Study on physical model of resist surface charge in electron beam mask writer EBM-9500PLUS

Haruyuki Nomura; Noriaki Nakayamada; Takehiko Katsumata; Rumi Ito; Yoshinori Kojima

doi:10.1117/12.2572199

20 September 2020 Study on physical model of resist surface charge in electron beam mask writer EBM-9500PLUS

Haruyuki Nomura, Noriaki Nakayamada, Takehiko Katsumata, Rumi Ito, Yoshinori Kojima

Proceedings Volume 11518, Photomask Technology 2020; 115180Z (2020) https://doi.org/10.1117/12.2572199
Event: SPIE Photomask Technology + EUV Lithography, 2020, Online Only

Conference Poster

Abstract

This paper introduces a simple physical model to quantitatively explain resist surface charge effect observed in EBM- 9500PLUS, our latest VSB mask writer designed for 7 nm+ generation. The model takes into account secondary electrons drawn to resist surface by an already-existing surface charge, and vertical diffusion of positive charge from resist surface to inner resist. In order to verify the model, we experimentally evaluated the surface charge densities after beam exposure on resists of different thickness (from 80 nm to 300 nm) and different dose sensitivities (from 7 μC/cm² to 100 μC/cm²). The introduced model successfully reproduced the exposure-dose-dependent and time-dependent behaviors of those surface charge densities experimentally obtained. The model enables us to predict the amount of surface charge, and serves as one of the barometers to select the preferable resist thickness and its dose sensitivity under the pattern density and the required IP accuracy for the given product layouts. Furthermore, although the mechanism of charging had been unclear for a decade or more, the model finally provides a quantitative physical validity of our charge effect correction (CEC) system.

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Citation Download Citation

Haruyuki Nomura, Noriaki Nakayamada, Takehiko Katsumata, Rumi Ito, and Yoshinori Kojima "Study on physical model of resist surface charge in electron beam mask writer EBM-9500PLUS", Proc. SPIE 11518, Photomask Technology 2020, 115180Z (20 September 2020); https://doi.org/10.1117/12.2572199

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