Symmetric beam line technique for a single-wafer ultra-high energy ion implanter

In order to fabricate highly sensitive image sensors, ultra-high energy ion beams, such as 5 MeV of boron, are required. SEN has developed the S-UHE, a single-wafer ultra-high energy ion implanter, to obtain such ultra-high energy beams. The S-UHE has adopted an electrostatic and symmetric, parallelizing lens system, the concept of which is already used in the MC3-II, a medium-current ion implanter, and the SHX, a single-wafer high-current implanter. This system provides very good uniformity, even when a large amount of outgassing from photoresist materials is generated. Since the ion beam energy is so high at the lens system, a compound electrostatic parallelizing lens system is introduced. Beam angles have been controlled within 0.05° for any recipe in experiments with the electrostatic parallelizing lens system. Another beam line element specifically adopted in the S-UHE is an electric quadrupole lens installed between the two dipole magnets, in order to suppress beam current loss. This electric lens can easily form achromatic ion beam transportation without any significant deformation of the magnetic field.