Effect of heavy inert ion strikes on cell density-dependent profile variation and distortion during the etching process for high-aspect ratio features

Abstract

Vertical scaling technique faces a physical limitation in 3D NAND device fabrication, even assuming superior etching technology. Another promising scaling technique to increase the storage density is lateral scaling, which increases the number of holes between slit and slit from four to nine and above. However, unpredictable small critical dimension, feature-to-feature variation, and distortion occur. To elucidate the profile deteriorations induced by the lateral scaling, we analyzed the effect of the angular etching yield dependency of the incident ion fluxes into a given feature using the multiscale technology computer-aided design methodology. As one of the inherent features of the gas, incident angle θmax in which the sputtering yield achieves its maximum value is a crucial factor for analyzing and modeling etching profiles. Moreover, the impact of the heavy inert ion strikes on the unpreferred etching profiles was investigated. In this study, the synergy of lower energy ions, larger fluxes, and larger θmax of heavy inert ions decrease the feature-to-feature variation, reducing hard mask distortion without the etch rate reduction.

Contribution of Ion Energy and Flux on High-Aspect Ratio SiO2 Etching Characteristics in a Dual-Frequency Capacitively Coupled Ar/C4F8 Plasma: Individual Ion Energy and Flux Controlled

“…Wang et al [ 14 ] found an etching mechanism transition from fluorocarbon (FC) film deposition to chemical sputtering in a C F /Ar/O gas mixture environment through HPEM and MCFPM simulation. Kwon et al [ 15 ] investigated the role of heavy ion impact on the feature-to-feature profile of SiO by using a multi-scale computer simulation. They found that heavy ion sputtering reduces the feature-to-feature distortion.…”

“…Because experimental and computational studies have revealed that ions inside the HAR feature play a significant role in HAR SiO etching [ 13 , 14 , 15 , 16 ], most simulation studies have focused on the validation of technologies for individual control of ion flux and energy. For instance, Kim et al [ 17 ] proved the capability of the individual control of ion flux and energy distribution by varying dual-frequency voltages through a two-dimensional particle-in-cell Monte Carlo collisions (PIC-MCC) simulation.…”