Modelling pattern dependent variations in semi-additive copper electrochemical plating: AP/DFM: Advanced patterning / design for manufacturability

Abstract

An empirical model is proposed for predicting layout-dependent thickness variations in the semi-additive copper electrochemical plating (ECP) process. These variations are believed to be caused by the uneven depletion of copper sulfate (CuSO4) during plating, causing low pattern density areas to plate faster than higher pattern density areas. Effective pattern density is extracted from the layout using a spatial filter, and then mapped to the growth rates using a non-linear function. Test structures are designed that represent a wide range of feature sizes and densities. After plating, these structures are profiled and used to fit the model, while similar structures are used to validate its accuracy. Comparisons between the validation predictions and the experimental results show an average Balanced Root Mean Squared Error (BRMSE) of 0.292 µm, and a corresponding R2 value of 0.90.