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Modeling of Pattern Dependencies in Multi-Step Copper Chemical Mechanical Polishing Processes

Copper Chemical Mechanical Polishing (copper CMP) processes are recognized to suffer from pattern dependent problems such as dishing and erosion [1], which lead to increased line resistance and thickness non-uniformity. The amount of dishing and erosion can be reduced if a well designed multi-step copper CMP process is used [2]. In a multi-step process a different slurry, different pad, and different polish process settings (down force, table speed, etc.) may be used in each step. To help design an optimal multi-step process, a pattern dependent multi-step copper CMP model is urgently needed. We present a mathematical pattern dependent model that predicts the amount of dishing and erosion across a die for a given multi-step process, and we show preliminary comparisons between the model prediction and experimental data.