Cuprous Ion As An Accelerant of Copper Damascene Electrodeposition

Abstract

Free cuprous formed inside trench accelerates trench via bottom. A drastic increase in current has been measured with N2 bubbling by initially dissolving the copper of the trench bottom electrode. The current densities increase with the narrower trench bottom electrode width. With O2 bubbling, the currents show a very low value and no difference in the trench bottom electrode width. These drastic differences in current densities with the O2 gas concentration in the electrolyte must be caused by the cuprous complex formed in the trench of the trench bottom electrode. The cuprous complex is free and not adsorbed by the electrode. For the basic bath with only Cl-, the current shows a marked increase. Cl- is an important additive for the acceleration, and the acceleration must be related to the free cuprous complex and electron bridge formation of Cl-. The constant potential measurements without dissolving the copper electrode, also, show that the free cuprous complex formed through electrodeposition is the accelerant.