Co-silanization engineering to construct molecular diffusion barrier for copper metallization on silicon

Abstract

Background

Diffusion barrier is important in the development of integrated-circuit (IC) technology because it is essential to maintain the electrical and structural integrity of the Cu/SiO₂/Si heterojunctions. With the advancement of ultrafine-pitch IC layouts, the thickness of diffusion barrier must downscale to few atomic layers which is a critical reliability issue for film coverage and continuity. Due to molecular self-assembling ability, organosilanes are promising candidates to construct the atomic-level diffusion barrier. However, uncontrolled self-assembling ability usually results in molecular self-polymerization, posing big challenges to the formation of a well-organized network structure.

Methods

In this study, co-silanization technology based on two organosilanes are proposed to overcome the uncontrolled molecular assembling problems. The co-silanized molecular nanolayer is constructed at the Cu/SiO₂ interface by interstitially filling the skinny 3-aminopropyltrimethoxysilane (APTMS) molecule into the gaps between stereoscopically bulky molecule like triphenylsilanol (TPS) or trimethoxyphenylsilane (TMPS).

Significant Findings

The co-silanized TPS@APTMS nanolayer exhibits better barrier efficacy against the Cu diffusion in terms of the suppression of Cu silicide formation as compared to the mono-silanized APTMS nanolayer. The better diffusion barrier efficacy is attributed to the strong steric hindrance effect of TPS molecule which assists the APTMS molecule to co-assemble into a well-oriented and organized network structure.