Application of HfN/Hf Bilayered Film as a Diffusion Barrier for Cu Metallization System of Si Large-Scale Integration

Abstract

As a preliminary examination for improving the reliability of the Cu metallization system of Si-LSI, we prepared Cu/Hf/Si, Cu/CuHf2/Hf/Si and Cu/HfN/Hf/Si contact systems, and compared their thermal stabilities. The change in crystal structure and the interdiffusion behavior were investigated by X-ray diffraction and Auger electron spectroscopy, respectively. In the case of Cu/CuHf2/Hf/Si, its thermal stability was slightly superior to that of Cu/Hf/Si without the CuHf2 layer. However, slight outdiffusion of Si to the Cu surface was also observed, similar to the case of Cu/Hf/Si. On the other hand, the Cu/HfN/Hf/Si system was satisfactorily stable up to 630°C. In addition, it was revealed that Hf silicide containing Hf3Si2 that has the lowest contact resistivity can be maintained at the Si interface up to 630°C.