Quantifying the Proximity Effect in Electron Beam Lithography

Abstract

Electron beam lithography (EBL) is a nanofabrication technique used to expose a substrate coated with an e-beam resist using a focused, accelerated beam of electrons. EBL has enabled fabrication of various nanostructures. One issue that typically arises when using an EBL machine is the proximity effect. The proximity effect is known to be caused by the backscattering of electrons, which exposes unwanted areas of the resist and thus degrades the resolution. This is because when backscattering occurs, electrons undergo wide-angle, elastic collisions, leading to neighboring areas being exposed. This study was designed to create a wide range of micro- and nanoscale patterns using EBL, including an artificial object (cello), real-world electrode contacts, and other miscellaneous designs while working around the issue of the proximity effect. While literature reviews were conducted to analyze existing design strategies to mitigate the impact of the proximity effect, it was found that adjusting the exposure parameter (e.g., dosage) had a significant impact on the proximity effect. A dosage of 260 μC/cm² produced the most optimal image after development of e-beam exposed resists. Removing overlapping lines and merging shapes together in the CAD design also helped limit the impacts of the proximity effect. This study shows the optimal dosage and design to mitigate the proximity effect and thus to enable high resolution nanoscale patterning for device applications.