Abstract: Lithography is a
critical process in the
fabrication of
integrated circuits.
The continuous
increase
in computing power
for more than half a
century has
depended in the
ability of printing
smaller
and smaller features,
which has required
the use of light
sources operating at
increasingly
shorter wavelengths.
There is keen interest
in the development
of high-power light
sources for
extreme ultraviolet
(EUV) lithography at
=13.5 nm and
future beyond
extreme ultraviolet
(BEUV) lithography
near =6.7 nm. The
work conducted in
this dissertation has
characterized
aspects of laser-
produced plasmas
(LPPs) that serve as
light sources for EUV
/ BEUV lithography.
The laser pulse
shape dependence
of the conversion
efficiency of =1.03
μm laser into in-band
13.5 nm EUV
emission in a Sn LPP
was studied as a
function of laser
pulse shape and
durations.
Laser pulses of
arbitrary temporal
shape with variable
energy and pulse
widths were
generated
using a
programmable pulse
synthesizer based on
a diode-pumped
chirped pulse
amplification
Yb: YAG laser. The
pulse synthesizer is
based on wave front
splitting and pulse
stacking for the
generation of
arbitrary shape laser
pulses of Joule-level
energy.

Pulses ranging from
hundreds of ps to
several ns were
generated with a
single laser. The
measurements
showed the CE
favors the use of
nearly square pulses
of duration longer
than 2
ns, in agreement
with
hydrodynamic/atomi
c physics
simulations. A
significant increase
in CE

was observed when
Q-switched pulses
was substituted by
square pulses of
similar duration.
Conditions were
observed at which
the EUV pulse
duration significantly
outlasts the laser
pulse
in the direction
normal to the target
surface, in contrast
at grazing angles the
measured EUV
pulse duration is
shorter and similar to
the laser pulse
duration. The
physics leading to
this
angular anisotropy is
discussed, along
with spectroscopic
characterization of
EUV emission and
at-wavelength
images that
characterize the
source size.

Another aspect of
this dissertation
includes a
comprehensive
study of the
emission from Gd
and Tb LPPs in the
=6.5 - 6.7 nm
region. BEUV
emission spectra
were measured as a
function
of laser pulse
duration (120 ps - 4
ns), emission angle,
and spatial location
within the plasma.
At-wavelength
images of the BEUV
emitting plasma
region were obtained
as a function of
irradiation
parameters. The
peak of the emission
spectrum was
observed to broaden
and to
shift to longer
wavelength as the
laser pulses is
shortened from ns to
hundreds of ps.
Transient
self-consistent
hydrodynamic/atomi
c physics
simulations show
that the picosecond
irradiation
creates significantly
hotter plasmas in
which the dominant
emission originates
from more
highly ionized
species. Gd LPP
emission driven by
nanosecond laser
pulses best matched
the
reflectivity band of
our La/B 4 C mirrors.
Spatially resolved
spectra of the Gd
LPP were acquired
for different laser
parameters and were
compared to
simulations. The CE
into in-band BEUV
emission was
determined by
integrating angularly
resolved
measurements
obtained using an
array of calibrated
energy monitors. A
maximum CE of
0.47% / 0.45% for
the Gd / Tb LPPs
was
obtained within a
0.6% bandwidth.
The results are of
potential interest
BEUV lithography.

Adviser: Jorge Rocca
Co-Adviser: NA
Non-ECE Member: Azer Yalin
Member 3: Carmen Menoni
Addional Members: Mario Marconi

Publications:
Liang Yin, Hanchen Wang, Brendan A. Reagan, Cory Baumgarten, Eric Gullikson, Vyacheslav N. Shlyaptsev, Jorge J. Rocca. 6.7-nm emission from Gd and Tb plasmas using a single laser for beyond-extreme-ultraviolet lithography. Phys. Rev. Applied 6, 034009 (2016)

Liang Yin, Hanchen Wang, Brendan Reagan, Cory Baumgarten, Vyacheslav Shlyaptsev, Eric Gullikson, Jorge Rocca. Study of Gd/Tb LPP emission near λ= 6.7 nm for beyond EUV lithography. Proc. SPIE 9776, Extreme Ultraviolet (EUV) Lithography VII, 97761M (March 18, 2016); doi:10.1117/12.2219840

Y Wang, L Yin, S Wang, MC Marconi, J Dunn, E Gullikson, JJ Rocca. Single-shot soft x-ray laser linewidth measurement using a grating interferometer. Optics letters 38.23 (2013): 5004-5007. (Co-first author)

B. A. Reagan, C. Baumgarten, M. Pedicone, H. Bravo, L. Yin, H. Wang, C. Menoni, and J. Rocca, Development of High Repetition Rate, High Energy Diode-Pumped Short Pulse Lasers and Applications, in Laser Congress 2017 (ASSL, LAC), OSA Technical Digest (online) (Optical Society of America, 2017), paper ATh1A.1.

Cory Baumgarten, Michael Pedicone, Herman Bravo, Hanchen Wang, Liang Yin, Carmen S. Menoni, Jorge J. Rocca, and Brendan A. Reagan. A 1 Joule, 0.5 kHz repetition rate picosecond laser. Optics letters 41, 3339-3342 (2016)

Cory M Baumgarten, Brendan A Reagan, Michael A Pedicone, Herman Bravo, Liang Yin, Hanchen Wang, Mark Woolston, Brandon Carr, Carmen S Menoni, Jorge J Rocca. Demonstration of a compact 500 Hz repetition rate Joule-level chirped pulse amplification laser. Lasers and Electro-Optics (CLEO), 2016



Liang Yin • 970-218-7697 • liangyin@rams.colostate.edu

Brendan A Reagan, Cory Baumgarten, Michael Pedicone, Herman Bravo, Hanchen Wang, Liang Yin, Carmen S Menoni, Jorge J Rocca. Diode-pumped high energy short pulse lasers and their applications. Photonics Conference (IPC), IEEE (2016).

Y. Wang, S. Wang, E. Oliva, L. Li, M. Berrill, L. Yin, J. Nejdl, B. M. Luther, C. Proux, T. T. T. Le, J. Dunn, D. Ros, Ph. Zeitoun & J. J. Rocca, Gain dynamics in a soft-X-ray laser amplifier perturbed by a strong injected X-ray field. Nature Photonics 8, 381–384 (2014)

Michael A Purvis, Vyacheslav N Shlyaptsev, Reed Hollinger, Clayton Bargsten, Alexander Pukhov, Amy Prieto, Yong Wang, Bradley M Luther, Liang Yin, Shoujun Wang, Jorge J Rocca. Relativistic plasma nanophotonics for ultrahigh energy density physics. Nature Photonics 7.10 (2013): 796-800.

Lu Li, Yong Wang, Shoujun Wang, Eduardo Oliva, Liang Yin, TT Thuy Le, Sameh Daboussi, David Ros, Gilles Maynard, Stephane Sebban, Bitao Hu, Jorge J Rocca, Philippe Zeitoun. Wavefront improvement in an injection-seeded soft x-ray laser based on a solid-target plasma amplifier. Optics letters 38.20 (2013): 4011-4014.

Lu Li, Yong Wang, Shoujun Wang, Eduardo Oliva, Liang Yin, TT Thuy Le, Sameh Daboussi, David Ros, Gilles Maynard, Stephane Sebban, Bitao Hu, Jorge J Rocca, Philippe Zeitoun. Wavefront of seeded soft x-ray laser based on a solid-target plasma amplifier. SPIE Optical Engineering+ Applications (2013).

David Alessi, Yong Wang, BM Luther, Liang Yin, DH Martz, MR Woolston, Yanwei Liu, M Berrill, JJ Rocca, Efficient excitation of gain-saturated sub-9-nm-wavelength tabletop soft-X-ray lasers and lasing down to 7.36 nm. Physical Review X, 1.2 (2011): 021023.

Program of Study:
MATH-531
ECE-650
ECE-506
ECE-507
ECE-641
ECE-795
ECE-799
NA