Dependence of Optical Emission Spectra on Argon Gas Pressure during Modulated Pulsed Power Magnetron Sputtering (MPPMS)

Abstract

Modulated pulsed power magnetron sputtering (MPPMS) of titanium was investigated as a function of argon gas pressure using optical emission spectroscopy (OES). Delays in discharge and the formation of comb-like discharge current waveforms due to splitting and pulsing were observed with a decrease in pressure. This observation corresponds to the evolution from MPPMS condition to deep-oscillation-magnetron-sputtering (DOMS)-like condition by changing discharge gas pressure. The optical emission intensities of the ionic species (Ar+ and Ti+) increased as the comb-like current waveforms were formed with decreasing Ar pressure. This behavior showed a marked contrast to that of the neutral species (Ar and Ti). The Ar pressure dependence of OES was revealed to be due to the plasma build-up stage, which is the initial generation process of plasma discharge in pulsed dc magnetron sputtering, from the temporal profile for the atomic-line intensities of the optically emitting species in MPPMS and DOMS-like plasmas.

Optical emission spectroscopy in deep oscillation magnetron sputtering (DOMS) of titanium

“…The experimental setup has been described in detail elsewhere. 27,31,32) The sputtering chamber was evacuated to a base pressure of 1 × 10 −5 Pa by a turbo molecular pump (Edwards, STP-A2203C). The DOMS was operated with Ar gas (99.999%) under a working pressure of 1.37 Pa.…”

“…The discharge current, voltage waveforms, and temporal profiles of the optical emission were monitored and recorded by a digital storage oscilloscope (LeCroy, LT344). 32) 3. Results and discussion…”