Ambient-Pressure X-ray Photoelectron Spectroscopy Characterization of Radiation-Induced Chemistries of Organotin Clusters

Abstract

Advances in extreme ultraviolet (EUV) photolithography require the development of next-generation resists that allow high-volume nanomanufacturing with a single nanometer patterning resolution. Organotin-based photoresists have demonstrated nanopatterning with high resolution, high sensitivity, and low-line edge roughness. However, very little is known regarding the detailed reaction mechanisms that lead to radiation-induced solubility transitions. In this study, we investigate the interaction of soft Xray radiation with organotin clusters to better understand radiation-induced chemistries associated with EUV lithography. Butyltin Keggin clusters (β-NaSn 13 ) were used as a model organotin photoresist, and characterization was performed using ambient-pressure X-ray photoelectron spectroscopy. The changes in relative atomic concentrations and associated chemical states in β-NaSn 13 resists were evaluated after exposure to radiation for a range of ambient conditions and photon energies. A significant reduction in the C 1s signal versus exposure time was observed, which corresponds to the radiation-induced homolytic cleavage of the butyltin bond in the β-NaSn 13 clusters. To improve the resist sensitivity, we evaluated the effect of oxygen partial pressure during radiation exposures. We found that both photon energy and oxygen partial pressure had a strong influence on the butyl group desorption rate. These studies advance the understanding of radiation-induced processes in β-NaSn 13 photoresists and provide mechanistic insights for EUV photolithography.

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

“…The ESI-MS spectrum of the tin-oxo cage compound was reported earlier by Dakternieks and coworkers, 32 who observed a main peak at m/z 1218, assigned to the dication [(nBuSn) 12 -O 14 (OH) 6 ] 2+ . This result was reproduced in our experiments (see ESI, † Fig.…”

“…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.…”

XUV Induced Bleaching of a Tin Oxo Cage Photoresist Studied by High Harmonic Absorption Spectroscopy

“…Cardineau et al [11] were the first to study tin oxo cages as EUV photoresists, and suggested that tincarbon bond cleavage is the key step in the radiation induced reactions. This model is also supported by computational [12] and experimental studies in more recent work [13][14][15]. Hinsberg and Meyers [16] proposed a numerical model describing the reaction process in metal oxide-based resists.…”

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

“…We use the tin density for a 20 nm thick β-NaSn 13 film, which was obtained by Rutherford back scattering, to estimate the initial butyl group coverage (θ 0 ) as ∼8.9 × 10 15 butyl groups/cm 2 . 25 Simplified equations derived from the transition-state theory 26 allow us to calculate reasonable values for ν at the desorption temperature T p = 696 K and chain length N = 4. This analysis yields ν min = 7.3 × 10 15 s −1 and ν max = 1.1 × 10 21 s −1 .…”