Fluorine-Rich Zinc Oxoclusters as Extreme Ultraviolet Photoresists: Chemical Reactions and Lithography Performance

Abstract

The absorption of extreme ultraviolet (EUV) radiation by a photoresist strongly depends on its atomic composition. Consequently, elements with a high EUV absorption cross section can assist in meeting the demand for higher photon absorbance by the photoresist to improve the sensitivity and reduce the photon shot noise induced roughness. In this work, we enhanced the EUV absorption of the methacrylic acid ligands of Zn oxoclusters by introducing fluorine atoms. We evaluated the lithography performance of this fluorine-rich material as a negative tone EUV photoresist along with extensive spectroscopic and microscopic studies, providing deep insights into the underlying mechanism. UV−vis spectroscopy studies demonstrate that the presence of fluorine in the oxocluster enhances its stability in the thin films to the ambient atmosphere. However, the EUV photoresist sensitivity (D 50 ) of the fluorine-rich oxocluster is decreased compared to its previously studied methacrylic acid analogue. Scanning transmission X-ray microscopy and in situ X-ray photoelectron spectroscopy in combination with FTIR and UV−vis spectroscopy were used to gain insights into the chemical changes in the material responsible for the solubility switch. The results support decarboxylation of the ligands and subsequent radical-induced polymerization reactions in the thin film upon EUV irradiation. The rupture of carbon−fluorine bonds via dissociative electron attachment offers a parallel way of generating radicals. The mechanistic insights obtained here will be applicable to other hybrid materials and potentially pave the way for the development of EUV materials with better performance.

A novel stable zinc–oxo cluster for advanced lithography patterning

“…19,20 Among the transition metals with 3d electrons, zinc (Zn)-based MOCs have gained much attention. The absorption cross section 21 of zinc–oxo clusters for 13.5 nm EUV 22,23 is an order of magnitude higher than that of organic polymers. Moreover, zinc–oxo clusters are nontoxic and in line with the concept of green lithography.…”

Novel hexameric tin carboxylate clusters as efficient negative-tone EUV photoresists: high resolution with well-defined patterns under low energy doses

“…There are three components corresponding to the sp 3 -and sp 2 -hydridized carbons together with the CO 2 -carbons, centered at 285.58, 287.00 and 289.72 respectively. 31 Aer EUV irradiation from 30 to 150 mJ cm −2 , a gradual 4-6% increase in the sp 2 -carbon contents is observed whereas the sp 3 -carbon loses 15-28% contents, and CO 2 -loss is up to 25-48%. This information indicates that decarboxylation reactions are the dominant pathway, but few vinyl tin groups can undergo radical polymerization to avoid a large loss of sp 3 -carbons.…”

Low-energy electron interaction with 2-(trifluoromethyl)acrylic acid, a potential component for EUVL resist material

“…This compound is chosen as an analog to the monomer unit of the widely used resist material poly-methyl methacrylate (PMMA) and its fluorinated derivatives that have in part shown good performance as potential EUVL resist materials, both in chemically amplified resists (CARs) 44,45 and as ligand components in metal-based oxo-clusters. 46 By using the acidic form of the methyl ester, the prerequisite for hydrogen bonding is provided and we show that this opens an efficient exothermic DEA channel. Furthermore, due to the strong inductive effect of the CF 3 group, we also expect the CH 2 hydrogens to be acidic and capable of hydrogen bonding to fluorine.…”