High-precision and high-efficiency copper removal by femtosecond laser in mixed hydrochloric acid‑oxygen atmosphere

Low-defect, high-efficiency, and high-precision copper (Cu) removal is critical for the development of high-density 3D-integration technology for integrated circuits (ICs). Herein, a hydrochloric acid (HCL)‑oxygen (O2) assisted femtosecond (fs) laser removal process was proposed for Cu removal in ICs. In the process, while fs-laser ablates Cu, the heat generated by fs-laser promotes the reaction between O2 and Cu to form copper oxide, and then HCL dissolves copper oxide. Based on the synergistic corrosion effect of the HCL and O2, Cu removal with high efficiency and high precision is realized by the HCL-O2 assisted fs-laser removal process. Compared with those in air atmosphere, the surface quality and removal efficiency of the Cu film processed by fs-laser in HCL-O2 atmosphere are improved by 41 % and 50 % respectively, indicating the application potential of HCL-O2 assisted fs-laser ablation process in Cu removal for ICs. Furthermore, the strategy of introducing chemical reaction into laser processing provides a way to develop new laser processing technology. © 2022 The Society of Manufacturing Engineers