Patent ID: 7595096

Claim:
A method of manufacturing vacuum plasma treated workpieces comprising the steps of (a) introducing at least one workpiece to be treated into a vacuum chamber; (b) treating said workpiece in said vacuum chamber, thereby establishing a plasma discharge in said vacuum chamber by a supply signal with maximum energy at a first frequency f 1 for which there is valid; 10 MHz≦f 1 ≦30 MHz (c) removing said workpiece treated from said vacuum chamber; (d) performing a cleaning inside said vacuum chamber, thereby establishing said plasma discharge by a supply signal with maximum energy at a second frequency f 2 higher than said first frequency; (e) repeating steps (a) to (d) at least one time, wherein said method further comprises selecting said second frequency f 2 to be: 30 MHz<f 2 <100 MHz raising said second frequency f 2 during the step (d), and increasing the Rf power at said second frequency f 2 in dependency of said raising said second frequency f 2 and to be below a critical power but avoiding initiation of sputtering.