193-nm photoresist shrinkage after electron-beam exposure

In addition to stability and collapse issues facing 193 nm resists, a new concern is rising regarding line width decrease when exposed to an electron beam (e-beam) during CD measurements using scanning electron microscope (SEM). Such an interaction between the measurement system and sample materials poses a great challenge in process development for 193 nm lithography which is believed to be next lithography node. This paper reports the investigation results of 193 nm resist line width slimming under e-beam. We have observed vertical, as well as lateral 193 nm resist shrinkage under e-beam exposure using VeraSEM 3D's unique sidewall imaging technology. We have observed different CD changing behaviors for lines and spaces, as expected. Repeated SEM CD measurements on space magnify the CD changing effect due to 3-5 times more resist exposed to the d-beam than a line. Hence, the influence of other competing effects form line edge roughness, carbonization etc. are reduced. By measuring a space or an edge width at a tilted view, the severity of resist shrinkage of different resist types can be compared directly with a high level of confidence.