| Summary: | 碩士 === 國立虎尾科技大學 === 光電與材料科技研究所 === 96 === International Technology Roadmap for Semiconductor (ITRS) predicted that the thickness of barrier will be reduced eventually to 1.6 nm in 2018 for 21 nm technology. In continuously reducing the thickness of diffusion barrier, while maintaining the low resistivity and highly thermal stability, in effectively preventing Cu diffusion is quite difficult.
This study aims at developing an ultrathin Ta-Si-C amorphous barrier for copper metallization and evaluating the barrier properties with different carbon concentration in Ta-Si-C films. The findings indicated that the as-deposited Ta-Si-C films had an amorphous structure, and the lowest electrical resistivity was 340 μΩ-cm for Ta34Si47C18/Si film. The amorphous Ta34Si47C18 film showed the first sign of nano-crystallization TaSi2 phase when the film was annealed at 700°C. However, Ta30Si44C25 and Ta26Si41C32 films showed the first sign of TaSi2 phase both at 800°C. Carbon addition indeed enhances the thermal stability of Ta-Si-C films. For evaluating the failure temperature, the Cu/Ta-Si-C/Si sandwiched film was annealed for 1 min at a temperature between 300°C and 900°C in Ar+H2 (5%) ambient by a rapid thermal annealer (RTA). The sandwiched Cu/Ta-Si-C (10, 5, and 2 nm)/Si film showed the failure temperature at least 800°C, 750°C, and 650°C, respectively.
Owing to the strong bonding between Ta and Si in ternary Ta-Si-C system, local diffusion of Si from certain regions within the amorphous matrix occurs, which then leads to the crystallization of amorphous Ta-Si-C structure. The introduction of C into Ta-Si barriers in this study inhibited the reaction between the barrier and underlying Si substrate at an elevated temperature, hence, the thermal stability for the barriers can be enhanced. The superior barrier properties of Ta-Si-C thin film reveals its potential to be used as a diffusion barrier in copper metallization.
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