Designing planar magnetron cathodes: analysis and experiment

Abstract

Summary form only given, as follows. Planar magnetron cathodes have arching magnetic field lines which concentrate plasma density to enhance ion bombardment and sputtering. Typical parameters are: helium at 1 to 300 milli-torr, 200 to 2000 gauss at the cathode, 200 to 800 volts, and plasma density decreasing by ten to a thousand times within 2 to 10 cm from the cathode. A 2D, quasineutral, fluid model yields formulas for the plasma density: n(x,y), current densities: j(x,y), j/sub e/(x,y), j/sub +/(x,y) the electric field: E/sub y/(y), and the voltage between the cathode surface and a distant plasma. Experiments shows that T/sub e/(3/spl rarr/8 eV) adjusts to ensure that /spl alpha//sub 0//spl tau/ /spl ap/2.5 in helium for ionization rate /spl alpha/(l0/sup 4//spl rarr/10/sup 5/s/sup -1/), and electron transit time to the unmagnetized plasma /spl tau/ (10/spl rarr/100 /spl mu/s). Helium glow discharge cathode fall A/sub 0//spl tau/ is about 2.5, though this occurs at much higher voltage.