New generation copper-based interconnection from nanoporous CuSn alloy film sintered at low temperatures

Abstract

Semiconductor devices require interconnections with high current-carrying capacity, capable of withstanding significant thermal stress. Third-generation semiconductors often operate under conditions that demand temperatures as high as 300 °C. To address this need, nanomaterials have emerged as promising candidates for on-chip interconnects due to their lower melting temperatures compared to their bulk counterparts. Recently, we introduced an innovative synthetic method for tin (Sn) coated nanoporous copper (np-Cu) material that leads to formation of a compact Cu₃Sn intermetallic (IM) bond by sintering at temperatures as low as 200 °C. Our research aims to further advance this approach by directly utilizing a np-CuSn film, with the potential to enable sintering at even lower temperatures. This manuscript outlines the development of a two-step synthesis process, involving the electrochemical deposition of a CuSn precursor alloy followed by partial dealloying, realized by oxidative removal of Sn. This process yields a np-Cu₆Sn₅ IM film. Our objective is to subject the synthesized IM nanomaterial to sintering between two copper surfaces, ultimately forming a Cu₃Sn IM joint. The successful creation of defect-free, densely packed pad-to-pad joints for electronic interconnections was achieved through sintering in a forming gas atmosphere at a pressure of 20 MPa and at various temperatures, including 300 °C, 250 °C, 225 °C, and 180 °C.