Applications of CVD tungsten in VLSI circuits

Selectively deposited tungsten can greatly improve metal step coverage in the contacts. At the same time, the etch-stop properties of tungsten allow one to tighten up a number of design rules leading to a reduction in die size. Blanket tungsten (with an etchback or as an interconnect by itself) has many of the same advantages. Device reliability is also greatly improved due to the refractory nature of tungsten and its high electromigration resistance. Critical process problems previously preventing the use of CVD tungsten, such as encroachment and adhesion, have been solved and have made tungsten a very attractive candidate for local interconnect, and also hold promise for meeting the stringent requirements of future ULSI circuits