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Lens Accelerator for Medium and High Current Ion Implantation Systems

IP.com Disclosure Number: IPCOM000052333D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Keller, JH: AUTHOR

Abstract

An arrangement is provided to overcome poor beam transport through an acceleration column at beam energies less than 10 OkV. This is achieved through use of an acceleration column such that the beam is accelerated from, for example, 35 kV to 105 kV in the first four gaps and, if a final voltage below 105 kV is desired, the beam is decelerated in the remaining gaps. If a final voltage greater than 105 kV is desired, then the beam is accelerated in the remaining gaps.

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Lens Accelerator for Medium and High Current Ion Implantation Systems

An arrangement is provided to overcome poor beam transport through an acceleration column at beam energies less than 10 OkV. This is achieved through use of an acceleration column such that the beam is accelerated from, for example, 35 kV to 105 kV in the first four gaps and, if a final voltage below 105 kV is desired, the beam is decelerated in the remaining gaps. If a final voltage greater than 105 kV is desired, then the beam is accelerated in the remaining gaps.

In high current ion implantation systems which use post acceleration, the normal acceleration column produces too much space charge blow-up for low acceleration, and if a single- or dual-gap accelerator is used, the beam is over- focused for voltages near 200 kV. In such acceleration columns, it is proposed to apply to the middle electrode a fixed voltage of approximately half of the maximum desired acceleration voltage. Then the first four gaps will always run in an accel mode. If the total voltage desired is less than this fixed voltage, the acceleration column will run in an accel-decel mode. The beam will be focused at the entrance and exit apertures and defocused at its highest energy, thus producing, with the possible exception of space charge, a net focusing effect. For acceleration voltages larger than one-half the maximum, the system runs as an accel-accel column. However, the beam still has maximum focusing at the entrance aperture where the space charge effect is the largest. It is also possible to design the system so that the beam has sufficient size at the entrance of the...