Designing planar magnetron cathodes: analysis and experiment

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.