nicola pinna atomic layer deposition 130118

8/10/2019 Nicola Pinna Atomic Layer Deposition 130118

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Atomic Layer Deposition

Nicola Pinna

Humboldt-Universitt zu Berlin, Institut fr Chemie, Brook-Taylor-Str. 2, 12489Berlin, Germany

E-mail: [email protected]


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Outline of the Presentation

1. Literature2. Introduction to Atomic Layer Deposition

3. Chemistry in ALD

4. ALD Reactors

5. Nanostructures

6. Applications


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Progress and future directions for

atomic layer deposition and ALD-based

chemistry. This issue of MRS Bulletin

details current progress in atomic layer

deposition, including the extension of ALDto new regions of the periodic table, and

molecular layer deposition and vapor in

filtration for synthesis of organic based thin

films. The cover image shows a diagram of

an ALD reaction schemea snapshot of the

reactants and products as they would be

flowing from left to right. This is a general,

stylized ALD reaction scheme to visualize

surface ligand exchange. The backgroundis a scanning electron microscopy image of

2 nm ALD-deposited Pt nanoparticles

uniformly dispersed on strontium titanate

nanocubes.

MRS Bulletin / Volume 36 / Issue 11 / November 2011, pp 899-906


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Atomic Layer Deposition

ALD is a method for depositing thin films onto various substrates withatomic scale precision.

The principle is similar to chemical vapor deposition (CVD), except thatthe ALD reactions are separated into two half-reactions by keeping the

precursor materials separate during the reaction.

ALD film growth is self-limited and based on surface reactions.Therefore, film thickness control can be as fine as one monolayer.


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N. Pinna | 18.01.2013Riikka L. Puurunen, J. Appl. Phys., 2005, 97, 121301


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Short History

1970s - The ALD technology was developed in Finland and patented.Technology for thin films electroluminescent (TFEL) flat panel display.Suntola, T. and Antson, J., Method for producing compound thin films, USPatent 4 058 430 (1977).At that time the technique was called Atomic Layer Epitaxy (ALE)

TFEL displays commercialized in 1980 were based on ALDAl2O3/ZnS:Mn/Al2O3 structures

Ein Flughafendisplay, dessen elektrolumineszenteBeschichtung durch das ALD-Verfahren hergestellt

wurde. Das Verfahren wurde fr diesen Zweck Endeder siebziger Jahre entwickelt.

Source: http://www.weltderphysik.de/gebiete/stoffe/duenne-schichten-und-oberflaechen/atomic-layer-deposition/

Source: http://lumineq.com/en/technology


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Short History

Mid-1980s to the mid-1990s - The ALD research was extremely active onthe epitaxial growth of III-V, II-VI, Si and Ge semiconductors

Beginning of the 21th-century- Microelectronic industry drives thedevelopment of the ALD due to the continuous scaling of microelectronicdevices1st application: ALD of Al2O3 insulating layers in DRAM capacitors due tothe need of rather thin and conformal coating of high aspect ratio

structures2007: Intel announces the use of HfO2-based high- gate oxides in CMOStransistors ALD


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Intel in 2007 introduced ALD of Hf-based oxide in 45 nm technology


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N. Pinna | 18.01.2013http://nano.tkk.fi/en/research_groups/microfabrication/research/microfabrication/


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Introduction to the Chemistry Employed in ALD

Oxides: Hydrolysis-Condensations Oxygen sources (H2O, H2O2, O3,...)

Nitrides: Aminolysis (e.g. NH3)

Sulfides: Sulfur, Hydrogen sulfide

Metals: O

2, H

2, etc.

Requirements for the precursors: Reasonably high vapor pressure in order to allow saturation of the chambervolume upon dosing Good thermal stability to avoid decomposition prior to the next step Must chemisorb onto the substrate to be coated


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Metal Precursors

M. Putkonen, Chapter 3: Precursors for ALD Processes


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Basic hydrolysis of alkoxysilanes (SN2)

Acid hydrolysis of alkoxysilanes (proton assisted SN1)


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Polycondensation


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Silica Growth in ALD: Base Catalyzed


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Silica Growth by ALD: Self-Catalyzed

a) Anchoring: surface hydroxygroups cleave Si-OEt bonds ofthe silane under self-catalysis bythe pendent amino group (green),causing chemisorption

b) Hydrolysis: remaining ethoxygroups are removed self-catalytically

c) Oxidation: the aminoalkyl armis removed by ozone


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Platinum thin films were grown at 300 C by atomic layer deposition (ALD) using(methylcyclopentadienyl)trimethylplatinum (MeCpPtMe3) and oxygen as precursors. Thefilms had excellent uniformity, low resistivity, and low-impurity contents.


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Plasma-enhanced ALD


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Plasma-enhanced ALD


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Molecular Layer Deposition

Illustration of surface chemistry forPPTA MLD using terephthaloyl chlorideand p-phenylenediamine as reactants.

S.M. George, B. Yoon, A.A. Dameron; Acc. Chem. Res. 2009, 42, 498-508.

Illustration of surface chemistry forpoly(aluminum ethylene glycol) aluconeMLD using TMA and EG as reactants.


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1. Nonhydrolytic Hydroxylation Reactions(Formation of M-OH species)

Reaction of alcohols with metal halides:

1) Coordination of the alcohol to the metal centre

2) a) Formation of metal alkoxide under elimination of HX

b) Formation of hydroxyl group and elimination of alkyl halide RX(if R is an electron-donor substituent, the nucleophilic attack ofthe chloride on the carbon group is favored)

A. Vioux: Chem. Mater. 1997, 9, 2292-2299

Nonaqueous Sol-Gel Routes to Oxides


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Aprotic Condensation Reactions

(M-O-M Bond Formation)

A. Vioux: Chem. Mater. 1997, 9, 2292-2299

Reaction between two metal alkoxides under ether elimination

Reaction between metal acetates and metal alkoxides under ester elimination

Reaction between metal alkoxides and metal halides under alkyl halide elimination

Nonaqueous Sol-Gel Routes to Oxides


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Alkyl Halide Elimination


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M-OR + RCOOH M-OOCR + ROH Eq. 1

M-OOCR + M-OR

M-O-M

+ RCOOR Eq. 2

Non-Aqueous Sol-Gel Routes Applied to ALD

Angew. Chem. Int. Ed. 2008, 47, 3592 - J. Phys. Chem. C 2008, 112, 12754,J. Mater. Chem. 2009, 19, 454 - Adv. Funct. Mater. 2011, 21, 658Patent WO 2008 098963 A2

Low oxidative character of carboxylic acids Large deposition temperature range

High quality and purity of the films No OH groups involved in the M-O-M bond formation

Metal Precursors: Hf(OtBu)4, Ti(OiPr)4, VO(OPr)3, Sn(OtBu)4 Oxygen Sources: Carboxylic acids e.g. acetic acid Deposition temperature: 50 350 C


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3rd TIP 2nd Ac.

3rd Ac. 3rd TIP

Ti-OCCD3

SiH

CH

10001500200025003000 Wavenumbers (cm-1)

COO

3rd cycle

14th cycle

Difference FT-IR spectra

14th TIP 13th Ac.

14th Ac. 14th TIP


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TiO2

Self-limiting growth!


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ALD Reactors

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Compact Reactors


B h


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Various types of typical ALD reactor systems. a) Cross-flow reactorsystem based on forced flow laterally across the wafer. b) systemwith single injector above the center of the wafer. c) shower headsystem; gas is injected through an array of injectors covering theentire wafer surface. d) Vertical batch reactor: 50150 wafers areprocessed simultaneously.

Batch Reactors

E. Granneman, P. Fischer, D. Pierreux, H. Terhorst, P. Zagwijn, Surf.Coatings Technol. 2007, 201, 8899

Copyrighted Content

Removed


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J. Meyer and T. Riedl. Chapter 6: Low-Temperature Atomic Layer Deposition


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Fluidized bed reactor Rotary reactor


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Fabrication of Nanostructures


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Nature Mater. 2006, 5, 627.


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Conformal coating of carbon nanotubes


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HfO2TiO2

VOx

Carbon nanotube

TiO2

VOx

SEM images recorded at

different accelerationvoltages using SE and BSEdetectors prove that thetubes are coated on the in-and outside surfaces.

Characterization:SEM

Nano Lett. 2008, 8, 4201 - Phys. Chem. Chem. Phys. 2009, 11, 3615 - Adv. Funct. Mater. 2011, 21, 658

Conformal coating of carbon nanotubes


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Characterization:HRTEM

High resolution imagingshows the amorphous

character of the asdeposited films.However, in the case ofVxOy films, annealing at150C induces

crystallization (V2O5).

HfO2 TiO2

VOx VOx after annealing @ 150C

Chemical Analysis


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Characterization: Electron Energy Loss Spectrometry (EELS)

Chemical Analysis

Effect of the CNTs functionalization


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J. Mater. Chem. 2012, 22, 7323



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J. Mater. Chem. 2012, 22, 7323

Applications in Energy Related Fields


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pp gy


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Gas Sensors


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3 mm

6mm

3 mm

6mm

Front sidegold electrodes

Back sideplatinum contacts

Cross section

0.3

8

mm

Alumina substrate

Sensing layer

50 m

Angew. Chem. Int. Ed. 2004, 43, 4345


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N. Pinna | 18.01.2013Nano Lett. 2008, 8, 4201 - Phys. Chem. Chem. Phys. 2009, 11, 3615 - Adv. Funct. Mater. 2011, 21, 658

SnO2 coated CNTs


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0 1000 2000 3000

40

42

44

46 a)

Time (sec)

Resistance()

NO2in

NO2out

Pure CNTs are p-type semi-conductors SnO2 coated CNTs are n-type semiconductors

formation of a p-n heterojunctionbetween the metal oxide film and support

Nano Lett. 2008, 8, 4201 - Adv. Funct. Mater. 2011, 21, 658

0 200 400 600 80010

4

10

5

Resistance

()

Time (sec)

5 ppm NO2

NO2 in

NO2 out


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Oxidative dehydrogenation of ethane toethylene at 650 C

SCIENCE, 2012, 335,1205


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N. Pinna | 18.01.2013NATURE CHEMISTRY, 2012, 4, 1031

nicola pinna atomic layer deposition 130118

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