Bi mode ion implantation with non-parallel ion beams

Abstract

A method for implanting ions into a workpiece, such as a semiconductor wafer, includes the steps of generating an ion beam, measuring an angle of non-parallelism of the ion beam, tilting the wafer at a first angle, performing a first implant at the first angle, tilting the wafer at a second angle, and performing a second implant at the second angle. The first and second angles are opposite in sign with respect to a reference direction and in magnitude are equal to or greater than the measured angle of non-parallelism. Preferably, the first and second implants are controlled to provide substantially equal ion doses in the workpiece.

1. A method for implanting ions into a workpiece, comprising the steps of:
 generating an ion beam;  
 measuring an angle of non-parallelism of the ion beam;  
 performing a first implant with the workpiece oriented at a first angle; and  
 performing a second implant with the workpiece oriented at a second angle, wherein the first and second angles are opposite in sign with respect to a reference direction and in magnitude are equal to or greater than the measured angle of non-parallelism.  
 
     
     
       2. A method as defined in  claim 1  wherein the steps of performing said first and second implants are controlled to provide substantially equal ion doses in the workpiece. 
     
     
       3. A method as defined in  claim 1  wherein the angle of non-parallelism is less than about 5°. 
     
     
       4. A method as defined in  claim 1  wherein the angle of non-parallelism comprises a half angle of divergence of the ion beam. 
     
     
       5. A method as defined in  claim 1  wherein the angle of non-parallelism comprises a half angle of convergence of the ion beam. 
     
     
       6. A method as defined in  claim 1  further comprising the step of generating the ion beam utilizing a parallelizing device. 
     
     
       7. A method as defined in  claim 1  further comprising the step of generating the ion beam without utilizing a parallelizing device. 
     
     
       8. A method as defined in  claim 1  wherein the reference direction comprises a direction of the ion beam at the workpiece. 
     
     
       9. A method as defined in  claim 1  wherein the reference direction comprises a selected implant angle relative to a direction of the ion beam at the workpiece. 
     
     
       10. A method as defined in  claim 1  wherein the first and second angles are equal in magnitude. 
     
     
       11. A method for implanting ions into a semiconductor wafer, comprising the steps of:
 generating an in  ion beam;  
 measuring an angle of non-parallelism of the ion beam;  
 tilting the wafer at a first angle;  
 performing a first implant at the first angle;  
 tilting the wafer at a second angle; and  
 performing a second implant at the second angle, wherein the first and second angles are opposite in sign with respect to a reference direction and in magnitude are equal to or greater than the measured angle of non-parallelism.  
 
     
     
       12. A method as defined in  claim 11  wherein said first and second implants are controlled to provide substantially equal ion doses in the wafer. 
     
     
       13. A method as defined in  claim 11  wherein the angle of non-parallelism of the ion beam is less than about 5°. 
     
     
       14. A method as defined in  claim 11  wherein the angle of non-parallelism of the ion beam comprises a half angle of divergence of the ion beam. 
     
     
       15. A method as defined in  claim 11  wherein the angle of non-parallelism of the ion beam comprises a half angle of convergence of the ion beam. 
     
     
       16. A method as defined in  claim 11  further comprising the step of generating the ion beam utilizing a parallelizing device. 
     
     
       17. A method as defined in  claim 11  further comprising the step of generating the ion beam without utilizing a parallelizing device. 
     
     
       18. A method as defined in  claim 11  wherein the reference direction comprises a direction of the ion beam at the wafer. 
     
     
       19. A method as defined in  claim 11  wherein the reference direction comprises a selected implant angle relative to a direction of the ion beam at the wafer. 
     
     
       20. A method as defined in  claim 11  wherein the first and second angles are equal in magnitude. 
     
     
       21. Apparatus for implanting ions into a semiconductor wafer, comprising:
 means for generating an ion beam;  
 means for measuring an angle of non-parallelism of the ion beam;  
 means for tilting the wafer at a first angle;  
 means for performing a first implant at the first angle;  
 means for tilting the wafer at a second angle; and  
 means for performing a second implant at the second angle, wherein the first and second angles are opposite in sign with respect to a reference direction and in magnitude are equal to or greater than the measured angle of non-parallelism.  
 
     
     
       22. A method for implanting ions into a semiconductor wafer, comprising the steps of:
 generating an ion beam;  
 tilting the wafer at a first angle with respect to the ion beam;  
 performing a first implant with the wafer tilted at the first angle;  
 tilting the wafer at a second angle that is equal in magnitude and opposite in sign with respect to said first angle; and  
 performing a second implant with the wafer tilted at the second angle, wherein the step of tilting the wafer at the first angle comprises tilting the wafer at a half angle of divergence of the ion beam.  
 
     
     
       23. A method as defined in  claim 22  wherein the step of tilting the wafer at a first angle comprises tilting the wafer at a half angle of divergence of the ion beam. 
     
     
       24. A method as defined in  claim 22  wherein the step of tilting the wafer at a first angle comprises tilting the wafer at a half angle of convergence of the ion beam. 
     
     
       25. Apparatus for implanting ions into a semiconductor wafer, comprising:
 an ion beam generator;  
 a measuring system for measuring an angle of non-parallelism of the ion beam; and  
 a tilt mechanism for tilting the semiconductor wafer at first and second angles, wherein the first and second angles are opposite in sign with respect to a reference direction and in magnitude are equal to or greater than the measured angle of non-parallelism, wherein first and second implants are performed at the first and second angles, respectively.  
 
     
     
       26. Apparatus as defined in  claim 25  wherein said measuring system comprises a movable beam profiler and one or more beam detectors. 
     
     
       27. Apparatus as defined in  claim 25  further comprising an ion optical element for parallelizing the ion beam. 
     
     
       28. Apparatus as defined in  claim 25  wherein the first and second angles are equal in magnitude. 
     
     
       29. A method for implanting ions into a workpiece, comprising:
   generating an ion beam;        performing a first implant with the workpiece oriented at a first angle relative to a reference direction; and        performing a second implant with the workpiece oriented at a second angle relative to the reference direction, wherein the first and second angles are opposite in sign with respect to the reference direction, and wherein the reference direction is a selected implant angle with respect to the workpiece.     
     
     
       30. A method as defined in  claim 29 , wherein the first and second implants are controlled to provide substantially equal ion doses in the workpiece. 
     
     
       31. A method as defined in  claim 29 , further comprising generating the ion beam utilizing a parallelizing device. 
     
     
       32. A method as defined in  claim 29 , further comprising generating the ion beam without utilizing a parallelizing device. 
     
     
       33. A method as defined in  claim 29 , wherein the first and second angles are equal in magnitude. 
     
     
       34. A method as defined in  claim 29 , wherein generating an ion beam comprises generating a scanned ion beam. 
     
     
       35. A method as defined in  claim 29 , wherein generating an ion beam comprises generating a ribbon ion beam. 
     
     
       36. A method as defined in  claim 30 , further comprising measuring an angle of non- parallelism of the ion beam, wherein the magnitudes of the first and second angles are equal to or greater than the measured angle of non - parallelism.   
     
     
       37. A method as defined in  claim 29 , wherein the first and second angles are equal in magnitude and wherein the first and second implants are controlled to provide substantially equal ion doses in the workpiece. 
     
     
       38. A method for implanting ions into a semiconductor wafer, comprising:
   generating an ion beam;        tilting the wafer at a first angle relative to a reference direction;        performing a first implant at the first angle;        tilting the wafer at a second angle relative to the reference direction; and        performing a second implant at the second angle, wherein the first and second angles are opposite in sign with respect to the reference direction, and wherein the reference direction is a selected implant angle with respect to the wafer.     
     
     
       39. A method as defined in  claim 38 , wherein the first and second implants are controlled to provide substantially equal ion doses in the wafer. 
     
     
       40. A method as defined in  claim 38 , further comprising generating the ion beam utilizing a parallelizing device. 
     
     
       41. A method as defined in  claim 38 , further comprising generating the ion beam without utilizing a parallelizing device. 
     
     
       42. A method as defined in  claim 38 , wherein the first and second angles are equal in magnitude. 
     
     
       43. A method as defined in  claim 39 , further comprising measuring an angle of non- parallelism of the ion beam, wherein the magnitudes of the first and second angles are equal to or greater than the measured angle of non - parallelism.   
     
     
       44. A method as defined in  claim 38 , wherein the first and second angles are equal in magnitude and wherein the first and second implants are controlled to provide substantially equal ion doses in the wafer. 
     
     
       45. Apparatus for implanting ions into a semiconductor wafer, comprising:
   an ion beam generator; and        a tilt mechanism for tilting the semiconductor wafer at first and second angles, wherein the first and second angles are opposite in sign with respect to a reference direction, wherein first and second implants are performed at the first and second angles, respectively, and wherein the reference direction is a selected implant angle with respect to the wafer.     
     
     
       46. Apparatus as defined in  claim 45 , further comprising an ion optical element configured to parallelize the ion beam. 
     
     
       47. Apparatus as defined in  claim 45 , further comprising a measuring system for measuring an angle of non- parallelism of the ion beam, wherein the magnitudes of the first and second angles are equal to or greater than the measured angle of non - parallelism.   
     
     
       48. Apparatus as defined in  claim 45 , wherein the first and second angles are equal in magnitude. 
     
     
       49. Apparatus as defined in  claim 45 , wherein the ion beam generator is configured to generate a scanned ion beam. 
     
     
       50. Apparatus as defined in  claim 45 , wherein the ion beam generator is configured to generate a ribbon ion beam. 
     
     
       51. Apparatus for implanting ions into a semiconductor wafer, comprising:
   means for generating an ion beam;        means for tilting the wafer at first and second angles; and        means for performing first and second implants at the first and second angles, respectively, wherein the first and second angles are opposite in sign with respect to a reference direction, and wherein the reference direction is a selected implant angle with respect to the wafer.