Effect of oxidation on electromigration in 2-µm Cu redistribution lines capped with polyimide

• DOI: 10.1016/j.rinp.2021.105048
• Publication Date: 2021-11-22T17:18:12Z
• Authors: I-Hsin Tseng; Po-Ning Hsu; Wei-You Hsu; Dinh-Phuc Tran; Benson Tsu-Hung Lin; Chia-Cheng Chang; K.N. Tu; Chih Chen
• Keywords: Nanotwinned copper; Electromigration; Physics; QC1-999; Oxidation; 0103 physical sciences; Fine pitch; Redistribution layers; 01 natural sciences

Polyimide (PI) has been adopted to protect the Cu from oxidation in the packaging industry. Electromigration (EM) of Cu redistribution layers (RDLs) capped with PI was investigated at 160 °C under 1.0 × 106 A/cm2. The results indicated that failure of fine-pitched (2-µm) is different from that of 10-µm RDLs, which is void formation. The failure of the 2-µm RDLs is mainly caused by severe oxidation during EM. To analyze the EM failure of the Cu RDLs with different pitches, the oxidation area of nanotwinned copper (nt-Cu) and regular Cu RDLs during EM was compared. We propose an oxidation equation to estimate the resistance increase of RDLs with various widths.