Preparation And Thermal Stability Study Of Carboxyl Chemically Modified APTMS Self-assembled Monolayer Diffusion Barrier

The traditional inorganic materials copper diffusion barrier have been extensively researched due to their good properties.However,the coverage of such diffusion barrier layer will be reduced and their compactness will be poor in devices less than 3 nm thick,especially in those with a large depth width ratio,thus it cannot be used as an ideal diffusion barrier material.Therefore,scientists have shifted their research direction to organic materials and self-assembled organic molecular layers have become new materials used as diffusion barrier.In this paper,the 3-aminopropyltrimethoxysilane(APTMS)diffusion barrier is self-assembled on the surface of Si(100)substrate by molecular self-assembly technology,and COOH-APTMS diffusion barrier is prepared by modifying the terminal carboxyl group of APTMS molecule.The surface morphology,composition and hydrophilicity of the self-assembled molecular layer were analyzed by scanning electron microscope(SEM),atomic force microscope(AFM),X-ray photoelectron spectroscopy(XPS)and de-ionized(DI)water contact angle measurement.The Cu/barrier/SiO₂/Si were prepared by magnetron sputtering.The mechanical properties and leakage current of the samples were characterized by four-point bending test and semiconductor analyzer.Then the Cu/barrier/SiO₂/Si were annealed in vacuum for 1h at 250?to 600?.The thermal stability of the samples was investigated by four-probe tester(FPP),X-ray diffractometer(XRD)and scanning electron microscope(SEM).The SEM and AFM test results show that the self-assembly conditions of APTMS and COOH-APTMS diffusion barrier affect the quality of the film.For APTMS,the quality of the film is the best when the self-assembly temperature is 70?and the self-assembly concentration is 3mmol/L.For COOH-APTMS,the quality of the film is the best after 3h modification.According to XPS test results,the APTMS and COOH-APTMS are bonded to Si matrix through Si-O-Si bonds,and the modified substance 1,3,5-tricarboxylbenzoic acid is bonded to APTMS through O=C-N bonds.The DI water contact angle results show that the contact angle of APTMS and COOH-APTMS are 64.6°±2°and 35.5°±2°respectively.The four-point bending test results show improved adhesion to Cu film after carboxyl chemically modified APTMS,and the interface toughness value was increased by 19.7%compared with that without modification.The leakage current test results show that the leakage current values of Cu/APTMS/SiO₂/Si and Cu/COOH-APTMS/SiO₂/Si are 10^-5A/cm²and 10^-6A/cm² respectively,and the leakage current value of the carboxyl chemically modified APTMS is one order of magnitude lower than APTMS,which indicates COOH-APTMS diffusion barrier exhibits better diffusion resistance performance.The XRD,SEM,and FPP test results show that Cu₃Si phase appears when annealing temperatures reach450°C and 550°C in Cu/APTMS/SiO₂/Si and Cu/COOH-APTMS/SiO₂/Si barriers respectively.It can be concluded that the thermal stability and reliability of diffusion barrier have been significantly improved by carboxyl chemically modification and COOH-APTMS is a more promising diffusion barrier material compared to APTMS.