Plasma Enhanced Atomic Layer Deposition of High Purity Titanium Nitride: Comparison of Hollow Cathode and Inductively Coupled Discharges

摘要

Inductively coupled plasma (ICP) sources are routinely used for plasma enhanced Atomic Layer Deposition (ALD) processing. While these sources are adequate for obtaining quality metal oxides, high purity metal nitrides present a greater challenge due to oxygen contamination from etching of the ICP's dielectric tube, as well as atmosphere permeation through elastomer seals. It is thus important to consider alternative types of plasmas for processing metal nitrides by ALD. The all-metal construction of hollow cathode plasma (HCP) sources overcomes these challenges. However, direct exposure of the metallic electrode to energetic ions can provide another film contamination source. In this study, we compare HCP and ICP sources for titanium nitride growth by plasma enhanced ALD (PEALD) using TiCl_4 and Ar/N_2/H_2 plasma. Films deposited using HCP are first optimized for growth rate and resistivity. Afterwards, two films, one obtained using each type of discharge, are compared for oxygen and chlorine concentration, resistivity, uniformity and growth per cycle. Our results indicate a significantly higher growth rates of 0.05 nm/cycle when using an HCP source as compared to an ICP (0.029 nm/cycle). The film deposited with an ICP, however, has lower resistivity and oxygen contamination. Considering that conditions were not identical for the two films, these results are preliminary. This work presents the results of our optimization and comparisons, discusses the scope of our results and the steps to be taken in further analysis.