High-energy ions and atoms sputtered and reflected from a magnetron source for deposition of magnetic thin films

In the magnetron sputtering process, moderate bombardment of particles on a substrate gives favorable effects on the deposited films, while excessive bombardment at high energies may cause film damage and surface roughness. To make these influences clear, high-energy ions and neutrals are comprehensively measured by a mass spectrometer with an energy analyzer in the case of magnetron sputtering of a Permalloy™ target $(80%Ni∕20%Fe)$⁠. Ni atoms sputtered from the target by a dc magnetron discharge (⁠$∼600V$⁠, $<0.2A$⁠) in argon below 4 Pa have an energy distribution function (EDF) spreading up to $∼8eV$⁠. A similar shape of EDF is also observed for $Ni+$ ions, which are produced possibly by electron-impact ionization of Ni atoms in gas phase. The EDF of $Ar+$ ions has a tail of extremely high energies of $∼150eV$⁠. Production of such energetic ions is tentatively explained in terms of resonant charge exchange of energetic Ar atoms reflected from the target after surface neutralization of $∼600eVAr+$ ions impinging on the target. The existence of energetic Ar atoms is verified by mass spectrometry with an extra-ionizer, and is also supported by a sputtering simulation code (TRIM).