Study on Cu layer adhesion s trength with Low Dielectric Constant Liners in Cu Interconnects

摘要

One of the primary candidates for the liner/etch stop layer in damascene process is silicon nitride (Si_3N_4). However, silicon nitride has a high dielectric constant of 7.0. To reduce the effective dielectric constant in Copper (Cu) damascene structure, dielectric SiCH (prepared by plasma enhanced chemical vapor deposition (PECVD) using trimethylsilane source) as the Cu diffusion barrier was studied. The dielectric constant of SiC:H used is 4.2. A systematic study was made on the properties of liner material and electro-chemically plated (ECP) Cu to enhance the adhesion strength in Cu/low-dielectric constant (k) multilevel interconnects. Though the effects of as Si_3N_4the liner have been much studied in the past, less is known about the relation between adhesion strength of ECP Cu layer and physical vapor deposited (PVD) Cu seeds, with seed thickness below 1000A. The annealing of Cu seed layer was carried out at 200℃ in N_2 ambient for 30 minutes was carried out to study the impact on adhesion strength and the microstructure evolution on the adhesion between ECP Cu and its barrier layer. In the study, our claim that SiCH barrier/etch stop layer is essential for replacing conventional Si_3N_4 layer in enhancing adhesion strength and interfacial bonding between Cu/dielectric interconnects.