Abstract
An extended set of coupled wave equations were derived to describe non-idealized lamellar multilayer grating structures with properties as obtained with state-of-the-art fabrication techniques. These generalized equations can include all relevant effects describing the influence of passivation and contamination layers, non-rectangular lamel profiles and sidewall scalloping. The calculations showed that passivation and contamination plays an important role in that it may significantly reduce peak reflectivity. However, we also derived a condition for layer thicknesses having negligible effects. Slightly positive tapered lamel profiles are shown to further reduce the bandwidth as compared to a rectangular lamel profile, whereas negative tapers significantly increased the bandwidth. The influence of intriguing effects, such as the sidewall scalloping caused by Bosch Deep Reactive Ion Etching, are also modeled. We identified the signature of such scalloping as additional side peaks in the reflectivity spectrum and present parameters with which these can be effectively suppressed.
Highlights
Lamellar multilayer gratings (LMG) are a newly emerging component for the extreme ultraviolet (EUV) and soft x-ray (SXR) spectral ranges
Lamellar multilayer gratings (LMG) are a newly emerging component for the EUV and soft x-ray (SXR) spectral ranges. They effectively suppress the detrimental influence of absorption, which limits the resolution of conventional multilayer (ML) mirrors, through the fabrication of a grating structure in such a ML mirror
According to Eq (16), layer thicknesses below 20 nm should have a negligible effect on the LMG optical performance
Summary
Lamellar multilayer gratings (LMG) are a newly emerging component for the EUV and soft x-ray (SXR) spectral ranges They effectively suppress the detrimental influence of absorption, which limits the resolution of conventional multilayer (ML) mirrors, through the fabrication of a grating structure in such a ML mirror. The effect of process specific features or any process artefacts of these fabrication methods may lead to non-ideal structures, such as non-rectangular shapes, materials intermixing and roughness. These may influence the reflectance of LMGs and such phenomena have not yet been investigated.
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call