Design and analysis of a Scanning Beam Interference Lithography ...

ptk-title-121202.eps
Design and analysis of a Scanning Beam
Interference Lithography system for patterning
gratings with nanometer-level distortions
by
Paul T. Konkola
April 3, 2003
Ph.D. Thesis Defense
Department of Mechanical Engineering
Massachusetts Institute of Technology
Committee:
Dr. Mark L. Schattenburg (Advisor)
Professor David L. Trumper (Chair)
Professor Alexander H. Slocum
MIT Space Nanotechnology Laboratory

Acknowledgments
Committee: Dr. Mark L. Schattenburg (Advisor)
Professor David L. Trumper (Chair)
Professor Alexander H. Slocum
ptk-acknowledgements-121202.eps
Carl Chen
Ralf Heilmann, Bob Fleming, Ed Murphy, Chulmin Joo, Chi Chang,
Craig Forest, Andy Lapsa, Juan Montoya, G.S. Pati, Yanxia Sun, Shi Yue,
David Carter, Jimmy Carter, Jim Daley, Juan Ferrera, Todd Hastings,
Dario Gil, Mike McGuirck, Mark Mondol, Euclid Moon, Tim Savas, Mike
Walsh
Space Nanotechnology Laboratory
Nanostructures Laboratory, Prof Henry Smith
Sponsors: DARPA and NASA
MIT Space Nanotechnology Laboratory

Research Objectives
Develop interference lithography, gratings, and fiducial
grids as metrological tools.
Research and develop methods for patterning and
measuring gratings with nanometer-level phase errors
over large areas (up to 300 mm diameter).
ptk-objective-033103.eps
MIT Space Nanotechnology Laboratory

Outline
• Contributions
• Motivation
• System concept
• System overview
• Error sources
• System performance and analysis
• Electronic architecture
• Error budget summary
• Conclusions
• Q&A
ptk-outline-033103.eps
MIT Space Nanotechnology Laboratory

Contributions (I)
MIT Space Nanotechnology Laboratory
ptk-contributions-033103.eps
• Design, analysis, and demonstration of the first patterning
machine based on an interference image and a scanned
substrate. The system can pattern and measure large-area
gratings with nanometer-level repeatability.

Contributions (II)
• Experimental results and models that enhance the
understanding of ultra-precision patterning.
• System of stage control and acousto-optic fringe
locking that achieves fringe phase control to the limits
of quantization and sampling rate.
MIT Space Nanotechnology Laboratory
ptk-contributions2-033103.eps

Moire
camera
Lithography
metrology
Application of Fiducial Grids
and Gratings to Metrology
Reticle
grating
Wafer
grating
Stage encoders
Linear
Encoder
Linear
Encoder
Read
Head
Encoder systems
Grating
direction
Linear
Encoder
Linear
Encoder
Linear
Encoder
Linear
Encoder
Linear
Encoder
Wafer
Stage
Reticle
Stage
Beam
Control
Scanning
E-beam
Detector
Scintillating
Fiducial Grid
E-beam Resist
Substrate
ptk-applications-032703.eps
Reference for electron
beam lithography
Signal
Processing
Feedback
Signal
MIT Space Nanotechnology Laboratory
t
Pattern

Variable
attenuator
Mirror
Traditional Interference Lithography
Beamsplitter
Beamsplitter
Spatial Filters
Grating period, = λ
2sinθ
2θ
Laser beam
λ = 351.1 nm
ptk-il-110901.eps
Phase displacement actuator
Substrate
Phase error
sensor
Mirror
MIT Space Nanotechnology Laboratory

ptk-distortion-111101.eps
Phase Distortion of Interfered Spherical Waves
y (mm)
10
8
6
4
2
0
-2
-4
-6
-8
-10
-10 -8 -6 -4 -2 0 2 4 6 8 10
λ
x (mm)
MIT Space Nanotechnology Laboratory

Stage distance
measuring
interferometer
Beam pickoff
SBIL System Concept
Mirror
2
Laser
Phase
error
sensor
Stage
error
+
+
Substrate
Controller
Phase
displacement
actuator
Much smaller beams
than traditional IL
Air bearing
XY stage
ptk-sbil-110201.eps
MIT Space Nanotechnology Laboratory
G

Y direction
X direction
Grating Scanning Method
Scanning
grating
image
Air-bearing
XY stage
Resistcoated
substrate
Intensity
Overlapping scans closely approximate
a uniform intensity distribution
Intensity
Scanning grating image
Summed
intensity of
scans 1-6
Individual
scan
MIT Space Nanotechnology Laboratory
X
ptk-scanmethod-040203.eps
Grating
period, Λ
X

Scanning Electron Micrograph of a SBIL
Written Grating
Λ = 400 nm
Silicon
Resist
ARC
Definition of grating phase: φ(x 1 ) - φ(x 0 ) = 2 π!
1
Λ(x) dx
ptk-semlines-032803.eps
MIT Space Nanotechnology Laboratory
x 0
x 1
x

Metrology block with
phase measurement
optics
Wafer
Chuck
X-Y air bearing
stage
Front of System
Receiving tower
for UV laser
(λ = 351.1 nm)
MIT Space Nanotechnology Laboratory
ptk-frontsystem-032703.eps
Optical bench with
interference lithography
optics
Refractometer
interferometer
X-axis interferometer
Granite base
Isolation system

SBIL Environmental Enclosure
Environmental parameters: Temperature
Pressure
Humidity
Particles
Acoustics
Air Handlers
Chamber
MIT Space Nanotechnology Laboratory
ptk-enclosure-032903.eps

SBIL Beam Conditioning Optics
ptk-beamconditioning-033003.eps
Optical parameters: polarization, beam size, wavefront curvature, power
λ/2 plate
Polarizer
Spatial
filter and
collimating
assembly
AOM AOM
+1/-1 order grating
Camera
UV Laser
MIT Space Nanotechnology Laboratory

SBIL Alignment Optics
Set interference angle for desired image period: Λ= λ
2sinθ
Picomotor
driven
mirrors
Alignment splitter
2θ
AOM's shutter
beams
Beam
overlap
PSD
From
splitter
UV Laser
Angle
PSD
Position
PSD
0 and -1 order reflections
from grating on chuck
MIT Space Nanotechnology Laboratory
ptk-alignment-033003.eps

Period Measurement and Beam Alignment
L R
Photodiode
Stage
Motion
⇒
Beamsplitter
Mounted on Stage
Grating Period Λ = D/N
D = Distance Travelled
by the Stage
N Fringes
MIT Space Nanotechnology Laboratory
Xcc_PM_BA.eps
Interference signal detected at
the photodiode as stage moves.

Stage
Control
DSP
System
Frequency
Synthesizer
AOM2
AOM1
f = 100Mhz
2
f = 100Mhz
1
PM2
Wafer
X-Y Stage
PM1
AOM3
f = 120Mhz
3
Writing Mode
Fringe locking error
ptk-writing-033003.eps
x fle = (PM1 - PM2)Λ/p - x die
{
Phase instability
above pick off
Displacement interferometer
error perpendicular to fringes
Λ: image period
p: phase meter counts per period
MIT Space Nanotechnology Laboratory

DSP
System
AOM2
AOM1
f = 90Mhz
2
f = 110Mhz
1
Reflected 0 order
and diffracted -1
order
PM4
Stage
Control
Frequency
Synthesizer
PM3
Grating
X-Y Stage
(b) Reading Mode
Reading Mode
Unobservable error
ptk-reading-033003.eps
x ue = PM4 Λ/p - PM3 Λ/p - x die
{
Fringe-to-grating motion
{
Phase instability
above pick off
Displacement interferometer
error perpendicular to fringes
Λ: image period
p: phase meter counts per period
MIT Space Nanotechnology Laboratory

Acousto-Optic
Modulator No.3
(AOM3)
(AOM2)
Spatial Filter
Assembly for
Left Arm
Collimating Lens
for Left Arm
Metrology Block with
Heterodyne Phase
Measurement Optics
Beam Pickoff
Window
Super-Invar
Chuck
{
Front Optics
Metrology Grating
Beam Diverting Mirror
Laser (λ=351.1 nm)
MIT Space Nanotechnology Laboratory
ptk-frontoptics-032703.eps
Polarizer
Position PSD
Angle PSD
CCD Camera
Neutral Density
Filters
HeNe Stage
Interferometer
Laser (Thermally
Enclosed)
X-Axis Stage
Interferometer

A A
Stage and Lithography Metrology
Phase sensing
optics, 4-in-1
monolithic splitter
Beam pickoff
Chuck
Y interferometer
Column
reference
Section A-A
MIT Space Nanotechnology Laboratory
ptk-metrology-032903.eps
HeNe laser
X, θ column
reference
interferometers

(Chuck)
Nominally zero CTE
mount assemblies

Super invar chuck
flexure mounted
to stage
Super invar
mounts for optics
Zerodur mirrors
bonded to chuck
Metrology Frames
Zerodur metrology block flexure
mounted to bench, super invar
inserts
ptk-metrologyframes-032903.eps
Refractometer
cavity, bonded
mirrors
x-axis column
reference mirror
MIT Space Nanotechnology Laboratory

ptk-chucksys-032903.eps
SBIL Chuck System with Metrology References
Beam overlap
position sensitive
detector (PSD)
Period measurement
beamsplitter
Reference grating
for length scale
calibration
Wafer chuck compatible
with 100 mm, 150mm,
200 mm and 300 mm
diameter wafers
Interferometer mirrors
MIT Space Nanotechnology Laboratory

SBIL Chuck System
Performance issues:
1) Heat sink
2) Thermally stable
3) Vibration sensitivity
4) Repeatable substrate clamping distortions
5) Critical metrology frame alignments
6) Light weight
Mirror
alignment
mounts (6X)
Flexures (3X)
Alignment and bonding features
Theaded hole for
leveling screw (3X)
MIT Space Nanotechnology Laboratory
ptk-chuck-032903.eps
Epoxy injection
ports (8X)

Ducts from AOM's
Air flow paths
ULPA filters
Air handler B Air handler A
ptk-airflow-033103.eps
MIT Space Nanotechnology Laboratory

Left
beam
Substrate
System Errors
2θ
Interference
pattern
x s
x d
x f
Right
beam
Column
mirror
Stage
mirror
Errors by subsystems Errors by physics
• Displacement interferometer (x d)
• Fringe locking interferometer (x f)
• Metrology-block frame(x f)
• Substrate frame (x s)
• Rigid body motions (x s and x f)
• Period Control
• Image Distortion
ptk-errors-033003.eps
• Thermal expansion
• Air index, wavelength
• Interferometric periodic
• Electronic
• Vibration
• Substrate clamping distortion
• Control
MIT Space Nanotechnology Laboratory

Gain, Dose error/ phase error
10 0
10 -1
10 -2
10 -3
10 -1 10 -4
Dose error transfer functions
10 0
¥
Dose = ! Intensity(t) dt
-¥
f n
Moving average (slit illumination)
Envelope
Gaussian weighted average (SBIL)
10 1
f n
ptk-doseerror-033003.eps
Moving average,
decade/decade roll off
f n
Gaussian filter has
very fast cut off.
= f τ, slit illumination
where
τ = integration time
= 0.8 f d/v, Gaussian
MIT Space Nanotechnology Laboratory

Gain, Dose error/ phase error
10 0
10 -1
10 -2
10 -3
10 -1 10 -4
Dose error transfer functions
10 0
¥
Dose = ! Intensity(t) dt
-¥
f n
Moving average (slit illumination)
Envelope
Gaussian weighted average (SBIL)
10 1
f n
ptk-doseerror-033003.eps
Moving average,
decade/decade roll off
f n
Gaussian filter has
very fast cut off
= f τ, slit illumination
where
τ = integration time
= 0.8 f d/v, Gaussian
MIT Space Nanotechnology Laboratory

Short Term Fringe-to-Substrate Stability
Dose(x, y) = B + A(y) sin(2π(x -x4 (y))/Λ)
where y = v t + yo Normalize dose amplitude
error, eA (%)
x 4 (nm)
6
-0.01
-0.015
-0.02
-0.025
Fringe-to-Substrate Stability
4
2
0
-2
-4
-6
0 0.5 1 1.5 2 2.5 3 3.5 4
Time (s), Timer period=0.1 ms.
-0.03
0 0.5 1 1.5 2 2.5 3 3.5 4
Time (s), Timer period=0.1 ms.
MIT Space Nanotechnology Laboratory
ptk-shorttermx4-033103.eps
x 4 raw, 3σ=3.89 nm
x 4 , 3σ=1.94 nm, d/v=0.02 s
Estimated Dose Amplitude Error Due to Phase Jitter
-0.005

DSP
System
AOM2
AOM1
f = 90Mhz
2
f = 110Mhz
1
Reflected 0 order
and diffracted -1
order
PM4
Stage
Control
Frequency
Synthesizer
PM3
Grating
X-Y Stage
(b) Reading Mode
Reading Mode
Unobservable error
ptk-reading-033003.eps
x ue = PM4 Λ/p - PM3 Λ/p - x die
{
Fringe-to-grating motion
{
Phase instability
above pick off
Displacement interferometer
error perpendicular to fringes
Λ: image period
p: phase meter counts per period
MIT Space Nanotechnology Laboratory

Short term unobservable error (x ue)
Fringe-to-substrate stability is very close to the unobservable error
for the Gaussian filtered data.
x ue (nm)
5
4
3
2
1
0
-1
-2
-3
-4
x ue raw, 3σ=3.34 nm
x ue , 3σ=1.95 nm, d/v=20 ms
-5
0 0.5 1 1.5 2 2.5 3 3.5 4
Time (s), Timer period=0.1 ms.
MIT Space Nanotechnology Laboratory
ptk-shorttermxue-033103.eps

x ue (nm)
Unobservable error over 56 seconds
5
4
3
2
1
0
-1
-2
-3
-4
x ue raw, 3σ=3.12 nm
x ue , 3σ=2.12 nm, d/v=20 ms
-5
0 10 20 30 40 50
Time (s), Resampled timer period=0.7 ms.
Data bandlimited from 0 to 714 Hz
MIT Space Nanotechnology Laboratory
ptk-midtermxue-033103.eps

ptk-xuepsd-033103.eps
Power Spectral Density of the Unobservable Error
Power spectrum of x ue (nm/sqrt(Hz))
10 0
10 -1
10 -2
60 Hz electrical, 3σ=1.1 nm
for 59.5 Hz to 60.5 Hz.
3σ=1.8 nm for 100 Hz to 714 Hz.
Thermal expansion, 0 to ≈0.04 Hz.
Vibrations
x ue raw, 3σ=3.12 nm
x ue , 3σ=2.12 nm, d/v=20 ms
Air index nonuniformity, 3σ=2.3 nm for 0 Hz to 59.5 Hz.
10
0 100 200 300 400 500 600 700
-3
Frequency (Hz), resolution=0.35 Hz
MIT Space Nanotechnology Laboratory

x ue compensated (nm)
x ue uncompensated (nm)
Refractometer
(∆n/n), ppm
MIT Space Nanotechnology Laboratory
ptk-longtermxue-033103.eps
Long term stability over one hour (0 to 1.4 Hz)
2
1
0
-1
-2
-5
-10
-15
0 500 1000 1500 2000 2500 3000 3500
Time (s), resampled timer period=360 ms.
-20
0 500 1000 1500 2000 2500 3000 3500
0.1
0.05
0
-0.05
Unobservable error after refractometer compensation (3σ= 1.4 nm)
Uncompensated unobservable errror.
Time (s), resampled timer period=360 ms.
Refractometer data
-0.1
0 500 1000 1500 2000 2500 3000 3500
Time (s), resampled timer period=360 ms.
Interferometer phase:
φ =
2π deadpath
λ

Power Spectrum of Long Term Unobservable
Error and Refractometer Data
Power spectrums (nm)/sqrt(Hz)
10 1
10 0
10 -1
Thermal expansion
0.7 nm, 3σ for 0 to 0.04 Hz.
10 -2
x ue uncompensated, 3σ= 8.3 nm
x ue compensated, 3σ= 1.4 nm
Refractometer correction, 3σ= 8.2 nm
10 -1
Refractometer correction
effective up to 0.04 Hz.
Frequency (Hz), resolution=0.0027Hz
10 0
ptk-refracpsd-033103.eps
MIT Space Nanotechnology Laboratory

Refractometer (∆n/n), ppm
x ue (nm)
10
5
0
-5
Refractometer calibration
-10
0 20 40 60 80 100 120
Time (s), resampled timer period=12 ms.
-0.04
-0.06
-0.08
-0.1
-0.12
-0.14
-0.16
Stage x position: 0.12 m
Calculated refractometer coefficient: 107 nm/ppm
Inner door
opened
Outer door
opened
x ue uncompensated
x ue compensated
Outer door
closed
Inner door
closed
-0.18
0 20 40 60 80 100 120
Time (s), resampled timer period=12 ms.
MIT Space Nanotechnology Laboratory
ptk-refraccalib-033103.eps

Refractometer coefficient
(nm/ppm)
Refractometer coefficient
error from fit (nm/ppm)
110
100
90
80
70
60
50
Refractometer performance
Refractometer calibration data
40
0.12 0.13 0.14 0.15 0.16 0.17 0.18
Stage x position (m)
10
5
0
Zero deadpath at x = 0.229 m
-5
2
0.12 0.13 0.14 0.15 0.16 0.17 0.18
Stage x position (m)
data
fit
3.5
2.5
MIT Space Nanotechnology Laboratory
3
ptk-refraccoef-033103.eps
Refractometer coefficient error is attributed to refractometer periodic error.
Residual error increases as sqrt(deadpath).
x ue after compensation
(3σ, nm)

x fle (nm)
4
3
2
1
0
-1
-2
-3
Fringe locking error (x fle)
Raw data, µ = -0.01, 3 σ=2.45 nm.
Dose phase error µ = -0.01, 3 σ =0.35 nm, d/v = 10 ms.
-4
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
time(s)
ptk-fle-040103.eps
MIT Space Nanotechnology Laboratory

Gain
Phase (deg)
10 4
10 2
10 0
10 -2
10 -4
50
0
-50
-100
-150
-200
-250
10 1
10 1
PMr
10 2
10 2
Fringe locking control
fr
Σ G(z)
fc
H(z) P(zz )
PMe
Controller Synthesizer
Zygo
Digital
Filter
+
-
+ +
Σ
PMu
-1
-PM1
f (Hz)
f (Hz)
10 3
10 3
1600 Hz Loop Transmission
cross over
Experimental loop transmission
Chan2/Chan1 same data
Zygo filter, 15 Khz Bandwidth
Synthesizer w/ discrete time effects
Discrete time controller
Sum of components
ptk-fringecontrol-040103.eps
MIT Space Nanotechnology Laboratory

Vibration and dynamic errors
x1
Stationary
refererence
for ω

x ue corrected for grating nonlinearity (nm)
Unobservable error during a scan
No noticeable increase in unobservable
error during constant velocity scan.
8
6
4
2
0
-2
-4
Scan start Scan stop
5nm/0.1 g vibration
sensitivity for the chuck
Constant velocity
-6
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
time (s)
y r -y o (m)
Velocity
ref (m/s)
Acceleration
ref (m/s 2 )
0.08
0.06
0.04
0.02
0.05
Stage Reference Profile
ptk-scan100-040103.eps
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0.1
time(s)
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0.5
0
-0.5
Scan length = 8cm
Max velocity=
0.1 m/s
time(s)
Max acceleration = 0.1g
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
time(s)
MIT Space Nanotechnology Laboratory

X axis acceleration error (g's)
Y axis acceleration error (g's)
4
2
0
x 10-3
Stage acceleration errors
X accel err, µ=-6.0e-8 g, 3σ=2.0e-3 g
X accel err, d/v = 20 ms, 3σ=6.6e-5 g
-2
CV accelerations
85 µg max. Static accelerations
-4
0 0.2 0.4 0.6 0.8 1
25 µg max.
1.2 1.4 1.6 1.8 2
Time (s), Timer period=0.2 ms.
4
2
0
-2
x 10-3
CV accelerations
240 µg max.
Y accel err, µ=4.2e-8 g, 3σ=1.3e-3 g
Y accel err, d/v = 20 ms, 3σ=3.6e-4 g
Static accelerations
15 µg max.
-4
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Time (s), Timer period=0.2 ms.
Scan start
Scan stop
MIT Space Nanotechnology Laboratory
ptk-stageaccel-040103.eps

X axis stage error (nm)
Y axis stage error (nm)
400
300
200
100
0
-100
-200
Stage Error During the Scan
-300
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
1000
Time (s), Timer period=0.2 ms.
Y axis
500
0
-500
-1000
-1500
X axis
-2000
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Time (s), Timer period=0.2 ms.
ptk-stageerrr-040103.eps
MIT Space Nanotechnology Laboratory

Power Spectrum (units/Hz 1/2 )
Vibration Errors are Proportional to the
Metrology Block Accelerations
10 0
10 -1
10 -2
1nm/1mg vibration sensitivity
10
100 150 200 250 300 350 400 450 500
-3
f (Hz)
X acceleration (mg/rtHz)
x ue (nm/rtHz)
MIT Space Nanotechnology Laboratory
ptk-xerrxuepsd-040103.eps

Power spectrum of
x (nm/sqrt(Hz)
nl
Ratio of Power spectrums.
moving/stationary
10 0
10 -1
10 -2
Power spectrum of unobservable error
for a static stage and a slow scan
Static stage
stage moving at 127 µm/s
10
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
-3
Frequency (Hz), resolution=2.44 Hz
Ratio of power spectrums for moving stage/stationary stage
10 2
10 1
10 0
Error removed from low frequencies.
10
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
-1
630 Hz 800 Hz 1260 Hz 1600 Hz
Frequency (Hz), resolution=2.44 Hz
ptk-nonlinearityratios-040103.eps
x phase meter
fundamental at
800 Hz
(=4 (127µm/s)/(.633µm))
PM4 fundamental at
315 Hz
(=(127µm/s)/(.401µm))
MIT Space Nanotechnology Laboratory

ptk-periodicpmx-040103.eps
Periodic error of x axis interferometer (±0.6nm P-V)
Periodic error (nm)
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
Experimental data
Reconstruction using DC and first two harmonics
0 50 100 150 200 250 300 350 400 450 500
mod(PM x , p) (counts)
MIT Space Nanotechnology Laboratory

ptk-periodicpm4-040103.eps
Periodic error of phase meter 4 interferometer
(±0.4nm P-V)
Periodic error (nm)
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
Experimental data
Reconstruction using DC, second, and fourth harmonics
0 50 100 150 200 250 300 350 400 450 500
mod(PM 4 , p) (counts)
MIT Space Nanotechnology Laboratory

Power spectrum of
θ (µrad/sqrt(Hz)
Ratio of Power spectrums.
moving/stationary
ptk-thetascanpsd-040103.eps
Power spectrum of the theta interferometer
for a static stage and a slow scan
10 -1
10 -2
10 -3
10 -4
10
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
-5
Frequency (Hz), resolution=2.44 Hz
10 2
10 1
10 0
Stationary stage
stage moving at 127 µm/s
Ratio of power spectrums for moving stage/stationary stage
Periodic error observed when there is no OPD change!
10
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Frequency (Hz), resolution=2.44 Hz
-1
400 Hz 800 Hz 1600 Hz
MIT Space Nanotechnology Laboratory

ptk-waferphasemap-012103.eps
Wafer phase mapping repeatability (2.9 nm, 3σ)
5
4
3
2
1
0
-1
-2
-3
60
-4
50
40
30
20
y (mm)
10
0
0
20
40
x (mm)
60
MIT Space Nanotechnology Laboratory
80
4
3
2
1
0
-1
-2
-3

MIT Space Nanotechnology Laboratory
ptk-readingmapcontf-040103.eps
Nonlinearity of a grating written by SBIL
0 10 20 30 40 50 60
0
10
20
30
40
50
x (mm)
y (mm)
x nl (nm)
-5
-5
-5
-2.5
-2.5
-2.5
-2.5
-2.5
-2.5
-2.5
0
0
0
0
0
0
0
0
0 0
0
0
0
0
0
0
0
0
0
0 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
0
0
0
0
0
0
0
-2.5
-2.5
-2.5
-2.5
-2.5
-2.5
-2.5
-2.5
-2.5
-2.5
0
0
0
0
0
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
0
0
0 0
0
2.5
2.5
5
5
-2.5
-2.5
-2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
-2.5
-2.5
-2.5
2.5
2.5
2.5
2.5
2.5
-2.5
5
-5
-5
2.5
5
2.5
-2.5
-2.5
2.5
-5
2.5
5
-7.5
-2.5
0
0
0
-2.5
-5
2.5
7.5
-2.5
2.5
-2.5
5
-7.5
5
-10
2.5
-2.5
5
0
7.5
5
5
-2.5
0
5
10
-10
0
2.5
-2.5
-2.5
0
7.5
2.5
2.5
2.5
5
-5
5
-5
-2.5
-2.5
5
2.5
5
2.5
-2.5
-5
-5
5
2.5
0
-2.5
2.5
7.5
-2.5
-5
0
-2.5
-2.5
0
5
0
-5
0
0
-5
2.5
2.5
2.5
7.5
5
0
-2.5
2.5
-2.5
2.5
-5
0
-5
0
5
7.5
5
0
2.5
7.5
5
0
-5
5
5
10
2.5
7.5
5
5
7.5
0
-5
5
2.5
5
0
5
2.5
0
2.5
-5
-5
2.5
-2.5
5
5
7.5
5
0
0
0
0
2.5
0
-5
2.5
-5
-5
0
-5
0
2.5
5
-5
5
-5
5
5
-5
5
5
-5
5
5
5
-5
5
0
-5
-5
-5
0
5
0
0
5
5
0
5
5
5
0
0
0
0
5
0
0
0
0
5
0
0
0
0
0
5
5
0
0
5
0
5
5
0
0
5
0
0
0
5
0
0
5
0
Particle defects
Particle defects

y (mm)
y (mm)
25
24
23
22
21
20
19
18
17
16
15
-5
-5
-10
-10
-15
-15
-20
-5
Errors Caused by Particles Between
the Wafer and the Chuck
-5
-20
-10
-10
-5
-15
-5
43 44 45 46 47 48 49 50 51
42 52
x (mm)
Calculated out-of-plane distortion (nm)
25
24
23
22
21
20
19
18
17
16
15
0
0
0
0
0
42
Grating nonlinearity (nm)
0
0
50
0
100
50
150
50
200
100
0
150
250
200
0
0
5
0 0
100
250
10
0
5
0
20
43 44 45 46 47 48 49 50 51
200
150
x (mm)
150
50
15
15
100
0
10
10
5
0
-5
5
100
0
100
150
50
0
0
-5
0
0
52
ptk-particles-040103.eps
White light interferogram formed between
a quartz wafer and the chuck
Rings around a particle
MIT Space Nanotechnology Laboratory

Analog Input:
Power Sensors.
Sensors, general.
D/A PMC
A/D PMC
IXC6 Master/
DSP/Power PC
Analog Output:
Stage Linear Amplifiers
Vibration Isolation Feedforward.
Analog Test Points.
PC
Host
ZMI 2002
VME Bus
ZMI 2002
Control Architecture
Realtime Control Platform LabVIEW-Based I/O
ZMI 2002
ZMI 2002
VME Rack
Digital Change
of State Board
TTL Digital
Input/Output
TTL Digital
Input/Output
ZMI 2001
Refractometer.
Lithography
Interferometers
Stage
Interferometers
Power
Supply
Stage Position Limits
Air-bearing Pressure Limit
LabVIEW PC Control Lines
Digital Frequency
Sythesizer
Reference clock from Zygo laser
Comm. to LabVIEW PC
Acousto-Optic
Modulators
NI IMAQ 1424
Frame Grabber
NI PCI-DIO-96
Digital I/O
NI 6034E
Analog I/O
NI 6034E
Analog I/O
MIT Space Nanotechnology Laboratory
PC
Internal PCI Bus
Position Sensing
Detectors
Picomotor Driver
Communication to
IXC6.
Picomotors
ptk-controlarch-040103.eps
Wavefront
Metrology
CCD

VMIVME-1181-000,
32bit digital change-of-state
input board.
VMIVME-2510B,
64bit TTL digital output I/O
VMIVME-2510B,
64bit TTL digital output I/O
ZMI 2001, Interferometer
Card, 1 axis
ZMI 2002, Interferometer
Card, 2 axes
ZMI 2002, Interferometer
Card, 2 axes
ZMI 2002, Interferometer
Card, 2 axes
ZMI 2002, Interferometer
Card, 2 axes
SBIL Realtime Control Platform
PC with Windows NT 4.0, Micron
400 Mhz, Pentium II. 128 Mb DRAM
Development tools: Code Composer
Studio (TI), IXCtools (Ixthos),
Tornado II (Wind River Systems).
512 Kbytes
SBSRAM
83 Mhz
PMC
Site #1
Ethernet
Port
DSP A
C6701, 167 Mhz
16 Mbytes
SDRAM
83MHz
IXStar
PCI - DSP
Serial
Port
DSP B
C6701, 167 Mhz
512 Kbytes
SBSRAM
83 Mhz
16 bit Host Port Bus
Host Port
Interface
4 Mbytes
Flash
MPC 8240
IOPlus
250 Mhz
64 Mbytes
SDRAM
100 Mhz
32 Bit 32 Bit 32 Bit 32 Bit
64 Bit PCI - PCI 64 Bit 66 MHz PCI - PCI
64 Bit
66 MHz Bridge
Bridge 66 MHz
PMC-16AO-12-2022,
12 Channel, 16bit DA
64 Bit, User
Defined I/O
to P0*
16 Mbytes
SDRAM
83MHz
XDS510
ISA-JTAG emulator
JTAG to
DSP Chain
64 Bit
PCI - PCI
Bridge
33 MHz
Universe II
PCI-VMEbus
VME64x Backplane
(11 Mbytes/s)
DSP C
C6701, 167 Mhz
512 Kbytes
SBSRAM
83 Mhz
IXC6 Quad DSP Board
16 Mbytes
SDRAM
83MHz
IXStar
PCI - DSP
MIT Space Nanotechnology Laboratory
ptk-052601-control.eps
512 Kbytes
SBSRAM
83 Mhz
PMC-16AIO-88-31,
8 Channel, 16bit DA and
8 Channel, 16bit AD
DSP D
C6701, 167 Mhz
64 Bit, User
Defined I/O
to P2
16 Mbytes
SDRAM
83MHz
PMC
Site #2

Error Budget Summary*
Errors by Subsystems
Error Category
Error
budget,
static
[±nm]
Error
budget,
worst case
[±nm]
Displacement interferometer 1.66 4.87
Fringe locking interferometer 1.58 1.58
Metrology block frame 0.51 0.51
Substrate frame 0.40 2.79
Rigid body error motions 0.12 0.12
rss error 2.38 5.86
Errors by Physics
Error category
Error
budget,
static
[±nm]
Error
budget,
worst case
[±nm]
Thermal expansion 0.68 2.46
Air index 2.00 5.00
Periodic error 1.02 1.02
Electronic 0.12 0.12
Vibration 0.08 0.08
Substrate clamping distortion 0 1.41
Control 0.40 0.40
rss error 2.38 5.86
*Assumes particle problem resolved. Does not include errors due to
image distortion and period control.
ptk-errorsummary-040103.eps
MIT Space Nanotechnology Laboratory

Conclusions
• I designed and analyzed the first patterning machine
based on an interference image and a scanned
substrate. I developed a method for patterning and
measuring gratings with nanometer level errors.
• I described and applied the SBIL metrology system.
The experimental results and models enhance the understanding
of ultra-precision patterning.
• Analysis suggests the following improvements:
Improvements
Error budget
static [±nm]
Error budget
worst case [±nm]
Error without improvements 2.38 5.86
Error without thermal expansion and index
terms 1.11 1.79
Error without periodic term 2.15 5.77
Error without thermal expansion, index, and
periodic terms 0.43 1.48
• Application of self calibration techniques will lead to
gratings with nanometer level accuracy.
MIT Space Nanotechnology Laboratory
ptk-conclusions-040103.eps