Nanoparticle/AMC Contamination Control and Metrology for the EUVL Systems

39 Pages·2012·2.98 MB·English

by  Zachary Holman

Nanoparticle/AMC Contamination Control
and Metrology for the EUVL Systems
David Y. H. Pui
Distinguished McKnight University Professor
Director of the Particle Technology Laboratory
Mechanical Engine ering Department

University of Minnesota
Outline
• Background and Motivation
• Protection Schemes for EUVL Masks
– Carriers at Atmospheric Pressure
– Scanners at below 100 mTorr
• Nanoparticle Metrology and AMC Issues
– Standardization of Nanoparticles
– Mask Deposition and AMC Issues
2
Background and Motivation
Conventional Optical Lithography Extreme Ultraviolet Lithography
Conductive Layer for
Light Source Electrostatic Chucking
Mo/Si
Low Thermal Expansion Substrate
Multilayers
Capping
Fused Silica Substrate
Layer
Buffer
13.4 nm
EUV Light Absorber Layer
Pellicle
Layer
• Pellicles are unavailable for protecting the EUVL masks due to high
absorption of EUV beam in most solid materials
• EUVL masks need to be protected against all particles > about 20 nm
3
Protection Schemes
The Intel project started in 2004. Particle contamination of EUVL photomasks
was unknown. It was feared that thousands of particles might deposit on the
mask during each operation. We need to investigate a broad range of
protection schemes.
Cover Plate
• Mask inside a carrier or scanner
Critical Surface
• Cover plate to reduce risk
C
volume
a
r
Particle Particle ir
• Critical surface upside down to Mask e
r

Trap Trap o
avoid gravitational settling r
EM ask- T s
c
(Cover plate underneath mask a
n
n
during shipping, storage, and
e
r

pump down)
• Electric field to make use of • Particle trap surrounding mask
electrophoresis to avoid particle penetration
from the side

• Thermal gradient to make use

of thermophoresis
Asbach et al., Journal of Nanoparticle Research 8:705-708 (2006) 4
Outline
• Background and Motivation
• Protection Schemes for EUVL Masks
– Carriers at Atmospheric Pressure
– Scanners at below 100 mTorr
• Nanoparticle Metrology and AMC Issues
– Standardization of Nanoparticles
– Mask Deposition and AMC Issues
5
Particle Detection Methods
Mask
Pin
▪ Surface particle detection
- Mask Scan: Lasertec M1350
- Wafer Scan: PMS SAS 3600 XP
Mask Carrier

Mask Blank

4” Wafer

▪ Airborne particle detection
- Laser particle counter (HS-LAS) for size distribution
- Aerosol Time-of Flight Mass Spectrometer (ATOFMS) for particle chemical
composition
Mask Carrier
Sampling Tube
Mask Blank
(I.D. 1.5 mm)
5 mm Hole
6
Effect of Secondary Packaging
Mask Blank
Witness Wafer
With Secondary Packaging Without Secondary Packaging
Vibration Table
Controlled Vibration
Witness Wafer Scan
▪ ISTA Procedure 1G at 1.15 G
rms (Deposited Particles)
▪ Vertical position
▪ Particle detection on 4” wafers
• Secondary packaging is
helpful in reducing particle
generation
ATOFMS (Aerosol Time-of-Flight Mass Spectrometers)

Particle
Inlet
start
000
Particle
333000000 111000000
µµµsss
stop
222000000 Sizing
Particle
+ -
+ -
Composition

y y
t t
i i
s s
n n
e e
t t
n n
I I
µ 2 µ 2
m / z t m / z t
8
D. Gross, Carleton College, Based on TSI, Inc. schematic.
Particle Source Identification
ATOFMS Mask Scan
▪ Complex organic compound or mixture -- ▪ Contact points between the
possibly polymer mask surface and pins
Particles come mostly from contact points between mask surface and pins
9
Yook et al., IEEE Trans. Semi. Manu. 20(2): 176-186 (2007).
Validation of Pozzetta Carrier Design on Particle
Generation during Real Shipping
Mask Scan
PZT600-51125
Mask
Pin
PZT600-69925
Mask
Standoff
• The pin-support generates considerable particles during shipping.
• The standoff-support generates almost no particles.
10