Methods And Apparatus For Generating Strongly-Ionized Plasmas With Ionizational Instabilities

Abstract

A plasma generator includes a chamber for confining a feed gas. An anode is positioned inside the chamber. A cathode assembly is positioned adjacent to the anode inside the chamber. A pulsed power supply comprising at least two solid state switches and having an output that is electrically connected between the anode and the cathode assembly generates voltage micropulses. A pulse width and a duty cycle of the voltage micropulses are generated using a voltage waveform comprising voltage oscillation having amplitudes and frequencies that generate a strongly ionized plasma.

What is claimed is: 
     
         1 - 13 . (canceled) 
     
     
         14 . A method of generating ions from sputtered target material atoms, the method comprising:
 a) supplying feed gas proximate to an anode and a cathode assembly comprising a sputtering target;   b) applying a magnetic field proximate to the cathode assembly;   c) generating a weakly ionized plasma by applying a first voltage waveform having a controlled amplitude and a controlled rise time that prevents forming an arc between the anode and the cathode assembly, an amplitude and a rise time of the first voltage waveform being sufficient to ignite and sustain a weakly ionized plasma from the feed gas;   d) generating a transient plasma from the weakly-ionized plasma by applying a second voltage waveform between the anode and the cathode assembly, the second voltage waveform having a controlled amplitude and a controlled rise time that prevents forming an arc between the anode and the cathode assembly, the controlled amplitude and the controlled rise time of the second voltage waveform being sufficient to shift an electron energy distribution in the weakly ionized plasma to higher energies that increase an ionization rate of sputtered target material atoms and feed gas atoms which results in a rapid increase in electron density and a formation of the transient plasma; and   e) generating a strongly-ionized plasma from the transient plasma by applying a third voltage waveform between the anode and the cathode assembly, the third voltage waveform having a controlled amplitude that is sufficient to maintain an ionization rate of sputtered target material atoms and feed gas atoms that forms the strongly ionized plasma.   
     
     
         15 . The method of  claim 14 , further comprising rotating the magnetic field proximate an anode and a cathode assembly. 
     
     
         16 . The method of  claim 14 , further comprising providing a substrate on the substrate support. 
     
     
         17 . The method of  claim 16 , further comprising controlling a temperature of the substrate. 
     
     
         18 . The method of  claim 16 , further comprising applying a negative voltage bias to the substrate support to attract positive ions from strongly ionized plasma to the substrate. 
     
     
         19 . The method of  claim 14 , wherein at least one of the first voltage waveform, second voltage waveform, and the third voltage waveform comprises voltage oscillations. 
     
     
         20 . The method of  claim 19 , wherein voltage oscillations generates discharge current oscillations. 
     
     
         21 . The method of  claim 14 , wherein each of the first voltage waveform, second voltage waveform, and the third voltage waveform comprise voltage oscillations. 
     
     
         22 . The method of  claim 21 , wherein at least one of the voltage oscillations generates current oscillations. 
     
     
         23 . The method of  claim 21 , wherein each of the voltage oscillations generates discharge current oscillations. 
     
     
         24 . The method of  claim 14 , wherein the strongly ionized plasma corresponds to more than 250 W/cm 2  on the sputtering target. 
     
     
         25 . A magnetron sputtering source comprising:
 a) means for supplying feed gas proximate to an anode and a cathode assembly comprising a sputtering target;   b) means for applying a magnetic field proximate to the cathode assembly;   c) means for generating a weakly ionized plasma that prevents forming an arc between the anode and the cathode assembly by applying a first voltage waveform having a controlled rise time;   d) means for generating a transient plasma from the weakly-ionized plasma by applying a second voltage waveform between the anode and the cathode assembly; and   e) means for generating a strongly-ionized plasma from the transient plasma by applying a third voltage waveform between the anode and the cathode assembly.   
     
     
         26 . A magnetron sputtering source of  claim 25  wherein the first voltage waveform comprises a controlled rise time being sufficient to ignite and sustain a weakly ionized plasma from the feed gas. 
     
     
         27 . A magnetron sputtering source of  claim 25  wherein the second voltage waveform comprises a controlled amplitude and a controlled rise time that prevents forming an arc between the anode and the cathode assembly. 
     
     
         28 . A magnetron sputtering source of  claim 25  wherein the controlled amplitude and the controlled rise time of the second voltage waveform is sufficient to shift an electron energy distribution in the weakly ionized plasma to higher energies that increase an ionization rate of sputtered target material atoms and feed gas atoms which results in a rapid increase in electron density and a formation of the transient plasma. 
     
     
         29 . A magnetron sputtering source of  claim 25  wherein the third voltage waveform comprises a controlled amplitude that is sufficient to maintain an ionization rate of sputtered target material atoms and feed gas atoms that forms the strongly ionized plasma.