Scanning Beam Interference Lithography - Space Nanotechnology ...
Scanning Beam Interference Lithography - Space Nanotechnology ...
Scanning Beam Interference Lithography - Space Nanotechnology ...
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<strong>Scanning</strong> <strong>Beam</strong> <strong>Interference</strong> <strong>Lithography</strong><br />
Paul T. Konkola<br />
Carl G. Chen<br />
Ralf K. Heilmann<br />
Chulmin Joo<br />
Mark L. Schattenburg<br />
Massachusetts Institute of Technology<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory
Objective and motivation<br />
System concept<br />
System overview<br />
Error sources and error budget<br />
Short term and long term phase stability results<br />
System electronic architecture<br />
Conclusions<br />
Outline<br />
ptk-outline-103102.eps<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory
<strong>Lithography</strong><br />
metrology.<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory<br />
ptk-applications-110601.eps<br />
Application of Fiducial Grids to Metrology<br />
Moire<br />
camera<br />
Reticle<br />
grating<br />
Wafer<br />
grating<br />
Encoder<br />
Plate<br />
Encoder<br />
Plate<br />
Stage<br />
encoders.<br />
Encoder<br />
Plate<br />
Reticle<br />
Stage<br />
Encoder<br />
Plate<br />
Read<br />
Head<br />
Wafer<br />
Stage<br />
Reference for electron<br />
beam lithography<br />
<strong>Beam</strong><br />
Control<br />
<strong>Scanning</strong><br />
E-beam<br />
Detector<br />
Scintillating<br />
Fiducial Grid<br />
E-beam Resist<br />
Substrate<br />
Signal<br />
Processing<br />
Feedback<br />
Signal<br />
t<br />
Pattern
Variable<br />
attenuator<br />
Mirror<br />
Traditional <strong>Interference</strong> <strong>Lithography</strong><br />
<strong>Beam</strong>splitter<br />
<strong>Beam</strong>splitter<br />
Spatial Filters<br />
Grating period, = λ<br />
2sinθ <br />
2θ<br />
Laser beam<br />
λ = 351.1 nm<br />
ptk-il-110901.eps<br />
Phase displacement actuator<br />
Substrate<br />
Phase error<br />
sensor<br />
Mirror<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory
ptk-distortion-111101.eps<br />
Phase Distortion of Interfered Spherical Waves<br />
<br />
<br />
y (mm)<br />
10<br />
8<br />
6<br />
4<br />
2<br />
0<br />
-2<br />
-4<br />
-6<br />
-8<br />
<br />
<br />
<br />
<br />
<br />
-10<br />
-10 -8 -6 -4 -2 0 2 4 6 8 10<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
λ <br />
<br />
<br />
x (mm)<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory
Stage distance<br />
measuring<br />
interferometer<br />
<strong>Beam</strong> pickoff<br />
SBIL System Concept<br />
Mirror<br />
2<br />
Laser<br />
Phase<br />
error<br />
sensor<br />
Stage<br />
error<br />
+<br />
<br />
+<br />
Substrate<br />
Controller<br />
Phase<br />
displacement<br />
actuator<br />
Much smaller beams<br />
than traditional IL<br />
Air bearing<br />
XY stage<br />
ptk-sbil-110201.eps<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory<br />
G
Y direction<br />
X direction<br />
Grating <strong>Scanning</strong> Method<br />
<strong>Scanning</strong><br />
grating<br />
image<br />
Air-bearing<br />
XY stage<br />
Resistcoated<br />
substrate<br />
Intensity<br />
Overlapping scans closely approximate<br />
a uniform intensity distribution<br />
Intensity<br />
<strong>Scanning</strong> grating image<br />
Summed<br />
intensity of<br />
scans 1-6<br />
Individual<br />
scan<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory<br />
X<br />
ptk-scanmethod-110201.eps<br />
Grating<br />
period, <br />
X
Optical Bench<br />
with IL Optics<br />
Phase<br />
Measurement<br />
Optics<br />
Wafer<br />
Stage<br />
SBIL System, Front View<br />
Laser (λ=351.1 nm)<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory<br />
Xcc_SBIL_front.eps<br />
Metrology<br />
Optics<br />
X-Axis<br />
Interferometer
All-Welded<br />
Stainless Steel<br />
Optical Bench<br />
Air Bearing<br />
Granite Block<br />
Active<br />
Vibration-Isolation<br />
System<br />
SBIL System, Rear View<br />
Laser (Λ=351.1 nm)<br />
<strong>Beam</strong> Steering<br />
System<br />
Y-Axis<br />
Interferometer<br />
ptk-sbil-rear.eps<br />
Magnetically Preloaded<br />
XY airbearing<br />
stage<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory
Super invar chuck<br />
flexure mounted<br />
to stage<br />
Zerodur mirrors<br />
bonded to chuck<br />
SBIL Metrology Frames<br />
Super invar mounts<br />
for optics<br />
ptk-metrologyframes-103102.eps<br />
Zerodur metrology block flexure<br />
mounted to bench. Super invar<br />
inserts. Column reference and<br />
refractometer mirrors bonded.<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory
SBIL Environmental Enclosure<br />
Specifications: 20±.005K critical zone temperature.<br />
20±.025K full volume temperature.<br />
40±0.8% relative humidity.<br />
16 Pa/m max pressure gradient.<br />
Acoustic SPL < 60 dB re 20 µPa<br />
in critcal octaves.<br />
Chamber<br />
Air Handlers<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory<br />
ptk-enclosure-103102.eps
2 plate<br />
Polarizer<br />
Spatial<br />
filter and<br />
collimating<br />
assembly<br />
SBIL <strong>Beam</strong> Conditioning Optics<br />
+1/-1 order grating<br />
AOM, 3 AOM, 2<br />
Camera<br />
UV Laser<br />
ptk-beamconditioning-110201.eps<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory
Picomotor<br />
driven<br />
mirrors<br />
SBIL Alignment Optics<br />
Alignment splitter<br />
2<br />
AOM's shutter<br />
beams<br />
<strong>Beam</strong><br />
overlap<br />
PSD<br />
From<br />
splitter<br />
UV Laser<br />
Angle<br />
PSD<br />
Position<br />
PSD<br />
0 and -1 order reflections<br />
from grating on chuck<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory<br />
ptk-alignment-111001.eps
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory<br />
ptk-fringelocking-111001.eps
SBIL Metrology Block optics<br />
4-in-1 monolithic beam splitter<br />
Fiber receiver (1 of 3) Nominally 0 thermal<br />
expansion coefficient<br />
mount assemblies<br />
ptk-metrologyblockoptics-103102.eps<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory
M M<br />
Stage and <strong>Lithography</strong> Metrology<br />
Phase sensing<br />
optics<br />
Chuck<br />
Y, column reference<br />
interferometers<br />
Column<br />
references<br />
Section M-M<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory<br />
ptk-metrology-110201.eps<br />
HeNe laser<br />
(Zygo)<br />
X, column<br />
reference<br />
interferometers
Chuck with Metrology References<br />
Reference grating<br />
for length scale<br />
calibration<br />
Substrate<br />
Vacuum<br />
chuck<br />
Image<br />
metrology<br />
grating<br />
Image<br />
metrology<br />
fiber<br />
Alignment and period<br />
calibration splitter<br />
Interferometer<br />
mirrors<br />
mm<br />
<strong>Beam</strong> overlap<br />
PSD<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory<br />
ptk-chuck-110201.eps
SBIL Chuck System<br />
ptk-chuck-40202.eps<br />
Performance issues:<br />
1) Heat sink<br />
2) Thermally stable<br />
3) Rigid constraint of substrate<br />
4) Coupling to interferometer mirrors even<br />
at high frequency<br />
5) Repeatable substrate clamping distortions<br />
6) Critical metrology frame alignments<br />
7) Light weight<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory
Period Measurement with a <strong>Beam</strong>splitter<br />
L R<br />
Writing<br />
<strong>Beam</strong>s<br />
Stage<br />
Motion<br />
<strong>Beam</strong>splitter<br />
Mounted on Stage<br />
Position Sensing<br />
Detector (PSD)<br />
Grating Period = D/N<br />
D = Distance Travelled<br />
by the Stage<br />
<strong>Interference</strong> Signal Detected<br />
as Stage Moves<br />
N Fringes<br />
ptk-PMprinciple-111001.eps<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory
Left<br />
beam<br />
Substrate<br />
System Errors<br />
2θ<br />
<strong>Interference</strong><br />
pattern<br />
x s<br />
x d<br />
Error Categories<br />
Stage interferometer (xd) Fringe locking and metrology frame(xf) Substrate frame (xs) Period Control<br />
Image Distortion<br />
x f<br />
Right<br />
beam<br />
Column<br />
mirror<br />
Stage<br />
mirror<br />
ptk-errors-110201.eps<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory
Error Budget Summary for SBIL<br />
Error Category<br />
error<br />
budget, e<br />
[±m]<br />
Non-plane wave 2.24E-09<br />
Period control 2.00E-09<br />
Substrate and Metrology Frame 3.01E-09<br />
Displacement Interferometer 3.45E-09<br />
<strong>Lithography</strong> Interferometer Phase 2.25E-09<br />
rss error 5.91E-09<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory<br />
ptk_3_16_01_error_budget.eps
Fringe - substrate phase, Λ=401.3021(nm)<br />
3<br />
2<br />
1<br />
0<br />
-1<br />
-2<br />
Long term fringe to substrate phase stability<br />
(1 hour, 0.3 mHz to 1.4 Hz)<br />
-3<br />
0 500 1000 1500 2000 2500 3000 3500<br />
Time (s), resampled timer period=360 ms.<br />
Phase error 3σ=1.8 nm<br />
ptk-longtermphase-103102.eps<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory
Fringe - substrate phase (nm)<br />
Refractometer (∆n/n), ppm<br />
5<br />
0<br />
-5<br />
-10<br />
-15<br />
0 500 1000 1500 2000 2500 3000 3500 4000<br />
Time (s), resampled timer period=360 ms.<br />
0.04<br />
0.02<br />
0<br />
-0.02<br />
-0.04<br />
-0.06<br />
-0.08<br />
Long term fringe to substrate phase stability<br />
with and without refractometer compensation<br />
Compensated Uncompensated<br />
Refractometer Data<br />
Door to<br />
cleanroom open<br />
-0.1<br />
0 500 1000 1500 2000 2500 3000 3500 4000<br />
Time (s), resampled timer period=360 ms.<br />
ptk-longtermphaserefrac-110102.eps<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory
ptk-shorttermphi4-110102.eps<br />
Short term fringe to substrate phase stability and estimated specifications<br />
using placement accuracy filter. (5 sec, 0.2 Hz to 5000 Hz)<br />
φ 4 (nm), Λ=401.3021nm<br />
Dose Amplitude fluctuation (%)<br />
6<br />
4<br />
2<br />
0<br />
-2<br />
-4<br />
φ 4 raw, 3σ=3.94e+000 nm<br />
φ 4 , 3σ=2.07e+000 nm, T ave =1.00e-002 s<br />
-6<br />
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5<br />
Time (s), Timer period=0.1 ms.<br />
0<br />
-0.01<br />
-0.02<br />
-0.03<br />
-0.04<br />
Estimated dose amplitude fluctuation due to phase jitter<br />
-0.05<br />
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5<br />
Time (s), Timer period=0.1 ms.<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory
ptk-shorttermphi4psd-110102.eps<br />
Power spectrum of the short term fringe to substrate<br />
phase stability and the estimated placement accuracy.<br />
Power spectrum of φ 4 (nm/sqrt(Hz))<br />
10 0<br />
10 -1<br />
10 -2<br />
10 -3<br />
10 -4<br />
10 -5<br />
10 -6<br />
φ 4 raw, 3σ=3.94e+000 nm<br />
φ 4 , 3σ=2.07e+000 nm, T ave =1.00e-002 s<br />
0 1000 2000 3000 4000 5000 6000<br />
Frequency (Hz), resolution=2.4414Hz, nfft = 4096<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory
X axis stage error (nm),<br />
cross axis<br />
Y axis stage error (nm),<br />
scan direction, ≈parallel<br />
to gratings<br />
30<br />
20<br />
10<br />
0<br />
-10<br />
-20<br />
-30<br />
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5<br />
Time (s), Timer period=0.1 ms.<br />
15<br />
10<br />
5<br />
0<br />
-5<br />
-10<br />
Stage position errors for X and Y axes<br />
X err, µ=-1.66e-001 nm, 3σ=2.43e+001 nm<br />
-15<br />
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5<br />
Time (s), Timer period=0.1 ms.<br />
Y err, µ=3.62e-002 nm, 3σ=1.07e+001 nm<br />
ptk-stageerrors-103102.eps<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory
Analog input:<br />
<strong>Beam</strong>overlap PSD.<br />
Power sensors.<br />
Sensors, general.<br />
D/A PMC<br />
A/D PMC<br />
IXC6 Master/<br />
DSP/Power PC<br />
Analog output:<br />
Stage linear amplifiers.<br />
Vibration isolation feedforward.<br />
Analog test points.<br />
PC<br />
host<br />
MI 2002<br />
SBIL System Architecture<br />
VME Bus<br />
MI 2002<br />
MI 2002<br />
MI 2002<br />
VME Rack<br />
Digital Change<br />
of State Board<br />
TL Digital<br />
Input/Output<br />
TL Digital<br />
Input/Output<br />
MI 2001<br />
Power<br />
Supply<br />
Digital frequency sythesizer<br />
(to AOM's).<br />
I 6508<br />
Digital I/O<br />
I 6034E<br />
Analog I/O<br />
I 6034E<br />
Analog I/O<br />
ptk-controlarch-102901.eps<br />
Realtime control platform Labview based I/O<br />
Refractometer.<br />
<strong>Lithography</strong><br />
interferometers.<br />
Stage<br />
interferometers.<br />
Reference clock from Zygo laser<br />
Stage position limits.<br />
Air bearing pressure limit.<br />
Labview PC control lines.<br />
Communication to Labview PC<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory<br />
PC<br />
Internal PCI Bus<br />
PSD's.<br />
Picomotor driver.<br />
Communication to<br />
IXC6.
VMIVME-1181-000,<br />
32bit digital change-of-state<br />
input board.<br />
VMIVME-2510B,<br />
64bit TTL digital output I/O<br />
VMIVME-2510B,<br />
64bit TTL digital output I/O<br />
ZMI 2001, Interferometer<br />
Card, 1 axis<br />
ZMI 2002, Interferometer<br />
Card, 2 axes<br />
ZMI 2002, Interferometer<br />
Card, 2 axes<br />
ZMI 2002, Interferometer<br />
Card, 2 axes<br />
ZMI 2002, Interferometer<br />
Card, 2 axes<br />
SBIL Realtime Control Platform<br />
PC with Windows NT 4.0, Micron<br />
400 Mhz, Pentium II. 128 Mb DRAM<br />
Development tools: Code Composer<br />
Studio (TI), IXCtools (Ixthos),<br />
Tornado II (Wind River Systems).<br />
512 Kbytes<br />
SBSRAM<br />
83 Mhz<br />
PMC<br />
Site #1<br />
Ethernet<br />
Port<br />
DSP A<br />
C6701, 167 Mhz<br />
16 Mbytes<br />
SDRAM<br />
83MHz<br />
IXStar<br />
PCI - DSP<br />
Serial<br />
Port<br />
DSP B<br />
C6701, 167 Mhz<br />
512 Kbytes<br />
SBSRAM<br />
83 Mhz<br />
16 bit Host Port Bus<br />
Host Port<br />
Interface<br />
4 Mbytes<br />
Flash<br />
MPC 8240<br />
IOPlus<br />
250 Mhz<br />
64 Mbytes<br />
SDRAM<br />
100 Mhz<br />
32 Bit 32 Bit 32 Bit 32 Bit<br />
64 Bit PCI - PCI 64 Bit 66 MHz PCI - PCI<br />
64 Bit<br />
66 MHz Bridge<br />
Bridge 66 MHz<br />
PMC-16AO-12-2022,<br />
12 Channel, 16bit DA<br />
64 Bit, User<br />
Defined I/O<br />
to P0*<br />
16 Mbytes<br />
SDRAM<br />
83MHz<br />
XDS510<br />
ISA-JTAG emulator<br />
JTAG to<br />
DSP Chain<br />
64 Bit<br />
PCI - PCI<br />
Bridge<br />
33 MHz<br />
Universe II<br />
PCI-VMEbus<br />
VME64x Backplane<br />
(11 Mbytes/s)<br />
DSP C<br />
C6701, 167 Mhz<br />
512 Kbytes<br />
SBSRAM<br />
83 Mhz<br />
IXC6 Quad DSP Board<br />
16 Mbytes<br />
SDRAM<br />
83MHz<br />
IXStar<br />
PCI - DSP<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory<br />
ptk-052601-control.eps<br />
512 Kbytes<br />
SBSRAM<br />
83 Mhz<br />
PMC-16AIO-88-31,<br />
8 Channel, 16bit DA and<br />
8 Channel, 16bit AD<br />
DSP D<br />
C6701, 167 Mhz<br />
64 Bit, User<br />
Defined I/O<br />
to P2<br />
16 Mbytes<br />
SDRAM<br />
83MHz<br />
PMC<br />
Site #2
Conclusions<br />
SBIL is a novel patterning tool for producing gratings and<br />
grids with nanometer level distortions.<br />
The system must satisfy challenging requirements for<br />
placement repeatibility, beam conditioning, and alignment.<br />
We have demonstrated long term placement stability of<br />
1.8 nm 3σ and short term placement stability of 2.1 nm 3σ.<br />
We can pattern large area gratings with unprecedented<br />
repeatibility.<br />
Future work will focus on self calibration to achieve nanometer<br />
level accuracy.<br />
MIT <strong>Space</strong> <strong>Nanotechnology</strong> Laboratory<br />
ptk-conclusions-103102.eps
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