Paper PS-TuP9
Controlled Layer-by-Layer Etching of Copper Thin Films

Tuesday, October 22, 2019, 6:30 pm, Room Union Station B

As the critical dimensions of semiconductor devices are reduced for their high performance, fast operating speeds and low operating power, aluminum interconnects are no longer used as a suitable electrode material, but instead of aluminum, the use of copper is increasing. Copper is known as an excellent interconnect material compared to aluminum due to its very low resistance and less electromigration phenomena that cause wire deformation and breakage. However, the damascene process presents some limitations in delineating fine patterns below tens of nanometers. To solve these fatal issues related with the damascene process, intensive researches about copper patterning has been performed using conventional dry etching. Currently, one promising way to etch copper films is cyclic etching. Cyclic etching, including surface modification and its removal, can effectively provide a good etch performance of silicon material. This etching technique is proceeded by inducing surface reactions and precise removal of the modified surfaces, resulting in the accurate control of the etch depth. These results are due to the nature of the self-limiting process and the removal of layers by layer. Various combinations of gases are possible for cyclic etching of the films

In this study, a two-step sequential cyclic etching of surface modification and ion bombardment are investigated. Surface modification and etch depth of the copper film are confirmed using a surface profilometer, a scanning probe microscope and a field emission scanning electron microscope (FESEM) as a function of various parameters such as the conditions of surface modification and bombardment energy of ions. In addition, etch profiles and etch mechanism of copper films in cyclic etching have been studied by FESEM, FETEM and X-ray photoelectron spectroscopy.