The pellicle prevents image errors due to contaminated particles in the EUV mask and protects the mask for a stable process. However, the lifetime of the pellicle could be shortened due to deformation and destruction caused by the collision of the particle defects in the chamber. Therefore, in order to increase the lifetime of the pellicle, it is required to develop an optimal pellicle material and structure that is resistant to deformation and destruction and has excellent mechanical stability. Accordingly, it is necessary to know the deformation caused by the particle collision and estimate the lifetime of the pellicles with different mechanical stability. In this study, we simulate the collision of particle defects for the pellicle and compare the mechanical stability depending on the single-layer pellicle materials.
For finer linewidth patterning, 0.55 numerical aperture (NA) should be used instead of the existing 0.33 NA. In 0.55 NA extreme ultraviolet lithography (EUVL), to alleviate the mask 3D effect and stochastic noise, which is stronger, it is necessary to develop an optimal phase shift mask (PSM) and multilayer mask for high NA. Mask structure is used PSM with composed of Ru-alloy/TaBO and multilayer composed of ruthenium (Ru)/silicon (Si), which is expected to be effective in mitigating mask 3D effect and improving imaging performance. The absorber reflectance was checked which is changed by variables such as pattern existence, target CD, and pitch ratio. In addition, by examining the relationship between the change in absorber reflectance and normalized image log slope (NILS), it was determined whether the mask structure for high NA was changed by the target pattern changes.
As semiconductor technology became more integrated, the numerical aperture (NA) of extreme ultraviolet (EUV) exposure technology has increased from 0.33 to 0.55 to realize finer patterning. High NA EUVL aims to enable 8 nm half pitch resolution. As the NA increases and a smaller linewidth needs to be implemented, the mask 3D effects on patterning will become more severe. For mass production of EUV, it is essential to find an optimal absorber structure to alleviate serious problems such as mask 3D effects and shadowing effects. Among the various factors constituting the EUV photomask, phase shift and reflectance of the absorber are the most important factors that determine the image quality. Through computational simulation, the optimal structure was selected in consideration of phase shift and reflectance, and imaging performance and process latitude were calculated.
One of the challenges to achieving high volume manufacturing (HVM) using extreme ultraviolet (EUV) is to improve the line width roughness of photoresist (PR). In EUV having high photon energy, the intensity of the light source is insufficient, and a large number of photons cannot enter the resist, and thus a fine pattern with small roughness cannot be made. Roughness is not determined by only one factor but is manifested by various and complex photochemical reactions such as non-uniform photon distribution, dose, acid diffusion, and the reaction of PR components. In the EUV lithography process, the roughness varies even under the same conditions owing to stochastic effects and random printing failures may occur. Ultimately, to develop PR that will be applied to the mass production of EUV, it is necessary to study the factors affecting roughness formation among various phenomena occurring inside the resist. Through computational simulation, line edge roughness and line width roughness were calculated by reflecting stochastic effects in various aspects such as the initial distribution of materials in PR, photon density, and acid. To implement a finer pattern using EUV lithography, we must alleviate roughness by controlling the acid diffusivity and chemical reaction of the quencher. On the other hand, the ionization energy, which affects the interaction between the electron energy and the acid, changed the acid generation efficiency, but as a result, did not significantly affect the roughness.
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