Contact structure using taper contact etching and polycide step

Abstract

A method and structure are disclosed related to tapered contact holes in VLSI and ULSI technologies. The contact hole is formed by taking advantage of two-tiered polycide lines formed with a step. The polycide lines with steps are further formed with oxide spacers. The resulting structure is then used to form contact hole in between the oxide spacers. Because the oxide spacers are used—without the need for a tightly toleranced mask—to delimit the area of the contact at the bottom of the hole, a larger area of contact is obtained in addition to the tapered edges that are formed. Polycide is chosen to be a multilayer structure comprising tungsten-silicide (WSi2) over poly-silicon (poly-Si). Next, polycide is patterned by etching with a recipe which etches the WSi2 faster than it etches the underlying poly-Si. The etching, therefore, results in a structure where the WSi2 forms a step over the poly-Si layer. A layer of TEOS oxide is then deposited over the step structure and etched, thus forming oxide spacers surrounding the step structure. A second layer of TEOS is deposited and etched forming contact holes with the desired, gentle slopes yielding at the same time wide contact area at the bottom of the hole with improved reliability.

Dependencies are inferred from the claim text.