Some non-resist component contributions to LER and LWR in 193-nm lithography

Abstract

Improvement of line edge roughness (LER) and line width roughness (LWR) is required for integration of semiconductor devices. This paper describes various process factors affecting LER/LWR of 193 nm resists such as mask layout (bright field/dark field), pitches, optical settings, substrates, film thickness, baking temperature and development condition. The origins of line roughness are discussed in view of aerial image contrast, transmittance of resists and pattern profiles. Bright field mask exhibited lower LER/LWR values than dark field mask, LER/LWR deteriorated as larger pitches and illumination condition affected roughness and these results are explained using normalized image log-slope (NILS). BARC dependence of line roughness is explained by pattern profile difference due to interactions between resist and BARC and in some cases BARC reflectivity. Contributions of film thickness, SB & PEB temperature and development condition to line roughness are also reported.

Sidewall roughness in nanolithography: origins, metrology and device effects

“…Both CD-SEM and CD-AFM measurements indicate that LER and LWR values increase as the image moves out of focus (Foucher et al ., 2007;Kudo et al ., 2007).…”

“…On the other hand, development concentration has been shown to affect LER, but the results are controversial, implying that these effects are strongly dependent on the resist chemistry (Kudo et al ., 2007).…”

“…Development time does not seem to have signifi cant infl uence on LER/ LWR (Kudo et al ., 2007), as also predicted in (Schnattinger and Erdmann, 2008). On the other hand, development concentration has been shown to affect LER, but the results are controversial, implying that these effects are strongly dependent on the resist chemistry (Kudo et al ., 2007).…”

“…It has been reported that substrates may have a signifi cant impact on LER, and the possible causes for these LER effects include surface morphology and substrate interactions, as well as residual refl ectivity (Kudo et al ., 2007). As resist thickness goes down in NGL, resist-substrate effects are expected to play a more important role in LER formation.…”