Films of the intermetallic compound CuTi₂ and their applications in Cu/CuTi₂/Si contact structures

To prepare constituent materials applicable to a Cu metallization technology of Si‐LSI, the preparation conditions of Cu‐Ti intermetallic compound films have been examined and the thermal stability of the Cu/CuTi 2 /Si contact structure has been studied using CuTi 2 compound films as a diffusion barrier. As a result, a stoichiometric intermetallic compound film of CuTi 2 was prepared successfully at a substrate temperature of 300°C by dc sputtering using a composite target with an area ratio of Cu : Ti = 51 : 49. From the study on the CuTi 2 /Si contact structure, it was revealed that the CuTi 2 phase was stable up to 500°C and a thin interface layer of Ti silicide was formed at the interface of CuTi 2 /Si but the excess diffusion and/or reaction have not been observed. Ti silicide layer formed at the interface is believed to be effective for low contact resistance. To examine whether or not CuTi 2 films are suitable for Cu metallization technology, the thermal stability of Cu/CuTi 2 /Si contact structure was examined. It was found that the structure is successfully stable up to 500°C and is useful for Cu metallization technology. The reason is believed to be as follows: the interface of Cu/CuTi 2 is in the chemical equilibrium state and CuTi 2 itself is a stable compound phase at high temperatures in the Cu‐Ti alloy system.