Process development for high scan speed ArF immersion lithography

Advances in Patterning Materials for 193 nm Immersion Lithography

“…Many experimental techniques have been devised to measure the kinetics of resist component extraction by water in order to meet these specifications. These techniques include simple contact of the resist surface to water confined in an O-ring or vial, flowing water through a specifically designed cell mounted on the wafer, or dragging a drop or puddle of fluid across the resist-coated wafer. ,,,− In an attempt to standardize leaching measurements, many vendors now utilize a dynamic method employing a multichannel flow cell (so-called dynamic WEXA)…”

“…Low surface energy materials such as organosilicon and fluorine-containing polymers have long been known to segregate to the surface of polymer blends during film formation . To take advantage of this phenomenon, small loadings (∼1−5 wt %) of tailored surface-active materials have been used to convert conventional 193 nm dry photoresists into immersion-compatible versions. ,− During spin-casting of the photoresist, these additives segregate to the resist surface to form a thin enrichment layer of the additive, which serves as an in situ topcoat barrier to reduce PAG leaching and control the water contact angles of the resist. These additives are sometimes also referred to as embedded barrier layers (EBLs) or water shedding agents (WSAs) .…”

“…Most of these correlations are consistent with the hypothesis that hydrophobic aggregates can precipitate and attach to a hydrophobic resist surface during development to create blob defects, while the more hydrophilic aggregates of resist-type additives would be more easily rinsed away from a hydrophilic resist surface during development . Accordingly, rinse treatments and alternative development processes have been found to be effective means to reduce the numbers of blob defects. ,,,,,− Alternatively, Hagiwara et al explored removing the hydrophobic additive material from the surface of the resist using an organic solvent in a “selective segregation removal” (SSR) process prior to development of the resist pattern …”

“…Studies comparing the lithographic performance of topcoat-free 193 nm immersion resists relative to that of standard topcoat/resist stacks have shown that optimized topcoat-free resist processes can achieve equivalent or superior lithographic performance, including resolution, process windows, sidewall angle/resist profiles, CD uniformity, line edge roughness (LER)/LWR, postexposure delay stability, and defectivity levels (see Figure ). ,,,,, …”