Development of Cu Etching Using O2 Cluster Ion Beam under Acetic Acid Gas Atmosphere

Cu etching was carried out at a low substrate temperature using a gas cluster ion beam (GCIB) under an acetic acid gas atmosphere. A very shallow Cu surface was oxidized by O2-GCIB irradiation. Reactions between copper oxide and acetic acid occurred, and the reaction products were desorbed by local heating owing to the O2-GCIB irradiation. Thus, Cu etching at a low substrate temperature (<60 °C) was achieved. By introducing acetic acid gas during O2-GCIB irradiation, the etching depth of Cu became almost 29 times higher than the depth achieved when the etching was carried out using O2-GCIB alone at an acceleration voltage of 5 kV. In addition to the etching of Cu, there was no surface roughening after O2-GCIB irradiation under acetic acid atmosphere.