Changes in the near edge x-ray absorption fine structure of hybrid organic–inorganic resists upon exposure

Abstract

We report on the near edge x-ray absorption fine structure (NEXAFS) spectroscopy of hybrid organic-inorganic resists. These materials are nonchemically amplified systems based on Si, Zr, and Ti oxides, synthesized from organically modified precursors and transition metal alkoxides by a sol-gel route and designed for ultraviolet, extreme ultraviolet (EUV) and electron beam lithography. The experiments were conducted using a scanning transmission x-ray microscope (STXM) which combines high spatial-resolution microscopy and NEXAFS spectroscopy. The absorption spectra were collected in the proximity of the carbon edge (∼290 eV) before and after in situ exposure, enabling the measurement of a significant photo-induced degradation of the organic group (phenyl or methyl methacrylate, respectively), the degree of which depends on the configuration of the ligand. Photo-induced degradation was more efficient in the resist synthesized with pendant phenyl substituents than it was in the case of systems based on bridging phenyl groups. The degradation of the methyl methacrylate group was relatively efficient, with about half of the initial ligands dissociated upon exposure. Our data reveal that such dissociation can produce different outcomes, depending on the structural configuration. While all the organic groups were expected to detach and desorb from the resist in their entirety, a sizeable amount of them remained and formed undesired byproducts such as alkene chains. In the framework of the materials synthesis and engineering through specific building blocks, these results provide a deeper insight into the photochemistry of resists, in particular for EUV lithography.

Unravelling the effect of fluorinated ligands in hybrid EUV photoresists by X-ray spectroscopy

“…In particular, the soft X-ray energy range promotes electronic transitions from the carbon K-edge (1s orbital), which directly corresponds to the detection of changes in the carbon backbone of the organic ligands. [46][47][48] C K-edge NEXAFS spectroscopy was performed for the two materials, ZrMc and fluorine-doped ZrMcF. For each compound, a spectrum of the thin film before exposure to EUV light was recorded as reference (Fig.…”

“…2 displayed clear, sharp peaks corresponding to electronic transitions from the C 1s orbital on the CQC terminal bond to the p* orbital of the methacrylate ligand, C 1sp*(CQC), at B284 eV and to the electronic transitions from the 1s orbital of the C atom on the carboxylate group to the p* orbital, C 1sp*(CQO), at B288 eV. 46,49 The fits of the relevant peaks contributing to the NEXAFS spectra are shown in Fig. 2, and their assignments to electronic transitions are listed in Table 1.…”

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

“…To gain insights into the chemical changes upon EUV exposure in fluorine-rich Zn­(TFMA) oxocluster, ex situ X-ray absorption spectroscopy (XAS) studies were performed using the STXM at the PolLux beamline at PSI. ,, The changes in the material as a function of EUV dose were observed especially in the near-edge region of the C K-edge spectra as it provides quantitative information on the types and amount of covalent bonding present in organic components. The spectra were measured in transmission mode,and thus, the whole thin film thickness was probed.…”

The x-ray absorption spectroscopy analysis of the negative-tone PAG bound resist

“…Therefore, the chemical structure was estimated by comparing the peak intensity ratio before and after EUV exposed samples. 13 After EUV exposure, the functional groups decompose and disappear compared to the sample before EUV exposure, thus the peak intensity ratio needs to be normalized by the total carbon content in the resist film. However, in this study, the spectrum was not measured up to 350 eV, which is defined as the total carbon content in reference.…”

“…However, in this study, the spectrum was not measured up to 350 eV, which is defined as the total carbon content in reference. 13 Therefore, it was normalized by dividing by the sum of all the peak areas. The ratios of each peak intensities for π*C=C, π*C=O, and σ*C-F bonding divided by the sum of all peak intensities were summarized in Table 1.…”