The Characterization of KrF Photoresists and the Effect of Different Chromophore Bulkiness on Line Edge Roughness (LER) for Submicron Technology

This research characterizes line edge roughness (LER), determines which resist has lowest LER for all process variations, and investigates the effect of chromophore bulkiness on LER. Three KrF photoresists with different chromophore bulkiness were evaluated. The characteristics evaluated were depth of focus (DOF), profile and resolution, LER, exposure latitude, iso-dense bias and CD linearity. Different feature sizes were tested from 100 nm to 190 nm. From the results, it is seen that resist PI has the lowest average LER for all process conditions and variations with a 3 sigma value of 10.074. This is followed by resist P5 and P6 with a 3 sigma LER value of 12.562 and 15.468. It is concluded that high chromophore bulkiness results in high UV activation. This is seen from the LER for resist P6 that is the highest out of all the photoresist. Reducing the chromophore bulkiness will reduce LER until it reaches a saturation point where reduction will not result in any lower LER. Reducing the chromophore bulkiness further beyond the saturation point will in fact increase the LER.