A New Approach to the Formation Mechanism of Tungsten Void Defect in Chemical Mechanical Polishing

• Published in: ECS journal of solid state science and technology Vol. 7; no. 11; pp. P693 - P697
• Main Authors: Kim, Hong Jin, Egan, Bryan, Shi, Xingzhao, Han, Ja-Hyung
• Format: Journal Article
• Language: English
• Published: The Electrochemical Society 2018
• ISSN: 2162-8769; 2162-8769; 2162-8777
• DOI: 10.1149/2.0291811jss

The advanced node semiconductor device fabrication needs tungsten chemical mechanical polishing as a critical process to enable transistor formation as well as metal interconnection. Accordingly, CMP induced defect concerns have drawn attention to the process integration. Tungsten voids by CMP are one of the major defects to detract device yield. Their formation mechanism has been known as electrochemical corrosion or an optical induced corrosion phenomenon associated with polishing slurry chemistry. However, this paper proposes a new mechanism of tungsten void formation. Different from known corrosion mechanisms, it is observed that tungsten void frequency has strong correlation with CMP in-situ cleaner brush lifetime. At early brush life, tungsten void forms more frequently. Moreover, this paper reveals that CMP brush cleaning play a critical role in the formation of tungsten voids. Tungsten etch rate dependence on brush condition, tungsten void defect density correlation to brush life, and surface chemical analysis of tungsten blanket wafers show that tungsten voids are induced by combined effect of friction force and oxidation in brush cleaner module, which is a new approach to the formation mechanism of tungsten void defect.