Sub-resolution assistance feature (SRAF) has become one of popular resolution enhancement technique because it is
the most easily applicable technique that can be adopted for sub-65 nm node technology. The SRAF can be realized, for
example, by locating lines having width below resolution limit around isolated feature. With the SRAF, intensity profile
of the isolated feature will be modified to dense-like one and, as a result, focus response of the isolated feature can be
improved up to dense feature level. Previous works on SRAF have focused mainly on the critical dimension (CD) margin
window. However, CD margin window is not sufficient to evaluate optimum SRAF configuration because process
margin degradation due to irregular pattern profile such as line edge roughness (LER) would become more prominent as
technology node goes beyond sub-65nm node. Therefore, appropriate methodology to optimize SRAF configuration both
for CD margin window and pattern profile is indispensable for those applications.
In this paper, we focus on the impact of SRAF configuration to pattern profile as well as CD margin window. The
SRAF configuration was adjusted by varying assistance feature to main feature distance and pitch of the assistance
features at mask level. Pattern profile was investigated by measuring LER with varying assistance feature parameters
quantitatively. From the results, we prove the impact of SRAF configuration both on pattern profile and CD margin
window. We also show that the experimental data can easily be predicted by calibrating aerial image simulation results to
measured LER. As a conclusion, we suggest methodology to set up optimum SRAF configuration with regard to both
CD margin window and pattern profile.
Recently, in order to increase the number of transistors in wafer by small feature size, optical lithography has
been changed to low wavelength from 365nm to 193nm and high NA of 0.93. And further wavelength is aggressively
shifting to 13.5nm for more small feature size, i.e., Extreme Ultra Violet Lithography(EUVL), a kind of Next Generation
Lithography(NGL)1. And other technologies are developed such as water immersion(193nm) and photo resist Double
Patterning(DP). Immersion lens system has high NA up to 1.3 due to high n of water(n=1.44 at 193nm), the parameter k1
is process constant, but 0.25 is a tough limit at a equal line and space, if we use immersion lens with 193nm wavelength
than limit of resolution is 37nm. Especially, Double Exposure Technique(DET) process is widely studied because of the
resolution enhancement ability using a same material and machine, despite of process complication. And SADP(Self
Aligned Double Patten) is newly researched for overlay and LER(Line Edge Roughness) enhancement.
In this paper, we illustrate the feasibility of the shift double pattern for 65nm-node flash using a 193nm light
dipole source and the possibility of decrease minimum feature size using a property of silicon shrinkage during thermal
oxidation process.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.