Apparatus and methods for ion implantation

In a method for implanting a target element with an ion beam comprising a preselected ion species and having a predetermined beam current level at least about several milliamperes, the steps of:

• creating an ion beam analyzing field having an associated ion dispersion plane for separating various ion species in an ion beam on the basis of mass;
• producing and directing into said ion beam analyzing field an ion beam including ions of said preselected species at or above said predetermined beam current level and having an associated overall ion beam envelope which retains an area of substantial extension in a plane parallel to said ion dispersion plane throughout the region of travel of said beam into said analyzing field;
• separating out of the analyzed ion beam exiting said analyzing field a beam of ions comprising said preselected ion species;
• and
• directing said beam of ions onto said target element.

The method claim of 42, wherein said step of creating an analyzing field comprises the step of creating an analyzing magnetic field between a pair of opposing magnetic pole faces to separate said ion beam into different beam paths based on the charge to mass ratio of ions entering said magnet field, and said step of producing a high current ion beam includes disposing in a position facing said magnetic field an ion source system comprising an ion source having an ion emitting region, an extraction electrode positioned in front of said region, and a second electrode positioned in front of said extraction electrode;

• and further comprising the steps of:
• applying a preanalysis acceleration voltage to said ion source;
• applying to said extraction electrode a bias potential having a value relative to said preanalysis acceleration voltage to extract and accelerate ions from said source;
• and
• applying to said second electrode a bias potential having a value relative to said bias potential value on said extraction electrode to reduce substantially the velocity of ions travelling between said extraction electrode and said second electrode.

In a system for implanting ions of a preselected chemical species into a target element, said ions being in the form of an ion beam having a beam current level at least about several milliamperes, in combination:

• source means for producing an ion beam including ions of said preselected chemical species at or above said beam current level;
• beam analyzing means for receiving said ion beam and selectively separating various ion species in said beam on the basis of mass to produce an analyzed beam exiting said analyzing means, and beam resolving means disposed in the path of said analyzed beam for permitting ions of said preselected chemical species to pass to said target element;
• said analyzing means having an ion dispersion plane associated therewith;
• said source means having an associated ion emitting envelope including an area of substantial extension in a plane parallel to said ion dispersion plane and producing an ion beam characterized by a beam envelope which retains an area of substantial extension in a plane parallel to said ion dispersion plane throughout the region between said ion emitting envelope and said analyzing means and which diverges substantially and continuously between said ion emittng envelope and said analyzing means, said ion beam being further characterized by ions entering said analyzing means travelling substantially either toward or from a common apparent line object perpendicular to said ion dispersion plane.

In a system for implanting ions of a preselected chemical species into a target element, said ions being in the form of an ion beam having a beam current level at least about several milliamperes, in combination:

• an ion source assembly comprising an ion source having a rectangular ion exit aperture, an extraction electrode disposed in front of said ion source for extracting a beam of ions therefrom, and a deceleration electrode disposed in front of said extraction electrode for decelerating said beam of ions;
• a beam analyzing magnet having a pair of opposed, separated magnet pole faces defining a beam flight region therebetween with a beam entrance region disposed in front of said deceleration electrode and a beam exit region whereat an analyzed version of said ion beam departs said magnet pole faces;
• a beam resolving slit disposed in front of said beam exit region of said analyzing magnet for passing ions of said preselected chemical species in said analyzed beam to said target element;
• said ion source assembly being disposed with respect to the ion dispersion plane of said analyzing magnet such that the longer dimension of said ion exit aperture is parallel to said ion dispersion plane;
• said ion source assembly producing an ion beam including ions of said preselected chemical species at a current level equal to or greater than said preselected beam current level such that the envelope of said ion beam comprises a beam ribbon which retains substantial extension in a plane parallel to said ion dispersion plane and diverges substantially in a plane perpendicular to said ion dispersion plane between said ion exit aperture and said beam entrance region of said analyzing magnet due to space charge of said beam in the region between said ion exit aperture and said extraction electrode;
• said ion source assembly being positioned closely adjacent said beam entrance region to limit said divergence of said ion beam envelope prior to entering said analyzing magnet.