Title: A study on high aspect ratio contac (HARC) etching process through independent control at low frequency bias using ICP system

Abstract

As the memory semiconductor market has grown rapidly in recent years, demand and technology development for next-generation memory semiconductors such as 3D NAND flash, RAM, and PRAM are required. In particular, in the case of a NAND flash, the structure is changing from a two-dimensional structure to a three-dimensional stacked-type NAND flash structure according to technological development. As the number of layers increases during the 3D NAND flash process, the HARC (High Aspect Ratio Contact) etching process is an essential process. However, as the vertical process is required, the difficulty of the process increases rapidly, and distortion of the etch profile such as necking and bowing occurs. In the next-generation HARC etching process, the concentration of radicals, ions, and ion energies is referred to as the impact key. However, current studies on the HARC etching process show that ion and radical concentrations and ion energies change simultaneously. Therefore, the concentration of radicals, ions and ion energies, the effects of each are not analyzed independently. Therefore, in this study, we propose a methodology that can independently control the concentration and ion energy of radicals and ions according to process parameters. Plasma analysis was performed using optical emission spectroscopy and DLP. This established radical and ion independent control conditions. The HARC etching process was performed according to low frequency (2 MHz) and high frequency (13.56 MHz) under each independent control condition using ICP. Analyze the SiO2 profile shape by scanning electron microscopy (SEM) after the HARC etching process. It suggests the direction of the HARC etching process by analyzing the correlation between ion and radical concentration and ion energy through plasma analysis and etching process results.