Charging Effect in Plasma Etching Mask of Hole Array

Abstract

It has already been found that the round shape of holes can be changed into hexagonal shape during plasma etching processes. This work aims to understand the mechanism behind such a shape change using particle simulation method. The distribution of electric field produced by electrons was calculated for different heights from the mask surface. It is found that the field strength reaches its maximum around a hole edge and becomes the weakest between two holes. The field strength is weakened as moving away from the surface. The spatial distribution of this electric field shows obvious hexagonal shape around a hole edge at some distances from the surface. This charging distribution then affects the trajectories of ions that fall on a mask surface so that the round hole edge is etched to become a hexagonal hole edge. The changing of this hole shape will again alter the spatial distribution of electric field to enhance the charging effect dynamically.

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

“…The E ‐field strength presents a reasonable trend of decreasing with height. The reason for this difference has been discussed in detail in our previous studies . Figure d–g schematically depicts these mentioned mechanisms for various values of A , respectively.…”

“…In this paper, the E ‐field hereinafter denotes their horizontal components. Although our previous studies have studied the distribution of the E ‐field, the mask pattern either was set as a perfect or an arbitrarily shaped hole . The roughness and etching rate were not considered.…”

“…The requirement for overcoming these artifacts has attracted a large number of theoretical and experimental studies on the charging effect. However, almost all of them only focused on the charging problem on the profile of a trench, except for our previous studies . In those papers, the charging effect for a mask, which was made of round holes aligned in a hexagonal array was studied, and the evolution of these round‐ as well as asymmetric‐shaped holes under charging were further simulated .…”

“…However, almost all of them only focused on the charging problem on the profile of a trench, except for our previous studies . In those papers, the charging effect for a mask, which was made of round holes aligned in a hexagonal array was studied, and the evolution of these round‐ as well as asymmetric‐shaped holes under charging were further simulated . It was found that the spatial E ‐field, which is established mainly by electrons according to the pattern of the mask, affects the trajectories of tardy ions, and hence, leads to an unexpected evolution of mask patterns occurrence, which will be definitely transferred to the substrate.…”

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].…”