Directed self-assembly (DSA) of high-χ block copolymer thin films is a promising approach for nanofabrication of features with length scale below 10 nm. Recent work has highlighted that kinetics are of crucial importance in determining whether a block copolymer film can self-assemble into a defect-free ordered state. In this work, different strategies for improving the rate of defect annihilation in the DSA of a silicon-containing, high-χ block copolymer film were explored. Chemo-epitaxial DSA of poly(4-methoxystyrene-block-4-trimethylsilylstyrene) with 5× density multiplication was implemented on 300 mm wafers by using production level nanofabrication tools, and the influence of different processes and material parameters on dislocation defect density was studied. It was observed that only at sufficiently low χN can the block copolymer assemble into well-aligned patterns within a practical time frame. In addition, there is a clear correlation between the rate of the lamellar grain coarsening in unguided self-assembly and the rate of dislocation annihilation in DSA. For a fixed chemical pattern, the density of kinetically trapped dislocation defects can be predicted by measuring the correlation length of the unguided self-assembly under the same process conditions. This learning enables more efficient screening of block copolymers and annealing conditions by rapid analysis of block copolymer films that were allowed to self-assemble into unguided (commonly termed fingerprint) patterns.
Limitations on current performances of the chemically amplified resists (CAR), as well as the productivity driven low exposure dose requirements (below 20 mJ/cm 2 ), have brought the researchers to look at a novel class of materials as possible alternative to the CA resists to simultaneously achieve resolution, line-width roughness (LWR) and sensitivity. In 2014, imec has started a new project to look into novel materials for EUV lithography with particular attention to metal containing materials (MCR) to explore alternative approaches that can offer superior characteristics in photoresist imaging: improved LWR and line collapse, high sensitivity and high etch resistance. In this paper we report the first assessment on the enablers of the MCRs from a manufacturing compatibility prospective, as metal cross-contamination and outgassing, to a device integration prospective through the patterning on the ASML NXE:3300 full field scanner exposure tool, the etch performances and new litho-etch integration scheme for 1x nm technology and below. The results obtained are highly promising and give a clear indication that other chemical paths in novel resist formulations are possible in advanced EUV lithography.
In the last years, the continuous efforts on the development of extreme ultraviolet (EUV) lithography has allowed to push the lithographic performance of the EUV photoresists on the ASML NXE:3300 full field exposure tool and today both chemically amplified (CAR) and metal-oxide (MOR) EUV photoresists have been introduced for patterning imec's 7nm node critical layers. However, the HVM requirement to have a cost-effective high sensitivity photoresist (< 20 mJ/cm 2 ) still remains a big challenge and further efforts are needed to improve the photoresist sensitivity without affecting resolution and patterning quality. In this work, we present the results of the best performing photoresists (both CAR and MOR) at low exposure dose for dense line-space patterns at 32nm pitch, dense contact holes at 36nm pitch and dense pillars at 38nm pitch, reporting the most critical patterning challenges for the investigated structures. Furthermore, we discuss the role of the substrate underneath the EUV photoresist and its impact on the lithographic EUV process setup from both patterning and light-matter interaction standpoint. Finally, we introduce the tone reversal process (TRP) as alternative capability for pillar patterning.
Double patterning technology (DPT) is a promising technique that bridges the anticipated technology gap from the use of 193nm immersion to EUV for the half-pitch device node beyond 45nm. The intended mask pattern is formed by two independent patterning steps. Using DPT, there is no optical imaging correlation between the two separate patterning steps except for the impact from mask overlay. In each of the single exposure step, we can relax the dense design pattern pitches by decomposing them into two half-dense ones. This allows a higher k 1 imaging factor for each patterning step. With combined patterns, we can achieve overall k 1 factor that exceeds the conventional Rayleigh resolution limit. This paper addresses DPT application challenges with respect to both mask error factor (MEF) and 2D patterning. In our simulations using DPT with relaxed feature pitch for each exposure step, the MEF for the line/space is fairly manageable for 32nm half-pitch and below. The real challenge for the 32nm half-pitch and below with DPT is how to deal with the printing of small 2D features resulting from the many cutting sites due to feature decomposition. Each split of a dense pattern generates two difficult-to-print line-end type features with dimension less than one-fifth or onesixth of ArF wavelength. Worse, the proximity environment of the 2D cut features can then become quite complex. How to stitch them correctly back to the original target requires careful attention. Applying target bias can improve the printing performance in general. But using a model-based stitching error correction method seems to be a preferred solution.
The evolutionary advances in photosensitive material technology, together with the shortening of the exposure wavelength in the photolithography process, have enabled and driven the transistor scaling dictated by Moore’s law for the last 50 years. Today, the shortening wavelength trend continues to improve the chips’ performance over time by feature size miniaturization. The next-generation lithography technology for high-volume manufacturing (HVM) is extreme ultraviolet lithography (EUVL), using a light source with a wavelength of 13.5 nm. Here, we provide a brief introduction to EUVL and patterning requirements for sub-0-nm feature sizes from a photomaterial standpoint, discussing traditional and novel photoresists. Emphasis will be put on the novel class of metal-containing resists (MCRs) as well as their challenges from a manufacturing prospective.
In the last years the continuous efforts on the development of EUV lithography has allowed to push the lithographic performances of the EUV photoresists on the ASML NXE:3100 full field exposure tool at imec. The latest chemically amplified photoresists can reach an ultimate resolution of 16 nm and 24 nm for line-space (L/S) and dense contacts (CH), respectively, but the major issue on EUV photoresists remains to simultaneously meet resolution, sensitivity, line-edge roughness (LER) for LS and local CD uniformity (LCDU) for CH, suggesting that the desired performance characteristics of EUV photoresists may require the development of new EUV materials. Aiming to this, imec has recently started a new project to look into novel materials for EUV lithography to explore alternative approaches that can offer superior characteristics in photoresist imaging: improved LER and line collapse, high sensitivity and high etch resistance. In this paper we report the first results from the exploration of new EUV alternative materials and the latest results from the conventional EUV photoresist evaluation and process optimization at imec towards the ASML NXE:3300 full field exposure tool.
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