A reactive gas cluster injection system with a scanning function was developed in order to increase the processing area. High-precision anisotropic etching with an aspect ratio of 7 was achieved for ClF<inf>3</inf>cluster etching without scanning. However, with scanning, the aspect ratio for etching decreased to 1.5 because the side walls were etched by the gas retained in the trench. By reducing the source gas pressure, increasing the target distance, and mixing He in the source gas, anisotropic etching with an aspect ratio of about 6.3 was achieved with this apparatus.