Controlling line width roughness (LWR) is a critical issue in extreme ultraviolet lithography (EUVL). High
sensitivity, high resolution, and low LWR are required for EUV lithography resist. However, simultaneously
achieving optimal properties through chemical tuning alone is difficult. The track process is one of the factors
that impacts LWR. Enhancing track processes in EUV lithography is thus critical to controlling LWR.
This paper describes an approach to mitigating LWR based on optimizing track-based and etch-based
processes. It also presents the results of our newly developed track-based smoothing process as well as the
results of combining several track-based techniques. The latest LWR performance from using track-based
techniques, optimized track processes, and etch-based techniques will be highlighted.
Moore's Law continues to drive improvements to lithographic resolution to increase integrated circuit transistor density,
improve performance, and reduce cost. For the 22 nm node and beyond, extreme ultraviolet lithography (EUVL) is a
promising technology with λ=13.5 nm, a larger k1 value and lower cost of ownership than other available technologies.
For small feature sizes, process control will be increasingly challenging, as small features will create measurement
uncertainties, yet with tighter specifications. Optical scatterometry is a primary candidate metrology for EUV
lithography process control. Using simulation and experimental data, this work will explore scatterometry's application
to a typical lithography process being used for EUV development, which should be representative of lithography
processes that will be utilized for EUV High Volume manufacturing (HVM). EUV lithography will be performed using
much thinner photoresist thicknesses than were used at the 248nm or 193nm lithography generations, and will probably
include underlayers for adhesion improvement; these new processes conditions were investigated in this metrological
study.
Line width roughness (LWR) control is a critical issue in extreme ultraviolet lithography (EUVL). The
difficulty of controlling LWR and the need to minimize it have grown as the sensitivity of materials and
resolution in the resist patterning process has improved. Another critical feature that has become difficult to
control in EUVL and 22nm half-pitch systems is pattern collapse. The increase of aspect ratio that comes from
further scaling promotes the onset of pattern collapse. Both pattern collapse and LWR are easily observed in
EUVL and leading-edge ArF immersion lithography.
This paper will demonstrate recent gains in LWR control in leading EUV films using track-based processes,
etch-based improvements, and the results of combined techniques. Also the use of a newly developed EUV-specific
FIRM™ rinse chemistry to reduce pattern collapse will be discussed along with future development
activities and industry requirements for both LWR and pattern collapse.
For extreme ultraviolet light lithography to be a viable process for the future development of computer chips, it is
necessary that clean photons are produced at the intermediate focus (IF). To measure the flux at the IF, the Center
for Plasma-Material Interactiosn (CPMI) at the University of Illinois at Urbana-Champaign has developed a Sn IF
flux emission detector (SNIFFED) apparatus that is capable of measuring charged and neutral particle flux at the IF.
Results will be presented that diagnose debris produced at the IF, as well as methods by which this debris can be
mitigated.
Advanced Materials Research Center, AMRC, International SEMATECH Manufacturing Initiative, and ISMI are
servicemarks of SEMATECH, Inc. SEMATECH, and the SEMATECH logo are registered servicemarks of
SEMATECH, Inc. All other servicemarks and trademarks are the property of their respective owners.
The availability of defect-free masks remains one of the key challenges for inserting extreme ultraviolet lithography
(EUVL) into high volume manufacturing, yet little data is available for understanding native defects on real masks. In
this paper, a full-field EUV mask is fabricated to investigate the printability of various defects on the mask. The
printability of defects and identification of their source from mask fabrication to handling were studied using wafer
inspection. The printable blank defect density excluding particles and patterns is 0.63/cm2. Mask inspection is shown to
have better sensitivity than wafer inspection. The sensitivity of wafer inspection must be improved using through-focus
analysis and a different wafer stack.
Extreme ultraviolet lithography (EUVL) is the most effective way to print sub-30 nm features. We characterized EUVL
readiness of the three major resist platforms for sub-30 nm half-pitch (HP) manufacturability using a full-field ASML
alpha demo tool (ADT) scanner and studied the extendibility of EUV chemically amplified resist (CAR). Based on an
"M-factor" analysis, which shows the maturity of EUV resist for 28 nm HP manufacturability, a polymer-bound
photoacid generator (PAG) resist was 78% ready, a PHS hybrid resist was 81%, and a molecular glass EUV resist was
58%. The polymer-bound resist showed good resolution for 25 nm HP using the ASML ADT. It also demonstrated fair
linewidth roughness (LWR) and a good lithographic process margin of 18% exposure latitude (EL) and 160 nm depth of
field (DOF) for 28 nm HP patterning compared with the other resist platforms, but its resist collapse and etch resistance
need to be improved for manufacturability. PHS hybrid resist showed a fair etch resistance and resist collapse
performance compared to the other resist platforms, but LWR needs to be improved. The molecular resist needs to
mature further, especially in resist collapse and iso-dense (ID) bias. When considering its many strong points and control
of lower acid diffusion, the polymer-bound PAG resist appears to be the most suitable platform for manufacturability and
EUV CAR extension. We therefore would like to encourage the development of next generation polymer-bound PAG
resist with a higher etch resistance.
A process window of 80 nm DOF was demonstrated for 26 nm HP patterning and a measurable DOF for 25 nm HP was
achieved with the polymer-bound PAG resist. Resist collapse and LWR are major issues for 22 nm HP patterning in
manufacturing. LWR improvements were achieved with various techniques, and resist collapse was greatly improved
with a novel approach that uses a residual resist layer. 16 nm HP line/space (L/S) image modulation and 18 nm HP
resolution were demonstrated with an EUV CAR, indicating that EUV CAR could be extended to sub-20 nm HP
patterning.
Extreme ultraviolet lithography (EUVL) is the most effective way to print sub-32 nm features. We have assessed EUVL
resist readiness for 32 nm half-pitch (HP) manufacturing, presenting process feasibility data such as resolution, depth of
focus (DOF), line edge roughness/line width roughness (LER/LWR), mask error enhancement factor (MEEF), resist
collapse, critical dimension (CD) uniformity, post-exposure delay (PED) stability, and post-exposure bake (PEB)
sensitivity. Using the alpha demo tool (ADT), a full field ASML EUV scanner, we demonstrate the feasibility of a k1
~0.593 resist process for 32 nm HP line/space (L/S) patterning. Exposure latitude (EL) was 13% at best focus, and DOF
was 160 nm at best dose using a 60 nm thick resist. By incorporating a spin-on underlayer, the process margin could be
improved to 18.5% EL and 200 nm DOF. We also demonstrate ADT extendibility using a state-of-the-art EUV
platform. A k1 ~0.556 resist process was demonstrated for 30 nm HP L/S patterns, providing a 13% EL, 160 nm DOF,
and a common process window with isolated lines. 28 nm HP patterning for a k1 ~0.528 resist process could be feasible
using a more advanced resist with improved DOF and resist collapse margin.
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