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

Abstract

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 electrons at the final image plane. As a result, 1024 point beams are successfully formed. In the final image, the measured beam size is less than 55nm, and the displacement due to distortion is less than 56nm, even on the off-axial beams. In addition, individual beam blanking by BLA is verified, and cross-talk at the BLA is confirmed to be negligible at present accuracy. Moreover, 65nm patterns can be simultaneously delineated by near- and off-axial beams. These results verify the concept of their single-column multibeam formation and indicate that this optics can be applied to lithography for manufacturing on semiconductor devices.