HIGH-CURRENT ARC - A NEW SOURCE FOR HIGH-RATE DEPOSITION

A new type of are evaporator, the so-called HCA (high-current pulsed are), was developed to increase the deposition rate by several times in comparison with conventional are evaporation units. This device makes use of pulsed are discharges with nearly sinusoidal current shapes (duration 0.1-1 ms, peak current > 5 kA), which are ignited repeatedly (0-300 s(-1)) in the centre of a circular cathode. The high pulse current drives the cathode spots radially at high velocity, but before touching the cathode border the are is switched off and another cycle is started in the centre. The new are evaporator can work with an average are current as high as 1000 A, This represents an increase of more than five times over the d.c. currents of 100-200 A usually used. The controllable are duration and repetition frequency mean that only a well defined circular area of erosion is affected by the are evaporation. Besides the high rate, there are some other advantages: the deposition rate can easily be controlled and adjusted in a range From zero to a maximum value. The pulsed are operates with peak deposition rates about 20 times higher than an ordinary are evaporation unit. Using this method a modified film structure and/or composition can be expected. The number of droplets will be strongly diminished. Using two or more evaporation units, films with a well defined modulated composition and structure (e.g. multilayer films with single film densities of some nanometres) can be produced effectively and with high reproducibility. All the advantages of vacuum are deposition (high degree of ionisation, ion energies of about 20-50 eV, option for reactive deposition) are enhanced or preserved.