Satoshi Wakamatsu

Approaches to rapid resist spreading on dispensing based UV-NIL

Reduction of resist filling time was investigated with the aim of improving UV-nanoimprint lithography (UV-NIL) throughput. A novel low volatility, low viscosity resist was developed to enable ink-jetting with minute resist droplets and imprinting under reduced air atmosphere. Direct observation of resist spreading showed that the resist filling process is composed of three steps: A) capillary bridge formation, B) resist spreading, and C) air bubble dissolution. Resist filling time was drastically decreased by changing the atmosphere from helium to a reduced air atmosphere of 0.02MPa. A comparison of 0.7pl and 6pl resist droplets showed that reducing resist droplet size while increasing area density also reduces resist filling time. Improved bubble dissolution speed is thought to result from imprinting under reduced air atmosphere. Moreover, ink-jetting smaller size resist droplets with higher density is thought to have an effect on reducing the time of each of the three steps, particularly bubble dissolution time. Combining dispensing-NIL with imprinting in vacuum is expected to improve UV-NIL throughput.

Fabrication of 20-nm half-pitch quartz template by nano-imprinting

We have been developing nanoimprint templates for the next-generation sub-20nm nanofabrication technology, with particular emphasis on duplicate fabrication of quartz templates created from Si masters. In general, the narrowing of pattern line widths is accompanied by concerns about whether resist will sufficiently fill such lines. Our development has concentrated on the filling property of resist in narrow lines and on pattern shape after release from the mold. Our findings indicated that pattern formability differs according to the type of resist monomer. We inferred that these differences are manifested in such behaviors as resist shrinkage after or during release of the mold. Using a novel resist that has good formability, we pursued quartz template duplication that employs UV-NIL. As a result, we demonstrated HP20nm quartz pattern formation using the duplication process. We were also verified NIL resist pattern resolution of HP17.5nm.

Design considerations for ultraviolet-nanoimprint lithography resists

Abstract. Design considerations for ultraviolet-nanoimprint lithography resists were investigated focusing on the major issues of ink-jetting performance, pattern formability, release property, and dry etching resistance. Regarding ink-jetting performance, small droplet ink-jetting of 0.7 pl was successfully demonstrated by adjusting the resist fluid property to the ink-jet coater and controlling the resist volatilization. Regarding pattern formability, a resist pattern was imprinted from a mold pattern of 28 nm in width and 60 nm in depth without pattern dimension change. It was thought that modulus control of the resist was more important than resist shrinkage in achieving excellent pattern formability. As for release property, resist with fluorine monomer and with nonreactive fluorine antisticking agent were compared. The results indicated that resist design has the capability to both reduce separation force and maintain a clear mold surface. The mold release agent decomposed with an increasing number of imprint shots, but the low release-force resist with nonreactive antisticking agent was able to control degradation of the mold release agent and thus improve release property endurance. Regarding etching resistance, it was found that increasing the ring parameter of resist is essential for high etching resistance, and resulted in improved etched pattern features of the substrate.

Design considerations for UV-NIL resists

Design considerations for UV-NIL resists were investigated focusing on the major issues of ink-jetting performance, pattern formability, release property, and dry etching resistance. Regarding ink-jetting performance, small droplet inkjetting of 0.7pl was successfully demonstrated by adjusting the resist fluid property to the ink-jet coater and controlling the resist volatilization. Regarding pattern formability, a resist pattern was imprinted from a mold pattern of 28nm in width and 60nm in depth without pattern dimension change. It was thought that modulus control of the resist was more important than resist shrinkage in achieving excellent pattern formability. As for release property, resist with fluorine monomer and with non-reactive fluorine anti-sticking agent were compared. The results indicated that resist design has the capability to both reduce separation force and maintain a clear mold surface. The mold release agent decomposed with increasing number of imprint shots, but the low release force resist with non-reactive anti-sticking agent was able to control degradation of the mold release agent and thus improve release property endurance. Regarding etching resistance, it was found that increasing the ring parameter of resist is essential for high etching resistance, and resulted in improved etched pattern features of the substrate.