Dependency of dishing on polish time and slurry chemistry in Cu CMP
✍ Scribed by V Nguyen; H VanKranenburg; P Woerlee
- Publisher
- Elsevier Science
- Year
- 2000
- Tongue
- English
- Weight
- 524 KB
- Volume
- 50
- Category
- Article
- ISSN
- 0167-9317
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✦ Synopsis
In this paper the influences of slurry chemistry and thickness of the copper layer on dishing will be discussed. The dishing is studied for different patterns and variable polishing times. We found that the concentration of the oxidiser and the thickness of copper layer have a strong impact on dishing. The larger Cu features develop dishing at a higher rate than smaller structures during overpolishing. The experimental results lead to the following hypothesis for the Cu removal and 21 surface passivation. The oxidizer (H O ) reacts with Cu in an acidic slurry (pH 4) and Cu ions are formed. The anions of 2 2 21
the carboxylic acid react with Cu ions and form an insoluble salt (R(COO) Cu) which passivates the surface. This 2 passivation layer is removed in protruding areas by mechanical abrasion. Once removed from the surface, the 'metallic soap' particles are swept away by the turbulent motion in the slurry.