Susumu Gotoh

New concept for high-throughput multielectron beam direct write system

A new multielectron-beam optical system with correction lens array (CLA) is proposed. The CLA is arranged between an electron source and reduction optics. The CLA can generate plural intermediate images of the electron source as a multisource, and moreover can compensate field curvature and distortion of the reduction optics. The proposed system was designed and optimized through simulations. The specifications are field size of 250 μm square, convergence beam angle of 10 mrad, 64×64 beams, individual beam size of φ25 nm, accelerating voltage of 50 kV, and demagnification ratio of 50. The practical resolution for various resist processes is estimated considering the Coulomb interaction effect, and the throughput is simulated. The proposed system offers the possibility of “maskless” electron beam lithography with throughput in excess of 50 wafers/h (8 in.) for the International Technology Roadmap for Semiconductors (ITRS) 100 nm and 70 nm nodes at 3 μC/cm2 resist sensitivity.

Optical properties of a multibeam column with a single-electron source

A novel single-column multi-electron-beam system, called a beam-split array, has been developed for a high-resolution, high-throughput lithography tool. In this system, a single electron beam is divided into 1024 beams by a multisource module (MSM) composed of an aperture array (a beam-dividing aperture), a static lens array (Einzel lenses for each divided beam), and a blanker array (BLA, blanking electrode pairs for each focused beam). The MSM is used to form multiple intermediate images of the electron source at the BLA. These images are demagnified to form final images through a projection optics consisting of a double lens doublet with a blanking aperture and deflector. To align the multiple beam paths in the MSM, aligners between these arrays are used, and the aligner conditions are determined by monitoring the blanking-aperture image. Moreover, because each beam current is about 0.1% of the total beam current on the specimen, a high-contrast transmission detection method is used to detect the electr...