Gestuurde zelfassemblage van blokcopolymeren als aanvulling voor extreem ultraviolet lithografie

Further downscaling of integrated circuit components requires semiconductor industry to innovate as the current workhorse, i.e. 193 nm immersion lithography, is reaching its limits. Single exposure EUV lithography (13.5 nm) is quickly advancing as next generation lithography method. However, the high energy of EUV light imposes several challenges. Besides a completely new exposure tool design, photon shot noise and secondary electron blur necessitate a novel photoresist design, as the current workhorse, chemically amplified resist, suffers from subsequent stochastic issues. Multipatterning techniques extended the capabilities of the EUV lithography predecessor, ArF immersion (ArFi) lithography, but introduced a high process complexity. In this thesis, the possibilities of complementing EUV lithography with block copolymer (BCP) directed self-assembly (DSA) are explored to overcome the stochastic issues associated with EUV patterning. BCPs can self-assemble into microchip-relevant lamellar or cylindrical structures with domain sizes ranging from 3 to 80 nm. The necessary orientational and translational order is induced in the BCP pattern by a photolithography-based guide pattern. As the BCP pattern defines the final pattern quality, it can be used to rectify EUV lithography patterns. Earlier studies focused on the pattern density multiplication ability of DSA. Starting from an ArFi lithography guide pattern, a threefold increase in pattern density could be achieved by applying a suitable BCP system, reaching EUV resolution. The introduction of commercial EUV lithography tools raised interest again in the pattern rectification ability of BCP DSA. The compatibility of EUV lithography and BCP DSA has been proven in the literature; however, at the start of this thesis, a flow combining the two had not been developed in a high-volume manufacturing compatible fab. We successfully set up an EUV + DSA process flow creating pitch 28-nm line space patterns by utilizing a polar surface treatment that modifies the surface energy of a cross-linked polystyrene underlayer in the trenches of an EUV resist pattern, thereby creating a guide pattern for PS-b-PMMA. PS-b-PMMA is a frequently used BCP for DSA applications. This EUV + DSA flow was used as an experimental base flow throughout this thesis. The transition of EUV + DSA to the fab allowed for a systematic study of its patterning performance and evaluation of its potential to reach the high-volume manufacturing targets of resolution, roughness and defectivity. Our study learns that the line edge roughness can be significantly improved by optimizing DSA material and process parameters. In particular, the most critical parameters are the BCP periodicity and BCP film thickness. Regarding defectivity, a combination of optical inspection and electron beam review pointed out that the BCP annealing temperature, as well as the chemistry and geometry of the guide pattern, play a key role. To conclude, a comparative study was conducted between our EUV + DSA process flow (1X DSA) and the previous ArFi + DSA process flow (3X DSA), both generating patterns with equal resolution. It reveals that the all-guided pattern of 1X DSA leads to more uniform and lower line roughness, as well as faster assembly kinetics. As a consequence of the fast assembly kinetics, DSA-specific dislocation defects could be eliminated from EUV + DSA patterning. The pattern rectification ability of EUV + DSA with respect to the EUV lithography guide pattern was studied by examining the EUV defect healing probability of BCP DSA. Artificial EUV defects provided a practical study case. Our strategy of studying these defects before and after DSA with scanning electron microscopy revealed that DSA can effectively restore the line space pattern for all EUV stochastic issues and other EUV defects up to three periods in size within three minutes. Contributing significantly to the healing of EUV defects and thus limiting defects in the BCP pattern are similar BCP and guide pattern pitch, higher BCP annealing temperatures and increased BCP guiding strength. Another critical parameter is again the BCP film thickness. Increasing the BCP film thickness eliminates all investigated artificial EUV defects in the BCP pattern. For EUV + DSA to be viable for implementation in high-volume manufacturing, the throughput of this process flow must be increased. Resist-assisted DSA appears promising, and one successful guide pattern for PS-b-PMMA DSA patterning is using a thin layer of patterned EUV Multi-Trigger Resist, neutral toward both blocks, on top of a cross-linked polystyrene underlayer. Line space patterns with similar roughness values to those of the earlier EUV + DSA patterns can be achieved with this simplified process flow. This new flow enables all-track processing, reducing the number of process steps before pattern transfer from five to three and the number of processing tools from four to two. This thesis provides insight from a high-volume manufacturing perspective on the patterning performance, possibilities, and BCP behavior of EUV + DSA. While the specifications for high-volume manufacturing have not yet been achieved, several pathways for improvement of the patterning performance and throughput are presented. These learnings can be applied to the design of EUV + DSA for future patterning applications.