Optimisation of a TiSi2 SALICIDE Process in a 0.18 um CMOS Technology with Dual Selective Etch Process TISE2

Abstract

The use of TiSi2 Salicide for sub-quarter micron technologies is principally limited by the line width dependence effect. An other important limitation is the reactivity of Ti with respect to silicon oxide and silicon nitride which may lead to shorts between poly and active area commonly named bridging . This last effect makes, the selective etch process very critical, especially because the selectivity between TiN/Ti and TiSi2 is poor with a conventional NH4OH:H2O2:H2O (SC1) chemistry and results in a loss of a substantial part of the formed silicide thickness and hence in an increase of the line resistance. In this paper we propose an original solution consisting in a two step etch called TISE2 for TItanium Selective Etch. This process allows an important reduction of the TiSi2 thickness loss and hence, of the sheet resistance of the lines.