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Roger H. French, Robert C. Wheland, Weiming Qiu, M. F.
Lemon, Edward Zhang, Joseph Gordon, Viacheslav A. Petrov, Victor F.
Cherstkov, Nina I.Delaygina, “Novel Hydrofluorocarbon Polymers for use as
Pellicles in 157 nm Semiconductor Photolithography”, Journal of
Fluorine Chemistry, 122, 63-80, 2003
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Roger
H. French, Robert C. Wheland, Weiming Qiu,
M. F. Lemon, Edward Zhang, Joseph
Gordon, Vlad Liberman, Andrew Grenville,
Rod Kunz, Mordechai Rothschild, “157nm Pellicles: Polymer
Design for Transparency and Lifetime”, Optical Microlithography XV,
SPIE 4691, 57, (2002).
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V.
Liberman, M. Rothschild, J. H. C. Sedlacek, A. Grenville, R. H. French,
“Behavior of Candidate Organic Pellicle Materials Under 157-nm Laser
Irradiation”, Optical Microlithography XV, SPIE 4691, 56, (2002).
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Roger
H. French, Joseph Gordon, David J. Jones, M. F. Lemon, Robert C. Wheland,
Edward Zhang, Fredrick C. Zumsteg, Kenneth G. Sharp, Weiming Qiu,
“Materials Design and Development of Fluoropolymers for Use as Pellicles
in 157nm Photolithography”, Optical Microlithography XIV, SPIE Vol. 4346,
(2001).
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R. H. French, R. C. Wheland, D. J. Jones, J. N.
Hilfiker, R. A. Synowicki,
F. C. Zumsteg, J. Feldman, A. E. Feiring, "Fluoropolymers for 157nm
Lithography: Optical Properties from VUV Absorbance and Ellipsometry
Measurements", SPIE Proceedings: Microlithography 2000, to be
published.
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Roger H. French1, Robert C. Wheland1,
Weiming Qiu1, M. F. Lemon1, Gregory S. Blackman1,
Edward Zhang2, Joseph Gordon2, Vlad Liberman3,
Andrew Grenville4, Rod Kunz3, Mordechai Rothschild3
1. DuPont Co. Central Research, E356-384, Wilmington DE
19880-0356.
2. DuPont Photomasks Inc. 4 Finance Dr., Danbury CT,
06810
3. Lincoln Laboratory, Massachusetts Institute of
Technology, Lexington MA 02420
4. Intel Corporation / International Sematech
The introduction of 157 nm as the next optical lithography wavelength
has created a need for new soft (polymeric) or hard (quartz) pellicle
materials. Pellicles should be
> 98% transparent to incident 157 nm light and, ideally, sufficiently
resistant to photochemical damage to remain useful for an exposure lifetime of
7.5 kJ/cm2.
The transparency specification has been met. We have developed families of experimental Teflon™AF (TAFx) polymers
with > 98% transparency which can be spin coated and lifted as
micron-scale, unsupported membranes. Still
higher transparencies should be possible once optimization of intrinsic
(composition, end groups, impurities, molecular weight) and extrinsic (oxygen,
absorbed hydrocarbons, contaminants) factors are completed. The measured
transparencies of actual pellicle films, however, are affected by many factors
other than absorption. Film
thickness must be precisely controlled so as to allow operation at the fringe
maxima for the lithographic wavelength. Roughness
and thickness uniformity are also critical. An important part of our program has thus been learning how to spin
membranes from the solvents that dissolve our pellicle candidates.
Meeting the durability specification at 157 nm remains a major concern. The 157 nm radiation durability lifetime of a polymer is determined by
two fundamental properties: the fraction of 157 nm radiation absorbed and the
fraction (quantum efficiency) of this absorbed radiation that results in
photochemical darkening. Originally it was assumed that lifetime increases uniformly
with increasing transparency. We
now have cases where materials with very different absorbances (TAFx4P and
46P) have similar lifetimes and materials with similar absorptions (TAFx46P
and 2P) have very different lifetimes. These findings demonstrate the importance of the relative quantum
efficiencies as the 157 nm light energy distributes itself along degradative
versus non-degradative pathways. In
an effort to identify chemical and structural features that control lifetime,
we have been studying model molecular materials, some quite similar to the
monomer units used to make our pellicle candidates. Several of these models have shown transparencies much higher and
lifetimes far longer than our best pellicle candidates to date.
Figure 1. Materials
development is a staged process.
Figure 2. Spectral
transmission of Pellicle TAFx3P-10665-6 .
Figure.
Photochemical Darkening and the Effect of Oxygen
Figure 7. Nanoindentations
taken with a 0.5 mN load in the unirradiated polymer (left side) and irradiated
area (right side).
Figure
In-situ Transmission to a Dose of 113 Joules/cm2.
Figure 11. In
situ transmission of Molecular Material 18 to a total dose of 113 Joules/cm2.
Figure 13. In
situ transmission of Molecular Material 18 to a total dose of 25 Joules/cm2.
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