astral research group at lappeenranta university of technology
DESCRIPTION
Presentation of thin film ALD research done in ASTRaL laboratory at Lappeenranta University of Technology's campus in Mikkeli, FinlandTRANSCRIPT
ASTRAL
• Advanced Surface Technology Reseach Group
• A material science research group at Lappeenranta University of
Technology
• Located in Mikkeli, Finland
Main research areas
Thin film deposition techniques and
applications, particularly for nanoscale
structures:
Atomic Layer Deposition (ALD)
• Conformality
• Uniformity
• Thickness control
• Hermeticity
• Ability to form nanolaminates
ALD – Atomic Layer Deposition
Atomically precise control of material layer
thickness, composition and structure
ALD – Atomic Layer Deposition
Chemical vapor deposition method with sequential self-limiting gas-
solids reactions
First atomic layer onto substrate is formed by chemisorption (in ideal
case), second layer with chemical reaction
Materials are built up one atomic layer at a time (cycle)
(In practice, due to the size of the molecules (steric hindrance), less
than 1 mono layer may be formed at a time)
Schematic of ALD Reactor
Al2O3 ALD – Model ALD system
Chemisorption of the first precursor onto the substrate
Substrate
O
H
O O
H
O O
H
Al
H
C H
H
H
C H
H Al
H
C H
H
H
C H
H
H
C H
H H
H
C H
H H
reaction products CH4
(A) AlOH * + Al(CH3)3 AlOAl(CH3)2* + CH4
Al2O3 ALD – Model ALD system
Inert gas purge to remove the excess of reaction products and unreacted
precursor
Substrate
O
Al
H
C H
H
H
C H
H
O
Al
H
C H
H
H
C H
H
H
C H
H H
H
C H
H H
Excess TMA
Passivated surface
O
Al
H
C H
H
H
C H
H
O
Al
H
C H
H
H
C H
H
O
Al
H
C H
H
H
C H
H
Al
H
C H
H
H
C H
H
H C
H
H
reaction products CH4
Purge after TMA pulse
(A) AlOH * + Al(CH3)3 AlOAl(CH3)2* + CH4
Al2O3 ALD – Model ALD system
Introduction of the second precursor
H2O pulse
Substrate
O
Al
H
C H
H
H
C H
H
O
Al
H
C H
H
H
C H
H
O
Al
H
C H
H
H
C H
H
O
Al
H
C H
H
H
C H
H
O
Al
H
C H
H
H
C H
H
O
H H
(B) AlCH3 * + H20 Al2OH * + CH4
Al2O3 ALD – Model ALD system
Surface reactions to produce desired film material
Substrate
O
Al
H
C H
H
H
C H
H
O
Al
H
H
C H
H
Al(CH3)3 + OH
O
Al
H
C H
H
H
C H
H
O
Al
O
Al
H
C H
H
H
C H
H
reation products CH4
O O
H
C H
H H
H
C H
H H
H
C H
H H
(B) AlCH3 * + H20 Al2OH * + CH4
Al2O3 ALD – Model ALD system
Self limiting growth of the film through surface passivation
Substrate
One atomic layer of
passivated surface
reaction products CH4
O
Al
O
Al
H
O O
H
O O
O
Al
O
Al
H
O O
H
O O O
O
Al
H
O O
H
C H
H H
H
C H
H H
H
C H
H H
H
C H
H H
H
C H
H H
Purge after H2O pulse
H
C H
H H
(B) AlCH3 * + H20 Al2OH * + CH4
Al2O3 ALD – Model ALD system
Process cycle repeated to reach required thickness
Substrate
O
Al
O
Al
O O
O O
O
Al
O
Al
O O
O O O
O
Al
O O O
Al Al
O
Al Al
O O
Al
O O O O O O
O
Al Al
O
Al Al
O O
Al
O O O O O O
O
H H
Al Al
O
Al Al
O O
Al
O
H H
O
H
2 Al(CH3)3 + 3 H20 Al2O3 + 6 CH4
Growth rate for Al2O3
1Å/Cycle
Batch system cycle
Precursor A
Precursor B
Purge
Purge
A
Purge
B
Purge
• Stationary substrate
• Sequential exposure
• Time sequenced gas pulses
Batch ALD systems
Beneq TFS500 • Batch system • Includes plasma chamber
(plasma chamber configuration was an ASTRaL design)
ASM F120 Beneq TFS200 (plasma ALD)
Spatial ALD
separate gas zones
A B purge
exhaust
purge purge
moving substrate
A purge B purge
Spatial ALD
flexible substrate coating head
Beneq TFS200R
ALD research in Mikkeli
Diffusion barrier layers on flexible substrates
• roll-to-roll ALD research
• water vapour and oxygen barriers
• paper-based packaging
• photovoltaic cells and organic light emitting diodes
Photocatalytic materials
• titanium dioxide, doped, structural investigations of crystal growth and activation
• water and air purification
Bioactive materials
• biocidal coatings
• antibacterial surfaces
• control of time profile of antibacterial release
• zinc oxide and zinc oxide-based nanolaminates
ALD research in Mikkeli
Surface functionalisation
• hydrophilic and hydrophobic surfaces
Polymer layers
• molecular layer deposition of PET
Sensor materials
• tin oxide gas sensors
Optoelectronic materials
• zinc oxide
• copper chloride
Process development
Summary
• Focus on atomic layer deposition
• Process, materials and applications research
• Unique facility for roll-to-roll ALD
• Open for collaboration
www.astral.fi
Contact Details
Project Coordinator
JANNE KEKÄLÄINEN
GSM +358 50 344 9494
http://www.linkedin.com/in/jannekekalainen
http://twitter.com/JanneKekalainen
_____________________________________
LAPPEENRANTA UNIVERSITY OF TECHNOLOGY
ASTRaL - Advanced Surface Technology Research Laboratory
Sammonkatu 12, FI-50130 Mikkeli, Finland
http://www.astral.fi/