Characterization of SAL605 negative resist at {lambda}=13 nm Page: 6 of 6
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short development times. This behaviour is consistent
with the results obtained by Gat et al. [3] with x-rays
(%=lnm) and with those of Fedynyshyn et al. [2] using
an electron beam.
Comparison of lithography prints of 0.35pm
features for different conditions indicates that a developer
normality of 0.27 yields better results than a normality
of 0.22. Also, the longer development time (td),
corresponding to higher contrasts result in steeper
sidewall angles for these 0.35 m lines and spaces.
Sidewalls of - 370 were obtained for td=15s and
N=0.27, whereas a longer development time, td,=90s
with the same normality improved this value to - 530.
Increasing the development time to 120s resulted in
sidewall angles of ~700. These conditions correspond to
increasing contrast values from y=1.6 to y=4.4
0
U6.00
5.00
4.00
3.00
2.00
1.00
n0 n. 65nm N=0.27
S110nm, N=0.27
* 110nm. N=0.22
" 65nm, N=0.22ii
0 50 100 150 200 250
Development time (s)
Figure 3. Dependence of the contrast of S
development time and developer normality.300
AL605 withFinally, we were able to simulate the exposure
curves obtained for different processing conditions,
using Prolith/2 [4], in order to infer the development
rate parameters for SAL605 used with TMAH, N=0.27.
Several parameters are used by this lithography
simulator. The Dill resist parameters [5] were:
A=0 m'1, B=4.4 m'' and C-cm2/mJ, and the
development rate parameters used in the Mack modcl [6]
were : R,,, =11nm/s, R=nin=Onm/s, mth=-1 and n=3.0.
Only two of these parameters were varied to fit the data,
n and C, which are related repectively to the contrast and
the sensitivity of the resist. All the other parameters
were either known or were measured experimentally.
The agreement of the simulation with the experimental
results is good, as can be seen in Fig.L.
The knowledge of these resist/development
parameters is essential to be able to model correctly the
printing of fine features in SAL605.Conclusions
We have completed a characterization of SAL605 at
X=13nm. The sensitivity was found to be -1mJ/cm2
and was insensitive to the processing conditions studied.
The contrast varied from y-1, for short development
times and low developer normality, to y-5 for longer
development times, thin resist and higher normality.
We have identified the best processing conditions for
EUV lithography, namely a developer normality of 0.27
and development times longer than -100s for 110nm
thick films and longer than 30s for 65nm films. These
conditions allow for steeper sidewalls.
Acknowledgments
This work was performed under the auspices of the U.S.
Department of Energy by the Lawrence Livermore
National Laboratory under contract number W-7405-
Eng-48.
References
1. R. Hostetler, "SAL 605 characterization at
=l3nm," internal memo; Lawrence Livermore
National Laboratory (1994)
2. T. H. Fedynyshyn, M. F. Cronin, L. C. Poli, and
C. Kondek, "Process optimization of the advanced
negative electron beam resist SAL605,"
J.Vac.Sci.Technol.B 8 1454-1460 (1990)
3. E. Gat, "X-ray Lithography at INRS,"
communication at the Lawrence Livermore National
Laboratory (July 1995)
4. Prolith/2 is a lithography simulator software
available from FINLE technologies, P.O. Box
162712, Austin, Texas 78716 USA
5. F. H. Dill, A. R. Neurcuthcr, J. A. Tuttle, and E. J.
Walker, "Modeling projection peinting of positive
photoresist", IEEE Trans. Elec. Dev. 22 (7) 456-464
(1975)
6. C. A. Mack, E. Capsuto, S. Sethi, and J.
Witowski, "Modeling and characterization of a
0.5pm deep ultraviolet process," J. Vac. Sci.
Technol. B 9 (6) 3143-3149 (1991)-
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La Fontaine, B.; Ciarlo, D.; Gaines, D. P. & Kania, D. R. Characterization of SAL605 negative resist at {lambda}=13 nm, article, May 24, 1996; California. (https://digital.library.unt.edu/ark:/67531/metadc668339/m1/6/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.