In this work, we report the lithography performance of main chain scission type resists exposed with the ASML NXE3300B EUV scanner. We also detail the advancements achieved in recent developments of the novel process conditions and the polymer properties of main chain scission type resist. With optimized resist thickness and resist developer, a resolution of 16 nm half-pitch for dense line-space pattern can be achieved with a low roughness but with a high dose over 70 mJ/cm2 is required for ZER01 series (based on Zeon’s resists for EB lithography). Therefore, Zeon developed ZER02 series (Zeon’s novel resists) for EUV lithography, with a modified polymer structure improving the EUV absorption. The lithographic capabilities of dense Line-Space (L/S) patterns and orthogonal contact hole (C/H) patterns with ZER02#1 is presented. For L/S pattern, a resolution of 16 nm half pitch was achieved at an exposure dose of 57 mJ/cm2, giving an unbiased LWR of 2.7 nm and an unbiased LER of 2.0 nm. For orthogonal C/H pattern, 44 nm pitch was resolved at 50.4 mJ/cm2, with a LCDU of 3.4 nm. In addition to the enhancement of the lithographic performance achieved, fundamental studies with Gel Permeation Chromatography (GPC) and Dissolution Rate Monitor (DRM) were conducted to understand the pattering mechanism of ZER02#1 under EUV exposure.
The interaction of 91.6 eV EUV photons with photoresist – in particular chemically amplified resist (CAR) – is different than exposure at 193 nm and 248 nm wavelengths. The latter is understood well and it is known that photons interact with electrons in the resist’s molecular valence orbitals (for chemically amplified resist (CAR) the photon interacts with the photo acid generator (PAG), which leads to a deprotection reaction on a polymer after a thermal catalytic reaction during a post-exposure-bake.). At EUV however, more steps are involved in the radiolysis process between the absorption of the photon and the final chemical modification. These are related to the generation of primary electrons and their decay to lower energy secondary electrons, and most of this steps are not well understood. In this paper, the reaction products from EUV and low energy electron exposure are examined using Residual Gas Analysis (RGA), which measures and analyzes the outgassing products related to the ongoing reactions. This investigation is applied firstly on a model CAR where details of the resist chemical constituents were known prior to testing. The measurement not only resolved information on the expected acid related reactions from the PAG and protection groups, but also exhibited direct scission reactions of the polymer, where some of them lead to polymerization reactions. Moreover, the measurement quantifies the balance between the different ongoing reactions, which were confirmed by contrast curve measurements. Based on learnings on the model resist, applied the measurement technique to commercial resists, where actual resist chemistry composition is not known. Despite that, it was found that information could be deduced to distinguish between acid related ongoing reactions and direct scission of reaction on the base polymer and quantify their relation. Moreover, different generations of commercial resists based on similar chemistry platform were investigated, which revealed that improvements in printing performance could be explained by PAG reaction yield increase.