Chemical Vapor Deposition of Metallic Films Using Plasma Electrons as Reducing Agents

Abstract

Metallic thin films are key components in electronic devices and catalytic applications. Deposition of a conformal metallic thin film require using volatile precursor molecules in a chemical vapor deposition (CVD) process. The metal centers in such molecules typically have a positive valence, meaning that reduction of the metal centers is required on the film surface. Powerful molecular reducing agents for electropositive metals are scarce and hampers the exploration of CVD of electropositive metals. We present a new CVD method for depositing metallic films where free electrons in a plasma discharge are utilized to reduce the metal centers of chemisorbed precursor molecules. We demonstrate this method by depositing Fe, Co and Ni from their corresponding metallocenes using electrons from an argon plasma as a reducing agent.

Area Selective Deposition of Metals from the Electrical Resistivity of the Substrate

“…9 We recently reported a new CVD method for deposition of metallic films where the free electrons in a plasma are used as reducing agents. 10 Since the method draws an electron 3 current from the plasma to an electrically biased substrate, a conducting surface is needed to close the electric circuit allowing the electron current to flow from the plasma discharge to the bias power supply without any charge build-up. Therefore, metallic films could be deposited on electrically conducting silver substrates, whilst the deposition process was hampered on poorly conductive silicon and inactive on insulating silicon dioxide substrates.…”

“…The deposition system setup and the experimental procedures of our new CVD method are described elsewhere. 10 Briefly, the depositions were carried out in a vacuum chamber equipped with a hollow cathode plasma source located in the top lid of the vacuum chamber. Argon was used as working gas at a flow rate of 70 sccm through the titanium hollow cathode.…”