Metrology for Nanometer Scale Science and Technology - Space ...
Metrology for Nanometer Scale Science and Technology - Space ...
Metrology for Nanometer Scale Science and Technology - Space ...
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<strong>Metrology</strong> <strong>for</strong> <strong>Nanometer</strong> <strong>Scale</strong><br />
<strong>Science</strong> <strong>and</strong> <strong>Technology</strong><br />
Mark L. Schattenburg, Ralf Heilmann <strong>and</strong> Henry I. Smith<br />
<strong>Space</strong> Nanotechnology Laboratory<br />
NanoStructures Laboratory<br />
~<br />
Massachusetts Institute of <strong>Technology</strong><br />
Cambridge, Massachusetts.<br />
China-US Symposium on Nano <strong>Science</strong> <strong>and</strong> <strong>Technology</strong><br />
Beijing, China<br />
May 17-20, 2004<br />
<strong>Space</strong> Nanotechnology Laboratory<br />
SNL<br />
Massachusetts Institute of <strong>Technology</strong>
Nanotechnology<br />
The Next Industrial<br />
Revolution?
<strong>Metrology</strong> <strong>and</strong> Industrial Revolutions<br />
Revolution<br />
1st Industrial Revolution<br />
~1750 - 1830<br />
2nd Industrial Revolution<br />
~1860 - 1920<br />
Semiconductor Revolution<br />
~1960 - 2015(?)<br />
Nanotechnology Revolution<br />
~2000 - ???<br />
Industry<br />
textile mills,<br />
trains, guns<br />
heavy industry<br />
mass production<br />
integrated circuits,<br />
computers, internet<br />
mass-produced<br />
nanosystems<br />
<strong>Space</strong> Nanotechnology Laboratory<br />
SNL<br />
Massachusetts Institute of <strong>Technology</strong><br />
<strong>Metrology</strong><br />
no interchangeable<br />
parts<br />
vernier calipers,<br />
gauge blocks<br />
~25 - 100 µm<br />
laser interferometer<br />
~100 nm - 1 µm<br />
nanometer-accurate<br />
length scales<br />
(encoders)<br />
~1 nm
MLS-2001-03-23.01.eps<br />
Computer<br />
Traditional Heterodyne<br />
Displacement Measuring Interferometer (DMI)<br />
Laser<br />
Fiber-optic<br />
Cables<br />
RS-232 / GBIP<br />
50%<br />
Beamsplitter<br />
Fiber-optic<br />
Pickup<br />
Electronics<br />
Two-axis<br />
Stage with<br />
Mirrors<br />
Interferometer<br />
Head<br />
DMI Limitations<br />
Moving arms create<br />
time-dependant cosine,<br />
Abbe, diffraction<br />
& other path errors.<br />
Air paths introduce large<br />
errors due to atmospheric<br />
disturbances:<br />
-> Temperature, Pressure<br />
-> Humidity, Turbulence<br />
System is bulky<br />
<strong>and</strong> expensive.<br />
Heavy stage mirrors<br />
limit stage scanning<br />
speed & accuracy.
Zygo-Interferometer.eps<br />
Wafer<br />
Reticle<br />
Lens<br />
Measurement<br />
Beams<br />
Lithography Scanner<br />
Substrate <strong>and</strong> Reticle Stages<br />
Collimated UV<br />
Light Beam<br />
Reticle Stage<br />
Mirrors<br />
Wafer Stage<br />
Mirrors<br />
Laser Head<br />
Scanner Mechanics<br />
Reticle is imaged onto wafer<br />
with ~4x reduction.<br />
Reticle <strong>and</strong> wafer stages<br />
are synchronously scanned<br />
during exposure.<br />
Tight pattern overlay (~30% CD)<br />
requires extremely high<br />
stage per<strong>for</strong>mance.<br />
Interferometer mirrors are<br />
drag on stage accuracy <strong>and</strong><br />
per<strong>for</strong>mance.<br />
Long, variable, unbalanced<br />
interferometer beam paths
Nanoscale Microscopy <strong>and</strong> Pattern Generators<br />
• Optical <strong>and</strong> electron microscopes<br />
• Proximal probes (AFM, STM, etc.)<br />
• Electron <strong>and</strong> laser beam writers, etc.<br />
Probe resolution Field size Stage accuracy?<br />
0.1 - 500 nm 1 µm - 1 mm > 30 nm - microns<br />
Stitching errors due to<br />
• Sample stage inaccuracies<br />
• Intra-field distortions<br />
Need metrology frame with sub-nm accuracy over many fields<br />
<strong>Space</strong> Nanotechnology Laboratory<br />
SNL<br />
Massachusetts Institute of <strong>Technology</strong>
2003 International <strong>Technology</strong> Roadmap <strong>for</strong> Semiconductors<br />
Year 2003 2004 2007 2010 2013 2016 2018<br />
CD (nm) 100 90 65 45 32 22 18<br />
dense line CD control (nm) 12 11 8 5.5 3.9 2.7 2.2<br />
Wafer Overlay Control (nm) 35 32 23 18 13 9 7<br />
W. Overlay <strong>Metrology</strong> Prec. (nm) 3.5 3.2 2.3<br />
1.8 1.3 0.9 0.7<br />
Solutions Exist Solutions Being No Known<br />
Pursued Solutions
MLS-2002-02-28.02.eps<br />
Nanoaccuracy in Nanophotonics<br />
Many nanophotonic structures<br />
depend on the coherent superpostion<br />
of scattering from sub-wavelength features.<br />
Integrated Optical Bragg Grating Devices<br />
Photonic Crystals<br />
DFB Lasers<br />
>1 mm<br />
Bragg Waveguide Channel Add-Drop Filter<br />
Accuracy Calculus<br />
Grating period = 244.4 nm<br />
period/50 ~5 nm placement accuracy<br />
~ 1 nm metrology frame accuracy<br />
Best-available e-beam tools<br />
have ~20 nm accuracy.<br />
244.4 nm<br />
InGaAsP Waveguide<br />
(M.H. Lim et al., JVST B 17, 3208 (1999))
Spatial-Phase-Locked E-beam Lithography<br />
SE detector<br />
electrontransparent<br />
fiducial grid<br />
electron beam<br />
e -<br />
e-beam resist<br />
X<br />
Y<br />
e -<br />
Signal<br />
Processing<br />
Feedback<br />
Loop<br />
secondary<br />
electrons<br />
substrate<br />
Grid Signal<br />
raster scan direction<br />
exposed pattern<br />
Field stitching errors <strong>and</strong> global placement accuracy<br />
relative to fiducial grid < 1.3 nm (1σ)<br />
(J.T. Hastings, F. Zhang, <strong>and</strong> H.I. Smith, JVST B 21, 2650 (2003))
2<br />
Patterned Magnetic Media<br />
(a)<br />
57 x 115 nm pillars<br />
Hc = 710 Oe<br />
100 nm<br />
1.20<br />
0.80<br />
0.40<br />
0.00<br />
-4000 -2000 0 2000 4000<br />
-0.40<br />
-0.80<br />
-1.20<br />
Applied Field, Oe<br />
out of plane<br />
in plane<br />
C.A. Ross et al., JVST B 17, 3168 (1999)<br />
Goal:<br />
Higher areal data storage density<br />
Problem:<br />
Superparamagnetic limit (KV > 40 kT)<br />
One solution:<br />
Patterned media<br />
Pitch 50 nm - 10 nm<br />
areal density 40 Gb/cm 2 - 1 Tb/cm 2<br />
Pattern placement metrology < 1 nm
Self-Assembly<br />
small pitch (< 25 nm)<br />
short-range order<br />
Joy Y. Cheng, C. A. Ross,<br />
E. L. Thomas, H. I. Smith,<br />
<strong>and</strong> G. J. Vancso,<br />
Adv. Mat. 15, 1599 (2003)<br />
"Templated Self-Assembly<br />
of Block Copolymers:<br />
Effect of Substrate<br />
Topography"<br />
Template-Assisted Self-Assembly<br />
small pitch, templateimposed<br />
long-range order<br />
Control defects: Template placement accuracy
v<br />
Displacement Measuring<br />
Interferometer<br />
Substrate Mirror<br />
Stage<br />
f f D<br />
- Long, unbalanced, timedependant<br />
optical paths in air<br />
- heavy stage mirrors<br />
- non-linearities<br />
- precision ~ 200 nm (lab)<br />
to ~ 2 nm (vacuum)<br />
<strong>Metrology</strong> Frames<br />
f<br />
v<br />
Substrate<br />
Optical Encoder<br />
Stage<br />
Stationary Grating<br />
f D<br />
θ<br />
f<br />
Optical<br />
Fiber<br />
- Short (sub-mm), constant<br />
optical paths<br />
- lightweight stage optics<br />
- accuracy depends on<br />
encoder plate accuracy<br />
(> 100 nm today)<br />
d<br />
f
Manufacture of Large Gratings<br />
Mechanical ruling:<br />
slow (weeks - months)<br />
inaccurate<br />
E-beam lithography:<br />
faster (days)<br />
stitching errors<br />
Interference lithography:<br />
fast<br />
problems? <br />
MIT 'B' Engine, Richardson Grating Labs<br />
(Courtesy Spectra-Physics)
MLS-2000-04-03.01.eps<br />
Spherical waves cause<br />
hyperbolic phase.<br />
Hyperbolic Phase<br />
Traditional Interference Lithography<br />
laser<br />
laser<br />
Figure errors & defects<br />
in collimating optics cause noise.<br />
Linear Phase + Noise
Optical<br />
Bench<br />
Interferometer<br />
Intensity<br />
Scanning-Beam Interference Lithography<br />
θ<br />
θ<br />
Laser<br />
XY Stage<br />
Air Bearing<br />
Granite Slab<br />
Grating<br />
Period<br />
p=λ/(2sinθ)<br />
X<br />
Substrate<br />
Y Direction<br />
Intensity<br />
X Direction<br />
Scan<br />
1<br />
Summed Intensity<br />
of Scans 1-6<br />
Scan<br />
2 Scan<br />
3<br />
Scan<br />
4<br />
Scan<br />
5<br />
Scan<br />
6<br />
Scanning<br />
Grating<br />
Image<br />
Air-Bearing<br />
X-Y Stage<br />
Resistcoated<br />
Substrate<br />
X
cc_readwrite3.eps<br />
DSP/<br />
Phase Meters<br />
Stage Error<br />
Frequency<br />
Synthesizer<br />
AOM2<br />
AOM3<br />
PM2<br />
Nanoruler Reading <strong>and</strong> Writing Modes<br />
Wafer<br />
XY Stage<br />
UV Laser Beam<br />
PM1<br />
f 3 =120 MHz<br />
AOM1<br />
DSP/<br />
Phase Meters<br />
PM4<br />
AOM2<br />
f2 =100 MHz f1 =100 MHz<br />
f2 =90 MHz<br />
Stage Error<br />
PM3<br />
XY Stage<br />
UV Laser Beam<br />
Writing Mode Reading Mode<br />
Frequency<br />
Synthesizer<br />
AOM1 AO<br />
f 1 =110 MHz
ptk-frontsystem-032703.eps<br />
The Nanoruler - A Scanning Beam Interference Lithography Tool<br />
<strong>for</strong> Large-Area Gratings<br />
<strong>Metrology</strong> block with<br />
phase measurement<br />
optics<br />
Wafer<br />
Chuck<br />
X-Y air bearing<br />
stage<br />
Receiving tower<br />
<strong>for</strong> UV laser<br />
(λ = 351.1 nm)<br />
Optical bench with<br />
interference lithography<br />
optics<br />
Refractometer<br />
interferometer<br />
X-axis interferometer<br />
Granite base<br />
Isolation system
ptk-enclosure-032903.eps<br />
Nanoruler Environmental Enclosure<br />
Temperature Control ±0.005 C<br />
Humidity Control ±1% RH
Grating written with MIT Nanoruler on 300 mm wafer:<br />
pattern placement repeatability < 3 nm (3σ)<br />
"ruling" time ~ 30 min.
Summary<br />
The nanotechnology revolution needs a metrology<br />
infrastructure that does not exist yet.<br />
Ultra-high accuracy encoders will enable a new<br />
dimensional metrology paradigm<br />
MIT is developing a novel grating patterning <strong>and</strong> metrology<br />
tool - the Nanoruler - based on Scanning-Beam Interference<br />
Lithography
Massachusetts Institute of <strong>Technology</strong><br />
Acknowledgments<br />
Graduate Students:<br />
Paul Konkola (Ph.D.'03)<br />
Carl Chen (Ph.D.'03)<br />
Juan Montoya<br />
Chulmin Joo<br />
Chih-Hao Chang<br />
Mireille Akilian<br />
Staff:<br />
Robert Fleming (SNL)<br />
James Carter (NSL)<br />
Sponsors:<br />
NASA, DARPA<br />
<strong>Space</strong> Nanotechnology Laboratory
ptk-xuepsd-033103.eps<br />
Power Spectral Density of the Unobservable Error -<br />
the Effect of Averaging through Scanning<br />
Power spectrum of x ue (nm/sqrt(Hz))<br />
10 0<br />
10 -1<br />
10 -2<br />
10 -3<br />
60 Hz electrical, 3σ = 1.1 nm<br />
from 59.5 to 60.5 Hz<br />
3σ = 1.8 nm from 100 to 714 Hz<br />
x ue raw, 3σ=3.12 nm<br />
x ue , 3σ=2.12 nm, d/v=20 ms<br />
Thermal expansion, 0 to ~0.04 Hz<br />
Air index non-uni<strong>for</strong>mity, 3σ = 2.3 nm from 0 to 59.5 Hz<br />
Vibrations<br />
Gaussian<br />
filtered data<br />
0 100 200 300 400 500 600 700<br />
Frequency (Hz), resolution=0.35 Hz<br />
Gaussian<br />
filtered data
Super invar chuck<br />
flexure mounted<br />
to stage<br />
Super invar<br />
mounts <strong>for</strong> optics<br />
Zerodur mirrors<br />
bonded to chuck<br />
<strong>Metrology</strong> Frames<br />
Zerodur metrology block flexure<br />
mounted to bench, super invar<br />
inserts<br />
ptk-metrologyframes-032903.eps<br />
Refractometer<br />
cavity, bonded<br />
mirrors<br />
x-axis column<br />
reference mirror<br />
MIT <strong>Space</strong> Nanotechnology Laboratory
p =<br />
Interference of Spherical Waves<br />
Phase discrepancy from a perfect linear grating<br />
λ 5<br />
-300 nm<br />
-100 nm d = 1 m,<br />
2 sin θ<br />
y (mm)<br />
10<br />
0<br />
-5<br />
300 nm<br />
500 nm<br />
100 nm<br />
θ θ<br />
0 nm<br />
-10<br />
-10 -5 0<br />
x (mm)<br />
5 10<br />
d<br />
-500 nm<br />
x<br />
cc_intro_priorart3.eps<br />
z<br />
y<br />
λ = 351.1 nm,<br />
p = 400 nm.
Coordinate Measuring Machines<br />
Shaping, assembly, alignment, <strong>and</strong> characterization of<br />
large-scale parts with sub-micron<br />
tolerances<br />
Examples:<br />
Diamond turning<br />
Grazing-incidence<br />
x-ray optics (astronomy)<br />
EUV lithography optics<br />
Need nanometer accuracy<br />
over meter scales<br />
1.6 m<br />
Spectroscopy<br />
X-Ray<br />
Telescope<br />
concept <strong>for</strong><br />
future x-ray<br />
telescope<br />
(J. Stewart et al.,<br />
NASA GSFC)
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