Enhanced cathodic arc source for arc plasma deposition

Abstract

An improved cathodic arc source and method of DLC film deposition with a carbon containing directional-jet plasma flow produced inside of cylindrical graphite cavity with depth of the cavity approximately equal to the cathode diameter. The generated carbon plasma expands through the orifice into ambient vacuum resulting in plasma flow strong self-constriction. The method represents a repetitive process that includes two steps: the described above plasma generation/deposition step that alternates with a recovery step. This step provides periodical removal of excessive amount of carbon accumulated on the cavity wall by motion of the cathode rod inside of the cavity in direction of the orifice. The cathode rod protrudes above the orifice, and moves back to the initial cathode tip position. The said steps periodically can be reproduced until the film with target thickness is deposited. Technical advantages include the film hardness, density, and transparency improvement, high reproducibility, long duration operation, and particulate reduction.

1 . A method of diamond-like carbon film deposition comprising:
 producing a carbon containing directional jet plasma flow with a cylindrical cathodic arc source, the cylindrical cathodic arc source comprising:
 a cylindrical graphite cathode and an anode formed from of a plurality of spaced baffles, wherein the cylindrical graphite cathode rod and the anode are separated by a shield, the shield further including an insulator tube with thin wall graphite bushing inside of the tube; 
 a bent solenoidal magnetic filter following the cathodic arc source; 
 a graphite cavity formed by extending the shield from the cathode top surface, creating a semi-confined space with a cavity orifice shaped identically to the cathode top surface. 
   
     
     
         2 . A method of diamond-like carbon film deposition comprising:
 generating carbon arc plasma in the cavity;   directing expansion of the plasma flow in form of macro-jet into ambient vacuum;   moving the cathode rod inside of the shield in direction of the orifice protruding above the orifice, and back to the initial cathode tip position; and   periodically reproducing the method until a film with target thickness is deposited.   
     
     
         3 . The method of  claim 1 , wherein an arc discharge current of the cathodic arc source is higher than 600 A. 
     
     
         4 . The method of  claim 1 , wherein the cavity orifice defines a diameter of approximately 5 mm to approximately 12 mm. 
     
     
         5 . The method of  claim 4 , wherein the anode defines a diameter that is approximately equal to the diameter of the cavity orifice. 
     
     
         6 . The method of  claim 1 , wherein the anode length does not exceed five times a diameter of the cavity orifice. 
     
     
         7 . The method of  claim 1 , wherein the diameter of the bent solenoidal magnetic filter is approximately two to four times a diameter of the cavity orifice. 
     
     
         8 . The method of  claim 1 , wherein the magnetic field strength inside of the bent solenoidal magnetic filter is approximately 1.5 to approximately 4 times the magnetic field strength sufficient to magnetize electrons. 
     
     
         9 . The method of  claim 1 , wherein the magnetic field strength in the central area of the bent solenoidal magnetic filter ranges between approximately 400 Gauss and approximately 1200 Gauss. 
     
     
         10 . The method of  claim 8 , wherein a current in the bent solenoidal magnetic filter solenoid is between approximately 400 Amps and approximately 800 Amps. 
     
     
         11 . The method of  claim 1 , wherein the cathodic arc source and the bent solenoidal magnetic filter are operated in a pulsed mode, and an arc pulse starts after a filter coil current pulse began, and ends before the filter coil current pulse ends. 
     
     
         12 . An apparatus for generation of directional carbon containing plasma flow in a cathodic arc source comprising:
 a cylindrical graphite cathode and an anode formed from of a plurality of spaced baffles, wherein the cylindrical graphite cathode rod and the anode are separated by a shield, the shield further including an insulator tube with thin wall graphite bushing inside of the tube;   a bent solenoidal magnetic filter following the cathodic arc source; and   a graphite cavity formed by extending the shield from the cathode top surface, creating a semi-confined space with cavity orifice shaped identical to the cathode top surface.   
     
     
         13 . The apparatus of  claim 12 , wherein the source comprising motion mechanism of the cathode rod inside of the shield along the graphite rod axis in the direction of the cavity orifice protruding above the cavity orifice to a reference point and back to the initial cathode tip position. 
     
     
         14 . The apparatus of  claim 12 , wherein a reference point for the graphite rod tip protruded position is determined by a laser beam directed in between the baffles of the anode crossing the cathode motion axis and a detector that controls the laser beam indicates a drop of intensity when the graphite rod crosses the laser beam propagation line. 
     
     
         15 . The apparatus of  claim 12 , wherein the source comprising a feedback scheme that passes the detector signal to a controller that controls the cathode motion mechanism and returns the cathode tip to its initial position.