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We introduce a complete methodology for process window optimization in proximity mask aligner lithography. The commercially available lithography simulation software LAB from GenISys GmbH was used for simulation of light propagation and 3D resist development. The methodology was tested for the practical example of lines & spaces, 5 micron half-pitch, printed in a 1 micron thick layer of AZ® 1512HS positive photoresist on a silicon wafer. A SUSS MicroTec MA8 mask aligner, equipped with MO Exposure Optics® was used in simulation and experiment. MO Exposure Optics® is the latest generation of illumination systems for mask aligners. MO Exposure Optics® provides telecentric illumination and excellent light uniformity over the full mask field. MO Exposure Optics® allows the lithography engineer to freely shape the angular spectrum of the illumination light (customized illumination), which is a mandatory requirement for process window optimization. Three different illumination settings have been tested for 0 to 100 micron proximity gap. The results obtained prove, that the introduced process window methodology is a major step forward to obtain more robust processes in mask aligner lithography. The most remarkable outcome of the presented study is that a smaller exposure gap does not automatically lead to better print results in proximity lithography - what the “good instinct” of a lithographer would expect. With more than 5'000 mask aligners installed in research and industry worldwide, the proposed process window methodology might have significant impact on yield improvement and cost saving in industry.
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LITHOGRAPHIC PROCESS WINDOW OPTIMIZATION FOR MASK
ALIGNER PROXIMITY LITHOGRAPHY
Reinhard Voelkela, Uwe Voglera, Arianna Bramatia, Andreas Erdmannb, Nezih Ünalc,
Ulrich Hofmannc, Marc Hennemeyerd, Ralph Zoberbierd, David Nguyene, Juergen Bruggere
a) SUSS MicroOptics SA, Rouges-Terres 61, CH-2068 Hauterive, Switzerland, [email protected], www.suss.ch
b) Fraunhofer Institut IISB, Schottkystr. 10, D-91058 Erlangen, Germany
c) GenISys GmbH, Eschenstr. 66, D-82024 Taufkirchen, Germany
d) SÜSS MicroTec Lithography GmbH, Schleissheimerstrasse 90, D-85748 Garching, Germany
e) École Polytechnique Fédérale de Lausanne, EPFL STI IMT, CH-1015 Lausanne, Switzerland
MASK ALIGNER LITHOGRAPHY EVOLUTION
SUSS MicroOptics, Reinhard Völkel, SPIE Advanced Lithography 2014, 9052-15 2
New illumination system: MO Exposure Optics®
better light uniformity & telecentric illumination
customized illumination
LAB: lithography simulation
full 3D resist development
Process window optimization
visualize and optimize mask aligner lithography
find robust process
improve yield resist
hei
ght
gap
Θ
wafer
photomask
20%
80%
sidewallangle
resist pit
200nmCD
half-pitch
Proximity lithography – shadow printing
Resolution of 3 – 5 m (half-pitch) for 30 – 50 m proximity gap
Resolution proximity gap
MASK ALIGNER LITHOGRAPHY 1963 - 2014
Wafer
Mask
SUSS MicroTec, LAB – 3D Workshop, April 24, 2013 3
Side lobes
Off-Axis
Apodization
DIFFRACTION RULES PROXIMITY LITHOGRAPHY
SUSS MicroOptics, Reinhard Völkel, SPIE Advanced Lithography 2014, 9052-15 4
MO EXPOSURE OPTICS: CUSTOMIZED ILLUMINATION
SUSS MicroOptics, Reinhard Völkel, SPIE Advanced Lithography 2014, 9052-15 5
LITHOGRAPHIC PROCESS WINDOW FOR MASK ALIGNER
SUSS MicroOptics, Reinhard Völkel, SPIE Advanced Lithography 2014, 9052-15 6
CD UNIFORMITY
SUSS MicroOptics, Reinhard Völkel, SPIE Advanced Lithography 2014, 9052-15 7
resist
hei
ght
gap
Θ
wafer
photomask
20%
80%
sidewallangle
resist pit
200nmCD
half-pitch
AZ® 1512 photoresist, 1m thick
Simulation in LAB software from GenISys GmbH
Resist prints in SUSS MA6 MOEO
Data analysis in Matlab
LINES & SPACES 5 MICRON (HALF-PITCH)
SUSS MicroOptics, Reinhard Völkel, SPIE Advanced Lithography 2014, 9052-15 8
SUSS LGO Optics (±1.4°) (proximity lithography settings)
PROCESS WINDOW (CD)
SUSS MicroOptics, Reinhard Völkel, SPIE Advanced Lithography 2014, 9052-15 9
B
A C
resist
hei
ght
gap
Θ
wafer
photomask
20%
80%
sidewallangle
resist pit
200nmCD
half-pitch
PROCESS WINDOW (SIDE LOBE PRINTING)
SUSS MicroOptics, Reinhard Völkel, SPIE Advanced Lithography 2014, 9052-15 10
resist
hei
ght
gap
Θ
wafer
photomask
20%
80%
sidewallangle
resist pit
200nmCD
half-pitch
PROCESS WINDOW (SIDEWALL ANGLE)
SUSS MicroOptics, Reinhard Völkel, SPIE Advanced Lithography 2014, 9052-15 11
resist
hei
ght
gap
Θ
wafer
photomask
20%
80%
sidewallangle
resist pit
200nmCD
half-pitch
AZ® 1512 photoresist, 1m thick
PROCESS WINDOW
SUSS MicroOptics, Reinhard Völkel, SPIE Advanced Lithography 2014, 9052-15 12
resist
hei
ght
gap
Θ
wafer
photomask
20%
80%
sidewallangle
resist pit
200nmCD
half-pitch
DEATH VALLEY OF PROXIMITY LITHOGRAPHY
SUSS MicroOptics, Reinhard Völkel, SPIE Advanced Lithography 2014, 9052-15 13
Resolution = Proximity Gap
OUTLOOK
14
3µm L&S 4µm L&S 5µm L&S 7µm L&S 10µm L&S
≈ 10 µm ≈ 20 µm ≈ 30 µm ≈ 55 µm >100 µm
𝐶𝑟𝑖𝑡𝑖𝑐𝑎𝑙 𝐺𝑎𝑝 ≅ 0.44𝐶𝐷2
λ
Broad band illumination
LG
O
PW
fo
r L
GO
P
ara
llel Illu
min
ati
on
CONCLUSION
SUSS MicroOptics, Reinhard Völkel, SPIE Advanced Lithography 2014, 9052-15 15
New illumination system: MO Exposure Optics®
better light uniformity & telecentric illumination
customized illumination
LAB: lithography & full 3D resist simulation
Process window optimization
visualize and optimize mask aligner lithography
find robust process, improve yield
JOIN OUR WORKSHOP ON THURSDAY MORNING
SUSS MicroOptics, Reinhard Völkel, SPIE Advanced Lithography 2014, 9052-15 16
SUSS.
Our Solutions
Set Standards
SUSS MicroOptics SA Rouges-Terres 61
CH-2068 Hauterive
Switzerland
Tel +41-32-564444
Fax +41-32-5664499
[email protected], www.suss.ch
17 SUSS MicroOptics, Reinhard Völkel, SPIE Advanced Lithography 2014, 9052-15
