Increase the removal rate of Cu at CMP
Chemical Mechanical Planarization (CMP) is a critical semiconductor manufacturing process used to remove excess material and create a flat wafer surface between fabrication steps. Planarity is essential because uneven topography can prevent accurate lithography, reliable interconnect formation, and successful integration of subsequent layers.
During copper CMP, the wafer is pressed face-down against a rotating polishing pad while slurry is supplied to the contact area. The slurry typically contains water, chemical additives, abrasive particles, and hydrogen peroxide as an oxidizer. Hydrogen peroxide reacts with the copper surface and forms an oxide layer, which is then removed by the polishing pad and abrasive particles.
The current copper removal rate is relatively low, which increases process time and limits equipment throughput. A common attempt to accelerate the process is to increase the H₂O₂ concentration in the slurry. However, engineers have found that this approach is effective only up to a certain concentration. Above that level, the Cu removal rate no longer increases and may decrease.
The purpose of this project is to understand the mechanism limiting the Cu removal rate and identify effective ways to increase CMP productivity without compromising process quality, uniformity, or wafer reliability.
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