is a schematic diagram showing a path of the substrate 10 in the transfer assembly 150 in the ion implantation system 100 illustrated in fig2 through 4 referring to fig5 the substrate 10 is transferred from the first chamber 151 toward the return chamber 157 in the first direction f and is transferred from the return chamber 157 in the second direction b opposite to the first direction f the second direction b is a direction from the return chamber 157 toward the first chamber 151 while the substrate 10 is transferred in the first direction f the first implantation region 11 is implanted with ions in the first process chamber 154 and the second implantation region 12 is implanted with ions in the second process chamber 155 also while the substrate 10 is transferred in the second direction b the second implantation region 12 is again implanted with ions in the second process chamber 155 and the first implantation region 11 is again implanted with ions in the first process chamber 154 that is the substrate 10 may be implanted with ions while the substrate 10 is transferred in the first direction f and may also be implanted with ions while the substrate 10 is transferred in the second direction b since the substrate 10 is implanted with ions twice as described above the uniformity of the ions implanted over the whole substrate 10 may be improved a sum of a first implantation amount of ions implanted while the substrate 10 moves in.