The current status of single ion implantation (SII) which has been proposed as a novel technology to suppress the fluctuation in dopant number in fine semiconductor structures is reported. The key to control the ion number is to detect secondary electrons (SEs) emitted from a target upon ion incidence. By improving the SE detection system, we have achieved the efficiency of 90% which ensures the reduction in the fluctuation of dopant number to 30% compared to the conventional ion implantation. The improvement for the better SE detection efficiency has turned out to also be effective for the precise beam alignment. The single ion incident position can now be successfully controlled with an error of less than 0.3 mu m.