Resolution limit in character projection e-beam system

Yoichi Tomo; Koji Matsuoka; Yoshinori Kojima; Akira Yoshida; Isao Shimizu; Masaki Yamabe

doi:10.1117/12.390058

21 July 2000 Resolution limit in character projection e-beam system

Yoichi Tomo, Koji Matsuoka, Yoshinori Kojima, Akira Yoshida, Isao Shimizu, Masaki Yamabe

Proceedings Volume 3997, Emerging Lithographic Technologies IV; (2000) https://doi.org/10.1117/12.390058
Event: Microlithography 2000, 2000, Santa Clara, CA, United States

Abstract

Character projection (CP) electron beam (EB) lithography is one of the promising technologies for the fabrication of random logic memory devices with less than 0.13 micrometer design rules. This is because not only the memory but also the logic cell can be allocated in a single CP area. Using CP EB lithography, moderate throughput and accurate CD control can be achieved compared with a variable shaped EB system. However, its resolution is mainly limited by the Coulomb interaction effect of the electron through the EB stencil mask. The Coulomb interaction effect depends on the electron optical column design of EB systems such as beam current, length of interaction, and beam semi-angle. At Selete, we have evaluated in parallel two CP EB direct writing (DW) machines Hitachi and ADVANTEST. This paper describes the resolution limit of these CP EBDW systems. In this study, 1:1 lines and spaces patterns (50% duty: severe Coulomb interaction condition) are evaluated at various current densities. We found that the ultimate resolution is improved by decreasing current density. And also we found that the focus position shifts beyond the wafer plane by increasing current density. Although the larger beam semi-angle can be effective to improve the resolution limit, it is difficult to change the beam semi-angle of existing columns at Selete. So we have simulated this effect by increasing the source diameter, which is equivalent to increasing the beam semi-angle. By comparing the 100 nm lines and spaces simulation results in the diameter of 7.2 micrometer (normal) and 20 micrometer, increasing the beam semi-angle proved to be effective in resolution enhancement if it is accompanied with simultaneous reduction of the lens aberration.

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Yoichi Tomo, Koji Matsuoka, Yoshinori Kojima, Akira Yoshida, Isao Shimizu, and Masaki Yamabe "Resolution limit in character projection e-beam system", Proc. SPIE 3997, Emerging Lithographic Technologies IV, (21 July 2000); https://doi.org/10.1117/12.390058

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KEYWORDS

Lithography

Logic

Optical simulations

Photomasks

Electron beam lithography

Semiconducting wafers

Electron beam direct write lithography

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