Accelerator-decelerator electrostatic lens for variably focusing and mass resolving an ion beam in an ion implanter

An electrostatic triode lens (36) for adjustably mass resolving an ion beam in a first plane and for adjustably focusing the ion beam in the first plane and an orthogonal second plane, said lens (36) comprising:

• (i) a terminal electrode (37) having first and second portions (37A, 37B) with a gap (d37) therebetween through which the ion beam passes;
• (ii) a resolving electrode (39) having first and second portions (39A, 39B) defining a gap (d39) therebetween through which the ion beam passes;
• and
• (iii) a suppression electrode (38), to which a variable voltage may be applied, disposed between said terminal and resolving electrodes and having first and second portions (38A, 38B) defining a gap (d38) therebetween through which the ion beam passes;
• and
• (iv) a movement mechanism (60, 62) for imparting simultaneous movement of said first portions of said suppression and resolving electrodes (38A, 39A) toward and away from said second portions of said suppression and resolving electrodes (38B, 39B), respectively.

An adjustable lens subassembly (40), for use in a beamline assembly intermediate a terminal and an end station in an ion implantation system, and for adjustably mass resolving an ion beam in a first plane and adjustably focusing the ion beam in the first plane and an orthogonal second plane, said lens subassembly (40) located proximate said terminal and comprising:

• (i) a suppression electrode (38), to which a variable voltage may be applied, having first and second portions (38A, 38B) defining a gap (d38) therebetween through which the ion beam passes;
• (ii) a resolving electrode (39) having first and second portions (39A, 39B) defining a gap (d39) therebetween through which the ion beam passes;
• and
• (iii) a movement mechanism (60, 62) for imparting simultaneous movement of said first portions of said suppression and resolving electrodes (38A, 39A) toward and away from said second portions of said suppression and resolving electrodes (38B, 39B), respectively.

A method of focusing an ion beam in orthogonal planes, using an adjustable electrostatic lens subassembly comprising a suppression electrode (38) and a resolving electrode (39), comprising the steps of:

• (i) providing a first gap between first and second portions (38A, 38B) of said suppression electrode (38), said first gap having a first distance (d38);
• (ii) providing a second gap between first and second portions (39A, 39B) of said resolving electrode (39), said second gap having a second distance (d39);
• (iii) directing an ion beam through said first and second gaps;
• (iv) altering the amount of voltage applied to said suppression electrode (38) to focus the ion beam in a first plane;
• and
• (v) simultaneously altering said first and second distances (d38, d39) to focus the ion beam in a second plane, said second plane being disposed substantially perpendicular to said first plane.