Beam parallelism in the ULVAC IW-630 medium current implanter

Precise control of the ion beam across the entire wafer must be maintained to ensure the incident beam is not aligned to a major crystallographic axis and that ions are not allowed to traverse great distances through the lattice structure with little energy. Such misalignments will greatly impact the penetration depth of the ions, as well as produce little lattice disorder which effects both implant dose uniformity and implant depth. Variations for typical medium current Implanters are +/- 0.5 degrees in tilt and +/- 2.0 degrees in twist. The IW-630 utilizes a newly designed optical system in conjunction with a mechanical scan and paralleling magnet to produce a horizontally scanned beam with parallelism less than 0.3°, independent of energy and species. This paper will present the method for measuring beam angles and illustrate the effects on 300mm wafers due to small variations in tilt angles.