Abstract
The integration of copper, diffusion barrier TaSix or TaN and sacrificial layer HSQ were investigated. We fabricated diffusion barrier layer, TaSix or TaN, sacrificial layer HSQ, develop the processes integration for Cu metallization and investigated the conduction mechanism of line-to-line leakage current for air-gap damascene structure.In order to get various thicknesses, we mixed solution with different ratio of HSQ and MIBK after spin on. The HSQ film is a good sacrificial layer with pre-bake temperature 350℃. It has a good mechanical strength during metal CMP and can be removed by BOE solution quickly and easily.The Cu air-gap damascene structures with diffusion barrier TaSix or TaN and sacrificial layer HSQ were fabricated. From leakage current measurements, the breakdown electric field of the Cu/TaN(200A)/SiO2 air-gap damascene structures is 0.94~1.1 MV/cm and the leakage current is about 1.02×10-4~2.27×10-4 A/cm2 before the breakdown occurring. The breakdown electric field of Cu/TaSix(200A)/SiO2 air-gap damascene structures is 0.73 MV/cm and the leakage current is about 5.9×10-6 A/cm2 before the breakdown occurring. The breakdown electric field of Cu/TaSix(100A)/SiO2 air-gap damascene structures is higher than 1.3 MV/cm and the leakage current is about 6.6×10-4~2.89×10-3 A/cm2 before the breakdown occurring. From the SEM pictures, we observed the trenches of damascene structures being not filled with the copper. Meanwhile, CMP will remove or shake the barrier layers. The breakdown electric field and the leakage current were enhanced. From various electrical leakage current analyses, we find that the dominant conduction mechanism of the Cu/TaSix or TaN/SiO2 air-gap damascene structures is space charge limited.