Ionized sputter deposition using an extremely high plasma density pulsed magnetron discharge

TLDR

The study investigates the temporal evolution of ionic fluxes in a novel high‑power density pulsed plasma discharge and how process parameters influence this behavior. The plasma is generated by 100‑µs pulses repeated at 50 Hz. The discharge achieves peak power densities of several kW cm⁻², yielding a dense plasma with ionic fluxes up to 1 A cm⁻², a composition that evolves from Ar to metal ions during the pulse, metal ions traveling ≈2500 m s⁻¹ at 6 cm, and a metal‑ion ionization fraction of about 40 % at 0.13 Pa.

Abstract

Time resolved plasma probe measurements of a novel high power density pulsed plasma discharge are presented. Extreme peak power densities in the pulse (on the order of several kW cm−2) result in a very dense plasma with substrate ionic flux densities of up to 1 A cm−2 at source-to-substrate distances of several cm and at a pressure of 0.13 Pa (1 mTorr). The pulse duration was ∼100 μs with a pulse repetition frequency of 50 Hz. The plasma consists of metallic and inert gas ions, as determined from time resolved Langmuir probe measurements and in situ optical emission spectroscopy data. It was found that the plasma composition at the beginning of the pulse was dominated by Ar ions. As time elapsed metal ions were detected and finally dominated the ion composition. The effect of the process parameters on the temporal development of the ionic fluxes is discussed. The ionized portion of the sputtered metal flux was found to have an average velocity of 2500 m s−1 at 6 cm distance from the source, which conforms to the collisional cascade sputtering theory. The degree of ionization of the sputtered metal flux at a pressure of 0.13 Pa was found to be 40%±20% by comparing the total flux of deposited atoms with the charge measured for the metal ions in the pulse.