Post-decel magnetic energy filter for ion implantation systems

A method for magnetically filtering an ion beam during an ion implantation into a workpiece, the method comprising:

• emitting ions from an ion source and accelerating the ions away from the ion source to form an ion beam;
• mass-analyzing the ion beam, wherein ions are selected;
• decelerating the ion beam once the ion beam is mass-analyzed;
• and
• magnetically filtering the ion beam downstream of the deceleration, wherein a magnetic field is formed for interce tin the ions in the ion beam exiting the decelerator to selectively filter undesirable ions and fast neutrals, wherein magnetically filtering the ion beam further comprises:
• placing first and second arcuately extending pole pieces on either side of an arcuate beam travel path so that inwardly facing pole surfaces are positioned on opposite sides of a magnetic field centerplane;
• positioning a primary field generating coil along the arcuately extending pole pieces for creating a primary bipolar magnetic field that extends across the magnetic field region from one of said first and second arcuately extending pole pieces to another of said first and second arcuately extending pole pieces interposing quadrapole field generating coils between inwardly facing surfaces of the first and second arcuate pole pieces and the magnetic field region;
• and
• selectively energizing the both the primary and the quadrapole field generating coils to provide a controlled quadrapole magnetic field in the region between the pole pieces.