Electron beam exposure system

Abstract

The invention relates to an electron beam exposure apparatus for transferring a pattern onto the surface of a target, comprising: a beamlet generator for generating a plurality of electron beamlets; a modulation array for receiving said plurality of electron beamlets, comprising a plurality of modulators for modulating the intensity of an electron beamlet; a controller, connected to the modulation array for individually controlling the modulators, an adjustor, operationally connected to each modulator, for individually adjusting the control signal of each modulator; a focusing electron optical system comprising an array of electrostatic lenses wherein each lens focuses a corresponding individual beamlet, which is transmitted by said modulation array, to a cross section smaller than 300 nm, and a target holder for holding a target with its exposure surface onto which the pattern is to be transferred in the first focal plane of the focusing electron optical system.

The invention claimed is: 
     
       1. A method for transferring a pattern onto a target exposure surface with a multi-beam lithography system, comprising the steps of:
 generating a plurality of beamlets;   individually modulating the intensity of each beamlet of said plurality of beamlets by means of a modulator device;   controlling said modulator device, using control signals, by means of a controller operationally coupled to said modulator;   individually adjusting said control signals.   
     
     
       2. The method according to  claim 1  in which timing of said control signals is adjusted. 
     
     
       3. The method of  claim 1 , in which timing of said control signals is individually adjusted. 
     
     
       4. The method according to  claim 1  in which modulation is performed as an “off” or “on” condition of a beamlet, by either deflecting said beamlet within the system, or by allowing free passage of said beamlet at said modulator, the condition thereby being controlled on the basis of available electronic pattern data, in which timing is adjusted by correcting an instance of deflection or passage of said beamlet, said correction being calculated by the controller. 
     
     
       5. The method of  claim 1 , said control signals having a timing base, and timing of the control signal of at least one beamlet is adjusted. 
     
     
       6. The method of  claim 1 , further comprising the step of determining a position of a beamlet, storing said position in a memory and comparing said position with a desired position. 
     
     
       7. The method of  claim 6 , wherein said position of a beamlet is the actual position of a beamlet on said exposure surface. 
     
     
       8. The method of  claim 6 , wherein said adjustment of said timing is based on the result of said comparing. 
     
     
       9. The method of  claim 1 , wherein said timing is adjusted locally. 
     
     
       10. The method of  claim 1 , wherein adjusting timing comprises correcting a timing window. 
     
     
       11. The method of  claim 1 , wherein said control signals have a timing base. 
     
     
       12. The method of  claim 11 , wherein said controller calculates a corrected timing window, and applies said corrected timing window to said timing base. 
     
     
       13. The method of  claim 11 , wherein said controller calculates a corrected timing window, and applies said corrected timing window to said timing base of an individual beamlet. 
     
     
       14. An electron beam exposure apparatus for transferring a pattern onto the surface of a target using a plurality of electron beamlets, comprising:
 a modulator array for receiving said plurality of electron beamlets, comprising a plurality of modulators for modulating the intensity of a beamlet of said plurality of beamlets;   a controller, operationally coupled to said modulator array, for controlling each modulator of said plurality modulators, said controller producing a plurality of control signals with at least one control signal for each modulator, and   an adjustor for allowing individual adjustment of a control signal.   
     
     
       15. The electron beam exposure apparatus according to  claim 14 , wherein said plurality of control signals having a timing base. 
     
     
       16. The electron beam exposure apparatus according to  claim 14 , wherein said adjustor is adapted for allowing individual adjustment of timing of a control signal. 
     
     
       17. The electron beam exposure apparatus according to  claim 14 , furthermore provided with a measuring device for measuring the actual position of at least one of said beamlets, and wherein the controller is provided with a memory for storing said actual position and a desired position, a comparator for comparing the desired position and the actual position of said at least one of said beamlets, and wherein the adjustor is operationally coupled to the controller for receiving instructions for adjusting a control signal issued to a modulator to compensate for the difference between said desired position and said actual position of said at least one of said electron beamlets. 
     
     
       18. The electron beam exposure apparatus according to  claim 14 , wherein the adjustor is operationally coupled to the controller for receiving instructions indicating the amount of the adjustments. 
     
     
       19. The electron beam exposure apparatus of  claim 14 , wherein the adjustor is adapted for adjusting timing of each control signal. 
     
     
       20. The electron beam exposure apparatus of  claim 14 , further comprising a beamlet generator, said beamlet generator comprising:
 a source for emitting at least one electron beam,   at least one beamsplitter for splitting said at least one emitted electron beam into said plurality of electron beamlets.   
     
     
       21. The electron beam exposure apparatus according to  claim 20 , further comprising a modulation array, comprising a beamlet blanker array comprising a plurality of beamlet blankers for the deflection of a passing electron beamlet and a beamlet stop array, having a plurality of apertures aligned with said beamlet blankers of said beamlet blanker array. 
     
     
       22. The electron beam exposure apparatus according to  claim 20 , further comprising a second electrostatic lens array located between said beamsplitter and said beamlet blanker array to focus said plurality of electron beamlets. 
     
     
       23. The electron beam exposure apparatus according to  claim 22 , wherein said beamlet blanker array is located in the focal plane of said second electrostatic lens array. 
     
     
       24. An electron beam exposure apparatus for transferring a pattern onto the surface of a target using a plurality of electron beamlets, comprising:
 a modulator array for receiving said plurality of electron beamlets, comprising a plurality of modulators for modulating the intensity of a beamlet of said plurality of beamlets;   a controller, operationally coupled to said modulator array, for controlling each modulator of said plurality modulators, said controller producing a plurality of control signals with at least one control signal for each modulator, said controller comprising an adjustor allowing individual adjustment of at least one control signal.   
     
     
       25. The electron beam exposure apparatus of  claim 24 , wherein said plurality of control signals having a timing base. 
     
     
       26. The electron beam exposure apparatus of  claim 24 , said adjustor allowing individual adjustment of timing of at least one control signal. 
     
     
       27. An electron beam exposure apparatus for transferring a pattern onto the surface of a target using a plurality of electron beamlets, comprising:
 a scanning deflector for scanning said plurality of electron beamlets over said surface of said target, comprising at least one array of electrostatic deflectors having at least one electrostatic deflector for each beamlet;   a controller, operationally coupled to said scanning deflector, for controlling each electrostatic deflector using a control signal;   an adjustor for adusting said control signal.   
     
     
       28. The electron electron beam exposure apparatus of  claim 27 , wherein said control signal has a timing base, and said adjustor being adapted for adjusting timing of said control signal. 
     
     
       29. An electron beam exposure apparatus for transferring a pattern onto the surface of a target using a plurality of electron beamlets, comprising:
 a scanning deflector for scanning said plurality of electron beamlets over said surface of said target, comprising at least one array of electrostatic deflectors having at least one electrostatic deflector for each beamlet;   a controller, operationally coupled to said scanning deflector, for controlling each electrostatic deflector using a control signal, said controller being adapted for adjusting at least one control signal.   
     
     
       30. The electron beam exposure apparatus of  claim 29 , wherein said controller is operationally coupled to said scanning deflector for controlling each electrostatic deflector using a control signal having a timing base. 
     
     
       31. The electron beam exposure apparatus of  claim 29 , wherein said controller being adapted for adjusting timing of at least one control signal. 
     
     
       32. The electron beam exposure apparatus of  claim 29 , wherein said controller generates a plurality of control signals, at least one control signal for each electrostatic deflector. 
     
     
       33. The electron beam exposure apparatus of  claim 32 , wherein said controller is adapted for adjusting timing of each control signal. 
     
     
       34. The electron beam exposure apparatus of  claim 32 , wherein said controller is adapted for adjusting timing of each control signal individually. 
     
     
       35. An electron beam exposure apparatus for transferring a pattern onto the surface of a target using a plurality of electron beamlets, comprising:
 a blanking deflection means for effectively realising an off/on condition for individual beamlets at said target surface, by deflecting such individual beamlets within the system;   a controller, operationally coupled to said blanking deflection means, for individually controlling electrostatic deflectors of said blanking deflection means, said controller using an individual control signal for each deflector of said deflection means, thereby determining said on and off condition for individual beamlets;   correction means, part of, or operationally associated with said controller for individually correcting a timing window of a beamlet adjusting the control signal of the blanking deflector for said beamlet.   
     
     
       36. An electron beam exposure apparatus for transferring a pattern onto the surface of a target using a plurality of electron beamlets, comprising:
 a blanking deflection device for effectively realising an off/on condition for individual beamlets at said target surface, comprising a plurality of deflectors for deflecting such individual beamlets within the system for realising said off/on condition;   a controller, operationally coupled to said blanking deflection device, for individually controlling electrostatic deflectors of said blanking deflection device, said controller using an individual control signal for each deflector of said deflection device, thereby determining said on and off condition for individual beamlets;   a correction device, part of, or operationally associated with said controller for individually correcting a timing window of a beamlet adjusting the control signal of the blanking deflector for said beamlet.   
     
     
       37. A method of exposing a pattern on a target with a multi-beam lithography system, said pattern divided according to a grid forming grid cells, the method comprising:
 providing a plurality of beamlets, the beamlets being arranged in an array;   providing a target to be exposed;   creating relative movement in a first direction between the plurality of beamlets and the target; and   moving the plurality of beamlets in a second direction, the second direction being different than the first direction;   wherein the method further comprises modulating each beamlet of the plurality of beamlets by means of control signals such that an exposure intensity of each grid cell is variable.   
     
     
       38. The method according to claim 37, wherein said modulating comprises discretely controlling a dose to be received at a corresponding grid cell. 
     
     
       39. The method according to claim 37, wherein the multibeam lithography system comprises a beamlet stop array, and wherein said modulating comprises deflecting a beamlet of the plurality of beamlets by a variable amount in accordance with a corresponding control signal such that a controlled part of the beamlet passes the beamlet stop array. 
     
     
       40. The method according to claim 39, wherein said deflecting is controlled so that discrete portions of the beamlet pass the beamlet stop array. 
     
     
       41. The method according to claim 40, wherein the discrete parts correspond to 0, ⅓, ⅔ and 1 times a maximum dose provided by a single beamlet. 
     
     
       42. The method according to claim 37, wherein said modulating comprises deflecting a beamlet of the plurality of beamlets by a variable amount in accordance with a corresponding control signal so that the beamlet does not move with respect to the target for a predetermined amount of time. 
     
     
       43. The method according to claim 42, wherein said predetermined time is longer than a minimum control time of the beamlet blanker array. 
     
     
       44. The method according to claim 43, wherein said predetermined time equals a discrete multiple of the control time. 
     
     
       45. The method according to claim 37, wherein providing a plurality of beamlets comprises providing an electron beam to an aperture array so that a plurality of beamlets of different sizes is formed. 
     
     
       46. The method according to claim 45, wherein the multibeam lithography system further comprises a beamlet blanker array provided with a plurality of modulators controllable by said control signals and a beamlet stop array, and wherein said modulating includes deflecting each beamlet of the plurality of beamlets by means of a corresponding modulator in accordance with a corresponding control signal such that a deflected beamlet is blocked by the beamlet stop array. 
     
     
       47. The method according to claim 45, wherein the aperture array is provided with apertures of three different aperture sizes, a first size arranged to allow passage of a certain current; a second size arranged to allow passage of half the current; and a third size arranged to allow passage of a fourth of the current, and wherein the control signals related to a single grid cell are at least directed to control the current passing through an aperture of the first size, an aperture of the second size and an aperture of the third size. 
     
     
       48. The method according to claim 37, wherein the first direction is perpendicular to the second direction. 
     
     
       49. A maskless lithography system for exposing a pattern in accordance with a grid forming grid cells on a target, comprising:
 a beamlet generator for generating a plurality of electron beamlets, the beamlets being arranged in an array;   a target holder for holding a target having a surface for receiving the pattern to be transferred;   an actuator for creating relative movement in a first direction between the plurality of beamlets and the target holder;   a scan deflection array for moving the plurality of beamlets in a second direction, the second direction being different than the first direction;   a modulation array for modulating individual beamlets of the plurality of beamlets; and   a controller arranged to provide control signals to said modulation array such that an exposure intensity of each grid cell is variable.   
     
     
       50. The system according to claim 49, wherein the control signals provided by the controller discretely control a dose to be received at a corresponding grid cell. 
     
     
       51. The system according to claim 49, wherein the modulation array comprises:
 a beamlet blanker array provided with a plurality of modulators controllable by said controller; and   a beamlet stop array.   
     
     
       52. The system according to claim 51, wherein a modulator of the plurality of modulators in said beamlet blanker array is arranged to deflect a corresponding beamlet of the plurality of beamlets in response to receipt of a corresponding control signal so that the deflected beamlet is blocked by the beamlet stop array. 
     
     
       53. The system according to claim 51, wherein a modulator of the plurality of modulators in said beamlet blanker array, in response to receipt of a corresponding control signal, is arranged to deflect a corresponding beamlet of the plurality of beamlets by a variable amount so that a variable part of the beamlet passes the beamlet stop array. 
     
     
       54. The system according to claim 51, wherein a modulator of the plurality of modulators in said beamlet blanker array is arranged to pass discrete portions of the beamlet through the beamlet stop array. 
     
     
       55. The system according to claim 54, wherein the discrete parts correspond to 0, ⅓, ⅔ and 1 times a maximum dose provided by a single beamlet. 
     
     
       56. The system according to claim 51, wherein the scan deflection array comprises a plurality of deflectors, and said controller is further arranged to provide control signals to said plurality of deflectors to deflect the beamlets such that, in use, the beamlets do not move with respect to the target for a predetermined amount of time. 
     
     
       57. The system according to claim 56, wherein said predetermined time is longer than a minimum control time of the beamlet blanker array. 
     
     
       58. The system according to claim 56, wherein said predetermined time equals a discrete multiple of the control time. 
     
     
       59. The system according to claim 49, wherein the beamlet generator comprises an aperture array provided with apertures of different aperture size such that a plurality of beamlets of different sizes is formed. 
     
     
       60. The system according to claim 59, wherein the aperture array is provided with apertures of three different aperture sizes, a first size arranged to allow passage of a certain current; a second size arranged to allow passage of half the current; and a third size arranged to allow passage of a fourth of the current, and wherein the control signals related to a single grid cell are at least directed to control the current passing through an aperture of the first size, an aperture of the second size and an aperture of the third size. 
     
     
       61. The system according to claim 49, wherein the first direction is perpendicular to the second direction. 
     
     
       62. An electron-optical arrangement, comprising:
 a first electrostatic lens array for focusing a plurality of beamlets;   a modulation array provided downstream from the first electrostatic lens array, and comprising a plurality of modulators for modulating the beamlets;   a deflector array comprising a plurality of electrostatic deflectors for deflecting a portion of the beamlets in a predetermined direction; and   a second electrostatic lens array for focusing the deflected beamlets.   
     
     
       63. The arrangement according to claim 62, wherein said beam splitter comprises an aperture array having apertures with diameters in the range of about 5-150 μm and with a pitch of about 50 to 500 μm. 
     
     
       64. The arrangement according to claim 62, wherein said beam splitter comprises an aperture array having about 5,000 to 30,000 apertures. 
     
     
       65. The arrangement according to claim 62, wherein said beam splitter comprises an aperture array having apertures with a size adjusted to compensate for non-uniform current density of said electron beam. 
     
     
       66. The arrangement according to claim 65, wherein each aperture has an area inversely proportional to a current density based on the respective beamlet to be transmitted through said aperture. 
     
     
       67. The arrangement according to claim 62, wherein said beam splitter comprises a number of aperture arrays in series along a path of the electron beam or plurality of beamlets, the aperture arrays having mutually aligned apertures, each subsequent aperture array along the path towards the first electrostatic lens array having apertures that are smaller than the apertures of a previous aperture array. 
     
     
       68. The arrangement according to claim 62, wherein said first electrostatic lens array is arranged to focus individual beamlets within the plurality of beamlets to a diameter in a range from about 0.1 to 1 μm. 
     
     
       69. The arrangement according to claim 68, wherein the first electrostatic lens array comprises two aligned plates with holes. 
     
     
       70. The arrangement according to claim 69, wherein the thickness of the plates is within a range from about 10 to 500 μm. 
     
     
       71. The arrangement according to claim 69, wherein the holes have a diameter within a range from about 50 to 200 μm, and a pitch within a range from 50 to 500 μm. 
     
     
       72. The arrangement according to claim 69, wherein the first electrostatic lens array further comprises insulators for supporting said plates. 
     
     
       73. The arrangement according to claim 68, wherein each electrostatic deflector comprises a first electrode connected to ground, and a second electrode connected to a circuit for receiving control data. 
     
     
       74. The arrangement according to claim 62, wherein the modulation array comprises:
 a beamlet blanker aperture array provided with said modulators, said modulators being further electrostatic deflectors for deflecting beamlets in a further predetermined direction; and   a beamlet stop array for terminating beamlets deflected by the further electrostatic deflectors of the beamlet blanker array.   
     
     
       75. The arrangement according to claim 74, wherein the first electrostatic lens array is arranged to focus individual beamlets within the plurality of beamlets to a diameter in a range from about 0.1 to 5 μm at the beamlet blanker array. 
     
     
       76. The arrangement according to claim 74, wherein the beamlet blanker array is located in an electrostatic focal plane of the plurality of electron beamlets. 
     
     
       77. The arrangement according to claim 76, wherein the beamlet stop array is positioned outside a focal plane of the plurality of electron beamlets. 
     
     
       78. The maskless lithography system according to claim 77, wherein the beam splitter comprises an aperture array having apertures with diameters in the range of about 5 to 150 μm and with a pitch of about 50 to 500 μm. 
     
     
       79. The arrangement according to claim 62, further comprising a beam splitter for splitting an incoming electron beam to generate the plurality of beamlets. 
     
     
       80. The arrangement according to claim 62, for use in a maskless lithography system for transferring a pattern onto the surface of a target. 
     
     
       81. The arrangement according to claim 80, comprising:
 an electron beam generator for generating an electron beam;   an electron-optical arrangement; and   a target holder for holding a target provided with a surface for receiving the pattern to be transferred.   
     
     
       82. An electron-optical arrangement, comprising:
 an electron source for emitting an electron beam;   an illumination system for collimating the electron beam;   a beam splitter for generating beamlets from the electron beam;   an array of electrostatic lenses for focusing the beamlets; and   a demagnifying lens arrangement, receiving the focused beamlets separated at a first pitch d1, directing the beamlets into at least one crossing, and projecting the beamlets on to a target surface at a pitch d2, wherein d2 is smaller than d1.   
     
     
       83. The arrangement according to claim 82, wherein the beam splitter comprises an aperture array having apertures arranged in a hexagonal pattern. 
     
     
       84. The arrangement according to claim 82, wherein the beam splitter comprises an aperture array having apertures with diameters in the range of about 5-150 μm and with a pitch of about 50 to 500 μm. 
     
     
       85. The arrangement according to claim 82, wherein the beam splitter comprises an aperture array having about 5,000 to 30,000 apertures. 
     
     
       86. The arrangement according to claim 82, wherein the beam splitter comprises an aperture array having apertures with a size adjusted to compensate for non-uniform current density of the electron beam. 
     
     
       87. The arrangement according to claim 86, wherein each aperture has an area inversely proportional to a current density based on the respective beamlet to be transmitted through said aperture. 
     
     
       88. The arrangement according to claim 82, wherein the beam splitter comprises a number of aperture arrays in series along a path of the electron beam or plurality of beamlets, the aperture arrays having mutually aligned apertures, each subsequent aperture array along the path towards the first electrostatic lens array having apertures that are smaller than the apertures of a previous aperture array. 
     
     
       89. The arrangement according to claim 82, wherein the electrostatic lens array is arranged to focus individual beamlets within the plurality of beamlets to a diameter in a range from about 0.1 to 1 μm. 
     
     
       90. The arrangement according to claim 89, wherein the electrostatic lens array comprises two aligned plates with holes. 
     
     
       91. The arrangement according to claim 90, wherein the thickness of the plates is within a range from about 10 to 500 μm. 
     
     
       92. The arrangement according to claim 90, wherein the holes have a diameter within a range from about 50 to 200 μm, and a pitch within a range from 50 to 500 μm. 
     
     
       93. The arrangement according to claim 90, wherein the electrostatic lens array further comprises insulators for supporting the plates. 
     
     
       94. The arrangement according to claim 82, wherein the modulation array comprises:
 a beamlet blanker aperture array provided with the modulators, the modulators being further electrostatic deflectors for deflecting beamlets in a further predetermined direction; and   a beamlet stop array for terminating beamlets deflected by the further electrostatic deflectors of the beamlet blanker array.   
     
     
       95. The arrangement according to claim 94, wherein the electrostatic lens array is arranged to focus individual beamlets within the plurality of beamlets to a diameter in a range from about 0.1 to 5 μm at the beamlet blanker array. 
     
     
       96. The arrangement according to claim 94, wherein the beamlet blanker array is located in an electrostatic focal plane of the plurality of electron beamlets. 
     
     
       97. The arrangement according to claim 94, wherein the beamlet stop array is positioned outside a focal plane of the plurality of electron beamlets. 
     
     
       98. The arrangement according to claim 94, wherein each electrostatic deflector comprises a first electrode connected to ground, and a second electrode connected to a circuit for receiving control data. 
     
     
       99. The arrangement according to claim 82, further comprising a second electrostatic lens array for projecting the beamlets onto the target surface, the second electrostatic lens array comprising two or more plates, each plate having a thickness within a range from about 10 to 500 μm. 
     
     
       100. The arrangement according to claim 82, further comprising a second electrostatic lens array for projecting the beamlets onto the target surface, the second electrostatic lens array comprising two or more plates, and the distance between consecutive plates being within a range from 50 to 800 μm. 
     
     
       101. The arrangement according to claim 82, further comprising a second electrostatic lens array for projecting the beamlets onto the target surface, the second electrostatic lens array comprising three or more plates, and the distance between consecutive plates being different from plate to plate. 
     
     
       102. The arrangement according to claim 82, further comprising:
 a modulation array comprising a plurality of modulators for modulating the beamlets;   a deflector array comprising a plurality of electrostatic deflectors for deflecting a portion of the beamlets in a predetermined direction; and   a second electrostatic lens array for focusing the deflected beamlets.