Influence of background gas pressure on copper film deposition and ion current in a hot refractory anode vacuum ARC

Abstract

A 200 A Hot Refractory Anode Vacuum Arc (HRAVA) was studied. The arc was sustained between a cylindrical Cu cathode and an Mo anode spaced ∼ 10 mm apart. In the HRAVA, metallic plasma (from cathode material) expands radially. He, N 2 or Ar gas was introduced into the arc chamber through an electrically controlled valve. Films were deposited onto glass microscope slide substrates. The angular film distribution and the influence of different background gases on films deposited by the HRAVA were measured. The film thickness was measured by profilometry. The ion current was measured by a circular flat probe. It was shown that the film thickness was uniform with respect to the azimuthal angle around the electrode axis within approximately 10%. The film thickness was independent of gas pressure p, below a critical value p cr. For p > p cr, the film thickness decreased with p, eventually reaching 0. The value of p cr was less for gases with larger molecular weight—60, 10 and 5 mTorr (0.67, 1.33 and 8 Pa) for He, N 2 and Ar, respectively. The ion current to a 78 mm 2 probe in vacuo increased with time and reached a saturation value of approximately 4.5 mA after about 60 s from arc ignition. The ion flux fraction in the total deposition mass flux was estimated to be about 60% in the fully developed HRAVA ( t = 60–90 s).