Memory cell with selective deposition of refractory metals

Abstract

Methods are provided for selective formation of oxidation-resistant caps for conductive plugs in semiconductor device fabrication. One embodiment of the present invention forms a sacrificial layer over a recessed polysilicon plug. The sacrificial layer is readily planarized using chemical mechanical planarization to isolate the cap within a recessed via. Then, an immersion plating process is used to replace the atoms of the sacrificial layer with atoms of a desired metal, such as platinum, thereby creating a metal cap isolated within the via. The advantages of planarization to isolate material within recessed via are thus obtained without having to planarize or otherwise etch the desired metal. The cap layer can be further reacted to form a barrier compound prior to forming a capacitor over the plug. Advantageously, the plug structure resists oxidation during fabrication of overlying capacitors that incorporate high dielectric constant materials.