Development of metal-organic cluster based negative tone resist: pre-screened through the helium-ion beam prelude to extreme ultraviolet lithography (EUVL) applications

EUV lithography (EUVL) is expected to offer a single-exposure solution down to 5 nm or below nodes. To successfully implement EUVL for sub-10 nm nodes on time, one major hurdle is the availability of compatible resists with sufficiently low line edge/width roughness (LER/LWR) and low exposure dose. Hence, the requirements of high-resolution patterning along with sub 10 nm feature size necessitates nanocluster size resist materials with high irradiation absorption coefficients, considerably high sensitivity, and permissible LER and LWR. To meet the aforementioned requirements, we formulated a negative tone metal-core (indium and copper) organic clusters resists such as In-MOCs and Cu-MOCs having a nanosize domain. In-MOCs is comprised of indium core as an inorganic metal building unit and methacrylic acid (MAA) as an organic ligand while the Cu-MOCs is comprised of copper metal core and trans 2,3 dimethylacrylic acid (DMA) organic ligand through the versatile sol-gel method. The incorporation of indium and copper metal provides the enhanced absorption of irradiation beams, while the MAA and DMA in the formulated resist showing radical polymerization could be easily crosslinked through the carbon-carbon bond with the minimal amount of exposure dose of He+ ions to form a negative tone resist. The designed resists exhibit a significantly higher sensitivity of ~12.76 μC/cm2 and ~14.93 μC/cm2 towards the helium ion beam for In-MOCs and Cu-DMA resists, respectively. The well-resolved half-pitch features of ~13 nm and the minimum line width of ~11 nm L/2S with the substantial helium-ion dose of ~30 μC/cm2 for In-MOCs resist, whereas, the well-resolved high resolution (HR) ~ 10 nm half-pitch (HP) and ~9 nm (L/2S) line patterns at a considerable He+ dose of ~35 μC/cm2 for Cu-DMA resist. The calculated LER and LWR for 13 nm half-pitch patterns are 2.56 ± 0.06 nm and 2.48 ± 0.08 nm, respectively for In-MOCs resist, while the computed line edge roughness (LER), line width roughness (LWR) for HR~10 nm (HP) line patterns are 2.24 ± 0.08 nm and 3.1 ± 0.09 nm, respectively for Cu-DMA resist.