“…Also, the extracted systematic variation is an interpolated map which cannot be described by an analytic expression nor can it be related to process parameters immediately, making it difficult to apply the extracted model for yield prediction. Ref found that, in CMOS fabrication, systematic variations on intrawafer and intradie levels can both be approximately described by a paraboloid function, i.e., a second-order bivariate polynomial. From our observation of the measured photonics wafer, we find that the IWS variation indeed corresponds roughly to such a paraboloid profile, but that it might be more accurate to apply a higher-order radial polynomial model.…”