Spatial and temporal development of the plasma potential in differently configured pulsed magnetron discharges

Abstract

T h e o p e n -a c c e s s j o u r n a l f o r p h y s i c s Abstract. Time-resolved emissive probe measurements have been performed to study the spatio-temporal development of the plasma potential in an asymmetric bipolar pulsed magnetron discharge. The influence of the substrate potential as well as of the substrate position has been investigated while the further conditions were the same. To access the entire potential range which was between −100 V and + 400 V and to obtain sufficient time-resolution of the emissive probe, different heating currents had to be used. The plasma potential has been found to be typically close to zero in the 'on' phase, about + 40 V in the stable 'off' phase and up to + 400 V at the beginning of the 'off' phase, which is in agreement with the results of other authors. However, the positive values in the 'off' phase are generally lower than those reported and stay mostly below the target potential. This is explained by macroscopic considerations of the quasineutrality of the plasma taking into account a magnetic and geometrical shielding of the target, acting as an anode in the 'off' phase, and the potential and position of the substrate holder and environment. New Journal of Physics

Ion Flux Characteristics in Pulsed Dual Magnetron Discharges Used for Deposition of Photoactive TiO2 Films

“…As can be seen in Figure 3 and 4, three distinct pulse phases can be identified within a pulse cycle on one magnetron: a standard highly negative voltage phase, a short‐lived (less than 1 µs) positive voltage overshoot and an almost steady‐state positive low‐voltage phase. This behavior is similar to that observed for usual asymmetric bipolar pulsed dc discharges with a single magnetron 13, 18, 20, 23, 27. However, the negative currents measured for both arrangements of our dual magnetron system (DF and DG) are much higher compared to the single magnetron systems (cf.…”

“…Pulsing the discharge has also been shown to have benefits for thin film properties due to changes in ion‐assisted deposition processes. Recently, valuable results contributing to the elucidation of the complicated phenomena in asymmetric bipolar pulsed dc discharges with a single magnetron have been published 13, 18–23…”

Ion Energy Distributions in Magnetron Sputtering of Zinc Aluminium Oxide

“…When the discharge is pulsed asymmetric bipolar, V T is modulated. In the ‘on’ phase it is negative with a deep valley of about −900 V about 2 µs after switching before it settles at a value of about −200 V. In the ‘off’ phase it attains high positive values of up to +260 V immediately after switching before, after some oscillations, it settles at about +40 V. V Pl has been found to follow these changes in the ‘off’ phase but keeps close to zero in the ‘on’ phase 9, 15, 22. Because the energy of the positive ions which are formed in the plasma bulk is determined by V Pl , the IEDFs reproduce the changes in V Pl .…”

“…The chamber contained a planar magnetron source which was equipped with a circular target of ZnO with 2 wt.‐% Al 2 O 3 (purity 99.95%) having a diameter of 100 mm. Further details of the magnetron source and its magnetic field are given elsewhere 15. The magnetron was operated with d.c. or pulsed d.c. For d.c., an MDX 1.5K power supply (Advanced Energy) was used in the power controlled mode with a discharge power of 100 W. Asymmetric‐bipolar operation with a positive target voltage in the ‘off’ phase of 10% of the average negative value during the ‘on’ phase was achieved by a Pinnacle Plus unit (Advanced Energy).…”

Transient plasma potential in pulsed dual frequency inductively coupled plasmas and effect of substrate biasing

“…τ=R sh C g . 28 As proposed by Welzel et al, 33 sheath resistance can be calculated by the ratio of voltage drop between probe and bulk plasma (k B T e ) and the electron thermal current through the sheath (A p en e  k B T e 2πm e ), when electron density (n e ) and the electron temperature (T e ) are known. By taking precautions, the probe setup capacitance to ground could be reduced upto ∼220 pF.…”