Study on the influence of contact glue layer growth condition on the quality of gap fill tungsten layer

In the 55nm technology node and beyond of integrated circuits, tungsten is used in contact layer interconnection. Before tungsten deposition, a contact glue layer consist of titanium and titanium nitride (Ti/TiN) is used to enhance adhesion, reduce resistance and prevent tungsten diffusion into the substrate. The growth condition of contact glue layer(s) determines the characteristic of gap fill tungstenfilm, such as grain orientation and grain size. The film quality of the gap fill tungsten critically impacts tungsten chemical mechanical polishing (WCMP) rate. In this paper, we focus on the relationship between Platen 2 (P2) polishing time range in WCMP process and the growth condition of contact glue layer, including titanium thickness and plasma treatment condition for titanium nitride. We found thicker titanium with more definitive grain orientation could improve the film quality of titanium nitride and the gap fill tungsten. However, if the titanium becomes too thick, the gap fill tungsten may not fill the contact hole due to overhang. Moreover, multiple times of plasma treatment during titanium nitride deposition also improves the grain orientation of both titanium nitride and the gap fill tungsten. However, plasma treatment will extend titanium nitride process time and reduces wafer per hour (WPH). We have determined the optimized condition of the glue layer(s) as 150A titanium and 3∗15A titanium nitride. With the optimized glue layer(s), we can get consistant gap fill tungsten film quality with reduced range in WCMP polishing time.