Paper MS+NC-MoM8
Chemical Vapor Deposition of Manganese Self-Aligned Diffusion Barriers for Copper Interconnections in Microelectronics

Monday, October 20, 2008, 10:40 am, Room 311

Barriers to prevent diffusion of copper (Cu) and oxygen were formed by chemical vapor deposition (CVD) using a manganese (Mn) precursor vapor that reacts with silica-containing surfaces of low-k dielectrics. The manganese metal penetrates a few nanometers into the silica surface to make highly conformal, amorphous and insulating manganese silicate (MnSi_xO_y) layers on the walls of trenches and vias in interconnects. These MnSi_xO_y layers were found to be excellent barriers to diffusion of Cu, oxygen and water. The adhesion of Cu to MnSi_xO_y was also found to be sufficiently strong to satisfy the semiconductor industry requirements. The MnSi_xO_y barrier/adhesion layers become part of the insulator structure, so that they maximize the space available for Cu in the trenches and vias. Thus MnSi_xO_y is a “zero-thickness” barrier that exceeds the ITRS requirements for interconnections in future microelectronic devices. The same Mn CVD process can be applied to cap interconnect structures after chemical-mechanical polishing (CMP). On the tops of Cu wires exposed by CMP, the CVD process forms Mn that is initially dissolved in the Cu near its upper surface. During subsequent deposition of an insulator on the Cu, Mn diffuses back to the upper surface of the Cu where it forms a MnSi_xO_y layer that is strongly adherent to the Cu. These capping MnSi_xO_y layers can increase the lifetime of interconnects against failure by electromigration.