Method and apparatus for altering material

Abstract

Methods and apparatus for thermally altering the near surface characteristics of a material are described. In particular, a repetitively pulsed ion beam system comprising a high energy pulsed power source and an ion beam generator are described which are capable of producing single species high voltage ion beams (0.25-2.5 MeV) at 1-1000 kW average power and over extended operating cycles (10 8 ). Irradiating materials with such high energy, repetitively pulsed ion beams can yield surface treatments including localized high temperature anneals to melting, both followed by rapid thermal quenching to ambient temperatures to achieve both novel and heretofore commercially unachievable physical characteristics in a near surface layer of material.

We claim:  
     
       1. A method of surface treating a material, comprising the step of irradiating a surface of the material with a repetitively pulsed ion beam, wherein each spatially contiguous pulse of the pulsed ion beam has a duration of ≦500 ns at an accelerating gap between a cathode and an anode assembly, a total beam energy delivered to the material of >1 Joule/pulse, an impedance of < about 100 Ω, an ion kinetic energy of>50 keV, and a repetition rate >1 Hz. 
     
     
       2. The method of  claim 1 , further including controlling the depth of surface treatment of the material by controlling the ion species comprising the ion beam. 
     
     
       3. The method of  claim 1 , further including controlling the depth of surface treatment of the material by controlling the kinetic energy level of the ion beam. 
     
     
       4. The method of  claim 1  further including controlling the depth of surface treatment by controlling the duration of the ion beam pulse between ≧30 ns and ≦200 ns. 
     
     
       5. The method of  claim 1 , further including the step of surface treating at least 100 cm 2  with each pulse of the ion beam. 
     
     
       6. The method of  claim 1 , further including the step of surface treating 100 to 1000 cm 2  with each pulse of the ion beam. 
     
     
       7. The method of  claim 1 , further including the step of thermally quenching the irradiated surface of material. 
     
     
       8. The method of  claim 7 , wherein the rate of quenching the irradiated material is at least 10 8  K/sec. 
     
     
       9. The method of  claim 2 , wherein the ion species are selected from the group consisting of argon, nitrogen, carbon, and protons. 
     
     
       10. The method of claim  1   2 , wherein the ion species are produced from molecules selected from the group consisting of gases, vaporizable liquids, and vaporizable solids. 
     
     
       11. The method of  claim 1  wherein the characteristic is the removal of surface contamination. 
     
     
       12. A method for altering the characteristics of a near surface layer of material, comprising: 
       (a) generating a repetitively pulsed ion beam, wherein the ion beam has an ion kinetic energy level >0.1 MeV, a pulse duration of ≦500 ns at an accelerating gap between a cathode and an anode assembly, a total beam energy delivered to the material of >1 Joule/spatially contiguous pulse, an impedance of < about 100 Ω, and a pulse repetition rate >1 Hz; and  
       (b) irradiating the surface of the material with the ion beam and thereby altering the near surface layer of the material defined by a predetermined depth from the irradiated surface.  
     
     
       13. The method of  claim 12 , further comprising varying the depth of the near surface layer thermally altered by controlling the kinetic energy of the ion species composing the ion beam. 
     
     
       14. The method of  claim 12 , further including varying the depth of the near surface layer thermally altered by varying the ion species composing the ion beam. 
     
     
       15. The method of  claim 12 , wherein the step of altering a near surface layer of material produces melting. 
     
     
       16. The method of  claim 12 , further including the step of thermally quenching the near surface layer of material. 
     
     
       17. The method of  claim 16 , wherein the rate of thermally quenching is at least 10 8  K/sec. 
     
     
       18. The method of  claim 16 , wherein the step of thermally quenching further includes retaining non-equilibrium microstructures within the near surface layer selected from the group consisting of: amorphous, disordered crystalline and nano crystalline phases. 
     
     
       19. The method of  claim 12 , wherein the near surface layer includes a layer of a first material and a layer of a second material and further including the step of controlling the predetermined depth of altering of material to include an interface between a  the layer of a first material and a  said layer of a second material for bonding the first material to the second material, wherein the layers of the first and second materials are included within the near surface layer. 
     
     
       20. The method of  claim 12  wherein the step of altering a near surface layer of material produces etching of polymers. 
     
     
       21. The method of  claim 12  wherein the step of altering a near surface layer of material produces cross-linking of polymers. 
     
     
       22. The method of  claim 12  wherein the step of altering a near surface layer of material produces polishing of the material. 
     
     
       23. The method of  claim 12  wherein the step of altering a near surface layer of material produces cleaning of the material. 
     
     
       24. The method of  claim 12  wherein the step of altering a near surface layer of material produces glazing of the material. 
     
     
       25. The method of  claim 12  wherein the material is a metal and the characteristic is hardness. 
     
     
       26. The method of  claim 25  wherein the metal is steel. 
     
     
       27. The method of  claim 12  wherein the characteristic is surface smoothness. 
     
     
       28. The method of  claim 27  wherein the material is a ceramic. 
     
     
       29. The method of  claim 27  wherein the material is a metal composition. 
     
     
       30. An ion beam generator for altering near surface layers of materials, comprising: 
       a) means for repetitively generating pulsed power signals at a rate >1 Hz, wherein the pulsed power signal has a duration of 30-500 ns, and  
       b) means for generating an ion beam in a magnetically confined plasma with the pulsed power signal, whereby pulsed ion beams are produced at rates >1 Hz and 30-500 ns in duration at an accelerating gap between a cathode and an anode assembly with a total beam energy delivered to the material of >1 Joule/spatially contiguous pulse and an impedance of < about 100 Ω.  
     
     
       31. The ion beam generator of  claim 30 , wherein the means for generating an ion beam includes: 
       an anode assembly comprising inner and outer anode rings defining an anode annulus there between,  
       a cathode assembly comprising inner and outer cathode rings defining a cathode annulus there between wherein the inner and outer cathode rings also contain slow magnetic coils which, when energized, act to magnetically insulate the accelerating gap between the anode electrode rings and the cathode electrode rings,  
       means to pre-ionize a gas introduced into the means for generating an ion beam, and  
       means for completely ionizing the gas into the plasma and for moving the plasma comprising fast driving magnetic coil means which move the plasma towards and through the anode annulus into an accelerating gap between the anode assembly and the cathode assembly, wherein both the means to pre-ionize and the fast driving coil means are located to the side of the anode assembly opposite to the cathode assembly,  
       wherein the inner and outer anode rings are configured so as to separate the magnetic field lines from the fast driving magnetic coil means from the magnetic field lines from the slow magnetic coils such that the magnetic field approaches zero across the cathode annulus at the time of beam acceleration and wherein the slow magnetic coils are located to the opposite side of the anode annulus relative to the fast driving magnetic coil means.  
     
     
       32. A process for uniformly altering a characteristic of a surface of a material to a depth of less than 50 microns by irradiating the surface with a repetitively pulsed ion beam, wherein each spatially contiguous pulse of the pulsed ion beam has a duration of ≦500 ns, a total beam energy delivered to the material of >1 Joule/pulse, an impedance of <100 Ω, and a repetition rate >1 Hz, such that continuous areas in excess of 50 cm 2  are created with the altered characteristic by each pulse. 
     
     
       33. A process for uniformly altering a characteristic of a surface of a material to a depth of less than 50 microns by irradiating the surface with a repetitively pulsed ion beam, wherein each spatially contiguous pulse of the pulsed ion beam has a duration of ≦500 ns, a total beam energy delivered to the material of >1 Joule/pulse, an impedance of <100 Ω, and a repetition rate >1 Hz, such that continuous areas in excess of 5 cm 2  are created with the altered characteristic by each pulse. 
     
     
       34. The method according to  claim 5  wherein a transition is created between a treated and untreated area of the material and the step of irradiating results in no significant edge effects at said transition. 
     
     
       35. The method according to  claim 6  wherein a transition is created between a treated and untreated area of the material and the step of irradiating results in no significant edge effects at said transition. 
     
     
       36. The method according to  claim 1  wherein the material is a metal. 
     
     
       37. The method according to  claim 1  wherein the material is a semiconductor. 
     
     
       38. The method according to  claim 1  wherein the material is a polymer. 
     
     
       39. The method according to  claim 1  wherein the material is a ceramic. 
     
     
       40. The method according to  claim 1  wherein said surface treatment comprises annealing. 
     
     
       41. The method according to  claim 1  wherein said surface treatment comprises modification of the surface microstructure of said material. 
     
     
       42. The method according to  claim 1  wherein said surface treatment comprises vaporization of at least a portion of said surface layer. 
     
     
       43. The method according to  claim 12  wherein the step of irradiating comprises thermally heating the material without significantly altering its atomic composition. 
     
     
       44. The method according to  claim 12  wherein the near surface layer includes a layer of a first material and a layer of a second material and further including the step of controlling the predetermined depth of altering of material to include an interface between the layer of a first material and the layer of a second material for mixing said first and second layer materials by liquid phase mixing. 
     
     
       45. The method according to  claim 12  wherein said step of altering further comprises implanting ions in said surface layer. 
     
     
       46. The method according to  claim 12  wherein said characteristic is hardness. 
     
     
       47. The method according to  claim 46  wherein said step of altering comprises producing surface ablations in said workpiece. 
     
     
       48. The ion beam generator according to  claim 30 , wherein the means for generating an ion beam includes: 
       
         an anode assembly comprising inner and outer anode rings defining an anode annular gap therebetween;  
       
       
         a cathode assembly comprising inner and outer cathode rings defining a cathode annulus there between wherein the inner and outer cathode rings also contain slow magnetic coils which, when energized, act to magnetically insulate the accelerating gap between the anode electrode rings and the cathode electrode rings;  
       
         means to pre - ionize a gas introduced into the means for generating an ion beam; and    
         means for completely ionizing the gas into the plasma and for moving the plasma comprising fast driving magnetic coil means which move the plasma towards and through the anode annulus into an accelerating gap between the anode assembly and the cathode assembly, wherein both the means to pre - ionize and the fast driving coil means are located to the side of the anode assembly opposite to the cathode assembly,    
       
         wherein the inner and outer anode rings are configured to separate the magnetic field lines from the fast driving magnetic coil means from the magnetic field lines from the slow magnetic coils in said annular gap at the time of beam acceleration and wherein the slow magnetic coils are located to the opposite side of the anode annulus relative to the fast driving magnetic coil means. 
       
     
     
       49. The method according to  claim 32  where a transition is created between an altered and unaltered area of the material and the step of irradiating results in no significant edge effects at said transition. 
     
     
       50. The method according to  claim 33  wherein a transition is created between a treated and untreated area of the material and the step of irradiating results in no significant edge effects at said transition. 
     
     
       51. An ion beam generator for altering near surface layers of materials, comprising: 
         a )  a magnetically switched, high energy, a low impedance pulsed power system for producing a repetitively pulsed power signal; and    
         b )  a magnetically confined anode plasma pulsed ion beam source having a cathode and an anode defining therebetween an acceleration gap for producing a pulsed ion beam, said ion beam being extractable from said ion beam source whereby said ion beam may propagate through an essentially magnetic field free region with little or no rotation.   
     
     
       52. The ion beam generator according to  claim 51  wherein the pulsed power signal has a duration of  30 - 500  ns. 
     
     
       53. The ion beam generator according to  claim 51  wherein the pulsed ion beam has pulses of  30 - 500  ns in duration in said acceleration gap with a total beam energy delivered to the material of > 1  Joule/spatially contiguous pulse and an impedance of < about  100  Ω. 
     
     
       54. The ion beam generator according to  claim 51  wherein: 
       
         said anode comprises an anode assembly having inner and outer anode rings defining an anode annular gap therebetween;  
       
       
         said cathode comprises a cathode assembly having inner and outer cathode rings defining a cathode annular gap therebetween, said inner and outer cathode rings further comprising a slow magnetic coil which, when energized, acts to magnetically insulate the accelerating gap;  
       
       
         a gas delivery assembly for introducing gaseous material upstream of the anode in the direction of flow of said gasious material;  
       
       
         means for preionizing said gaseous material;  
       
       
         a fast driving magnetic coil for ionizing said gaseous material into a plasma and for moving the plasma into the accelerating gap;  
       
       
         wherein the inner and outer anode rings are configured so as to separate the magnetic field lines from the fast driving magnetic coil from the magnetic field lines from the slow magnetic coil at the time of the beam acceleration, said slow magnetic coil being positioned opposite the anode annular gap relative to the fast driving magnetic coil. 
       
     
     
       55. The ion beam generator according to  claim 51  wherein said pulsed power system is operable to deliver voltage of less than about  2 . 5  MV. 
     
     
       56. The ion beam generator according to  claim 52  wherein said pulsed power system operates at an impedance of less than about  100  Ω. 
     
     
       57. The ion beam generator according to  claim 51  wherein said magnetically confined anode plasma source is operable to provide pure beams of a predetermined ion species. 
     
     
       58. The ion beam generator according to  claim 54  wherein said gas delivery assembly comprises a nozzle for introducing a gas puff proximate to said fast driving coil. 
     
     
       59. The ion beam generator according to  claim 58  wherein said nozzle is a supersonic nozzle. 
     
     
       60. The ion beam generator according to  claim 54  wherein said means for preionizing means comprises an electric field generator for inducing an electric field in the gas. 
     
     
       61. The ion beam generator according to  claim 54  wherein said gas delivery assembly comprises a source of gas for forming a plasma. 
     
     
       62. The ion beam generator according to  claim 61  wherein said gas is selected from group comprising hydrogen, nitrogen and argon. 
     
     
       63. The ion beam generator according to  claim 61  further comprising a source of gas, said source of gas comprising a vaporizable liquid or metal. 
     
     
       64. The ion beam generator according to  claim 61  wherein said gas source comprises at least one of a vaporizable liquid or metal and a gas selected from the group comprising hydrogen, nitrogen and argon. 
     
     
       65. The ion beam generator according to  claim 54  further comprising a vacuum chamber enclosing a target plane where material may be positioned for treatment, wherein said ion beam propagates through said vacuum chamber to said target plane. 
     
     
       66. The ion beam generator in accordance with  claim 65  wherein the vacuum chamber includes said essentially magnetic field free region and said ion beam is extracted from said ion beam source into said magnetic field free region with little or no rotation. 
     
     
       67. The ion beam generator according to  claim 65  further comprising means for forming a virtual cathode consisting of electrons emitted by said cathode, said virtual cathode extending proximate to the anode assembly to thereby increase the ion flow across the accelerating gap. 
     
     
       68. The ion beam generator according to  claim 51  wherein an output of said high energy, low impedance pulsed power system is applied to said anode to accelerate ions from a plasma in said magnetically confined anode plasma source to thereby form said pulsed ion beam. 
     
     
       69. The ion beam generator according to  claim 51  wherein said repetitively pulsed power signal produces a pulsed ion beam at a frequency of > 1  Hz. 
     
     
       70. A method of forming a pulsed ion beam using a magnetically confined anode plasma, an ion beam source having an anode assembly, a cathode assembly, a slow magnetic field coil associated with said cathode assembly, a fast driving magnetic field coil, an acceleration gap between said anode assembly and cathode assembly, a gas injection device, and a target plane, comprising the steps of: 
         a )  introducing a gas puff into a region between said fast driving coil and said anode assembly;    
         b )  pre - ionizing said gas;    
         c )  energizing said fast driving magnetic field coil to create a plasma from said preionized gas;    
         d )  guiding said plasma into a magnetically confined plasma layer in the anode assembly;    
         e )  applying pulsed energy to said accelerating gap using a magnetically switched pulsed power system to thereby accelerate ions from said plasma to form a pulsed ion beam; and    
         f )  extracting said ion beam from the plasma layer and directing said pulsed ion beam through an essentially magnetic field free region toward said target plane with little or no rotation thereof.   
     
     
       71. The method according to  claim 70  wherein the step of extracting comprises the steps of propagating and focusing said pulsed ion beam at said target plane with little or no rotation thereof. 
     
     
       72. The method according to  claim 70  wherein the gas is selected from the group consisting of hydrogen, nitrogen and argon. 
     
     
       73. The method according to  claim 70  wherein the gas is generated from high vapor pressure liquid or metal. 
     
     
       74. The method according to  claim 70  further comprising the step of forming a virtual cathode proximate to end opposite said anode assembly. 
     
     
       75. The method according to  claim 74  wherein said step of forming a virtual cathode comprises forming a virtual cathode using electrons from said cathode assembly. 
     
     
       76. The method according to  claim 75  wherein the electrons are confined so as to form a sheath extending from the cathode assembly to the anode assembly in an ion emitting region of the anode assembly. 
     
     
       77. The method according to  claim 70  wherein the step of applying pulsed power the anode assembly comprises applying pulsed power of less than about  2 . 5  MV. 
     
     
       78. The method according to  claim 77  wherein the magnitude of the applied voltage is determined based on the desired depth of penetration of the ions into the material to be irradiated. 
     
     
       79. The method of  claim 76  further comprising maintaining the impedance of said ion beam source at < about  100  Ω. 
     
     
       80. The method according to  claim 71  further comprising the step of maintaining a vacuum of at least about  1 × 10   −3    Torr in the region between said plasma layer and said target plane during substantially the entire interval between ion pulses.   
     
     
       81. The method according to  claim 71  wherein the step of directing further comprises propagating said ion beam through a magnetic field free region and then focusing said ion beam on a material surface positioned on said target plane. 
     
     
       82. The method according to  claim 81  further comprising the step of separating said target plane from said ion beam source by at least about  20  cm. 
     
     
       83. The method according to  claim 70  further comprising the step of pulsing said ion beam at a repetition rate of > 1  Hz. 
     
     
       84. A method of producing a high energy vapor for depositing films comprising the step of: 
         a )  generating a repetitively pulsed ion beam using a magnetically confined anode plasma ion beam source and magnetically switched pulsed power source applied to an acceleration gap thereof, wherein the ion beam has an ion kinetic energy level > 0 . 1  MeV, a pulse duration of < 500  ns at said acceleration gap, a total beam energy delivered to the material of > 1  Joule/spatially contiguous pulse, and an impedance of < about  100  Ω;    
         b )  extracting the pulsed ion beam from said source with little or no rotation thereof; and    
         c )  irradiating the surface of a material with the ion beam to vaporize a surface layer thereof.   
     
     
       85. The method according to  claim 84  further comprising the step of: 
       
         depositing said vaporized material on a substrate to thereby form a film on said substrate. 
       
     
     
       86. The method according to  claim 84  wherein said repetitively pulsed ion beam has a pulse repetition rate of > 1  Hz.