Mechanism of chemical mechanical planarization induced edge corrosion of copper line for Cu/Low-k SiOC interconnects

For complementary metal-oxide-semiconductor (CMOS) technology beyond 90 nm with a very narrow line width, one critical issue is the line edge corrosion in Cu interconnects and the succeeding via process failure. The mechanism of Cu line edge corrosion resulting from the hydrophobic characteristic of low-k SiOC dielectric after the chemical mechanical planarization (CMP) process was studied in detail through the scanning electron microscopy (SEM) analysis and contact angle measurements. The hydrophobic characteristic of low-k dielectric induces a high surface tension that pushes the H₂O₂ molecules contained in CMP slurry toward the edge of the Cu line, thus enhancing the corrosion reaction. We illustrate the mechanism comprehensively using a schematic model.