In situ Studies of ALD Processes & Reaction Mechanisms Erwin Kessels [email protected] www.tue.nl/pmp
This tutorial presentation will give …(1) an overview of methods for in situ studies of ALD processes &
reaction mechanisms; and(2) some insight into these processes and mechanisms
Don’t expect:• A comprehensive overview• Techniques explained in large detail
Do expect:• Focus on what can be learned from the methods• Their pros and cons articulated & practical comments• An overview based mainly from own experience
Department of Applied Physics – Erwin Kessels
For more information & feedbacksee blog:
www.AtomicLimits.com
Atomic layer deposition (ALD)
Department of Applied Physics – Erwin Kessels
A B A Bt In situ studies:
• Quartz crystal microbalance• Spectroscopic ellipsometry• Mass spectrometry• Gas phase infrared spect.• Surface infrared spect.• Optical emission spect.• X-ray photoelectron spect.• X-ray diffraction• Sum-frequency generation• Adsorption calorimetry• Scanning tunneling micros.• …
In situ studies of ALD processes
Department of Applied Physics – Erwin Kessels
• Quartz crystal microbalance• Spectroscopic ellipsometry• Mass spectrometry• Gas phase infrared spect.• Surface infrared spect.• Optical emission spect.
• X-ray photoelectron spect.• X-ray diffraction• Sum-frequency generation• Adsorption calorimetry• Scanning tunneling micros.• …
Discussed today:
In situ studies of ALD processes
Department of Applied Physics – Erwin Kessels
• Quartz crystal microbalance• Spectroscopic ellipsometry• Mass spectrometry• Gas phase infrared spect.• Surface infrared spect.• Optical emission spect.
• X-ray photoelectron spect.• X-ray diffraction• Sum-frequency generation• Adsorption calorimetry• Scanning tunneling micros.• …
Discussed today:
Monitoring (linear) film growth
Department of Applied Physics – Erwin Kessels
0 50 100 150 200 250 3000
10
20
30
40(a)
Al2O3
Ta2O5
TiO2
Film
thick
ness
(nm
)
Elam et al., Rev. Sci. Instr. 73, 2981 (2002).Langereis et al., J. Phys. D: Appl. Phys. 42, 073001 (2009).
EllipsometryQCM
Al2O3
Al2O3: 1.1 ÅTa2O5: 0.8 ÅTiO2: 0.04 Å
Material Growth per cycle
Al2O3 1.2 Å (100 °C)
Ta2O5 0.80 Å (225 °C)
TiO2 0.45 Å (200 °C)
AB cycles
ALD saturation curves
Department of Applied Physics – Erwin Kessels
(b)
(a)
0 20 40 60 80 1000.00
0.05
0.10
0.15
0.20
Gro
wth
per C
ycle
(nm
/cyc
le)
Dose time (ms)0 1 2 3 4 5
Purge time (s)
CVD
0 20 40 60 80
Subsaturation CVD
H2O dose (ms)0 1 2 3
Purge time (s)
Al(CH3)3 precursor Purge H2O reactant Purge
ALD of Al2O3 from Al(CH3)3 and H2O (200 ⁰C)
20 ms – 2 s – 40 ms – 1 sAl(CH3)3 – purge – H2O – purge
Vary one parameter while keeping other constant:
Quartz crystal microbalance (QCM)
Department of Applied Physics – Erwin Kessels
• Cheap device and relatively easy-to-implement on many reactors• Directly measures mass gain/loss in quantitative way• Very helpful for process development• Very sensitive to variations in pressure, gas flows and temperature
Measures mass variation of a quartz crystal resonator from its frequency change
Precursor Reactant
Pump
QCM sensor = quartz crystal in resonator housing
QCM 1
QCM 2
Elam et al., Rev. Sci. Instr. 73, 2981 (2002).Rocklein and George, Anal. Chem. 75, 4975 (2003).
Quartz crystal microbalance (QCM)
Department of Applied Physics – Erwin Kessels www.inficon.com
• Cheap device and relatively easy-to-implement on many reactors• Directly measures mass gain/loss in quantitative way• Very helpful for process development• Very sensitive to variations in pressure, gas flows and temperature
Measures mass variation of a quartz crystal resonator from its frequency change
QCM – Monitoring mass gain (Al2O3)
Department of Applied Physics – Erwin Kessels Elam et al., Rev. Sci. Instr. 73, 2981 (2002).Wind et al., J. Phys. Chem. A 114, 1281 (2010).
s-OH
s-OAl(CH3)x s-AlOH
s-AlCH3
Mass gain/loss can be monitored per half-cycle
Spectroscopic ellipsometry (SE)
Department of Applied Physics – Erwin Kessels
• Directly measures thickness, very helpful for (fast) process development • Yields also insight into many other material properties (optical/electrical) • Optical modelling can be challenging for some layers/materials• Rather expensive and requires special ports for optical access
Measures change of polarization of light upon reflection (multiple wavelengths)
Precursor Reactant
Pump
Broadband light source
+polarizers
Polarizers +
spectrograph +
detector
Window +
Protection valve
Window +
Protection valve
Langereis et al., J. Phys. D: Appl. Phys. 42, 073001 (2009).See blog post about ellipsometry & ALD at www.AtomicLimits.com
Spectroscopic ellipsometry (SE)
Department of Applied Physics – Erwin Kessels
Measures change of polarization of light upon reflection (multiple wavelengths)
www.cambridgenanotechald.comSee blog post about ellipsometry & ALD at www.AtomicLimits.com
• Directly measures thickness, very helpful for (fast) process development • Yields also insight into many other material properties (optical/electrical) • Optical modelling can be challenging for some layers/materials• Rather expensive and requires special ports for optical access
Spectroscopic ellipsometry – Saturation (TiN)
Department of Applied Physics – Erwin Kessels
0 50 100 150 200 250 3000
4
8
12
16
20
Film
thick
ness
(nm
)
Number of cycles
15 s
60 s
15 s
30 s
0 20 40 60 80 100 120 1400.00
0.02
0.04
0.06
0.08
0.10
Gro
wth
rate
(nm
/cyc
le)
Plasma exposure time (s)
single deposition run separate depositions
Langereis et al., J. Phys. D: Appl. Phys. 42, 073001 (2009).
TiN
Monitor film thickness while changing precursor/reactant dosing timeprovides a fast method to determine saturation curves
Spectroscopic ellipsometry – Nucleation (Pt)
0 100 200 300 400 500 60002468
101214
Th
ickne
ss (n
m)
Number of cyclesDepartment of Applied Physics – Erwin Kessels
100 nm
ALD of Pt from MeCpPtMe3 and O2 on “foreign” Al2O3 substrate (300 ⁰C)
Mackus et al., Chem. Mater. 25, 1905 (2013).
Nucleation delay on
Al2O3
Spectroscopic ellipsometry – Resistivity (Pt)
Department of Applied Physics – Erwin Kessels Leick et al., J. Phys. D 49, 115504 (2016).
Imaginary part of dielectric function ε
Drudeterm
(resistivity)
Lorentz terms
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.00
20
40
60
80
100
Photon energy (eV)
53 nm
10 nm
5 nm
3.5 nmDie
lect
ric fu
nctio
n ε 2
ALD of Al2O3 [Case study]
Department of Applied Physics – Erwin Kessels
s-OH*+ Al(CH3)3 s-OAl(CH3)2 + CH4
s-AlOH + CH4s-AlCH3* + H2O
Prototypical ALD process
Precursor: Al(CH3)3
Reactant: H2O
Temperature: 25-400 ⁰C
A - 1st Half Cycle
B - 2nd Half Cycle
Simplified reaction scheme:
Mass spectrometry ― Reaction products (Al2O3)
Department of Applied Physics – Erwin Kessels
Gas phase reaction products
0 25 50 75 10010-11
10-10
10-9
10-8
H2O
Mas
s sp
ectro
met
ry s
igna
l (A)
Time (s)
CH4
Al(
CH
3)3
Al(
CH
3)3
Al(
CH
3)3
Al(
CH
3)3
H2O
H2O
H2O
H2O
0 25 50 75 10010-11
10-10
10-9
10-8
H2O
Mas
s sp
ectro
met
ry s
igna
l (A)
Time (s)
CH4
0 25 50 75 10010-11
10-10
10-9
10-8
H2O
Mas
s sp
ectro
met
ry s
igna
l (A)
Time (s)
CH4
Al(
CH
3)3
Al(
CH
3)3
Al(
CH
3)3
Al(
CH
3)3
H2O
H2O
H2O
H2O
Al(CH3)3 dosing: CH4
H2O dosing: CH4
Vandalon and Kessels, J. Vac. Sci. Technol. A 35, 05C313 (2017).
Quadrupole mass spectrometry (QMS)
Department of Applied Physics – Erwin Kessels
• Easy-to-implement on all types of reactors (with differential pumping)• Wide range of species can be detected (but heavy masses difficult)• All reaction products measured (not only from substrate)• QMS cracks molecules into fragments complicating data interpretation
Precursor Reactant
Pump
Mass filter
Detector
Valvewith
pinhole
Pump (p < 10-5 Torr)
Ionization of gas extracted from the reactor & mass filtering of the ions
Quadrupole mass spectrometry (QMS)
Department of Applied Physics – Erwin Kessels
• Easy-to-implement on all types of reactors (with differential pumping)• Wide range of species can be detected (but heavy masses difficult)• All reaction products measured (not only from substrate)• QMS cracks molecules into fragments complicating data interpretation
Ionization of gas extracted from the reactor & mass filtering of the ions
Mass spectrometry ― Reaction products (Al2O3)
Department of Applied Physics – Erwin Kessels
0 25 50 75 10010-11
10-10
10-9
10-8
H2O
Mas
s sp
ectro
met
ry s
igna
l (A)
Time (s)
CH4
Al(
CH
3)3
Al(
CH
3)3
Al(
CH
3)3
Al(
CH
3)3
H2O
H2O
H2O
H2O
0 25 50 75 10010-11
10-10
10-9
10-8
H2O
Mas
s sp
ectro
met
ry s
igna
l (A)
Time (s)
CH4
0 25 50 75 10010-11
10-10
10-9
10-8
H2O
Mas
s sp
ectro
met
ry s
igna
l (A)
Time (s)
CH4
Al(
CH
3)3
Al(
CH
3)3
Al(
CH
3)3
Al(
CH
3)3
H2O
H2O
H2O
H2O
CH4 probed at 16 (CH4+); 15 (CH3
+), etc.
H2O probed at 18 (H2O+); 17 (OH+); 16 (O+)
Vandalon and Kessels, J. Vac. Sci. Technol. A 35, 05C313 (2017).
Mass spectrometry probes mass/charge ratios
Gas-phase infrared spectroscopy (FTIR)
Department of Applied Physics – Erwin Kessels
• Calibration is quite straightforward to yield absolute densities• High sensitivity for certain species but not all species can be detected• All reaction products measured (not only from substrate)• Confinement of reaction products might be necessary for sufficient S/N ratio
Absorption of infrared light (from FTIR interferometer) by rovibrational transitions
Precursor Reactant
Pump
IR light source +
Interferometer IR detector
IR window +
Protection valve
IR window +
Protection valve
Gas-phase infrared spectroscopy (FTIR)
Department of Applied Physics – Erwin Kessels
• Calibration is quite straightforward to yield absolute densities• High sensitivity for certain species but not all species can be detected• All reaction products measured (not only from substrate)• Confinement of reaction products might be necessary for sufficient S/N ratio
Absorption of infrared light (from FTIR interferometer) by rovibrational transitions
Department of Applied Physics – Erwin Kessels Vandalon and Kessels, J. Vac. Sci. Technol. A 35, 05C313 (2017).
Gas-phase FTIR ― Reaction products (Al2O3)
QMS and gas-phase FTIR installed in exhaust
Department of Applied Physics – Erwin Kessels
Precursor Reactant
Pump
Mass Spectrometer
(p < 10-5 Torr)
Infrared gas cell
(p up to 1 atm)
IR light source +
Interferometer
IR detector
Can quite easily be implemented in industrial (spatial) ALD equipment
Gas-phase FTIR in exhaust of spatial ALD setup
Department of Applied Physics – Erwin Kessels
Reaction products: O3, combustion products and CH4
1000 1500 2000 2500 3000 3500 4000
H2OCH4
COAbso
rban
ce
Wavenumber (cm-1)
CH4
CO2
O3H2O
Spectrum of O2 plasma reactant step during plasma-assisted spatial ALD of Al2O3
Mione et al., to be published (2018).
Surface infrared spectroscopy (FTIR)
Department of Applied Physics – Erwin Kessels
• Direct measurement of surface groups created, removed or incorporated• Probes only surface groups which are changing every (half-)cycle• Poor S/N ratio for some species – long integration times required• Requires dedicated reactor with optical access and IR-transparent substrate
Precursor Reactant
Pump
IR light source +
Interferometer IR detector
IR window +
Protection valve
IR window +
Protection valve
Absorption of infrared light by vibrational transitions by (surface) groups
Chabal et al., Surf. Sci. Rep. 8, 211 (1988).
Various configurations infrared spectroscopy
Department of Applied Physics – Erwin Kessels
Gas phase species Surface species - wafer
Surface species – particles(enlarged surface area by particles)
Surface species – ATR element(multiple reflections at surface)
Chabal et al., Surf. Sci. Rep. 8, 211 (1988).
Surface FTIR – Surface groups (Al2O3)
Department of Applied Physics – Erwin Kessels
4000 3500 3000 2500 2000 1500 1000
Wavenumber (cm-1)4000 3500 3000 2500 2000 1500 1000
Abso
rban
ce
Wavenumber (cm-1)
5×10-5
Thermal ALD
Al(CH3)3
-CH3
-CH3
-CH3
-CH3-OH
-OH
H2O or O2 plasma
Thermal ALD
Plasma ALDPlasma ALD
150 °C 150 °C
Langereis et al., ECS Transactions 16, 247 (2008).
-CH3 and -OH are surface groups for both thermal and plasma ALDDifferential spectra: show changes per half cycle
Plasma-enhanced ALD of Al2O3 [Case study]
Department of Applied Physics – Erwin Kessels
s-OH*+ Al(CH3)3
s-AlOH + CO + CO2 + H2Os-AlCH3* + 3O
Precursor: Al(CH3)3
Reactant: O2 plasma
Temperature: 25-400 ⁰C
s-OAl(CH3)2 + CH4
A - 1st Half Cycle
B - 2nd Half Cycle
Simplified reaction scheme:
Department of Applied Physics – Erwin Kessels
Ar H2 N2 O2
Plasma radiation – feed gas dependent
Profijt et al., J. Vac. Sci. Technol. A 29, 050801 (2011).
Optical emission spectroscopy (OES)
Department of Applied Physics – Erwin Kessels
• Ideally suited for process monitoring of plasma-based processes• Extremely easy to implement & cheap• Yields only information about excited species – not ground state species • Typically yields very indirect and qualitative information
Mackus et al., J. Vac. Sci. Technol. A 28, 77 (2010).
Measures (visible) radiation from excited species decaying to lower levels
Precursor Reactant
Pump
Optical fiber
SpectrographImaging lenses
Spectrograph
Window+
Protection valve
Option 1 Option 2
Optical emission spectroscopy (OES)
Department of Applied Physics – Erwin Kessels Mackus et al., J. Vac. Sci. Technol. A 28, 77 (2010).
• Ideally suited for process monitoring of plasma-based processes• Extremely easy to implement & cheap• Yields only information about excited species – not ground state species• Typically yields very indirect and qualitative information
Measures (visible) radiation from excited species decaying to lower levels
Optical emission spectroscopy – Plasma (Al2O3)
Department of Applied Physics – Erwin Kessels
0400800
12001600 Pure O2 plasma O2 O
300 400 500 600 700 8000
400800
12001600 ODuring ALD
HβOH
CO
Hα
Emiss
ion
inte
nsity
(a.u
.)
Wavelength (nm)
Plasma half-cycle
AlOH* + CO2 + H2OAlCH3* + 4O
CO2 + H2O + e COex + Hex + ... + e
Plasma is “disturbed” by reaction products
Heil et al., Appl. Phys. Lett. 89, 131505 (2006).Knoops et al., Appl. Phys. Lett. 107, 014102 (2015).
0 s 0.4 s 0.8 s 1.2 s 1.6 s 2.0 st:
Atomic layer deposition (ALD)
Department of Applied Physics – Erwin Kessels
A B A Bt Discussed next:
ALD merits:• Conformality• Uniformity• Growth control
Advanced methods:• Sum-frequency generation• Adsorption calorimetry
Conformality – Reaction- vs. diffusion-limited
Department of Applied Physics – Erwin Kessels
s0 << 1
s0 → 1
Knoops et al., J. Electrochem. Soc. 157, G241 (2010).Elam et al., Chem. Mater. 15, 3507 (2003).
Anim
atio
n -s
0<<
1An
imat
ion
-s0
→ 1
Conformality test structures
Department of Applied Physics – Erwin KesselsYlilammi et al., J. Appl. Phys. 123, 205301 (2018).
Gao et al., J. Vac. Sci. Technol. A 33, 010601 (2015).
PillarHall™ LHAR structures
Fabricated by Si micromachining
= 500 nm
Conformality tests – sticking probability (Al2O3)
Department of Applied Physics – Erwin KesselsSee presentation Karsten Arts – AF2-Tuesday afternoon at 5 pm
Ylilammi et al., J. Appl. Phys. 123, 205301 (2018).
100 150 200 250 300 350
10-5
10-4
10-3
Sum-frequency generation
(Initi
al) S
ticki
ng p
roba
bilty
s0
Substrate temperature (°C)
PillarHall structures
Initial sticking probability s0
Sticking probability of H2O during H2O step
Sticking probability of H2O <10-4 H2O is not very reactive with –CH3
Good agreement with sum-frequency generation (SFG, see later)
Uniformity – O3 surface loss (ZnO)
Department of Applied Physics – Erwin Kessels
0 20 40 600
5
10
15
20
25
ZnO
Film
Thi
ckne
ss (n
m)
Reactor position (cm)
150 cycles
5 s O3
10 s O3
20 s O3
Knoops et al., Chem. Mater. 23, 2381 (2011).
Zn(C2H5)2O3
flow
Surface loss/recombination of O3
Depends on surface termination
Uniformity – O3 surface loss (ZnO)
Department of Applied Physics – Erwin Kessels
0 20 40 600
5
10
15
20
25
ZnO
Film
Thi
ckne
ss (n
m)
Reactor position (cm)
150 cycles
5 s O3
10 s O3
20 s O3
10 20 30
Norm
alize
d Q
MS
m/z
= 4
8
Time (s)
20 s
O3 exposure
5 s 10 s
Knoops et al., Chem. Mater. 23, 2381 (2011).
Zn(C2H5)2O3
flowQMS
C2H5-term. surfaceLow O3 loss
ZnO surfaceHigh O3 loss
Growth control - initial growth on foreign surfaces
Department of Applied Physics – Erwin Kessels
Spectroscopic ellipsometryALD Al2O3 on SiO2 and Si(111):H surfaces
On foreign surfaces initially no “ideal” ALD film growth
Additional insight is necessary for
• Ultrathin films• Area-selective ALD• Etc.
Vandalon et al., to be published (2018).
Sum frequency generation (SFG)
Department of Applied Physics – Erwin Kessels
• Highly sensitive & specific for surface groups (sub-surface species not probed)• Good time resolution, reaction kinetics can be followed in time• Can give absolute values of reaction cross-sections/sticking probabilities etc.• Very complex method requiring highly dedicated setup with laser-system
Nonlinear optical technique with 2 laser beams probing vibrational transitions
Precursor Reactant
Pump
Tunable IR laser beam(broadband, fs resolution)
800 nm laser beam(ps resolution)
Sum-frequency radiation(broadband, fs resolution)
Vandalon and Kessels, J. Vac. Sci. Technol. A 35, 05C313 (2017).
Sum frequency generation (SFG)
Department of Applied Physics – Erwin Kessels
• Highly sensitive & specific for surface groups (sub-surface species not probed)• Good time resolution, reaction kinetics can be followed in time• Can give absolute values of reaction cross-sections/sticking probabilities etc.• Very complex method requiring highly dedicated setup with laser-system
Nonlinear optical technique with 2 laser beams probing vibrational transitions
Vandalon and Kessels, J. Vac. Sci. Technol. A 35, 05C313 (2017).
Sum frequency generation – Al2O3 on Si(111):H
Department of Applied Physics – Erwin Kessels
Si-H stretch @ 2083 cm-1
Al(CH3)3 reacts with Si(111):H breaking the Si-H bonds
Frank et al., Appl. Phys. Lett. 82, 4758 (2003). Vandalon et al., to be published (2018).
10 ms Al(CH3)3pulses
or translated into sticking probability s0 = (1.9±0.2)x10-3
Reaction cross-section σ= (3.1±0.3)x10-18 cm2
Initial growth of Al2O3 on SiO2 and on Si(111):H
Department of Applied Physics – Erwin Kessels
Spectroscopic ellipsometryInitial growth:
1st cyle on Si(111):Hs0 = (1.9±0.2)x10-3
1st cycle on SiO2
s0 = (1.2±0.1)x10-3
Steady-state growth:
x-th cycle (x>>1)s0 = (3.9±0.4)x10-3
Vandalon et al., to be published (2018).
Area-selective ALD (see tutorial Parsons)
Department of Applied Physics – Erwin Kessels
Differences in nucleation behavior (initial growth) are often exploited to achieve area-selective ALD
Fundamental insight (preferable with quantitative information) in initial growth is required
Linear growth on growth area
Nucleation delayon non-growth
area
Selective growth
Number of cycles
Thic
knes
s
Growth area Non-growth area
Growth area Non-growth area
Mackus, ALD2017 tutorial (2017).
Adsorption calorimetry
Department of Applied Physics – Erwin Kessels
• Provides additional thermodynamic and mechanistic insight• Can be used to verify and benchmark (half-cycle) reactions – also from DFT• New to the field of ALD – needs follow up work• ….
Measures half-cycle reaction heats pyroelectrically using a LiTaO3 crystal disk
Precursor Reactant
Pump
Lownsbury et al., Chem. Mater. 29, 8566 (2017).
QCM
Calorimeter
Adsorption calorimetry
Department of Applied Physics – Erwin Kessels
• Provides additional thermodynamic and mechanistic insight• Can be used to verify and benchmark (half-cycle) reactions – also from DFT• New to the field of ALD – needs follow up work• ….
Measures half-cycle reaction heats pyroelectrically using a LiTaO3 crystal disk
Lownsbury et al., Chem. Mater. 29, 8566 (2017).Photos courtesy of Alex Martinson (Argonne National Lab)
Adsorption calorimetry – Reaction heats (Al2O3)
Department of Applied Physics – Erwin Kessels Lownsbury et al., Chem. Mater. 29, 8566 (2017).
s-OH*+ Al(CH3)3 s-OAl(CH3)2 + CH4
s-AlOH + CH4s-AlCH3* + H2O
A - 1st Half Cycle:
B - 2nd Half Cycle:
ΔH = -343 kJ/mol
ΔH = -251 kJ/mol
First-principle calculations
Department of Applied Physics – Erwin Kessels Widjaja and Musgrave, Appl. Phys. Lett. 80, 3306 (2002).
s-OH*+ Al(CH3)3 s-AlOH + CH4s-AlCH3* + H2O
A - 1st Half Cycle B - 2nd Half Cycle
s-OAl(CH3)2 + CH4
So far calculated reaction heats have remained untested with respect to experiment
Concluding remarks
Department of Applied Physics – Erwin Kessels
• Various analytical tools for in situ studies of ALD have been discussedQMS, gas phase FTIR, QCM, SE, surface FTIR, OESMany more exist. Combine tools if you can!
Concluding remarks
Department of Applied Physics – Erwin Kessels
• Various analytical tools for in situ studies of ALD have been discussedQMS, gas phase FTIR, QCM, SE, surface FTIR, OESMany more exist. Combine tools if you can!
• Focus can be on• Film growth & properties• Reaction mechanisms• Process monitoring & control
Concluding remarks
Department of Applied Physics – Erwin Kessels
• Various analytical tools for in situ studies of ALD have been discussedQMS, gas phase FTIR, QCM, SE, surface FTIR, OESMany more exist. Combine tools if you can!
• Focus can be on• Film growth & properties• Reaction mechanisms• Process monitoring & control
• Take it to the next level (quantitatively!)• Sticking probabilities• Reaction heats• Transient states• ….Combine experiments with theory/simulations!
Acknowledgements
Department of Applied Physics – Erwin Kessels
Plasma & Materials Processing group
Co-workers:
Dr. Adrie MackusDr. Harm Knoops
Dr. Fred RoozeboomDr. Marcel Verheijen
Dr. Ageeth BolDr. Adriana Creatore
&Many PhD students
and postdocs
For more information & feedbacksee blog:
www.AtomicLimits.com
ALD Academy (www.ALDacademy.com)
Dr. Erwin KesselsDept. of Applied Physics
Eindhoven University of Technology
Dr. Gregory ParsonsDept. of Chemical and Biomolecular Engineering
North Carolina State University
Mission: educate students and professionals on the principles, applications and future advancements of ALD and related atomic-scale processes.