Tin based hybrid resist for Extreme UV Lithography

Full text: The semiconductor industry is continually focusing on the miniaturization of the transistors to increase the density of the integrated circuits (ICs). The Extreme Ultraviolet Lithography (EUVL) has been strongly suggested as a candidate to decrease the node dimensions lower than 10 nm [1]. The high energy of the EUV photons (13.5 nm) produces a high yield of secondary electrons which degrade the lithographic pattern. In the present work, a new resist was produced containing a heavy atom (tin) as a EUV absorption center in a polymeric formulation MAPDST-co-TPMA. Synchrotron radiation (SR) experiments were carried out at the Brazilian Synchrotron Light Source (LNLS). Electron beam lithography investigations were carried out using Raith eLine PLUS exposure tool. The films were irradiated at 103.5 eV during fixed periods of time between 15 and 300s. The XPS and NEXAFS showed a fast photofragmentation of the sensitive sulfoniumtriflate group and a typical polarity switch mechanism promoted by EUV radiation could be seen. The tin is directly bonded to three aromatic rings. The NEXAFS spectra showed that the aromatic rings were preserved even after 120s of irradiation. However, the ester groups were strongly affected by EUV radiation after 30s of irradiation. Although the tin was oxidized immediately after irradiation, its relative concentration keeps constant when the thin films were exposed for 300s. This preliminary e-beam investigation, as a prelude to EUVL, reveals that resolution enhancement of hybrid copolymer resist MAPDST-co- TPMA from 20 nm to 15 nm lines is mainly because of the attachment of inorganic tin unit in the poly(MAPDST) matrix. The above results may indicate that the incorporation of a heavy atom can decrease the dispersion of the energy on the resist leading to improvement of the lithography resolution. [1] S. Wang, et al, Chem. Soc. Rev. 46 (2017), 4855–4866. (author)