Negative-tone imaging with EUV exposure for 14nm hp and beyond
2015
Manipulation of dissolution properties by changing organic solvent developer and rinse material provides a novel
technology to obtain fine pattern beyond the limitation of imaging system based on alkaline developer. QCM study
showed no swelling character in negative-tone imaging (NTI) process even for current developer of n-butyl acetate
(nBA). Actually, NTI process has shown advantages on resolution and line-width roughness (LWR) in loose pitch
around 30 ~ 45 nm hp as a consequence of its non-swelling character. On the other hand, bridge and collapse limited its
resolution below 20 nm hp, indicating that non-negligible amount of swelling still exists for tight pitch resolution. We
investigated effects of solubility parameter of organic solvents on resolution below 20 nm hp. A bridge was reduced with
a decrease in the solubility parameter dp from nBA. On the other hand, much lower dp caused film remaining due to its
extremely slow Rmax. Based on these results, we newly developed FN-DP301 containing organic solvent with smaller
dp than nBA. Although rinse solvent gave negligible effects on bridge, there is a clear improvement on pattern collapse
only in case of using new rinse solvent of FN-RP311.
Lithographic performances of NTI process using nBA and FN-DP301 together with the other organic solvents were
described in this paper under exposures with an E-beam and a EUV light. It is emphasized that 14 nm hp resolution was
obtained only using FN-DP301 as a developer and FN-RP311 as a rinse under E-beam exposure. NTI showed 43% faster
photospeed in comparison with PTI at 16 nm hp, indicating that NTI is applicable to obtain high throughput with
maintaining resolution. In addition, sub-20 nm trench was obtained using NTI without bridge under EUV exposure, all of
which are attributed to the low swelling character of NTI process. Similarly, NTI was able to print 20 nm dots using
NXE:3100 with only a little peeling. Conversely CH patterning was significantly worse with NTI compared to PTI, that
is, only 36 nm contacts with 60 nm pitch was resolved under EUV exposure.
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