Aluminum Thinning onto Blanket and Etched Back Tungsten Plugs: Simulation of Geometrical Effects

The blanket and etch back technique has been been introduced successfully in process flows for vias and contact holes filling. The possibility of application of such technique also to stacked vias and contacts for multi-metal processes is connected to stronger requirements. A thinning of the aluminum film in the area of the plug contact sometimes has been observed. Two possible causes were considered: a reduced aluminum nucleation on the tungsten material, and geometrical effect. A work of simulation indicated that the plug recession can explain the observed thinning of aluminum. This result was also confirmed by Auger Electron Spectroscopy.