Studies of the impact dynamics of single tin
nanoparticles
Robert E. Continetti
Dept. of Chemistry and Biochemistry
University of California, San Diego
CaliBaja Center for Resilient Materials and Systems Inauguration Symposium
UC San Diego, May 24, 2016
Structure, Dynamics and Collisions of Nanoparticles
Aerosol and Nanoparticle Research Program
Particle Characterization / Impact Dynamics
•
Particle Analysis by Hypervelocity Impact - Motivation
•
Extreme Ultraviolet (EUV, 13.5 nm) Light Sources for Photolithography
(Cymer/ASML) – Understanding Tin Contamination
•
Aerosol Impact Machine - Realization
• Electrospray Ionization (ESI)
• Nanoparticle Electrostatic Trap (NET)
• Linear Accelerator
• Characterization and Impact Dynamics
•
Production of Charged Nanoparticles: Next Steps
•
Aerosol Impact Machine: Next Steps
Analyzing Aerosols and Nanoparticles via
Hypervelocity Impact
Broad Goals:
• growth and aging of aerosols and nanoparticles in electrostatic
RF traps
• controlled fragmentation through (variable) hypervelocity impact
• particle composition and phase depth profiling by impact
• particle/substrate interactions: chemical and physical
Measurements:
• Determine mass and charge of single dust, aerosol and nanoparticles
• Examine dust and nanoparticle impacts in an intermediate velocity range
- 0.5 - 5 km/sec - analytical and fundamental studies (dynamics)
• Measure desorbed species and product angular distributions to infer
radial composition profiles and particle phases
(mass spectrometric and ion imaging)
• Electron microscopy studies of particle deposition and substrate
interactions
EUV Generation: Tin Contamination
Public
How does Cymer generate EUV radiation?
EUV
30 micron diameter tin droplet
EUV
Laser light
tin ions
“debris”
electrons
1. High power laser interacts with liquid tin
producing a plasma.
2. Plasma is heated to high temperatures
creating EUV radiation.
3. Radiation is collected and used to pattern
wafers.
Laser interacts with Tin droplets to produce the plasma
Public
• Liquid Sn droplets are fired at kHz rep rate and high velocities.
• The laser must be timed and aimed to precisely hit each droplet for stable
EUV production.
Droplet Generator
Collector
IF Protection
..........
optics
optics
Beam Transport and
Focusing System
3 Stage
20kW CO2
Laser
Droplet Catcher
EUV Source Vacuum Vessel
(inside the scanner)
The Aerosol Impact Machine
ESI:
NET:
LINAC:
Detection:
VUV laser:
generation of highly charged droplets and nanoparticles
trapping and m/z analysis of single trapped particles
acceleration to final velocity using particle-specific pulse seq.
imaging impact dynamics and particle-substrate interactions
examining neutral desorption products
Single Particle Trapping in the
Nanoparticle Electrostatic Trap (NET)
Image Charge
Signal
Phase-Controlled Ejection of Single Nanoparticles into the
Linear Accelerator (LINAC)
Phase-controlled ejection of a single nanoparticle.
Purple trace (3): trapped particle charge pickup signal in the NET.
Blue trace (2): FPGA-controlled ejection pulse with user-defined
phase relative to the trapped particle oscillation.
Green trace (4): charge pickup signal following the LINAC.
ESI: production of charged colloidal drops
Charge vs. velocity (Energy selection at 500 eV*q)
Charge histogram
Electrospray Ionization Ion Source
Colloidal 150 nm (nominal) Sn nanoparticles
Post-Acceleration Velocity
(meters/sec)
Acceleration of Tin Particles to > 500 m/s
Measuring Particle Impact Dynamics Reflection
Shielding/mounting
Target material
ICD Tube
Image Charge Detection – measure recoil velocity projection on
surface normal
Measuring Particle Reflection
Scattering
acceptance
angle
5.95˚
19.75˚
Measurement of Particle Recoil Velocities
Normal incidence Sn/solvent on Si
Image Charge Detection – measure recoil velocity projection on surface
normal
Pre-Collision
Detection
Post Collision
Detection
(measured at ~55%
of original velocity)
• The broadening of the second peak in time corresponds
to a decrease in velocity of the rebounding particle.
Tin/Solvent Rebound Velocity – Normal Incidence on Si
Rebound Velocity Dependence on Incident Velocity
Dashed line: incident velocity equals the rebound velocity.
Low velocities (<100m/s) rebound velocity a large fraction of the incident velocity
Peak in distribution has incident velocity 150 m/s, recoil ~45 m/s (30%)
Tin/solvent Nanoparticles Incident on Si and Mo Surfaces
Normal incidence
Rebound
Fractions
Particle
Count
> 250 m/s reflection drops to near zero
Tin/solvent Nanoparticles Incident on Si and Mo Surfaces
Normal incidence
Rebound
Fractions
Particle
Count
No evidence for Sn deposition on Mo targets (SEM)
observed… Leidenfrost effect? Desolvate!!
Normal Incidence Rebound Experiments
Sn containing solution and blank solution
Rebound Velocity Dependence on Incident Velocity
Sn containing solution on Mo
Blank solution on Si
Observed signals must be solvent-dominated: droplets? Ice?
Deposition Experiments
SEM imaging of Sn on Carbon Tape
Particles sprayed through capillary onto carbon tape in ESI ‘arm’
No mass selection
Area shown on right
Area covered with Sn
Edge of Sn rich area.
Beam Collimation and Thermalization Aerodynamic Lens
Heating tube and Aerodynamic Lens Assembly
Aerodynamic lens elements
Differential Pumping Aperture
Allows heating of injected
particles to ~600°C
Thermal Coax wrapped
around 0.25’’ thin walled tube
0.012’’ ID transfer capillary
(~2’’ long)
Characterization of the Nanoparticle Beam using the
Aerodynamic Lens (ADL)
Particle Size – Evidence for Desolvation
The size distribution is significantly smaller than previously observed (200230nm compared to 500-700nm).
Characterization of the Nanoparticle Beam using the
Aerodynamic Lens (ADL)
Particle Impact Dynamics:
Deflected Velocity Map Imaging
• Prompt ions
• Photoions
• Detailed Angular Distributions – Plume Profiles
Velocity map imaging electrostatic optics, Mo target and load lock structure for
normal incidence measurement of tin nanoparticle scattering.
Charged Nanoparticle Sources: Next Steps
• Laser-induced acoustic desorption / laser ablation coupled with
Quadrupole Ion Trap (QIT) – charge states too low for detection in the
NET
• High voltage needle ‘dust gun’ – hard to trap energetic particles: use in
conjunction with Aerodynamic Lens for thermalization
• Electrospray ionization (ESI) of colloidal Sn solutions with energy
selection – continue to optimize for production of tin particles
• Laser induced forward transfer (LIFT) source – past evidence of liquid
nanoparticle generation with other metals – particle charging capability
unconfirmed
• Dust experimental source
chamber (DESC) – test
chamber for evaluating
different particle sources
Charged Nanoparticle Sources: Next Steps
• Laser-induced acoustic desorption / laser ablation coupled with
Quadrupole Ion Trap (QIT) – charge states too low for detection in the
NET
• High voltage needle ‘dust gun’ – hard to trap energetic particles: use in
conjunction with Aerodynamic Lens for thermalization
• Electrospray ionization (ESI) of colloidal Sn solutions with energy
selection – continue to optimize for production of tin particles
• Laser induced forward transfer (LIFT) source – previous
demonstrations of liquid nanoparticle generation with other metals –
particle charging capability unconfirmed
• Dust experimental source
chamber (DESC) – test
chamber for evaluating
different particle sources
Controlled Atmosphere Electrospray Source
Heated gas inlet
Transfer
Capillary
Sliding feedthrough
for electrospray
positioning
Glass tube to allow visual
inspection of electrospray
Gas, liquid and
electrical
feedthroughs
• Use of inert, reducing or oxidizing atmospheres
• Control of particle velocity in aerodynamic lens
Aerosol Impact Machine: Next Steps
•
Single particle mass, charge and acceleration
demonstrated up to 1 km/sec
•
Particle reflection measurements demonstrated
•
Demonstrate Sn reflection and deposition
• SEM analysis – deposition
• Mass spectrometric analysis of desorbed ions
•
Measure Product Angular Distributions (ionic and neutral)
•
Sn nanoparticles (ASML/Cymer - EUV Lithography)
•
impact dynamics - phase dependence; solid/liquid;
aerosols and nanoparticles
Acknowledgments
Team AIM
Morgan Miller
Dr. Brian Adamson
Joseph Taulane
$$
Dr. Silvia De Dea
NSF-MRI Instrument Development Program
Cymer/ASML