zzaeff QpSQQQ

p

QS z=⇒

Example: for Qz=5 l/min and p=10 mbar

S = 30 m3/h

Pump needs to be leak tight and or explosive

media fulfill ATEX-regulations

Pressure controller

• PID controlled throttle valve

• pressure gauge

• resistive (gas dependent)

• capacitive (independent of gas)

Membrane

valves Filter 2

µm

Reaction gas premixing

Quarztube

Check valvesMass Flow

Controller

Coil

Inductive reaction furnace (1300 °C)SiH4

100%, or 10%, 1% in H2

Ar

H2

20-100 kHz

10-500 sccm

10-500 sccm

100-5000 sccm

O2

H2

bypass

Schematic flow diagram of a CVD-reactor

Pin: 3 bar

Baratron

0,1 – 1000 mbar

Pressure

controllerExhaust

gas

Exhaust

cleaningVacuum pump

65m3/h

cooling

trapCyclonC3H8

CH4

H2

100-5000 sccm

O2

Cl2

SiCl4

Bubbler

Removing environmentally pollutant, corrosive or explosive

gases from the exhaust .

• Gaswashers (comparable to wash bottle, but bigger)

• Gasburner

• Dry bed absorber

Exhaust gas treatment

• Combined systems

Construction plan of reactor (CAD)

Scrubber

Electronics & induction generator Safety gas monitoring

CVD-Reactor

Inductively

heated cold wall

reactor

Gas mixing chamber Reaction chamberVacuum pump

Computer

reactor

Precursors:

SiH4, SiHCl3, SiCl4,

CH4

Temperature:

350-1500 °C

Pressure:

5-1000 mbar

Flange with pressure head Pyrometer

Quarz

tube

Sample

Reaction chamber

Modes of deposition

CVD

Sample

Quarz

frit

Inductor

ALD

TPCVD

2µm2µm

500 nm

Pristine Si-CVD

Characterisation of CVD-Si/C

EDX

Further analysis of the interface

(Si-C-contact, SiOx-formation):

→ TEM, XPS, FTIR

Variaion of the deposition parameters:

→ pressure, temperature, concentraGon

Deposition at porous structures:

→ increase the amount of acGve material

Pressure variation in Si-CVD process

70 mbar 50 mbar

30 mbar 10 mbar

900 °C 1100 °C1000 °C

Temperature variation in Si-CVD process

1200 °C

EDX FTIR

Stuctural analysis of deposited films

O EFTEM Si EFTEM

TEM (Si@1100°C A)ATR-FTIR

XPS

Si@1100°C A Si@1100°C B Si@1100°C C

Stuctural analysis of deposited films

Si@1100°C A Si@1100°C B Si@1100°C C

XPS (continuation)

Si-CVD on titanium foil

TiCl3

• Deposition of Si at around 1020°C

• Formation of solid solution from

β-Ti and Ti3Si at hot zone?

• Etching of Ti foil by

HCl forming TiCl31144°C→1000°C

Si?

β -Ti

Foil thickness: 0.5 mm

R. J. Nemanich et al., Reactions of thin film titanium on silicon studied by Raman spectroscopy, Appl. Phys. Lett. 46, 670 (1985)

D.P. Riley, Synthesis and characterization of SHS bonded Ti5Si3 on Ti substrates, Intermetallics, 14, 770–775, 2006

β-Ti

Pristine coal

Gas C 94,00Si 2,92Fe 1,45

C 94,3Al 1,81Si 1,51Fe 1,26Ca 0,40Mg 0,27S 0,26Ti 0,14

Si-CVD on activated carbon (Epibon)

C 93,20Si 3,72Fe 1,19Al 1,08Cl 0,31Ca 0,18Ti 0,11S 0,08

Fe 1,45Al 1,20Ti 0,16Cl 0,12Ca 0,09P 0,04S 0,03

Si-CVD on carbon foam

Gas

Pristine foam

Si(A) 1,06

Si(B) 0,57

A

Gas

Si(C) 0,42

Si(D) 0,39

Si(E) 0,40

Si(F) 0,52

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