Charge-induced pattern displacement in E-beam lithography

Abstract

Electron beam lithography (EBL) requires conducting substrates to ensure pattern fidelity. However, there is an increasing interest in performing EBL on less well-conducting surfaces or even insulators, usually resulting in seriously distorted pattern formation. To understand the underlying charging phenomena, the authors use Monte Carlo simulations that include models for substrate charging, electron beam-induced current, and electric breakdown. Simulations of electron beam exposure of glass wafers are presented, exposing regular patterns which become distorted due to charge-induced beam deflection. The resulting displacements within the patterns are mapped and compared to experimental displacement maps obtained from patterns in PMMA resist on glass substrates. Displacements up to several hundreds of nanometers were observed at a primary beam energy of 50 keV. Also, various scan strategies were used to write the patterns, in the simulations as well as the experiments, revealing their strong effect on pattern distortion, in shape and in magnitude. A qualitative, in some cases even quantitative, good agreement was found between the simulations and the experiments, providing enough confidence in Monte Carlo simulations to predict charge-induced pattern displacement and shape distortion and to find smart scan strategies to minimize the effects of charging.

Charging effect induced by electron beam irradiation: a review

“…Arat et al [147] have investigated this problem quantitatively by using a Monte Carlo method; for the sake of simplicity, the following discussion is focused on their simulation of exposing a single SiO 2 substrate at the primary energy of 50 keV with the resist being assumed not to exist.…”

“…Due to the beam deflection, the actual exposure position will be displaced from the prescribed pixel, which is an important problem as it lowers down the EBL quality. Arat et al [ 147 ] have investigated this problem quantitatively by using a Monte Carlo method; for the sake of simplicity, the following discussion is focused on their simulation of exposing a single SiO 2 substrate at the primary energy of 50 keV with the resist being assumed not to exist.…”

“…In (a)-(d), the red dot array denotes the pattern to be exposed and the blue arrows denote the scanning order of the dots. Adapted with permission from Ref [ 147 ]. Copyright [2019], American Vacuum Society…”

“…The displacement magnitudes can also be known from the color map in each figure. Adapted with permission from Ref [ 147 ]. Copyright [2019], American Vacuum Society…”

A wafer-scale fabrication method for three-dimensional plasmonic hollow nanopillars

“… 23–26 A key element for manufacturing well-organized multidimensional nanoplasmonic substrates is implementing patterning steps. Well-known patterning steps include colloidal lithography, 27,28 nanoimprint lithography (NIL), 29 charged beam lithography, 30 and photolithography. 31,32 Each technique has its limitations, as there is usually a trade-off between resolution, pattern design versatility (to be called “pattern-ability” here), time consumption, and cost.…”