We present the results of high-NA (0.55 NA) exposure using dry resist for various use cases such as aligned T2T structure, logic metal PnR (place and route) and memory bit-line-periphery (BLP) - storage node landing pad (SNLP) DRAM structures. In single exposure, we successfully print dark field metal logic PnR down to P20 nm, with T2T CD similar to 19 nm and LCDU 3 sigma similar to 4 nm. For dark field regular T2T structure, a LCDU 3 sigma of similar to 3.5 nm is demonstrated for P28 nm T2T CD similar to 13 nm, while for P20 LCDU 3 sigma of similar to 3.8 nm is achieved for T2T CD similar to 16 nm. For the memory DRAM use case, we demonstrate patterning of BLP and SNLP in a single EUV exposure at pitch 28 nm having dose reduced by similar to 40% with respect to 0.33 NA P34 nm single exposure. We also demonstrate the on-wafer depth of focus (DoF) increase by pupil optimization. Our results indicates that the high NA single exposure can be a potential solution to replace complex multipatterning technology.

Background: Recently, High Numerical Aperture Extreme Ultraviolet Lithography (High NA EUVL) started delivering its first wafers, showing its potential by printing 18 and 16nm pitch line/space. However, as features size is dropping below 10nm, questions are raised on the ability of the current metrology procedures and tools to properly characterize such small targets. In particular, it is critical to assess the impact of limited spatial resolution and identify possible ways forward. Aim: A high-resolution, low damage strategy based on high Landing Energy (LE) is proposed. Approach: High LE setting (15keV) and standard low LE (500eV) best-known methods are compared using both rigorous simulation and experiments. The comparison is performed for Metal Oxide Resist as well as for Chemical Amplified Resist, After Development Inspection (ADI) and After Etch Inspection (AEI). Results: Our results indicated that the 15keV setting provides 3x better resolution and less ADI damages as compared to the 500eV setting. AEI damages, throughput and precision are comparable. Conclusions: Using high LE provides the needed resolution for High NA EUVL, with similar or better impact in terms of damages compared to low LE.

2024 will be recorded as the year where the first 0.55 High Numerical Aperture (HNA) wafer was first exposed using an Extreme Ultraviolet (EUV) scanner. In this presentation, we will dive into the initial findings from our dedicated defectivity wafers using the High NA scanner. Firstly, we will look at the printability and evolution of the programmed defects (PD) from mask to wafer through the two main patterning steps: after lithography (ADI) and after etching (AEI) into the TiN hard mask. The objective is to study the evolution of the defect surface and its progression through various sizes and shapes. Subsequently, we will discuss the potential surge of specific defect types, including microbridges, stochastic defects, and line edge roughness variations, which arise from higher resolution and tighter failure-free latitude. Additionally, the asymmetry on mask in horizontal features (with an 8x magnification in Y compared to 4x in X) might introduce different defect mechanisms. To characterize those, we use a combination of multiples tool and techniques such as optical inspection for large areas and ebeam tools for failure free latitude determination.

Extreme Ultraviolet (EUV) patterning technology was deployed for the mass production of 7nm logic devices in 2018 and recently achieved 5nm. The demand for device scaling has produced more complex processes and expensive multiple-patterning requirements. Broad consensus on the direction of EUV technology has triggered the semiconductor industry to aggressively push new resist material development, particularly designed to overcome stochastic issues, which coincides with the establishment of the single-print capability infrastructure for the high numerical aperture (NA) EUV scanner. Although standard chemically amplified resists (CAR) have been struggling to overcome stochastic issues, they have improved significantly to demonstrate 24nm resolution with single exposure patterning using ASML's NXE3400B. At the point of use filtration, ultrahigh molecular weight polyethylene (UPE) filters have been widely used to eliminate traditional sources of defectivity, such as particles and aggregates in photoresist materials thanks to their high retention efficiency and excellent photochemical compatibility. However, newly designed UPE filters with innovative membrane morphology are needed to further lower defectivity rates. This paper describes our efforts to optimize filtration and improve photoresist defectivity. A comparative study of the patterning performance of various POU filters is presented. Several filters utilizing a variety of retention ratings and membrane designs were installed on a TEL Clean TrackTM Lithius ProTM Z series. An EUV CAR resist was filtered and coated on wafers that were subsequently exposed, etched in hardmask stack, and analyzed for patterning defect performance. This study examines the efficacy of optimized filter design to reduce defects and provides a recommendation to achieve lower defect density.

Extreme Ultraviolet lithography with a numerical aperture of 0.55 will bring an improved optical contrast for contact hole layers and via layers. This improved optical contrast should lead to a reduction in the number of stochastic defects for these layers. To quantify this reduction, an adequate inspection methodology is required that can detect, in addition to the standard missing and merging defects, contact holes that are only partially opened. In this work we demonstrate a technique that uses backscattered electrons to detect these defects. In the first phase the beam-settings in a top-down scanning electron microscope are optimized to visualize holes that have been confirmed to be partially opened contact holes by either voltage contrast or transmission electron microscope. In the second phase these beam conditions are implemented on a massive metrology e-beam tool that has an increased throughput and therefore can collect information on millions of contact holes. In the last phase we show how this inspection can be used to enlarge the failure free latitude on a 36nm hexagonal contact hole pattern and to optimize the litho and etch conditions to minimize the number of stochastic defects on product wafers.

In this paper we will present initial results for logic and memory features imaged with the TWINSCAN EXE:5000 at the ASML-imec high NA lab after successful etch pattern transfer. For logic applications random logic metal designs (consisting of tight pitches and aggressive tip-to-tips) and corresponding via structures have been characterized for A14 and A10 nodes. As well, bidirectional designs enabled by high NA will be described. For memory applications, results from BLP/SNLP layer for D1d and D0a nodes will be presented.

Extreme Ultraviolet (EUV) lithography poses an ever greater challenge to RLS (resolution, line edge roughness, and sensitivity) than previous photolithography methods as lithographers try to achieve sub-14nm pitch in a single-exposure. Additionally, EUV is particularly susceptible to stochastic imaging defects. Although standard chemically amplified resists (CARs) can be exposed with EUV, these materials struggle to achieve resolution targets at manufacturable doses due to limitations in laser source power and resist sensitivity and contribute to stochastics by nature of their random distribution of components. An innovative approach with Inpria Metal Oxide Resists (MORs) can offer an alternative to overcome both EUV resolution and sensitivity limitations, as well as address stochastic defects. On the other hand, traditional sources of defectivity, such as particles, present another challenge, especially when moving toward high-volume manufacturing. Ultrahigh molecula r weight polyethylene (UPE) membrane filters have been used for metal oxide EUV resist filtration because of their high retention efficiency and excellent photochemical compatibility. However, newly designed UPE filters with innovative membrane morphology are needed to further lower defectivity rates with these new resists. This paper describes efforts to continue to improve metal oxide EUV resist defectivity through filtration optimization. A comparative study of the patterning performance of various Point-of-Use (POU) filters is presented. Several filters utilizing a variety of retention ratings and membrane designs were installed on a TEL Clean TrackTM Lithius ProTM Z series. A metal oxide EUV resist was filtered and coated on wafers that were subsequently analyzed for patterning defect performance. This study examines the efficacy of optimized filtration design to reduce defects and provides a recommendation to achieve lower defect density.

EUV lithography has already introduced in high volume manufacturing and continuous improvements has allowed to resolve pitch 24nm line and space (L/S), pitch 32nm contact hole and pillar pattern with single exposure at even numerical aperture (NA) 0.33. However, pattern roughness, local critical dimension uniformity (LCDU) and process related defects are still major challenges with decreasing critical dimensions (CD). Pitch downscaling also require the use of thinner photoresist mask to prevent pattern collapse from high aspect ratios. Thinner photoresist mask is challenging for pattern transfer because the resist "etch budget" is becoming too small to prevent pattern break during plasma etch transfer. It is required to investigate a co-optimization of lithography processes, underlayers and etch processes to further EUV patterning extension. In this paper, our latest developed process solutions to extend the limits of EUV patterning will be reported. The advanced performance for metal oxide resists (MOR) will be introduced, with a focus on defect mitigation, dose reduction strategies and CD stability.

High-NA EUV lithography is currently under development to keep up with device node scaling with smaller feature sizes. In this paper, the most recent advances in EUV patterning using metal oxide resists (MOR) and chemically amplified resists (CAR) are discussed. A newly developed resist development method (ESPERT™) was examined on MOR with 24 nm pitch line and space (L/S) patterns and 32 nm pitch pillars for preparation of high-NA EUV patterning. The patterning results showed improved sensitivity and pattern collapse margin. CAR contact hole patterning at 28 nm pitch was also examined by stochastic lithography simulation. The simulation results indicate that resist film thickness needs to be optimized for target pitches.

Extreme Ultraviolet (EUV) lithography poses an ever greater challenge to RLS (resolution, line edge roughness, and sensitivity) than previous photolithography methods, as lithographers try to achieve sub-14 nm pitch in a single-exposure [1-2]. Additionally, EUV is particularly susceptible to stochastic imaging defects[3]. Although standard chemically amplified resists (CAR) can be exposed with EUV, these materials struggle to achieve resolution targets at manufacturable doses due to limitations in laser source power and resist sensitivity and contribute to stochastics by nature of their random distribution of components. An innovative approach with metal-oxide resist can offer an alternative to overcome both EUV resolution and sensitivity limitations, as well as address stochastic defects[4-5]. On the other hand, traditional sources of defectivity, such as particles, presents another challenge, especially when moving toward high volume manufacturing. Ultrahigh molecular weight polyethylene (UPE) filters have been used for metal oxide EUV resist filtration because of their high retention efficiency and excellent photochemical compatibility. However, other filters with innovative materials are needed to further lower defectivity of these new resists. This paper describes efforts to continuously improve metal oxide EUV resist defectivity through filtration optimization. A comparative study of the patterning performance of various Point-of-Use (POU) filters is presented. Several filters utilizing a variety of retention ratings and membrane designs were installed on a TEL Clean TrackTM LITHIUS ProTM Z EUV series. A metal oxide EUV resist was filtered and coated on wafers that were subsequently analyzed for after etch inspection (AEI) patterning defect performance. This study examines the efficacy of optimized filtration design to reduce defects and provides a recommendation to achieve lower defect density.

Filters for Extreme Ultra-Violet (EUV) lithography chemicals, like chemically amplified photoresist (CAR), are attractive because of their capabilities to remove aggregated species and reduce microbridges in high volume manufacturing. Unlike bulk filters used in high-flow circulation mode, point-of-use (POU) filter is used in single-pass mode, so the retention performance and cleanliness become the most critical factors. Earlier presentations have demonstrated the benefit of reducing on-wafer defectivities through filtration of EUV photoresists with the state-of-the-art HDPE membranes filters, Pall® sub-1nm HDPE (XPR3L). In this study, we present a novel HDPE filter specifically designed to provide high retention performance, which is mainly enabled by an improvement in retention characteristics of membrane and cleanliness in finished POU filters. The membrane was designed to have a finer pore size and better pore geometry to improve defect retention. To expedite the filter start-up process, optimized device cleaning process was applied to further improve initial cleanliness, which was indicated by GC-MS, LC-MS/MS and ICP-MS measurements, etc. Finally, the POU filters were evaluated at imec EUV cluster consisting of TEL CleanTrack™ LITHIUS Pro™-Z and ASML NXE:3400B, and comparative defect data was obtained from patterned wafers with 16nm L/S.

Background: Focus-exposure process window measurement and analysis is an essential function in lithography, but the current geometric approach suffers from several significant deficiencies. Aim: By clearly identifying the problems with the Geometric Process Window approach, a new process window measurement and analysis method will be proposed to address these problems. Approach: The Probabilistic Process Window proposed here takes metrology uncertainty into account and rigorously calculates the expected fraction of in-spec features based on settings for best dose/focus and presumed random errors in dose and focus. Using the fraction of in-spec features thus calculated, a much more rigorous determination of the trade-off between exposure latitude and depth of focus can be performed. Results: The Probabilistic Process Window approach is demonstrated on focus-exposure data generated from a standard extreme ultraviolet lithography process at three different pitches, showing the value of this method. Conclusions: The new Probabilistic Process Window approach offers clear advantages in accuracy for both depth of focus determination and best dose/focus determination. Consequently, its use is preferred both for process development applications and high-volume manufacturing.

Extreme ultraviolet (EUV) lithography has already introduced in high volume manufacturing and continuous improvements has allowed to resolve pitch 24 nm line and space (L/S), pitch 32 nm contact hole and pillar pattern with single exposure at even numerical aperture (NA) 0.33. However, pattern roughness, local critical dimension uniformity (LCDU) and process related defects are still major challenges with decreasing critical dimensions (CD). Pitch downscaling also require the use of thinner photoresist mask to prevent pattern collapse from high aspect ratios. Thinner photoresist mask is challenging for pattern transfer because the resist “etch budget” is becoming too small to prevent pattern break during plasma etch transfer. It is required to investigate a co-optimization of lithography processes, underlayers and etch processes to further EUV patterning extension. In this paper our latest developed technology and process solutions to extend the limits of EUV patterning will be report.

EUV (extreme ultraviolet) lithography has been introduced in high volume manufacturing in 2019 and continuous improvements have allowed to push the lithographic performance to the limits of 0.33 NA single exposure. However, stochastic failures, pattern roughness and local critical dimension uniformity (LCDU) are still major challenges that need to be addressed to maintain node shrinkage and improve yield. Together with pitch downscaling, photoresist thickness is decreasing to prevent pattern collapse. A lower depth of focus is also expected with high NA EUV which might even thin further down the resist layer. Being able to transfer the patterns with good fidelity is therefore getting very challenging because the resist “etch budget” is becoming too small to prevent pattern break during plasma etch transfer. A co-optimization of lithography processes, underlayers coating and etch processes is essential to further support the EUV patterning extension. In this report, recently developed hardware and process solutions to stretch the limits of EUV patterning will be presented. The latest performance for both chemically amplified resists (CAR) and metal oxide resists (MOR) will be introduced, with a focus on defect mitigation, dose reduction strategies and CD stability.

In the last years, the continuous efforts on the development of extreme ultraviolet lithography (EUVL) have allowed to push the lithographic performance of the EUV photoresists on the ASML NXE:3400 full field exposure tool, however, stochastic resist roughness, local critical dimension uniformity (LCDU) and pattern defectivity at nano-scale are still the major limiting factors of the lithographic process window of EUV resist when looking at sub-40nm pitches for both linespace (LS) and contact hole (CH) applications, especially in the low exposure dose regime [1]. To be effective during the lithographic EUV resist screening evaluation phase for such tight pitches, imec has implemented since 2018 [2] additional metrology analysis after resist development inspection (ADI) to further quick feedback on the quantification of nano-failures (nano-bridges, broken lines, merging or missing contacts) induced by a stochastic EUV patterning regime, and thus to improve the resist design at lithographic step in a faster manner. In this work, we have further extended the examination of the resist performance introducing additional metrology analysis after pattern transfer in a silicon nitride (SiN) substrate. We present the characterization results on 40nm and 36nm pitch staggered dense contact holes looking at both lithographic and etching knobs to mitigate the patterning process stochastic issues, confirming that the holistic litho-etch approach is an important and necessary step in the development path of EUV advanced patterning applications towards high volume manufacturing and high-NA EUV lithography.

One of the critical challenges for delivering next nodes or high-NA extreme ultraviolet (EUV) lithography to high volume manufacturing (HVM) in the semiconductor industry is to have a high-performance EUV resist process. The high-performance resist process needs to simultaneously meet multiple requirements, such as high resolution, high sensitivity, low roughness, a low defect level, and good global CD uniformity (CDU). In this paper, we will introduce a new wet development (DEV) method to improve the performance of metal oxide resists (MOR), which is named ESPERTTM** (Enhanced Sensitivity develoPER Technology). This newly invented method can meet multiple requirements together where it is not possible with the conventional development method. With 36 nm pitch pillar patterns, we have confirmed with after etch inspection (AEI) data that the new method produced 22% improvement in EUV dose and 7% improvement in LCDU, simultaneously. No pattern collapse was observed at least up to 15.4 nm pillar size. In the case of 30 nm pitch line/space (L/S) pattern, the improvements were 26% in EUV sensitivity and 12.3% in LWR also with AEI results. Furthermore, the new method could also shift the bridging cliff 0.5 nm to the larger line CD while its global CDU was improved 2.6 times. The new data achieved by the new wet development method make us believe that MOR are mostly ready for HVM and this new method is also aiming to be used in high NA EUV lithography in the near future. **) ESPERTTM is trademarks of Tokyo Electron Limited.