TUNGSTEN PLUG ETCHBACK AND SUBSTRATE DAMAGE MEASURED BY ATOMIC-FORCE MICROSCOPY

Filling contact and vias holes with chemical vapor deposited (CVD) tungsten (W) eliminates the problems encountered with poor metal step coverage when using sputtered metals. The most common method of forming W plugs is to etchback a blanket layer of W leaving only the plugs intact. One major problem to overcome in this processing is the need for selectivity to the underlying barrier metal. In this study, we have varied the overetch chemistry and as a result the W:TiN selectivity and the degree of roughening of the TIN surface. Each of the samples was then analyzed using atomic force microscopy (AFM) to determine the effect of the processing parameters on the roughness of the resultant barrier metal surface and of the Al sputtered onto the barrier metal. The grain size of the Al was also determined and studied as a function of the roughness of the barrier metal.