Substrate planarization studies on IBAD substrates

To achieve high critical currents in second generation superconductors deposited on metallic substrates, substrate average roughness and texture of the buffer layer are key factors. This study is about Planarization of ion beam assisted deposition (IBAD) substrates using an inductively coupled radio frequency (RF) discharge operating at 13.56MHz. The inductively coupled discharge system was constructed using a pancake coil antenna. Linearized substrates were created by exposure to an Ar plasma for varying Ar pressures (8 mTorr - 1 Torr) and time 15 minutes to 1hr. Surface roughness was measured using atomic force microscopy (AFM) as well surface profilometer. Unpolished Inconel substrates have been studied under varying RF plasma conditions, such as pressure (8 mTorr to 1 Torr), RF power (50 Watts to 200watts) and etch time (15 to 60 minutes) to determine the effects on substrate roughness. Average surface roughness (Ra) of the planarized samples was measured using AFM and KLA-TENCOR surface profilometer (SP). The best Ra observed on plasma etched substrate is 4 nm under 240 mTorr pressure and 100 watts RF power and 30 minutes time from AFM analysis. The Ra values for Inconel substrates vary between 35- 51 nm under varying conditions. Our initial results suggest that there is a decreasing tendency in Ra with the increase of Ar pressure.