Simulation and construction of an efficient Freeman ion source for an ion implanter

Beam envelope in ion implanters must be compressed as much as possible, otherwise the fabrication process will be failed and the stability of the machine and uniformity of the beam at the wafer will be affected by that. To improve beam envelop, investigations are applied to the following parameters: the influence of emissive surface, extraction electrode scheme, extraction voltage, accelerator electrode scheme, gap of electrodes and acceleration voltage with the aid of SIMION computer program. In simulations, the profound influences of extraction electrode angle and extraction voltage are investigated. Extractor angle of 48.8 degree, the beam emittance compressed to 1.44 cm mrad. The extraction angle decreased to 22.8 degree to optimize the beam emittance and it revealed that the beam envelop divergence optimized 5% in comparison with extractor angle of 48.8 degree. Furthermore, the beam emittance reduced in growth of extraction voltage. In simulation, optimum beam emittance obtained in acceleration voltage of -0.5kv while in experiment, it is figured out that acceleration voltage enhancement selection in fixed design of electrodes and 20kv extraction voltage causes in variation of beam emittance. As the voltage decreased to -0.5kv, the beam diverged further at the downstream of the system.

کلیدواژه ها:

ion implanter ، freeman ion source ، beam emittance ، plasma meniscus ، extraction system