Thin absorber extreme ultraviolet photomask based on Ni–TaN nanocomposite material

Abstract

We study the use of random nanocomposite material as a photomask absorber layer for the next generation of extreme ultraviolet (EUV) lithography. By introducing nickel nanoparticles (NPs) randomly into a TaN host, the nanocomposite absorber layer can greatly reduce the reflectivity as compared with the standard TaN layer of the same thickness. Finite integral simulations show that the reduction in the reflectivity is mainly due to the enhanced absorption by the Ni NPs. The fluctuation in reflectivity induced by scattering and random position of the NPs is found to be on the order of 0.1%. Based on these observations, we build an effective medium model for the nanocomposite absorber layer and use the transfer matrix method to identify optimal absorber designs that utilize cavity effects to reduce the required volume fraction of Ni NPs. We further perform a process simulation and show that our approach can greatly reduce the HV bias in the lithography process.

Attenuated phase shift mask for extreme ultraviolet: can they mitigate three-dimensional mask effects?

“…7 Ni is a typical high-k metal absorber example, which has been investigated in previous studies. 5,8,9 AttPSM1 stands for an "ideal" attenuated phase shifter material, which was designed based on standard thin-film considerations [see Eq. 1].…”

Comparative study of extreme ultraviolet absorber materials using lensless actinic imaging

“…4,16 However, obtaining thin, smooth, and defect-free Ni layers on ML stacks without damaging the ML is extremely difficult. 17,18 Also, in the case of HSQ, the index of refraction depends on the development parameters after electron beam exposure, as density and composition may vary. 19 The given range corresponds to a density between 1.57 and 2.17 g∕cm 3 .…”

Nanoscale focused electron beam induced etching of nickel using a liquid reactant

“…Consequently, different materials have been investigated as an EUV absorber layer [28][29][30], including Al-Cu, Cr, Ta, TaN Ti, and TiN in which material properties such as film stress and etch selectivity have been considered [31]. Among all the studied materials, nickel has gained significant interest as an absorber layer due to its high absorption coefficient in the 13.5 nm region [32][33][34][35][36][37][38][39].…”