Focus Blur Model to Enhance Lithography Model for Optical Proximity Correction

摘要

The concept of focus blur encompasses the effect of laser bandwidth longitudinal chromaticaberration and scanner stage vertical vibration. The finite bandwidth of excimer laser sourcecauses a corresponding finite distribution of focal planes in a range of 100nm or larger for theoptical lithography system. Similarly, scanner vertical stage vibration puts the wafer in a finitedistribution of focal planes. Both chromatic aberration and vertical stage vibration couldintroduce significant CD errors, hence can no longer be ignored in current lithography processesdevelopment and OPC development that require CD control within a few nanometers. Wedeveloped several methodologies to model the laser chromatic aberration and vertical stagevibration in OPC (Optical Proximity Correction) modeling tool. Extensive simulations were doneto calculate chromatic aberration and vertical stage vibration focus blur's impact on lithographypatterning for a variety of test structures. Chromatic aberration and vertical stage vibration focusblur effect was further included as an regression term in experimental OPC model calibration tocapture its impact on litho patterning, and significant benefit to OPC model calibration wasobserved.