Method and apparatus for plasma generation

Abstract

In a simple method and device for producing plasma flows of a metal and/or a gas electric discharges are periodically produced between the anode and a metal magnetron sputtering cathode in crossed electric and magnetic fields in a chamber having a low pressure of a gas. The discharges are produced so that each discharge comprises a first period with a low electrical current passing between the anode and cathode for producing a metal vapor by magnetron sputtering, and a second period with a high electrical current passing between the anode and cathode for producing an ionization of gas and the produced metal vapor. Instead of the first period a constant current discharge can be used. Intensive gas or metal plasma flows can be produced without forming contracted arc discharges. The selfsputtering phenomenon can be used.

1 - 36 . (canceled) 
     
     
         37 . A method for producing plasma from a metal and/or a gas in a chamber and between a anode and cathode of said metal or metals, said chamber having crossed electric and magnetic fields and said gas at a low pressure, said method comprising:
 generating periodic repeated double-pulse electrical discharges wherein each double-pulse discharge comprises first and second pulsed electrical discharges between the anode and the cathode to produce metal plasma,
 wherein said first pulsed electrical discharge occurs during a first time period and is generated by a low electrical current supplied by a first power supply, said low electrical current passing between the anode and cathode for achieving a sputtering discharge producing a metal vapor by magnetron sputtering, and 
 wherein said second pulsed electrical discharge occurs during a second time period and is generated by a high electrical current supplied by a second power supply, said high electrical current passing between the anode and cathode for ionizing the gas and the metal vapor, said high electrical current being higher than said low electrical current, 
 wherein during the second time periods the driving current between the anode and the cathode is μ 2 S, wherein μ 2  is measured in A/cm 2  and has a value in the range of 1-10 A/cm 2  and S is the active surface of the cathode measured in cm 2 , and 
   wherein said first time period is longer than said second time period.   
     
     
         38 . A method according to  claim 37 , wherein said double-pulse discharges are produced with a frequency of 100 Hz-20 kHz. 
     
     
         39 . A method according to  claim 37 , wherein during the first time period when the discharges are low the deposition rate increases with increasing discharge current, and during the second time period when the discharges are high the deposition rate decreases with increasing discharge current. 
     
     
         40 . A method according to  claim 37 , wherein said sputtering discharges in said first time periods are low intensity current quasi-stationary discharges and said ionization discharges in said second time periods are high intensity current non-quasi-stationary discharges in crossed electric and magnetic fields. 
     
     
         41 . A method according to  claim 37 , wherein during the first time periods the driving current between the anode and the cathode is μ1S, where μ1 is measured in A/cm 2  and has a value in the range of 0.1-1 A/cm 2  and S is the area of the active surface of the cathode measured in cm 2 . 
     
     
         42 . A method according to  claim 37 , wherein during the first time periods have a duration β1D, where β1 is measured in μs/cm and has a value in the range of 0.1-3 μs/cm and D is the diameter of a circular cathode or the smaller dimension of a rectangular cathode measured in cm. 
     
     
         43 . A method according to  claim 37 , wherein said second time periods have a duration of β2D, where β2 is measured in μs/cm and has a value in the range of 0.1-1 μs/cm and D is the diameter of a circular cathode or the smaller dimension of a rectangular cathode measured in cm. 
     
     
         44 . A method according to  claim 37 , characterized by the additional step of providing in the chamber a magnetron magnetic configuration of balanced type having a maximum value in the range of 0.07-0.3 T of the radial component of the magnetic field at the active surface of the cathode. 
     
     
         45 . A method according to  claim 37 , characterized by the additional step of providing in the chamber a mixture of sputtering and reactive gases at a pressure in the range of 10 −10 -10 −2  Torr. 
     
     
         46 . A method according to  claim 37 , characterized by the additional step of providing in the chamber a magnetron magnetic configuration of unbalanced type having a maximum value in the range of 0.04-0.3 T of the radial component of the magnetic field at the active surface of the cathode. 
     
     
         47 . A method according to  claim 37 , characterized by the additional step of providing in the chamber a magnetron magnetic configuration of the type having a cusp-shaped axially symmetric magnetic configuration having a maximum value in the range of 0.04-0.3 T of the radial component of the magnetic field at the active surface of the cathode. 
     
     
         48 . A method according to  claim 37 , wherein the first pulse discharge is separated from the second pulse discharge by a delay. 
     
     
         49 . A method according to  claim 48 , wherein no driving current is produced during said delay. 
     
     
         50 . A method according to  claim 49 , wherein said delay has a duration t=cD, where c is measured in s/cm and having a value in the range of 5*10 −8 -1*10 −6  s/cm and D is the diameter of the cathode measured in cm. 
     
     
         51 . A method according to  claim 38 , wherein said double-pulse discharges are produced with a frequency of 0.5-2 kHz. 
     
     
         52 . A device for producing plasma flows of a metal and/or a gas comprising:
 a chamber for maintaining a gas at a low pressure;   an anode and a magnetron sputtering cathode, the cathode comprising a metal or metals for metal plasma production,   a magnet assembly for making electric discharges in crossed electric and magnetic fields;   a power supply assembly for periodically producing electric discharges between the anode and the cathode, said power supply assembly comprises first and second power supplies,
 wherein said first power supply delivers to said anode and cathode first pulses low electric current driving pulses for producing a gas/metal vapor by magnetron sputtering of the cathode and said second power supply delivers to said anode and cathode second high electric current driving pulses for ionizing the gas and/or metal vapor produced in the chamber, 
 wherein the driving current of said second pulses between the anode and the cathode is μ2S, wherein μ2 is measured in A/cm2 and has a value in the range of 1-10 A/cm2 and S is the active surface of the cathode measured in cm2, 
 wherein the driving current of said second pulses is higher than the driving current of said first pulses, and 
 wherein said first pulses have a longer duration than said second pulses; and 
   a timer for periodically triggering pulses to the first and second power supplies such that said the first and second pulse discharges are provided as double-pulse electrical discharges, comprising a first pulse for a sputtering discharge and second pulse for an ionizing discharge, wherein the first pulse ends before the second pulse begins.   
     
     
         53 . A device according to  claim 52 , characterized in that at least one of the power supplies is dimensioned to generate for a resistive load of 1 ohm pulses having peak voltages in the range of 0.4-4 kV. 
     
     
         54 . A device according to  claim 52 , wherein said power supplies comprise a capacitor connected in parallel to a charger circuit. 
     
     
         55 . A device according to  claim 52 , wherein during the first pulses when the discharges are low the deposition rate increases with increasing discharge current, and during the second pulses when the discharges are high the deposition rate decreases with increasing discharge current.