Relationship between edge roughness in mask pattern and charging in plasma etching

Abstract

The edge roughness (ER) developed in the mask pattern during the plasma etching process harms the perfect pattern transformation from mask to substrate. To understand and ultimately manipulate plasma-induced ER, this study investigated the interplay between charging and nanoscale roughness of an isolated rough mask hole in the plasma etching process using a modeling framework, which consisted of a surface etching module, a surface charging module, and a profile evolution module. Specifically, on the one hand, the distributions of the spatial electric field (E-field) and etching rate were simulated for the rough mask surface being etched. It is revealed that the distribution of the etching rate is similar with that of E-field clinging to the mask surface, and both of them reach their maximum strength around the mask hole edge and gradually becomes uniform/nonuniform with the decrease of the value of the dominant amplitude/wavelength of roughness; on the other hand, a string algorithm was used to simulate the evolution rule for a rough profile of a mask hole with etching time under various values of roughness parameters. The simulated evolution of the profile has good agreement with experimental observation. The charging effect contributes to the enhancement of the root mean square roughness. Additionally, the influence of roughness parameters on the charging time versus root mean square was also examined. The mechanism behind these results was analyzed systematically. This study will greatly contribute toward improving the physical and chemical properties of the mask or optimizing the etching technique.K E Y W O R D S charging, particle simulation, plasma etching, roughness

Wafer-scale fabrication and modification of silicon nano-pillar arrays for nanoelectronics, nanofluidics and beyond

“…The IF influences the amount of deflection the ions experience when entering the etched structure and depends on the charging of the sidewalls, which alters the field locally and adds to the lateral velocity component. The IF is most prominent at the mask-substrate interface [30,31]. The amount of charge on the sidewalls depends on the interplay between charge transport at the interface of the bulk material, and the physical and/or chemical adhesion of the ionic constituents.…”

Deep neural network-based reduced-order modeling of ion–surface interactions combined with molecular dynamics simulation

“…Typically, highly collimated ions are needed to produce fine HAR contact holes during plasma processing [6,7]. To guarantee the precise shape of the HAR pattern, the effects of localized disturbances in the process should be considered, such as variations in the mask pattern shape [4,8], sheath curvature at the wafer edge [5,7], and the local charging effect inside the trench [9,10], as these disturbances significantly influence the trajectories of energetic ions, thus altering the etched profile substantially.…”

A hybrid modeling framework for simulating plasma-surface interactions of rough polymeric substrates

“…Lee et al [136] surmised that large electrostatic potential fluctuations due to stochastic charging could lead to profile irregularities as the trench size was reduced to nanometer scale. Zhang et al [158][159][160][161] presented a computational research regarding plasma induced surface charging on the top surface of mask holes. Through the years they examined cases in which the mask pattern either was set as a perfect [161] or an arbitrarily shaped hole [159,160] or cases with mask holes having rough edges [158].…”

“…Zhang et al [158][159][160][161] presented a computational research regarding plasma induced surface charging on the top surface of mask holes. Through the years they examined cases in which the mask pattern either was set as a perfect [161] or an arbitrarily shaped hole [159,160] or cases with mask holes having rough edges [158]. The key idea was that if the shape of the mask hole was initially asymmetric or rough due to nonperfect mask fabrication, or/and nonuniform plasma sources), the distribution of the negative electric field on the hole edge (emerged from the isotropic electron flux restricted in the upper hole region) distorted correspondingly.…”

“…Ishchuk et al [146] also used a continuum description of the interface and the string technique for the profile evolution; the objective was to investigate notching during plasma etching of a Si trench on a SOI wafer. The string technique was also utilized by Zhang et al [158,159] to investigate the evolution of the horizontal cross sectional profiles of mask holes with asymmetric [159] or rough [158] edges under the influence of the charging effect. Finally, Dai et al [144] studied the effect of bias on the evolution of Si trenches under a Chlorine plasma by using a discrete description of the substrate and a MC model for the profile evolution.…”