cobaltsilicon

Cobaltsilicon, commonly referred to as cobalt silicide, denotes binary intermetallic compounds formed from cobalt and silicon. The most studied phases are cobalt monosilicide (CoSi) and cobalt disilicide (CoSi2). These materials are produced in silicon-based devices through silicidation, a diffusion-driven reaction between a cobalt layer and the silicon substrate induced by heat. The specific phase that forms depends on processing conditions such as temperature, annealing time, cobalt thickness, and silicon doping; CoSi tends to form at lower temperatures while CoSi2 is favored at higher temperatures or longer annealing, yielding films with distinct electrical properties.

Properties and synthesis: CoSi and CoSi2 crystallize in different structures and offer high thermal stability and good chemical compatibility with silicon. CoSi2, in particular, generally provides lower resistivity and forms uniform, conformal films on silicon, which is advantageous for microelectronic contacts. Both phases are valued for their ability to form adherent, silicon-compatible films that can serve as electrical contacts.

Applications and limitations: In semiconductor manufacturing, cobalt silicides are used as contact electrodes for source and drain regions and as low-resistance interconnects, helping reduce contact resistance and improve device performance. They also act as diffusion barriers to silicon. Challenges include achieving precise control over phase formation and stoichiometry at nanoscale dimensions, preventing cobalt diffusion or agglomeration, and integrating silicidation steps with other fabrication processes. Ongoing research addresses improving uniformity, thermal stability, and compatibility with advanced device architectures.

See also: Silicide, Nickel silicide, Titanium silicide.