Tungsten, copper, diffusion barriers
The Center of Microtechnologies relies on more than a decade of experience and expertise in microelectronics metallization. After silicide and salicide technology being a core research field of the forerunner institute "Technikum Mikroelektronik" in the 1980s, tungsten processing evolved as a major topic of microelectronics metallization from the late 1980s until the mid 1990s. Beginning with blanket tungsten CVD on different liners to fill the inter-metal level connections (vias), the focus changed more and more to selective processing for via fill and aluminium interconnect encapsulation. The main milestones achieved include: CVD equipment prototype development for blanket tungsten deposition (joint development with equipment manufacturer "Elektromat Dresden"), blanket tungsten via fill technology using Ti/Mo liners and tungsten etchback, selective tungsten technology for via fill in aluminium metallization using a commercial PRECISION 5000 cluster tool, selective tungsten encapsulation of aluminum interconnects having an interconnect lifetime which is four to seven times higher than the conventional interconnects.
As soon as the early 1990s, the need for a new interconnect material with a higher lifetime and lower resistivity than aluminium was realised. Intensive research and development was established together with the European and U.S. industry to make copper technology worthwhile and applicable to integrated circuits. Outstanding results were achieved:
First time liquid delivery system applied for copper MOCVD using CupraSelectTM precursor (Schumacher Corp., 1994), a viable copper dry etch process (1996) and in co-operation with Applied Materials, Inc. the first production-worthy copper etch tool and process (1998), basic and extensive investigation into different diffusion barriers using combined analytical and electrical techniques (1994-1998), successful application of integrated CVD TiN barrier and copper processing for Damascene fill (1998) and interchip via fill for Vertical System Integration VSITM (2001).
More information (PDFs)
Prof. Dr. Stefan E. Schulz