Hybrid metal−organic cluster resist materials, also termed as organo-inorganics, demonstrate their potential for use in next-generation lithography owing to their ability for patterning down to ∼10 nm or below. High-resolution resist patterning is integrally associated with the compatibility of the resist and irradiation of the exposure source. Helium ion beam lithography (HIBL) is an emerging approach for the realization of sub-10 nm patterns at considerably lower line edge/width roughness (LER/ LWR) and higher sensitivity as compared to electron beam lithography (EBL). Here, for the first time, a negative tone resist incorporating nickel (Ni)-based metal−organic clusters (Ni-MOCs) was synthesized and patterned using HIBL and EBL at 30 keV. This resist comprises a nickel-based metal building unit covalently linked with the organic ligand: m-toluic acid (C 8 H 8 O 2 ). Dynamic light scattering confirmed a narrow size distribution of ∼2 nm for metal−organic cluster (MOC) formulations. High-resolution ∼9 nm HIBL line patterns were well developed at a sensitivity of 22 μC/cm 2 and at a significantly low LER and LWR of 1.81 ± 0.06 and 2.90 ± 0.06 nm, respectively. Analogous highresolution patterns were also observed in EBL with a sensitivity of 473 μC/cm 2 . Hence, the Ni-MOC-based resist investigated using HIBL and EBL elucidates the ability of its potential for the sub-10 nm technology node, under standard processing conditions.

Given the current need for resist materials for patterning transistors with ultralow nodes, there has been a quest for developing resists with improved performance for nanoscale patterning with good contrast. The present work demonstrates polymeric resists (MAPDST-TIPMA) developed through the integration of a radiation-sensitive monomer (MAPDST) with an organoiodine functionality (TIPMA) for sub-16 nm patterning using electron-beam and helium ion beam lithography. The structural integrity was established by several spectroscopic techniques particularly NMR, FTIR, XPS, and GPC. These polymeric resists possess weight-average molecular weight (M w) in the range of 10000–12000 with low PDI. While the resists 3a and 3b were synthesized with feed ratios of 80:20 and 70:30 of the monomers MAPDST and TIPMA, respectively, the actual microstructure compositions were calculated, using XPS and GPC data, to be ∼94:6 and 91:9, respectively. The present resists have the potential for patterning 16 nm line/space features when exposed to e-beam. Also, 15 nm features were successfully patterned using MAPDST-TIPMA resists. The line edge roughness (LER) and line width roughness (LWR) of the 20 nm L/3S features were calculated to be 2.48 and 3.6 nm, respectively. Moreover, complex nanofeatures of different shapes were successfully patterned using 3b. A critical analysis of nanofeatures using AFM revealed that the patterns are very well developed with a sharp wall profile. The normalized resist thickness (NRT) curve was established to evaluate the sensitivity of the present resist which was calculated to be 341 μC/cm2 at 20 keV. The nature and slope of the NRT curve indicated that MAPDST-TIPMA is a negative tone resist with good contrast. Finally, the resist was found to be highly sensitive to He+ beam (sensitivity ∼6.21 μC/cm2) resulting in 20 nm L/S as well as 15 nm features with a good wall profile.

Since the fabrication of micro-/nanoelectronic devices are marching toward ultralow node technology with dense patterns to meet the current industry demands, continuous advancement is needed in terms of material design and lithographic techniques. In this perspective, helium ion beam lithography (HIBL) has gained tremendous attention of the scientific society to realize high-performance device fabrication with advanced technology. Salient features of the helium ion beam including sub-nanometer spot size, high-intensity lighter ion (with respect to gallium and neon ions) make the HIBL technique a competitive next-generation lithography tool. This review describes, in brief, the significance of HIBL technology in comparison with electron beam lithography (EBL); however, it presents in detail the development made in the area of resists for HIBL. One of the important characteristics of He + beam is, reduced backscattering leads to minimizing the proximity effects in contrast with EBL. Furthermore, it emphasizes the developments of various resist materials to perform high-resolution patterns at comparable line-edge roughness/line-width roughness (LER/LWR) values. HIBL performances of various classes of materials are presented here to give a overall conception of the technique. The materials including organic, inorganic, organic−inorganic hybrids, and nanoscale materials which have shown promising patterning under He + beam irradiation have been included and discussed in this work.

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