Masaru Mitsui

Improvement of total quality on EUV mask blanks toward volume production

Total quality on EUV mask blanks have to be improved toward future volume production. In this paper, progress in EUV blank development and improvement in flatness, bow and ML blank defects as critical issues on EUV blanks were reported. Steadily progress in flatness improvement was made in the past five years by improving polishing processes. A LTE substrate with a high flatness of 78 nm PV in 142 mm square area was achieved in average. Annealing process was developed to make small bow of less than 600 nm after ML coating. It was confirmed that annealed ML blank has stable performance in bow and centroid wavelength values through mask making process. Small bow of less than 300 nm was successfully demonstrated using annealing process and a CrN back side film with high compressive stress. Low defects of 0.05 defects/cm2 at 70 nm SiO2 sensitivity inspected by a Lasertec M1350 was demonstrated on a multilayer (ML) blank with a LTE substrate as best. Small defects over 50 nm in a M7360 were effectively reduced by improvement of polishing process consisting of local polish, touch polish and cleaning.

Development of deep-UV MoSi-based embedded phase-shifting mask (EPSM) blanks

Embedded phase-shift mask (EPSM) has an advantage in comparison with several other phase-shifting mask approaches because of its simple structure and fabrication process. We tried to modify MoSi-based EPSM blanks by re-examining the material and by optimizing sputtering condition in order to produce more useful EPSM blanks for Deep UV lithography technology. New MoSi-based EPSM blanks for which Nitrogen gas is used as the reactive sputtering gas has been developed. And it has been confirmed that the New MoSi-based EPSM (MoSi-N) blanks are superior to HOYA previously developed one (MoSi-ON) in chemical durability, manufacturing stability and Dry Etching property.

Development of novel W/Si materials for the single-layered attenuated phase-shifting mask

A novel material system of metal W corpuscles dispersed in silicon dioxides layer (W/Si film) has been developed for the single-layered attenuated phase-shifting mask (SAttPSM) for i-line. The W/Si film has been proved to have a wide flexibility in designing the optical transmittance and the film thickness by changing the sputtering conditions such as the O2 ratio to the sputtering gas (O2 and Ar) flow rate and the RF power supplied. The W/Si shifter film are also found to have some electric conductivity, which again depends on the sputtering conditions, tough chemical durability against both hard acid and basic solutions, and sufficient adhesion to quartz substrate SAttPSM, fabricated with the W/Si film and having the thickness of 1575 angstroms and the transmittance of 6.3%, showed the phase-shifting angle of 177.9 at i-line wavelength. The depth of focus around 0.35 micrometers hole pattern was widened from 0.6 micrometers to 1.4 micrometers .