Nonscalability of alpha-particle-induced charge collection area

The scalability of alpha-particle-induced soft errors has been evaluated. We have irradiated individual sites in and near a PN-junction area with single alpha particles and measured the charge collected at the junction. As the PN-junction size is reduced, the charge collected by diffusion upon the incidence of alpha particles at the outer area around the junction increases relative to the charge collected upon direct incidence at the junction area. This suggests that the soft-error- sensitive area is not scaled down even if memory cell size is reduced.