Improved Performance of Apex-E Photoresist with the Application of the Electric Field Enhanced PEB

摘要

This paper describes a systematic and rigorously controlled set of experiments showing the effectiveness of the Electric Field Enhanced Post Exposure Bake (EFE-PEB) with 248 nm KrF(ASML) exposures on Apex-E photoresist (IBM) where feature sizes ranged from 0.3 um to 0.5 um. Experimental results showed a significant improvement in process latitude and resist sensitivity for features with a kl technology factor of 0.68 and below. The experiments were executed using a 248nm KrF stepper (ASML), NA 0.5, and Apex-E photoresist (IBM), which has a relatively high acid diffusivity. An improved experimental setup rigorously controls PEB time, PEB temperature, development time, focus drift, and other environmental variables. Cross sectional SEMs of five line arrays with L = S ranging from 337 nm to 500 um show deeper trenches when the electric-field treatment was used. Exposures that were intentionally out of focus cleared 600 nm deep in 1 um thick photoresist in the control group, but did clear the full lum with the application of the Electric Field during the PEB. A dose matrix experiment showed an 8% decrease in the dose to clear and two-fold increase in focus latitude. This comprehensive study demonstrated an increase in anisotropic acid diffusivity with the application of the electric field and confirmed that the EFE-PEB offers a relatively inexpensive and simple method for improving photoresist performance.