Method of making mixed nitride films with at least two metals

DETAILED DESCRIPTION It is an object of the present invention is to solve the aforementioned problems by providing mixed nitride films particularly adapted to different requirements.
The problem is solved by the invention in that in a mixed nitride film with at least two metals the concentration of the metals is variable as a function of the film thickness.
In particular the concentration here can be continuously variable.
Mixed nitride films of this nature can be prepared in the form Ti.
sub.
x Al.
sub.
1-x N or Ti.
sub.
x Al.
sub.
1 -(x+y)V.
sub.
y N.
For preparing such mixed nitride films during vaporization of the metal alloy, a variable voltage is applied to the substrate and varied as a function of the film thickness on the substrate.
The invention builds on the vaporization known per se of a cathode of a starting alloy by means of an arc source and the condensation on the substrate, with the substrate now, however, being at any potential up to approximately four hundred volts compared to the alloy cathode.
Vaporization can take place in the manner known in the reactive mode if nitrogen is introduced as a reaction gas.
The invention permits preparation of mixed nitride films with two or more metals.
If such two- or three-component alloy systems are vaporized at a pressure of 1 Pa (Pascal) in a nitrogen atmosphere, for example, the effect observed initially and unexpectedly is that the metals in the film can be found in changed concentrations compared to the starting alloy.
In particular, it can be observed that the ratio of the metals are a function of the voltage and specifically in such a way that the concentration of the metal with the lower melting point decreases with increasing negative substrate voltage.
The latter effect in accordance with the principles of the invention could initially not be expected, since the "flash"-like vaporization from the rapidly migrating cathode spot of the arc actually permits uniform vaporization, a fact factually verified at substrate potentials around zero volts