Abstract
Abstract The purpose of this study is to fabricate the SiNx capped Cu/Ta/SiO2 air-gap damascene structure. It included the integration of the sacrificial layer HSQ, diffusion barrier layer Ta, copper electroplating, and the passivation layer SiNx. The electric characteristic of the air-gap damascene structure was investigated, and discussed the leakage current and breakdown field. For the sacrificial layer, we spun HSQ with MIBK at ratio=2:1 on SiO2 substrate. It was found that with pre-bake temperature 350℃3min, HSQ was a good sacrificial layer. The cage-network-like HSQ can be removed by BOE solution easily from the interface with SiO2.For CMP, the Cu lines were defined with width/space = 0.5/0.5μm. The slurry mixed with Al2O3 particle (0.05μm)、 HNO3 and citric acid. The polishing down pressure /back pressure varied 5.0/4.0、4.0/3.0、3.0/2.0 psi to remove Cu film. The slurry for Ta is mixture of Levasil Silica 50CK、H2O2, and H2O. From the SEM pictures, the best CMP condition for the structure can be determined. The optimum D.P/B.P=5/2 psi is applied to remove Ta film. The SiNx capped Cu/Ta/SiO2 air-gap damascene structure with diffusion barrier layer Ta (150□), the sacrificial layer HSQ and capped layer SiNx (200□) was fabricated. The SiNx capped samples were studied by the I-V measurement. The leakage current measurement was done at different temperature(RT、50℃、100℃、150℃、180℃), and leakage current mechanism can be analyzed. The breakdown electric field was also measured at different temperature (RT、100℃、195℃) and analyzed. The SEM images were taken in order to correlate to the electrical breakdown measurements.