Investigation of sputtered TaC/sub x/ and WC/sub x/ films as diffusion barriers for Cu metallization

Physical and electrical properties as well as thermal stability of sputter-deposited TaC/sub x/ and WC/sub x/ films were investigated. The 60 nm-thick TaC/sub x/ and WC/sub x/ film shows a resistivity of around 385 /spl mu//spl Omega/-cm and 227 /spl mu//spl Omega/-cm, respectively. The allowable thermal stability of TaC/sub x/ layer was found around 700/spl deg/C which is about 50-100/spl deg/C higher than that of WC/sub x/ layer. It was found that the failure of the TaC/sub x/ and WC/sub x/ barrier layers is mainly attributed to the diffusion of Cu through the grain boundaries or localized defects of the barrier layers into Si substrate.