Cu microvia filling by pulse-reverse electrodeposition with a single accelerator

Abstract

Cu electrodeposition processes are widely employed to achieve defect-free interconnections in electronic devices. Typically, combinations of three additives—an accelerator, a suppressor, and a leveler—are used for bottom-up filling of Cu in microscaled features. However, the use of multiple additives adds complexity to electrolyte maintenance and can lead to reliability issues in the process. To address this challenge, we have developed a single-accelerator filling technique using pulse-reverse electrodeposition for microvias. During pulse-reverse electrodeposition, the anodic steps produce a large amount of Cu+ ions near the electrode surface. These Cu+ ions can form complexes with Cl− ions or CuCl layers, thereby enhancing the adsorption of the accelerator, SPS. This phenomenon depends on the electrolyte convection. Under strong forced convection, Cu-Cl species are removed, leading to subsequent deactivation of SPS, whereas Cu-Cl species remain stable under mild convection conditions. Based on this convection-dependent behavior of SPS and Cl, Cu electrodeposition is promoted at the bottom of microvias while the SPS is selectively deactivated outside the microvias where the strong electrolyte motion exists. As a result, without any polymeric suppressor and organic leveler, the microvias are successfully filled with Cu.