Low temperature silicon nitride grown by very high frequency (VHF, 162MHz) plasma enhanced atomic layer deposition with floating multi-tile electrode

Abstract

Important issues for silicon nitride (SiNx) plasma enhanced atomic layer deposition (PEALD) are lowering the process temperature and minimization of plasma damage. In this study, the characteristics of PEALD SiNx films deposited at a low processing temperature of 100 °C with di-isopropylamino silane (DIPAS) and N2 plasma excited by using a very high frequency (VHF, 162 MHz) floating multi-tile electrode capacitively coupled plasma (CCP) source and a conventional VHF CCP source are reported in addition to the characteristics of both plasma sources. The PEALD SiNx film deposited with the floating multi-tile electrode exhibited higher growth rate (∼ 0.6 Å/cycle), higher N/Si ratio film (N/Si ∼ 0.98, even though it is lower than the stoichiometric ∼1.33 of N/Si for Si3N4) with no trace of carbon, lower surface roughness, and higher conformality in a trench compared to those deposited by the conventional CCP. In addition, improved electrical properties of the SiNx films such as lower leakage current, lower interface trap density, and higher breakdown voltage of PEALD SiNx film were obtained with the floating multi-tile electrode. These enhanced properties of SiNx films deposited by the floating multi-tile electrode are believed to be related to the higher plasma density, higher radical density, and lower ion energy bombarding the substrate observed for the multi-tile electrode through the enhanced power efficiency of the differentially-coupled multi-tile plasma source.