Study and Control of the Interfacial Mass Transfer of Resist Components in 193nm Immersion Lithography

Advances in Patterning Materials for 193 nm Immersion Lithography

“…For example, around 50% of the PAG was depleted from the top 25 nm of a IBM-V2 methacrylate resist ( 1 ) film as a result of water contact . Various experimental measurements of PAG extraction indicate that 5−10% of the total PAG content can be leached from the resist film. ,, Liquid scintillation counting (LSC) experiments with resists containing 14 C-labeled components showed that 30−50 ng/cm 2 of PAG was extracted, with most of the extraction occurring in the first 10 s and minimal extraction after 30 s . Base extraction was found to be ∼2 ng/cm 2 and to occur on the same time scale .…”

“…Despite the inability of the topcoats to prevent water penetration into the resist film, they are an effective means by which to prevent PAG leaching into the immersion fluid. Typically, greater than 90% reduction in the amount of PAG leaching is observed with the use of a topcoat. ,,,,, Interestingly, topcoats are unable to reduce PAG leaching levels in direct proportion to their thickness. ,, In general, PAG leaching with a topcoat is predominantly from the topcoat surface with little PAG diffusion through the topcoat film itself. ,, Analysis of topcoat−resist film stacks reveals that PAG and other resist components can migrate into the topcoat film during casting. ,,,− For certain topcoat−resist pairs, this intermixing layer is substantial (see Figure ) . The intermixing of resist components with the topcoat is strongly dependent on the polarity of the topcoat casting solvent, with alcoholic solvents causing increased intermixing relative to less polar ethereal or hydrocarbon solvents. ,, In addition, the presence of a strong intermixing layer generally results in a region with slower dissolution rate during development, increased surface roughness after development, and T-top formation in the final resist profiles. , …”