Molecular n-type dopant implants

The use of dimer As₂⁺ or P₂⁺ ions at ultra-low energies can lead to substantial throughput advantages compared with the use of monomer As⁺ or P⁺ ions. Here we investigate the differences in the as-implanted damage from dimer and monomer ions using high resolution Rutherford backscattering and Thermawave measurements. Use of dimer ions leads to more damage as revealed by the formation of a thicker amorphous layer than from monomer ions. The amorphization threshold for 3-keV As⁺ is found to be between 0.5 and 1×10¹⁴ cm^-2. Using As₂⁺, however, the amorphization threshold is reduced to an atomic arsenic dose less than 0.5×10¹⁴ cm^-2. Despite these rather significant differences in the as-implanted damage from monomers and dimers, the diffusion and dopant activation of arsenic are found to be identical following spike-annealing for ultra-shallow junction formation.