铜互连的终结？

Core Viewpoint - The copper interconnect era may be nearing its end as copper is no longer the optimal metallization choice for interconnects below 10 nanometers, despite its unmatched performance for larger feature sizes [1][2]. Group 1: Challenges of Copper Interconnects - Copper faces significant challenges in miniaturization, particularly below its average free path length of 40 nanometers, where its resistivity increases sharply [1]. - When line widths fall below 10 nanometers, electron scattering can cause line resistance to increase by approximately 10 times compared to bulk material [1]. - The requirement for diffusion barrier layers complicates the manufacturing of extremely small features, as the actual copper line thickness is reduced to 2 to 4 nanometers for a nominal 10 nanometer line width [1]. Group 2: Potential of Ruthenium as an Alternative - Ruthenium is emerging as a potential alternative conductor due to its lower resistivity and superior electromigration resistance compared to copper for lines with a critical dimension of 17 nanometers or smaller [2]. - Ruthenium can be easily etched, allowing for more flexible process integration, although it poses challenges in deposition and removal [2][5]. - The compatibility of ruthenium with copper is crucial, as copper will likely remain the preferred metal for lines wider than 20 nanometers [2]. Group 3: Research and Development Efforts - Samsung's collaboration with IMEC has led to findings that reducing the thickness of the barrier layer can lower overall line resistance, and that copper does not mix with ruthenium at the bottom of vias [3]. - The use of self-assembled monolayers (SAM) to prevent barrier layer deposition at the bottom of vias has shown promise in maintaining electromigration performance [3]. - Research indicates that ruthenium's deposition conditions and crystalline structure are still being explored to optimize its performance in semiconductor applications [4][5]. Group 4: Future Implications - The introduction of ruthenium as a via or line material could signify a transformative change in semiconductor manufacturing, although such changes are expected to be gradual [5]. - Current research is focused on achieving consistent deposition and removal of ruthenium across millions of features on thousands of wafers [4][5]. - The semiconductor industry is laying the groundwork for the eventual transition away from copper interconnects, although this shift will not happen immediately [5].