Hydroxy-phenyl Zn(II) porphyrin self-assembled monolayer as a diffusion barrier for copper-low k interconnect technology

In this paper, we have studied the application of metallated porphyrin self-assembled monolayer (SAM) as a copper diffusion barrier for low-k inter-metal dielectric (IMD) CMOS technologies. SAM formed on hydrogen silesquioxane (HSQ), which is a low-k dielectric, has been demonstrated to be effective in preventing diffusion of copper ions into the porous dielectric. This has been shown by fabricating Cu-HSQ-Si and Cu-SAM-HSQ-Si metal-insulator-semiconductor test structures. Bias-temperature stress (BTS) studies have been done to investigate the effectiveness of SAM as a diffusion barrier. Formation of SAM on HSQ has been characterized using Fourier Transform Infra-red Spectroscopy studies. Thermogravimetric analysis (TGA) of hydroxyl-phenyl Zn(II) porphyrin has been used to verify thermal stability of the molecule under back-end-of-line (BEOL) process conditions.