Eliminating Half Wafer Shading Defects in Lithography Track Tools using Open Shutter Method

In this paper, we discuss how we addressed an increase in defectivity in our lithography track tools, specifically the half wafer shading (HWS) defect. This defect signature appears as a concentration of particles on half of the wafer and was correlated to an airflow issue in the bake units making it more susceptible to particle contaminants from the external environment. Using a simple modification of the hardware functionality by permanently opening the bake unit shutter, we were able to resolve the HWS defect signature. A mist test was done to validate the open shutter method and CFD simulation was used to understand the failure mechanism. With this method, we eliminated the HWS defect on product wafers.