Silicided

Silicided refers to materials that have undergone silicidation, the formation of metal silicides by the reaction of silicon with a metal. In semiconductor processing, silicidation typically forms a thin, continuous silicide layer at a metal–silicon interface by depositing a metal on silicon or polysilicon and then annealing. The resulting compounds include titanium silicide (TiSi2), cobalt silicide (CoSi2), nickel silicide (NiSi), and platinum silicide (PtSi); these silicides are selected for relatively low resistivity and compatibility with standard CMOS processing.

Formation methods vary. Common approaches include deposition of a metal followed by thermal treatment to drive interfacial reactions, or selective deposition in areas where silicon is exposed to create self-aligned silicide (salicide) structures. In salicide schemes, silicide forms only on silicon regions, reducing sheet resistance in source/drain contacts and gate regions while leaving surrounding areas unaffected.

Properties and applications vary with the specific silicide. Metal silicides generally offer lower resistivity than doped polysilicon and possess good thermal stability, making them attractive for electrical contacts and interconnects in integrated circuits. They can also serve as diffusion barriers and contact metallizations in certain device architectures. Phase behavior, such as TiSi2’s transitions between different crystal forms, can influence resistivity and reliability.

Challenges include silicon consumption during silicidation, possible void formation or agglomeration, and phase transformations that affect performance and stress. Process integration must manage temperature budgets and material compatibility, particularly as device dimensions shrink.