Patent ID: 6973636
Filing Date: 2005-12-06
Classification: G03F

Abstract:
1. A method of identifying forbidden pitches for a lithographic exposure tool, comprising: selecting a set of exposure conditions; performing a simulation of an actual lithographic exposure process using a computer model, wherein the performing of the simulation comprises: determining whether the DOF values are greater than a focus budget of the exposure tool for a set of frequently used pitches; if the DOF values are not greater than the focus budget of the exposure tool for the set of frequently used pitches, selecting a new set of exposure conditions and re-performing the simulation using the new set of exposure conditions; if the DOF values are greater than the focus budget of the exposure tool for the set of frequently used pitches, performing a verification test comprising: for at least some of the exposed pattern pitches, comparing the corresponding actual DOF value with the focus budget of the exposure tool; and if the actual DOF value is not greater than the focus budget of the exposure tool, designating that actual DOF value's corresponding pattern pitch as a forbidden pitch.