Effects of Additives and Heat Treatment on the Electrical Properties of Cobalt Interconnect Plating

doi:10.3901/JME.2022.02.066

Abstract

Abstract: As on-chip interconnect dimension shrinks below 10 nm node, cobalt (Co) is proposed to replace copper as the interconnect material due to its short electron mean free path, super electromigration resistance and excellent diffusion barrier properties. Superconformal Co filling can be achieved by electrodeposition with suppressors, which will simultaneously cause the resistivity increase. Heat treatment is usually carried out to improve the electrical properties. However, little attention has been paid to the combined effect mechanism of suppressors and heat treatment on the electrical properties of Co. To study the combine effect mechanism, electrochemical behaviors of three suppressors, dimethylglyoxime (DMG), polyethyleneimine (PEI) and 2-mercapto-5- benzimidazolesulfonic acid (MBIS) are evaluated, Co coatings are prepared by electrodeposition with these suppressors, and the crystal structure, grain size and impurities change of Co coatings before and after annealing are characterized. The results showed that the sheet resistance of Co increased with the increase of the suppressor concentration. 0.02 wt.% DMG, 0.001 5 wt.% PEI and 0.002 wt.% MBIS have similar inhibition abilities. The corresponding three Co coatings have HCP crystal structure and similar grain sizes, and they did not significantly change after annealing at 300℃. The initial sheet resistances and sheet resistances drop rates of three Co coatings after annealing at 300℃ are both 0.02 wt.% DMG > 0.0015 wt.% PEI > 0.002 wt.% MBIS. These differences were mainly caused by the differences of the initial impurities contents and the impurities decrease after annealing respectively. This research can provide theoretical support for selecting the suitable additives and annealing processes to produce Co interconnects with super electrical properties.

Key words: cobalt electrodeposition, suppressors, heat treatment, grain size, impurities, sheet resistance

CLC Number:

TN405

CHEN Shuhui, ZHANG Mengyun, TAN Lingyue, LI Ming, HANG Tao. Effects of Additives and Heat Treatment on the Electrical Properties of Cobalt Interconnect Plating[J]. Journal of Mechanical Engineering, 2022, 58(2): 66-75.

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