Balancing ion parameters and fluorocarbon chemical reactants for SiO2 pattern transfer control using fluorocarbon-based atomic layer etching

Abstract

In manufacturing, etch profiles play a significant role in device patterning. Here, the authors present a study of the evolution of etch profiles of nanopatterned silicon oxide using a chromium hard mask and a CHF 3 /Ar atomic layer etching in a conventional inductively coupled plasma tool. The authors show the effect of substrate electrode temperature, chamber pressure, and electrode forward power on the etch profile evolution of nanopatterned silicon oxide. Chamber pressure has an especially significant role, with lower pressure leading to lower etch rates and higher pattern fidelity. The authors also find that at higher electrode forward power, the physical component of etching increases and more anisotropic etching is achieved. By carefully tuning the process parameters, the authors are able to find the best conditions to achieve aspect-ratio independent etching and high fidelity patterning, with an average sidewall angle of 87°± 1.5°and undercut values as low as 3.7 ± 0.5% for five trench sizes ranging from 150 to 30 nm. Furthermore, they provide some guidelines to understand the impact of plasma parameters on plasma ion distribution and thus on the atomic layer etching process.

Mechanism understanding in cryo atomic layer etching of SiO2 based upon C4F8 physisorption

“…One of the main solutions to perform anisotropic ALE of SiO 2 is to use fluorocarbon-based plasmas to deposit a very thin FC modified layer on the surface. This layer can then be etched using Ar or O 2 plasma at low ion energy bombardment 2,3,[6][7][8][9][10][11] . However, some drifts were reported in the processes, with an increase of the etch amount per cycle (EPC) due to the fluorine contamination of the reactor walls [8][9][10]12 .…”

Clean SiO2 atomic layer etching based on physisorption of high boiling point perfluorocarbon

“…To resolve these challenges, Dallorto et al explored methods to reduce contamination on the chamber walls by decreasing the substrate temperature below −10 °C in 2019. 22 In addition, G. Antoun et al explored a new method named "cryo-ALE" of SiO 2 by using the physisorption of C 4 F 8 gas on the cooled surface of materials, instead of physisorption of CF x by PFC plasma in 2019 and 2021. 23,24 It was proved that cryo-ALE based on C 4 F 8 physisorption could work at −120 °C or below (cryogenic temperature is defined as the temperature from −150 °C to absolute zero temperature, but, they used the term "cryo" for experiments done at −120 °C or below).…”