Effect of Oxygen on Thermal and Radiation-Induced Chemistries in a Model Organotin Photoresist

Abstract

Organotin photoresists have shown promise for next-generation lithography because of their high extreme ultraviolet (EUV) absorption cross sections, their radiation sensitive chemistries, and their ability to enable highresolution patterning. To better understand both temperatureand radiation-induced reaction mechanisms, we have studied a model EUV photoresist, which consists of a charge-neutral butyl−tin cluster. Temperature-programmed desorption (TPD) showed very little outgassing of the butyl−tin resist in ultrahigh vacuum and excellent thermal stability of the butyl groups. TPD results indicated that decomposition of the butyl−tin resist was first order with a fairly constant decomposition energy between 2.4 and 3.0 eV, which was determined by butyl group desorption. Electron-stimulated desorption (ESD) showed that butyl groups were the primary decomposition product for electron kinetic energies expected during EUV exposures. X-ray photoelectron spectroscopy was performed before and after low-energy electron exposure to evaluate the compositional and chemical changes in the butyl−tin resists after interaction with radiation. The effect of molecular oxygen during ESD experiments was evaluated, and it was found to enhance butyl group desorption during exposure and resulted in a significant increase in the ESD cross section by over 20%. These results provide mechanistic information that can be applied to organotin EUV photoresists, where a significant increase in photoresist sensitivity may be obtained by varying the ambient conditions during EUV exposures.

UV and VUV-induced fragmentation of tin-oxo cage ions

“…To achieve sufficient photon absorption in thin films, and potentially higher etch resistance, metal-containing photoresist materials have been proposed as alternatives. [7][8][9][10][11][12][13] An example of an organometallic photoresist material is the tin-oxo cage (see Fig. 1), 14,15 first described by Puff and Reuter in 1989.…”

Role of low-energy electrons in the solubility switch of Zn-based oxocluster photoresist for extreme ultraviolet lithography

“…More recently, MS was also applied to investigate the electron-induced chemistry of Sn oxoclusters as an example of metal-containing molecular resist. 9,23 In these studies, electron-stimulated desorption (ESD) experiments revealed that 80 eV electrons can induce fragmentation of ligands from the clusters and showed how the structure of the cluster affects the efficiency for removal of particular ligands upon electron impact. 23 As a novel example of metal-oxoclusters, Zn-tetranuclear oxoclusters surrounded by trifluoroacetate (TFA) and methacrylate (MA) ligands (Zn(MA)(TFA)) (Fig.…”

“… 9,23 In these studies, electron-stimulated desorption (ESD) experiments revealed that 80 eV electrons can induce fragmentation of ligands from the clusters and showed how the structure of the cluster affects the efficiency for removal of particular ligands upon electron impact. 23 …”

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

“…During the scattering, more molecules can be ionized so that secondary electrons are generated, which have a broad distribution of kinetic energies in the 0-80 eV range. 14 Therefore, the chemistry induced by EUV photons is the result of the electron-induced chemistry [17][18][19] and the chemical a Advanced Research Center for Nanolithography, Science Park 106, processes that the ionized molecules undergo. Furthermore, the probability of absorbing EUV photons by molecules is mainly determined by their elemental composition rather than by the selection rules based on the characteristics of the frontier molecular orbitals that apply in photochemistry.…”