As semiconductor device fabrication moves towards 2 nm technology nodes with EUV lithography, new EUV absorber materials will be needed to replace the current Ta-based EUV photomasks. The industry is looking for new absorber materials with a low refractive index (n) and a high extinction coefficient (k), to produce an attenuated phase-shift EUV photomask capable of minimizing 3D effects. The challenge is that these new materials are often difficult to etch. To identify the etching pathway for new EUV material candidates, this paper proposes the approach of thermodynamic characterization for various chemistries as etching byproducts. The Gibbs free energy of formation for these compounds can be collected at standard state conditions, so the potential for such chemical reactions can be evaluated. Meanwhile, the volatility of these reaction products can be estimated by the respective boiling points, which can be calculated from respective heats of vaporization at reduced pressures typically found in a plasma etch chamber. Collectively, this information can help to screen for new low-n / high-k absorber materials, to focus the selection only to candidates with potential etching feasibilities.
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