Micro-pattern Corrosion Screening on Bimetallic Corrosion for Microelectronic Application

The continued miniaturization of the integrated circuit, leading to minute dimensions (< 10 nm) in microelectronic architecture, can greatly accelerate the on chip corrosion into a severe reliability threat. Particularly, various interfaces between multilayered film stacks create dissimilar contacts with significant galvanic potential difference. This can promote on-chip corrosion under semiconductor processing conditions. In this paper, an efficient micro-pattern corrosion screening metrology combined with electrochemical and x-ray photoelectron scattering techniques, is utilized to study bimetallic corrosion and its inhibition in wafer cleaning solutions. Cu/Ru bimetallic contact was found to exhibit a higher corrosion rate than the Cu/Ta contact. In alkaline ammonium citrate solution, higher dissolved oxygen content significantly accelerated Cu corrosion. The increased alkalinity (pH > 12) at Cu/Ru interface, caused by enhanced oxygen reduction reaction on Ru, is proposed to generate more NH3 for sustaining fast Cu corrosion. Effects of different plasma chemistries like CF4, CF4 + O2, CH2F2, C4F8 and SF6 on the Cu corrosion in tetramethylammonium hydroxide (TMAH) were also investigated. Plasma treatments using higher fluorine content gases showed higher Cu corrosion rate in TMAH. Benzotriazole showed limited corrosion inhibition to plasma treated Cu/Ru micro-patterns in pH 14 TMAH solution. Contrastingly, pyrazole demonstrated as an effective corrosion inhibitor suppressing Cu corrosion rate down to the desirable < 1 A°/min level.