Experimental investigation of the Coulomb effect in electron projection lithography (EPL)

Jiro Yamamoto; Fumio Murai; Akemi Moniwa

doi:10.1117/12.472270

1 July 2002 Experimental investigation of the Coulomb effect in electron projection lithography (EPL)

Jiro Yamamoto, Fumio Murai, Akemi Moniwa

Proceedings Volume 4688, Emerging Lithographic Technologies VI; (2002) https://doi.org/10.1117/12.472270
Event: SPIE's 27th Annual International Symposium on Microlithography, 2002, Santa Clara, California, United States

Abstract

Electron projection lithography (EPL) is a promising tool for next-generation lithography. However, beam blur due to the Coulomb effect becomes significant and degrades resolution when a high beam current is used to improve throughput. Suppressing the impact of the Coulomb effect is thus necessary to make EPL a practical tool for fabricating ULSI devices. We discuss the influence of the Coulomb effect in EPL based on our experimental results obtained using a Nikon experimental EPL column. To investigate the influence of the Coulomb effect on exposure results, we prepared three kinds of mask with different opening rates to vary the beam current on a wafer over a wide rage without affecting the lens illumination. We found that the Coulomb effect decreased the dose and focus latitude, and that the optimum focus condition varied within a sub-field. Furthermore, we found that the beam blue caused by the Coulomb effect was increased by shrinkage of the rectangular pattern end. Such shrinkage is also a problem in optical lithography, and complex pattern reshaping is necessary to correct it. The shrinkage becomes greater as the beam current increased. We estimated the amount of beam blue caused by the Coulomb effect by fitting our results through an energy deposition simulation. Our overall conclusion s that pattern reshaping and low-Coulomb-effect optics will be necessary to overcome the Coulomb effect.

Citation Download Citation

Jiro Yamamoto, Fumio Murai, and Akemi Moniwa "Experimental investigation of the Coulomb effect in electron projection lithography (EPL)", Proc. SPIE 4688, Emerging Lithographic Technologies VI, (1 July 2002); https://doi.org/10.1117/12.472270

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KEYWORDS

Photomasks

Semiconducting wafers

Electron beam lithography

Lithography

Distortion

Projection lithography

Optical simulations

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