Study of the Influence of Mo–Si Structural Parameters on the Optical Properties of Masking Coatings for Photomasks

This paper investigates the possibility of using thin-film coatings based on molybdenum-silicon (Mo–Si) alloy as opaque masking layers for a new generation of photomasks (opaque Mo–Si on glass, OMOG) intended for nanometer-range 193 nm wavelength lithography technologies. The relevance of this work is due to the limitations of classic binary photomasks (BIM) of the “chromium on glass” (COG) type, which does not allow the required resolution to be achieved due to the need to form thick chromium layers to achieve optimal optical density. The work investigates the dependence of the optical density of Mo–Si films on their composition and thickness. To this end, a series of samples were formed on different types of substrates and measurements of optical, structural, and elemental parameters were carried out using spectrophotometry, atomic force microscopy, and energy dispersive analysis. It is shown that the use of Mo–Si films allow the required optical density to be achieved with a smaller layer thickness compared to traditional chrome coatings, which contributes to improving the etching process when forming a topological pattern on a photomask (PM). The results confirm the promise of using Mo–Si films as a masking material for photomasks with a design standard of 32–28 nm.