Photoreactions of Tin Oxo Cages, Model EUV Photoresists

Abstract

Organotin oxo cage compounds have an electronic absorption band in the UV spectral range ( max ~220 nm) associated with a d electronic transition. Irradiation at 225 nm of thin films of these materials leads to loss of carbon, as shown by X-ray Photoelectron Spectroscopy. Photolysis of solutions of the compounds causes a decrease and slight broadening of the absorption band, consistent with replacement of the organic groups. Quantum chemical calculations support the breaking of the tin-carbon bonds as the primary process, both in electronically excited states and in oxidized states that can be expected to be the result of EUV photoionization.

Photo-induced Fragmentation of a Tin-oxo Cage Compound

“…The LUMO is located on the central belt of the cage and consists mainly of Sn d-orbitals. The tin cage was previously shown to undergo photoreactions upon 225 nm exposure in solution, but the photoproducts could not yet be firmly identified [22]. We aim here at shedding light onto the photofragmentation in the gas phase, i.e.…”

“…In an initial set of experiments, we exposed the tin cage to UV light ranging from 4 to 7 eV (310 nm to 177 nm). In this range the tin cage in solution shows a strong absorption centered around 220 nm [22]. The Highest Occupied Molecular Orbital (HOMO) is primarily located on the six-coordinated Sn atoms and has a Sn-C -bonding character.…”

Extreme ultraviolet patterning of tin-oxo cages

“…The chemical changes upon exposure to short-wavelength UV light are discussed elsewhere. 16,17 2 Materials and Methods…”

Photochemical conversion of tin-oxo cage compounds studied using hard x-ray photoelectron spectroscopy

“…According to quantum-chemical calculations, using density functional theory, the lowest electronically excited triplet state is of a σ → d type. 27 In this state, the Sn─C bond is easily broken to form two radicals. If present, oxygen and H 2 O can directly react with the Sn radicals and increase the oxidation states of Sn atoms, which corresponds to the results shown in Fig.…”