A novel lithography design and verification methodology with patterning failure

We made a new model for the pattern failure, which was the pattern collapse and the pattern bridging, of the resist patterns of 43nm 1:1 lines and spaces (L/S) exposed as a focus-exposure matrix, in order to explain and predict the process window of the pattern failure. It was found that the conventional 'Imax-Imin' model was unable to be fitted to the experimental pass/fail data. Instead of the Imax and Imin, we selected the critical dimension (CD) and the normalized image log slope (NILS) as the model input. The new 'CD-NILS' model corresponded well to the experimental pass/fail data. The good correspondence was assumed to be due to the properly selected model input. The pattern collapse, which occurs during the drying of the water at the rinse of the resist patterns, is expected to be accelerated by the smaller line CD and the larger line width roughness (LWR) due to smaller NILS. The pattern bridging, which occurs at the resist development, is expected to be accelerated by the larger line CD and the larger LWR. The CD-NILS model predicted the process window precisely when a new process condition (= a new illumination in this case) was adopted. It suggests that the CD-NILS model is a powerful methodology for predicting the process window in order to optimize the process condition and to optimize the lithography design.