Synthesis of pentameric chlorotin carboxylate clusters for high resolution EUV photoresists under small doses.

This work reports the synthesis and characterization of a novel pentameric tin chloro cluster, (vinylSn)3Sn2Cl5O2(OH)2(t-BuCO2)6 (1), and explores its application as an efficient negative-tone photoresist in a 1 : 2 weight ratio blend with [(n-BuSn)12O14(OH)6](BF4)2 (2). Through e-beam lithography, a small high-resolution pattern (HP = 20 nm) is achieved for the blend photoresist (3) at a dose of 2080 µC cm-2. Additionally, EUV lithography demonstrates the development of a high-resolution pattern (HP = 16 nm) at an EUV dose of 70 mJ cm-2. Mechanistic studies by reflective FTIR indicate a significant decomposition of Sn-carbon and SnO2(t-Bu) moieties starting at J = 35 mJ cm-2, which is accompanied by growth of the Sn-O absorption intensity. A collapse of the cluster frameworks of clusters (1) and (2) is observed at J > 70 mJ cm-2. High-resolution X-ray photoelectron spectroscopy (HRXPS) reveals that low EUV light predominantly decomposes Sn-butyl and Sn-Cl bonds. As EUV doses increase, primary photolytic reactions involve cleavage of Sn-butyl, Sn-O2CBut, and Sn-vinyl bonds. Notably, the photolytic decomposition of Sn-Cl bonds is distinctive, with only two out of five bonds being cleaved, even at high EUV doses, resulting in a break in film growth at J = 27-35 mJ cm-2 in the EUV contrast curve. Moreover, HRXPS analysis suggests that radical propagation on the vinyltin end of the blend is unlikely, providing concise mechanistic insights into the photochemical processes governing the behavior of this advanced photoresist.

Highly hydroxylated hafnium clusters are accessible to high resolution EUV photoresists under small energy doses.

This work reports the success in accessing high-resolution negative-tone EUV photoresists without radical chain growth in the aggregation mechanism. The synthesis of a highly hydroxylated Hf6O4(OH)8(RCO2)8 cluster 3 (R = s-butyl or s-Bu) is described; its EUV performance enables high resolution patterns HP = 18 nm under only 30 mJ cm-2. This photoresist also achieves high resolution patterns for e-beam lithography. Our new photoresist design to increase hydroxide substitutions of carboxylate ligands in the Hf6O4(OH)4(RCO2)12 clusters improves the EUV resolution and also greatly reduces EUV doses. Mechanistic analysis indicates that EUV light not only enables photolytic decomposition of carboxylate ligands, but also enhances the Hf-OH dehydration. One additional advantage of cluster 3 is a very small loss of film thickness (ca. 13%) after the EUV pattern development.

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

Synthesis of two novel tin carboxylate clusters (RSn)6(R'CO2)8O4Cl2 is described, and their structures have been characterized by X-ray diffraction. These clusters have irregular ladder geometry to form very smooth films with small surface roughness (RMS <0.7 nm) over a large domain. EUV lithography can be used to resolve half pitches (HPs) in the order of 15-16 nm with line width roughness (LWR = 4.5-6.0 nm) using small doses (20-90 mJ cm-2). Cluster 1 (R = n-butyl; R'CO2 = 2-methyl-3-butenoate) contains only a radical precursor and cluster 2 (R = vinyl, R'CO2 = 2-methylbutyrate) bears both a radical precursor and an acceptor; the latter is much better than the former in EUV and e-beam photosensitivity. For these clusters, the mechanisms of EUV irradiation have been elucidated with high resolution X-ray photoelectron spectroscopy (HRXPS) and reflective Fourier-transform infrared spectroscopy (FTIR). At low EUV doses, two clusters undergo a Sn-Cl bond cleavage together with a typical decarboxylation to generate carbon radicals. The n-butyl groups of cluster 1 are prone to cleavage whereas the vinyl-Sn bonds of species 2 are inert toward EUV irradiation; participation of radical polymerization is evident for the latter.

Embedded Micro-detectors for EUV Exposure Control in FinFET CMOS Technology.

An on-wafer micro-detector for in situ EUV (wavelength of 13.5 nm) detection featuring FinFET CMOS compatibility, 1 T pixel and battery-less sensing is demonstrated. Moreover, the detection results can be written in the in-pixel storage node for days, enabling off-line and non-destructive reading. The high spatial resolution micro-detectors can be used to extract the actual parameters of the incident EUV on wafers, including light intensity, exposure time and energy, key to optimization of lithographic processes in 5 nm FinFET technology and beyond.

Detectors Array for In Situ Electron Beam Imaging by 16-nm FinFET CMOS Technology.

A novel in situ imaging solution and detectors array for the focused electron beam (e-beam) are the first time proposed and demonstrated. The proposed in-tool, on-wafer e-beam detectors array features full FinFET CMOS logic compatibility, compact 2 T pixel structure, fast response, high responsivity, and wide dynamic range. The e-beam imaging pattern and detection results can be further stored in the sensing/storage node without external power supply, enabling off-line electrical reading, which can be used to rapidly provide timely feedback of the key parameters of the e-beam on the projected wafers, including dosage, accelerating energy, and intensity distributions.