For etchings of LSI and MEMS, a dry etching makes the process simple. In the present study, helium ion etching for polycrystalline copper was conducted, and after that the surface uniformity was examined. The irradiated surface showed unevenness with a roughness of sub-micron size, caused by growth of blisters. When the ion was injected obliquely to the surface, the roughness was reduced owing to the selective etching for the protuberance parts. However, the blisters still existed and the roughness was not significantly reduced. For the irradiated surface, annealing with temperature of 1000 K was conducted for the blisters to be ruptured. After the annealing, the blisters disappeared and the surface significantly became smooth. Thus, the ion irradiation followed by annealing can be recognized as a useful etching method. (C) 2004 Published by Elsevier B.V.