Characterization of the linear arc discharge (LAD) source for film deposition

Abstract

The linear arc discharge (LAD) source is a parallel plate hollow cathode with a magnetic field perpendicular to the plates near the outlet slit of the cathode. The hollow cathode discharge is generated by radio frequency (rf) power and is confined mainly to the outlet region of the cathode slit. The magnetic confinement increases the power density thereby forming hot linear zones along the cathode plates at the cathode outlet. These zones represent the main supply of the cathode material, and in a cathode arc regime they contribute substantially to the thermionic emission of electrons. The plasma density measured by a double Langmuir probe 15 cm below the cathode outlet reaches the order of 10 12 cm −3 already at rf power ≥300 W. The growth rate of Ti films decreases as a second order polynomial function of the cathode outlet to substrate distance. The growth rate of TiN films depends on the content of nitrogen in Ar. At a N 2 content in Ar of less than 0.5%, the reactive film growth rate can reach or even exceed the growth rates of pure Ti metal films. Characteristics of the hollow cathode discharge exhibit a gradual dependence on the distance between the cathode plates in the range 6–2 mm. A dramatic change of the hollow cathode characteristics was found at the distance of 300 ±50 μm between the plates.