Scanner fleet management utilizing programmed hotspot patterns

This paper proposes new scanner fleet management utilizing programmed hotspot patterns. We have developed a methodology to control and adjust critical parameters of scanner, such as effective illumination shape and numerical aperture (NA), to obtain the same lithography performance. The purpose is to improve hotspot patterns and depth of focus (DOF) of each scanner. The method is carried out with a test mask having programmed hotspot patterns that are likely to become fatal errors for circuit reliability in wafer processing. Actual circuit patterns whose patterning fidelity is sensitive to the critical parameters are selected as the programmed hotspots. The mask also has various lithography process monitor marks, such as flare monitor pattern, MEF evaluation pattern and aberration monitor pattern, for OPE control and simulation. Using the same test mask for every scanner, we can reveal the variation of lithography performance within a "scanner fleet". The hotspot patterns on the mask and the patterns printed onto wafers are inspected by Die-to-Database (D2DB) EB inspection and a wafer D2DB EB inspection, respectively. Using those D2DB inspection systems, we can evaluate quantitatively the change of pattern shape from drawing data to wafer. The OPE adjustment and OPC feedback are corrected by using the simulation data acquired for the D2DB inspection. The quality of the evaluation provides accurate scanner fleet control, resulting in high productivity and cost effectiveness at wafer fabrication.