Brian C. Sapp

Predicting substrate-induced focus error

The ever-shrinking lithography process window dictates that we maximize our process window, minimize process variation, and quantify the disturbances to an imaging process caused upstream of the imaging step. Relevant factors include across-wafer and wafer-to-wafer film thickness variation, wafer flatness, wafer edge effects, and design-induced topography. We present our effort to predict design-induced focus error hot spots based on prior knowledge of the wafer surface topography. This knowledge of wafer areas challenging the edge of our process window enables a constructive discussion with our design and integration team to prevent or mitigate focus error hot spots upstream of the imaging process.

Predicting and reducing substrate induced focus error

The ever shrinking lithography process window requires us to maximize our process window and minimize tool-induced process variation, and also to quantify the disturbances to an imaging process caused upstream of the imaging step. Relevant factors include across-wafer and wafer-to-wafer film thickness variation, wafer flatness, wafer edge effects, and design-induced topography. We quantify these effects and their interactions, and present efforts to reduce their harm to the imaging process. We also present our effort to predict design-induced focus error hot spots at the edge of our process window. The collaborative effort is geared towards enabling a constructive discussion with our design team, thus allowing us to prevent or mitigate focus error hot spots upstream of the imaging process.