Self-Aligned Rapid Thermal Nitridation of TiSi2 in NH3 Ambient as a Diffusion Barrier Layer for Selective CVD-Al Contact Plug Formation

Abstract

Diffusion barrier properties and selectivity required for selective chemical vapor deposition (CVD)-Al contact plug formation are remarkably improved by the self-aligned rapid thermal nitridation (RTN) of TiSi2 layer in NH3 ambient at 865° C for 30 s. This treatment enables the formation of a nonstoichiometric TiSix layer with a low concentration of nitrogen within 10-20 nm below its surface. However, nitridation is thought to occur particularly along the grain boundaries, resulting in high diffusion-barrier integrity against aluminum diffusion through the grain boundaries. In addition, this treatment provides favorable selective growth from the bottom of contact holes by reducing the number of nucleation sites on the inner side of contact holes. Therefore, our newly developed process is very promising for contact plug formation of complementary metal-oxide-semiconductor (CMOS) using the salicide process.