Correlated Model for Wafer Warpage Prediction of Arbitrarily Patterned Films

Increasing power and efficiency requirements are driving a need for more metal content in the silicon back end. After being subjected to high temperature passivation processes, the film stress can increase significantly and lead to warped wafers. Warpage of various metalized wafers was characterized across a broad range of variables. In addition to metal film content and wafer dimensions as primary factors for the warpage, we find a strong dependence on the design of the artwork itself. A methodology was thus developed to predict wafer warpage of arbitrarily patterned films. A multi-scale finite-element-based modeling approach was used for converting a patterned composite film stack into an effective orthotropic film for efficient wafer-level stress and warpage analysis. A robust modeling correlation to the measured warpage was achieved across many variables, in terms of both warpage magnitude and shape.