Novel self-aligned W/TiN/TiSi₂ contact structure for very shallow junctions and interconnections

Abstract

This letter describes a novel structure for very large scale integrated contact and interconnect technology that involves selective deposition of W on self-aligned TiN/TiSi2. The TiN layer serves to protect reaction between WF6 and TiSi2 and underlying Si during W deposition as well as to promote adhesion of W layer and minimize contact resistance. The selective deposition of W on TiN, very difficult with conventional hydrogen reduction process, is accomplished by employing a recently developed silane reduction process. The structure prevents silicon consumption leading to the encroachment commonly found in tungsten deposited directly on silicon in very shallow junctions. It is demonstrated that such a structure results in low contact resistance and junction leakages and is applicable to subhalf-micron devices. Tungsten with low resistivity of 8-9 μΩ cm can be achieved at room temperature with the resulting drop by a factor of 3-4 at liquid-nitrogen temperature making the structure more attractive for low-temperature application.