Application of HfN/Hf bilayered film as a diffusion barrier for Cu metallization system of Si large-scale integration

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 Anger 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 degrees 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 degrees C.