This PDF file contains the front matter associated with SPIE Proceedings Volume 12750, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

In this publication, we consider stitching enablement for High NA EUVL, specifically ‘zooming in’ on vertical line stitching used to create a physical connection between fields on wafer. We discuss stitching CD metrology and analysis using experimental and simulation results for pitch 36 nm dense lines. Experimental results were obtained on the NXE:3400B scanner at imec. CD uniformity across wafer and through slit are investigated as well as the impact from image to image overlap variation and the contribution of reticle CD errors and mask 3D shadowing. In the previous publications, we gave an overview of stitching challenges and various interactions in the stitching zone. In this publication, we focus on the aerial image interaction. Along a stitched vertical line, there are variations in CD creating a certain CD profile. These CD variations were modeled in a rigorous simulator but also observed experimentally. In order to characterize this behavior, we perform CD profile metrology at the stitch. We investigate the root causes of CD variability at the stitch and propose control mechanisms of stitching optimization. A key control mechanism being optical proximity correction (OPC) as well as overlay control.

Anamorphic magnification in high NA EUV will reduce the maximum wafer area of a single lithographic exposure field in half compared to current exposure equipment. Large die exceeding this area will require the use of two separate masks which must be stitched together. There is a preference within the industry to stich the fields together “at resolution” using features of the same dimension and pitch as those elsewhere in the design. Stochastic lithography simulation is used to model the effects of field stitching on patterning performance with regards to the defectivity process window as a function of X and Y registration. It is observed that the best defectivity performance conditions may vary significantly from those that produce the optimum CD uniformity.

The use of a 4F² cell configuration is very typical in emerging memory devices to enable higher densification and implementation of cross-point memory architecture. The pitch scaling as well as the device performance of these memories mainly rely on the patterning process of the orthogonal array vertical pillars. In this paper, we screen several lithography approaches to optimize the 36nm and 34nm pitch pillar patterning using single exposure EUV (extreme ultraviolet) lithography. The main process knobs used for this screening work are the UL (underlayer) material selection and different flavors of the ESPERT^TM photoresist development process from TEL^TM. The results for 34nm pitch with 17nm target CD show that LCDU can be improved from 1.77nm to 1.53nm with a similar dose-to-size requirement and slightly better WCDU for ESPERT^TM 3 process in SiC compared to imec POR process. For 36nm pitch, on the other hand, with 18nm ADI CD target, LCDU has been improved from 1.68nm to 1.47nm with a similar WCDU and slightly lower dose-to-size. Moreover, the failure rate for missing and bridging pillars is much lower for ESPERT^TM 3 compared to our reference process for both 34nm and 36nm pitch process.

In this work we continue to validate both by experiment and simulations the lines and spaces (LS) printing performance in terms of background printing and mask 3D effects with a dark field (DF) low-n absorber mask with 13% absorber reflectivity vs. a traditional Ta-based absorber mask. The brightness of the low-n absorber is the reason for a brighter background, what can have an impact on the remaining resist height after exposure. We experimentally verify by AFM the remaining resist height for different pitches through dose and through focus vs. the background for exposure with low-n and Ta-based absorber masks. It is also expected that such low-n absorber masks are more sensitive to mask 3D effects. Therefore, we study M3D effects on horizontal LS and 2Bars. There we evaluate Pattern Shift through focus as well as a 2Bar CD asymmetry through slit and through focus. We also measure MEEF for various LS pitches.

Dual monopole exposure has been proposed1 as a way to improve imaging performance in EUV lithography by reducing the loss of contrast from image fading caused by the image shifts for the two poles of a dipole source. Simulations showed that the imaging advantages can be significant, with more than 15% image contrast improvements predicted. This paper presents experimental wafer data to demonstrate and verify the predicted advantages. The observed imaging enhancements include: • 18% better NILS (Normalized Image Log-Slope) for 28nm pitch patterns. • Better tip-to-tip patterns enabling gaps as much as 3nm smaller than normal patterning. Tip-to-tip LCDU and exposure latitude were improved at the same time, for better overall T2T capability. • Best focus offsets between three pitches: P28, P56 and P96 was reduced from 30nm range to nearly zero. • Smaller LWR (Line-Width Roughness), as much as 20% depending on pitch. • Reduced micro-bridging defects in the “stochastic cliffs” of narrow trenches, as large as a 40X defect density reduction for narrow trenches with 82nm pitch. Our experimental results validate the substantial imaging advantages seen by initial simulations. In addition to verifying dual monopole imaging advantages, our experiments have measured the pole-to-pole image shift δx_P2P, an important parameter relating to image contrast which has never been measured before. This important parameter depends on the detailed mask structure as well as the specific shape and location of the source poles. Our measured δx_P2P was consistent with simulated expectations.

Pattern placement error has historically been related to overlay in DUV lithography, where continuum approximations, transmissive masks, and telecentric stepper/scanners are used. EUV lithography does not enjoy such properties: stochastic phenomena – both optical and chemical – strongly affect the printed pattern even at relatively relaxed k1 factors, while non-telecentric optical paths complicate across-focus as well as across-slit pattern behavior. Both randomness and optical non-idealities contribute to unpredictable and uncorrectable feature edge misplacement as stochastic and systematic pattern placement errors, which must be taken into consideration in the overlay budget. For low-NA (NA = 0.33) EUV lithography, stochastic and systematic pattern misplacement are controlled by printing very relaxed pitches, often greater than 34 nm, which correspond to a k₁ > 0.4 (in ArFi lithography production lines run at pitches ≈ 80 nm, where k1 < 0.3). This allows for the optimization of the mask and source to control the edge placement across focus and slit. Moreover, sacrificing some throughput keeps the printed features large enough to receive enough photons to preserve the stochastic phenomena under a controllable level. In high-NA (NA = 0.55) EUV lithography arrival angles are larger – up to 33° – and simulations show that this has dire consequences for pattern placement control. Moreover, high-NA EUV lithography is expected to enter production for the 14A node, with a line/space minimum pitch of 17-19 nm (k₁ ≈ 0.37) where the edge placement error budget will be further reduced. We compare the overall pattern placement control of a well-established low-NA exposure configuration for lines/spaces at a pitch of 36 nm (k₁ = 0.44) with different high-NA solutions to print 22 nm (k₁ = 0.45) lines/spaces.

EUV resist materials play a vital role in enabling advanced lithographic technologies for high-volume manufacturing (HVM) targeting nodes below 5 nm. In this study, we report an extensive performance characterization of available EUV photoresists for future high-NA EUV lithography. We investigated the performance of various resists using the EUV interference lithography tool at the Swiss Light Source (SLS) within the framework of a collaboration between the Paul Scherrer Institute and ASML. This paper highlights the major improvements we observed in 2023 and presents the best performing resists of 6 different vendors for half-pitch (HP) 14 and below. Important performance characteristics considered in this study are resolution or HP, dose-to-size (DtS) and line-width roughness (LWR). To evaluate the overall performance of the resists, we used the Z-factor. We investigated both chemically amplified resists (CAR) and non-CAR materials. CARs from two vendors achieved a resolution down to 11 nm half-pitch, while multitrigger resists (MTR) reached a resolution of 13 nm. A new metal organic resist (MOR) achieved a resolution down to 11 nm. MTR and one CAR material achieved the lowest Z-factor to date. In addition, we investigated the effect of underlayers on the performance of MOR and compared the performance of the new MOR to the predecessor. We, finally, discuss the overall progress in resist performance over the recent years. We observed a steady improvement across several resist platforms, which is encouraging for global EUV resist development towards high-NA EUVL.

One of the key steps in the pattern formation chain of extreme ultraviolet (EUV) lithography is the development process to resolve the resist pattern after EUV exposure. A simple traditional development process might be insufficient to clear the holes in contact-hole (CH) patterns and often causes missing hole defects around target-CD. In prior papers, a new development method named ESPERT™ (Enhanced Sensitivity develoPER Technology™) has been introduced to improve the performance of metal oxide-resists (MOR) for line/space (L/S) and pillar patterns. ESPERT™ as a chemical super resolution technique effectively apodized the MOR chemical image, improving chemical gradient and reducing scums. In this work, this development technique was optimised for CH patterns to reduce both the local CD uniformity (LCDU) and to reduce the levels of missing contact holes at a lower exposure dose. This is made possible thanks to the capability of the updated version of ESPERT™ that can effectively remove the scums (resist residues) inside CH to extend the missing hole defect margins. The high development contrast of the new development technique results also in a much higher exposure latitude. Using 0.33 NA EUV scanners on 36-nmpitch hexagonal patterns, the new development enhanced exposure latitude (EL), failure free latitude (FFL), and failure free dose ranges at both ADI (after development inspection) and AEI (after etch inspection) for two diverse types of MORs. For instance, in the case of the reference MOR developed by ESPERT™, CHs were nicely transferred to a TiN layer, even for small CD holes of 14.7 nm. If compared to the data by conventional development, using the new method, the EL was increased from 16.0% to 49.1%, the FFL was extended from 2 nm to 6 nm, and the failure free dose range was increased from 13.3% to 72.2%. It was also possible to have EUV dose-to-size (DtS) of 28 mJ/cm² with EL of 49.9% at ADI, using the new development. With all those advantages, this new development method is expected to be the solution for CH pattern formation of negative tone MORs in EUV lithography.

In 2019, finally, extreme ultraviolet (EUV) lithography has been applied to high volume manufacturing (HVM). However, the performance of EUV resist materials are still not enough for the expected HVM requirements, even by using the latest qualifying EUV resist materials. The critical issue is the stochastic issues, which will be become defectivity. The analyzing summary of the stochastic factors in EUV lithography was classified, which described 2 (two) major stochastic issues, which are Photon stochastic and Chemical stochastic. In the past, speaking of the stochastic issue was basically considered from low photon number from EUV light source, which means photon shot noise. It was still critical concerning point, even with recent progress on source power improvement. However, the stochastic issue is not only from them but also from EUV materials and processes, called Chemical stochastic. The Chemical stochastic means caused from resist materials and processes for lithography, materials uniformity in the film, reactive uniformity in the film, and dissolving behavior with the developer. From a material point of view, chemically amplified resist (CAR) has still high potential for high volume manufacturing. Therefore, we have been studying to improve CAR performance for next generation node. In this paper, we will focus on Chemical stochastic improvement, like materials location uniformity and dissolving behavior improvement by using negative-tone development (NTD, using organic solvent-based developer). CAR-NTD had a potential for improving Chemical stochastic because of their properties, which were low swelling and smooth dissolving behavior. However, the pattern collapse was easily observed for preparing fine patterns with the standard developer. Newly proposed novel formulated organic solvent-based developer will be expected to improve the pattern collapse issue and Chemical stochastic. Lithographic performance will also be reported and discussed.

As the semiconductor chip size continues to decrease, extreme ultra violet lithography (EUVL) is becoming a vital technology to achieve the high resolution patterning required for sub-7 nm node technologies. The patterning resolution of EUVL is highly dependent on the performance of EUV photoresists (PR) which can lead to variations in the patterning process and affects the overall quality of the semiconductor. Although there are several traditional methods to determine a patterning performance of PR, it becomes more challenging as scale tighten. To this end, we develop a new analysis method, named ‘W-curve’, defining EUV PR resolution using ADI SEM images, that visualizes micro-bridge and -break defect cliffs and local CD uniformity at the same time. Using W-curve method, 3 different PR performance at 36 nm-pitch line/space pattern was clearly distinguished. Also, the obtained result was well correlated with time-series trend data and electric test data. Therefore, we believe that W-curve method could provide a new insight for understanding EUV PR performance and improve patterning performance in a facile and versatile manner.

Background: Natural physical phenomena occurring at length scales of a few nm produces variation in many aspects of the EUV photoresist relief image: edge roughness, width roughness, feature-tofeature variability, etc. 1,2,3,4. But the most damaging of these variations are stochastic or probabilistic printing failures 5, 6. Stochastic or probabilistic failures are highly random with respect to count and location and occur on wafers at spectra of unknown frequencies. Examples of these are space bridging, line breaking, missing and merging holes. Each has potential to damage or destroy the device, reducing yield 6, 10. Each has potential to damage or destroy the device, reducing yield 6, 10. The phenomena likely originates during exposure where quantized light and matter interact1 . EUV lithography is especially problematic since the uncertainty of energy absorbed by a volume of resist is much greater at 13.5 nm vs. 248 nm and 193 nm. Methods: In this paper, we use highly accelerated rigorous 3D probabilistic computational lithography and inspection to scan an entire EUV advanced node layout, predicting the location, type and probability of stochastic printing failures.

In our previous works, a convolutional neural network was developed which predicted diffraction amplitudes from extreme ultraviolet masks very fast. In this work, we reduce both the time for preparing the training data and the time for image intensity integration. We reduce the time for preparing the training data by applying weakly guiding approximation to 3D waveguide model. The model solves Helmholtz type coupled vector wave equations of two polarizations. The approximation decomposes the coupled vector wave equations into two scalar wave equations, reducing the computation time to solve the equations. Regarding the image intensity integration, Abbe’s theory has been used in electromagnetic simulations. Transmission cross coefficient (TCC) formula is known to be faster than Abbe’s theory, but TCC formula cannot be applied to source position dependent diffraction amplitudes in electromagnetic simulations. We derive source position dependent TCC formula starting from Abbe’s theory to accelerate the image intensity integration.

In this contribution we describe a Tachyon based flow to measure mask error systematics and simulate their impact to wafer level, as well as determining the contribution of these errors to OPC model calibration error. The dataset consists of 1000 OPC model calibration patterns for an N5 via layer for which we have a quadruplet of post-OPC GDS, simulated mask contour, mask CDSEM image and wafer CDSEM image as shown in Figure 2. First we examine the error at the mask using a combination of MXP (for metrology) and Tachyon LMC (for contour comparison) software products. Again using LMC we can simulate to wafer level using the simulated mask contour, and the measured mask contour as input. This allows us to correlate mask error to expected wafer error. Finally we calibrate OPC models to the measured wafer data using the various mask representations (postOPC Manhattan, simulated and measured) as input and observe the effect on OPC model error. This is done using Tachyon FEM+ with term based resist models of varying complexity.

For several decades, the National Institute of Standards and Technology (NIST) has actively supported metrology programs for extreme ultraviolet (EUV) lithography. We will describe our existing programs in optics lifetime, reflectometry, and radiometry. Recent developments include developing quantitative models for both carbonization and oxidation of optics under UV illumination and use of a cryogenic radiometer to calibrate transfer-standard detectors from 4 nm to 400 nm. We describe two programs currently in planning. The first of these is development of a method to calibrate high-power pulsed radiation detectors using a calorimeter. Our current primary standard detectors for 13 nm are based on synchrotron radiation with incident powers of a few microwatts or less. EUV production tools need to measure pulse trains with many hundreds of watts of average power. We will begin this work on our existing low-power detector-calibration facility and use higher-power beamlines with overlapping power ranges and the linearity of synchrotron radiance with stored beam current to extend the calibrations to higher powers. Second, we present a Mueller matrix ellipsometry and scatterometry system covering the far-to-extreme ultraviolet spectral range. This system is expected to achieve the requisite variable polarization and diattenuation control with an entirely reflective optical system. By extending scatterometry to short wavelengths, we intend to demonstrate improved sensitivity and accuracy of parameter retrieval from microfabricated devices. These programs complement NIST’s existing far- and extreme-ultraviolet radiometry and metrology programs and expand our support for critical semiconductor manufacturing.

Background: Accurate measurement of local critical dimension uniformity (LCDU) and local pattern placement errors (LPPE) caused by stochastics is a critical task in metrology for advanced technology nodes, especially for EUV lithography. Aim: Optimizing the settings of a metrology tool to either reduce biases in LCDU and LPPE measurement, or to reliably measure and remove those biases, is critical to stochastics metrology accuracy. Approach: Four different scan modes and two different scan orientations are compared for the measurement of staggered arrays of contact holes on a scanning electron microscope (SEM), and both biased and unbiased LCDU and LPPE are compared. Results: The Hitachi SEM scan modes designed for the measurement of 2D patterns have the minimum sensitivity to scan orientation and differences in X and Y metrology results. Further, measuring and subtracting SEM biases increases the accuracy of the best scan mode results, but also reduces the differences between scan modes by 3X. Conclusions: SEM scan modes designed for 2D patterns produce lower bias in the measurement of contact hole LCDU and LPPE. Measuring and removing biases produce the maximum accuracy for all scan modes.

On product overlay (OPO) is one of the most critical parameters for continued scaling according to Moore’s law. Besides the lithography scanner, also non-lithography processes contribute to the OPO performance. For example, processes like etching and thin film deposition can introduce stress, or stress changes, in the thin films on top of the silicon wafers. In general, the scanner Higher Order Wafer Alignment model up to 3rd order (HOWA3) has proven to be adequate to correct for most process-induced wafer distortions. This model is typically used with 28 wafer alignment marks placed across the wafer to correct for more global stress-induced distortions. It is evident that if the stress variation manifests itself on shorter length scales, either more alignment marks are needed in combination with a more sophisticated wafer alignment model, or an alternative measurement of the wafer distortion is required. A viable alternative to characterize local wafer deformations is by measuring the free-form wafer-shape change due to processing. In case the wafer-shape change can be translated into a wafer distortion map, it can be complementary to what is already captured by the scanner wafer alignment model. In this paper, we would like to explore this functionality that is based on a new method to measure the free-form wafer shape. Wave Front Phase Imaging (WFPI) generates the wafer shape by registering the intensity of the light reflected off the patterned or blank silicon wafer surface at two different locations along the optical path. The wafer is held vertically to allow for the free-form wafer shape to be measured without being affected by gravity. We show data acquired on specialty made silicon wafers using a WFPI lab tool that acquired 16.3 million data points on a 300mm wafer with 65μm spatial resolution. The obtained free-form wafer-shape measurements are fed into existing prediction models and the resulting wafer distortion maps are compared with scanner measurements.

It is renowned that underlayers can enhance photoresist performance in extreme ultraviolet lithography via chemical/physical interactions, but these effects are elusive to identify. Using factorial analysis, we pinpoint which underlayer parameters have or have not an effect on the lithography patterning quality of chemically amplified and metal oxide resists in three proposed experiments. Experimental factors were underlayer thickness, density, surface roughness, surface energy and composition; the outputs were: dose, exposure latitude, line roughness and its correlation length.

To investigate the development kinetics, this study categorized the dissolution dynamics in tetraalkylammonium hydroxide (TAAH) aqueous solutions into six classes based on frequency and impedance variations during the development process using quartz crystal microbalance (QCM) measurements. These classifications were examined against various material attributes via decision trees and support vector machine (SVM) models. The feature values included in this analysis comprised the length of alkyl chains, molecular weight, solute concentration, viscosity of developers, protection ratios, molar masses, contact angles, and surface free energy of polymer. Accuracy for the test dataset was approximately 0.80 and 0.75 for the decision trees and SVM, respectively, when validated.

In extreme ultraviolet (EUV) resists, due to the high energy of the incident photons, most of the radiation chemistry arises from the emitted electrons and not the EUV photons themselves. The absorption of an EUV photon by a resist film leads to the emission of primary electrons, which, through a cascade of inelastic scattering events, cause excitation of molecules and emission of secondary electrons. Because the electrons are playing a leading role in EUV patterning by initiating the majority of chemical transformations, it is important to characterize their generation, transport, and energy distribution. In this work we investigate the emission of electrons in model EUV photoresists using photoelectron spectroscopy. The photoelectron spectroscopy reveals variations in the energy distributions and abundances of emitted electrons for different resist compositions (bare polymer, PAG, and quencher concentrations). EUV exposure of resists induces a change of the electron emission spectra, mostly affecting emission of slow secondary electrons. By applying this approach to each resist component, we begin to decipher the role of resist components in electron generation, capture, and transmission.

As the power of EUVL (extreme ultraviolet lithography) scanners increases, the thermal load and hydrogen plasma environment applied to the pellicle become harsher. If the core material of the pellicle membrane is unstable in the EUV environment, reliability depends on the top-most layer (capping). However, the loss of EUV transmission restricts the thickness of the capping and raises concerns related to hydrogen radicals or protons. In our previous report, we introduced molybdenum carbide (Mo₂C) as a new pellicle material with high EUV transmittance (91.4 %), transmission uniformity (3σ=0.49 %, 5×5 mm²), and chemical stability against a hydrogen plasma. In this report, we demonstrate the stability against high-intensity (30 W/cm²) EUV irradiation and hydrogen plasma for Mo₂C membranes. Large-area (≥5×5 cm²) Mo₂C membranes with high EUV transmittance (≥88 %) were fabricated using MEMS technology. The membranes were tested for thermal load test using an 808 nm infrared laser under the same conditions producing up to 3000 wafers in the EUV scanner. The chemical properties of the membranes were evaluated using an inductively coupled plasma device in a high-temperature (<900 °C) hydrogen gas and plasma environment. Furthermore, the EUV transmittance for the Mo₂C membrane and the difference after thermal load and hydrogen plasma evaluation were characterized by EUV coherence scattering microscopy. Consequently, we show the feasibility of high-volume manufacturing (HVM) Mo2C pellicles by fabricating the membrane over 5 × 5 cm₂.

Next generation of high-NA extreme ultraviolet (EUV) photolithography introduces higher power levels and faster reticle accelerations, enabling breakthrough in scanner efficiency. This results in higher temperatures and mechanical stresses on the EUV pellicles. Here we demonstrate scalable carbon nanotube (CNT) membrane mass production from a floating catalyst chemical vapor deposition (FC-CVD) reactor, using a direct dry deposition method. This direct high volume fabrication method yields highly uniform CNT networks with high strength and purity, enabling exceedingly thin CNT pellicles with high transparency at EUV. This end-to-end manufacturing process, starting from reagent gases, enables control and reproducibility over the final nanomaterial product. Control over synthesis allows tailoring of the carbon nanotube diameter and wall count (SWCNT or FWCNT), as well as control over the CNT network morphology such as the density, bundle size, and orientation of CNTs. The combination of this direct fabrication method with the exceptional mechanical and thermal properties of CNTs creates a versatile membrane platform, which can be further modified with post process steps such as purification to remove metal impurities. To enable conformal and thin coatings on CNTs, wet and dry functionalization steps are demonstrated to match the surface chemistry of CNTs to the specific deposition chemistry used in atomic layer (ALD), chemical vapor (CVD), or physical vapor (PVD) deposition processes. Thicker and denser CNT membranes with appropriate coatings are also suitable for other roles, such as filtering debris from an EUV source, blocking DUV photons and electrons, and providing a gas seal for differential pressure.

EUV lithography is a key technology in the semiconductor industry and using pellicle that protects reticle from contamination during lithography process has become increasingly important. In this paper, different types of pellicles showing 82~>95% EUV transmittance and wafer moves 5K~50k under different transmittances, scanner powers and resists have been demonstrated for high volume wafer production at this work. For pellicle particle quality, we developed new inspection tool to achieve >1um pinhole-free and with significant defectivity reduction compared to previous one. Almost no fall-on rate is validated for real wafer production. Furthermore, this work develops full infrastructure, which include pellicle-making, pellicle-mounting and through pellicle inspection are validated to provide simple and robust production capability. Our EUV pellicle frame design shows fully compatibility with advanced 193nm reticle pelliclemounting process. Now previous EUV pellicle solution is ready to support advanced nodes application. The other key indices for high wafer throughput and cost reduction are high pellicle transmittance and durability. The pellicle optical performances (EUV transmittance, EUVT uniformity and EUV reflectance) are comparable to the previous solution. Moreover, no negative effects on wafer critical dimension uniformity (CDU) regarding to mask with and without pellicle mounting. In this work, a high-volume manufacturing (HVM) EUV pellicle with excellent defect and durability have been successfully qualified for the needs of advanced node productions.

The EUV lithography optics program continues to enable the progress of the semiconductor roadmap with higher productivity and finer imaging resolution. ZEISS Starlith® lithography optics systems with a numerical aperture (NA) of 0.33 and an optical resolution of 13 nm half-pitch are being produced in high volume for integration into ASML´s NXE scanners, which have established themselves as industry workhorses in leading edge semiconductor manufacturing. Even finer imaging resolution will be achieved with the Starlith® 5000 for ASML´s EXE scanners, with NA = 0.55 and an optical resolution of 8 nm half-pitch, with highly flexible illumination and an anamorphic projection optics featuring a central obscuration. The first Starlith® 5000 illuminator and projection optics box have been delivered to ASML. The outlook includes future roadmap extensions for low-k₁ imaging at increased productivity and potential further improvements of the single exposure resolution capabilities.

This paper explores the effects of optimizing the post-exposure bake (PEB) process on controlling the variability of Tip-To-Tip (T2T) structures within metallization layers. To gauge variability control, we evaluated Local Critical Dimension Uniformity (LCDU) and Global Critical Dimension Uniformity (GCDU) during the After Development Inspection (ADI) phase. Each of the PEB process optimizations had a unique impact on both LCDU and GCDU. The combination of adjusting the PEB temperature and optimizing the PEB chamber environment produced the most favorable results. This led to a notable improvement of 18.4% in LCDU and 20.1% in GCDU, respectively.

In this contribution the design, realization, and characterization of a transmission grating spectrograph (TGS) designed for spectral characterization and monitoring tasks at extreme-ultraviolet (EUV) wavelengths are presented. The overall dimensions of the EUV-TGS have been minimized to allow for easy integration in existing beamlines and setups while maintaining sub-Ångström spectral resolution. The main module (length = 40 mm) of the realized EUV-TGS consists of a spectral and a spatial filter and a high-resolution phase-shifting transmission grating with a grating structure periodicity of 80 nm. For spectral characterization and monitoring of a plasma-based EUV radiation source, a two-dimensional detector is positioned in close proximity to the main module. The realized spectrograph prototype can be moved in and out of the beam path, and therefore does not affect spot profiling and general beam alignment tasks. The structural and optical design and performance measurements of the EUV-TGS are presented, demonstrating that this ultra-compact spectrograph can be easily integrated into EUV setups that will benefit from an inline diagnostic option.

Extreme ultraviolet (EUV) lithography is a critical technique for fabricating advanced semiconductor devices, and the development of a high numerical aperture (NA) system for future 3 nm nodes is currently in progress. The current Tabased EUV masks exhibit limited imaging performance attributed to mask 3D effects, thereby necessitating the development of alternative EUV masks. In this study, we propose platinum (Pt)-based alloys as the potential absorber materials that offer benefits in terms of both mask manufacturing and imaging performance. Despite the superior imaging performance of Pt due to its optical properties, its adoption as a mask absorber is difficult because of its low etchability. Therefore, tungsten (W) which has high reactivity with fluorine-based etch gas was introduced as an alloy material to lower intermolecular binding energy, and argon (Ar) ion implantation was employed to amorphize the thin film. We evaluated the etching properties of ion-implanted Pt-W alloy thin films using CF₄/O₂/Ar gas. As a result, we verified that the etch rate of the implanted alloy was about 1.86 times higher than that of Pt, resulting in a higher sidewall angle in patterns. Furthermore, based on PROLITH 2022a simulation tool, we confirmed that Pt-W alloys showed about 2.4 NILS at 34 nm thickness which is higher than the current Ta-based mask, and the best focus shift has been mitigated by 33 %. In conclusion, Pt-based materials have the potential to apply as the next-generation absorber for EUV masks that can achieve fine patterning and enhance imaging performance.

The chip size progressive shrinkage imposes more stringent requirement on the fine geometry processing with the technology revolution in the semiconductor industry. Until EUV mass production is available, Selfaligned double patterning (SADP), as well as self-aligned quadruple patterning (SAQP), is the dominate technique applied to achieve smaller Bit Line/Word Line (metal pitch) profile beyond lithography limitation. Conventional metal pitch is formed through Tungsten (W) deposition in the trench after SADP flow, however, the process variation in SADP scheme worsens the metal pitch length uniformity due to Aspect-ratio dependent etching (ARDE) effect. Such metal pitch length nonuniformity directly affects the resistance in the circuit as well as the device performance. Firstly, this paper starts with a deep investigation on the Critical dimension (CD) variation in the traditional SADP scheme from analytical study, followed by the conventional CD control mechanism for individual step. Secondly, it highlights current CD tuning limitation and introduces a novel tuning method. Lastly this paper describes the procedure to build up the new tuning mechanism conceptually and provides applicable suggestions for the industry implementation. Such novel tuning mechanism achieved 32% CD variation reduction.

A novel alloy, exhibiting extremely low thermal expansion, high temporal stability and superior Young’s modulus, has been developed based on the super invar (Fe₆₄Ni₃₁Co₅). The average coefficient of thermal expansion (CTE) of the alloy, α_18-28, is found to change with Fe content, C_Fe, and can be approximated by the linear equation of α_18-28 = −0.4789C_Fe + 29.927 around room temperature. This linear approximation suggests that the CTE of the alloy can be regulated to zero near C_Fe of 62.5%, in contrast to the conventional super invar alloy, which is frequently used as the structural support components for stable optical systems and has a CTE of approximately 0.5 × 10⁻⁶ K⁻¹ around room temperature. Based on these findings, we have successfully achieved an extraordinarily low thermal expansion of −0.046 × 10⁻⁶ K⁻¹ average CTE in the temperature range between 18°C and 28°C through precise control of the chemical composition. the carbon content was reduced to below 0.02% to suppress the carbon-dependent expansion over time, which is known to occur in high carbon invar-based alloys. As a result, the dimensional change over the years of our developed cast alloy is less than 0.05 ppm/year. The low Young’s modulus due to the coarse and columnar grains microstructure in the cast alloys can be improved by 30% with a grain refinement technique using cryogenic and recrystallization thermal treatments.

In this work, we introduce main chain scission resists with new concept for High-NA’s generation and report their lithography performance. Zeon has developed a new resist (ZR12A, R&D sample) in order to improve both resolution and lithography performance because conventional Zeon resists generated worse resolution and kissing(C/H), pinching(L/S) defects at tight pitch by top loss. The concreate approaches in order to improve the challenges are that to make scission reaction efficient and to get developability at exposed area higher in changing both monomers and functional groups. Zeon aims to make clear threshold between exposed and un-exposed area and improve low contrast and sensitivity at tight patterns especially. The lithography performance of ZR12A with their approaches were able to improve LCDU and margin with low LCDU on litho-performance compared to ZER02#04DM. Additionally, ZR12A has good etching resistance and can improve LCDU in AEI as well at this paper.

Gigaphoton Inc. presents a Sn-LPP EUV light source for mask inspection tools. It is based on a minimum-mass Sn droplet generator with an in-line Sn fuel supply system, a double-pulse laser irradiation scheme with precise shooting control and a debris mitigation technology with H₂ buffer-gas flow. A brightness of 120W/mm² sr at the plasma point without reflectivity degradation of the EUV collector mirror after 500 hours continuous operation has been demonstrated with a very low EUV energy 3σ-value of 5%.

The power of EUVL (extreme ultraviolet lithography) scanner continues to increase, making the heat dissipation characteristics of EUV pellicles increasingly crucial. The thermal and chemical stability of the EUV pellicles, which have a multilayer thin film structure, relies on the capping layer, and the thermal stability of the capping layer is determined by its emissivity (ε). However, it is challenging to directly measure the ε of an ultrathin film, such as the capping layer of the EUV pellicle. Although a method to obtain the ε of a target material is employed which measure the ε of the whole layer with a target material on a support membrane having low ε, no approach has been proposed to exclude the measurement changes caused by the support membrane. In this study, a methodology for obtaining the ε of a multilayer nanomembrane is proposed. Ruthenium (Ru) with a high ε at nanoscale was deposited on SiN_x membranes to have varying thicknesses. The ε of SiN_x film and Ru deposited SiN_x film were precisely characterized by infrared spectroscopy according to Kirchhoff's law. Based on transfer matrix method (TMM), the ε of Ru layers was theoretically calculated, fitting by DrudeLorentz oscillator model. Finally, reliability was verified by comparing the measurement results through a free-standing membrane without a support. In this way, if the contribution of a single element to the ε of a multilayer or composite membrane can be derived, engineering for a high-emissive layer that combines various components will be possible and used as EUV pellicle and further application research.

In extreme ultraviolet (EUV) resists, due to the high energy of the incident photons, most of the radiation chemistry arises from the photon-generated primary and secondary electrons and not the EUV photons themselves. These electrons are generated by a cascade of inelastic scattering events, have a wide range of energies, and play a leading role in EUV patterning by initiating chemical transformations. To characterize electron-induced chemical transformations we exposed photoresist films to an electron beam 7-9 mm in diameter with energies varied from 20 to 80 eV to study the effect of fast primary electrons as well as slow secondary electrons on photoresist materials. Chemical changes of poly-tert-butyl methacrylate (tBMA), poly-methyl methacrylate (PMMA), and poly-4-hydroxystyrene (PHS) were characterized in-situ during exposure using a quadrupole residual gas analyzer (RGA). Full RGA spectra were used to identify the outgassed compounds from samples, and the time dependence of key chemical fragment masses was studied to observe the depletion of fragments from the sample over time. Transmission FTIR data were collected through exposed spots to quantify the changes in chemical bond structure. The number of molecules lost from each resist was estimated by the integrated partial pressure rise observed in RGA and compared to the total thickness change of exposed areas measured using ellipsometry.

Development of new EUV resists is required for next-generation EUV lithography. A resist in which a large amount of photoacid generator (PAG) is introduced into the polymer side chain has been reported as a high-resolution nonchemically amplified negative-tone resist. In this study, we synthesized a new high-PAG loading-type negative-tone resist as a model resist, evaluated EUV sensitivity by flood exposure, and also performed carbon K-edge and sulfur Ledge X-ray absorption spectroscopy (XAS) analysis. The synthesized high-PAG loading bound resist had a 79 mol% PAG unit in the polymer side chain. After the EUV exposure, the resist behaved as a negative-tone resist in the alkaline developer and a positive-tone resist in the organic developer. From the results of the XAS analysis, the possible decomposition mechanisms of the PAG unit in the polymer were estimated.

Recently, chip makers have selectively adopted the EUV pellicle to mitigate yield reduction caused by the particle issue originating from the Sn droplets of a laser-produced plasma source. However, other research groups have proposed the critical size of particles based on simulated data with illumination pupil control, underscoring the necessity of experimental investigation using an optical system that emulates that of an EUV scanner. In this study, we demonstrate the effect of a particle on the pellicle on diffracted light shape and investigate its impact on mask imaging performance. This investigation was conducted through pellicle imaging using Sn particle-patterned pellicles and a coherent scattering microscope, which is an actinic inspection tool that uses a coherent harmonic source. As a result, we confirmed that the light intensity decreased to 4.031%, and the scattered light spread up to 146.01% when a 10 µm-sized particle on the pellicle blocked a specific mask diffraction order. To study this particle's effect on mask imaging performance, pattern images were reconstructed from particle-affected diffraction patterns using a phase retrieval algorithm. Eventually, a critical dimension variation of 51.15 nm and a pattern shift of 48.57 nm were confirmed with a 200 nm critical dimension of the mask pattern, as a result of particle-induced spatial frequency and phase variation. Therefore, the critical defect size of the pellicle should be determined based on the most severe lithographic variations resulting from the mask diffraction light blocked by the particles.

The technological advance of High Numerical Aperture Extreme Ultraviolet Lithography (High NA EUVL) has opened the gates to extensive researches on thinner photoresists (below 30∼nm), necessary for the industrial implementation of High NA EUVL. Consequently, images from Scanning Electron Microscopy (SEM) suffer from reduced imaging contrast and low Signal-to-Noise Ratio (SNR), impacting the measurement of unbiased Line Edge Roughness (uLER) and Line Width Roughness (uLWR). Thus, the aim of this work is to enhance the SNR of SEM images by using a Deep Learning denoiser and enable robust roughness extraction of the thin resist. For this study, we acquired SEM images of Line-Space (L/S) patterns with a Chemically Amplified Resist (CAR) with different thicknesses (15∼nm, 20∼nm, 25∼nm, 30∼nm), underlayers (Spin-On-Glass - SOG, Organic Underlayer - OUL) and frames of averaging (4, 8, 16, 32, and 64∼Fr). After denoising, a systematic analysis has been carried out on both noisy and denoised images using an open-source metrology software, SMILE 2.3.2, for investigating mean CD, SNR improvement factor, biased and unbiased LWR/LER Power Spectral Density (PSD). Denoised images with lower number of frames present unaltered Critical Dimensions (CDs), enhanced SNR (especially for low number of integration frames), and accurate measurements of uLER and uLWR, with the same accuracy as for noisy images with a consistent higher number of frames. Therefore, images with a small number of integration frames and with SNR∼< 2 can be successfully denoised, and advantageously used in improving metrology throughput while maintaining reliable roughness measurements for the thin resist.

Extreme ultraviolet (EUV) lithography has pushed the limits of optical lithography techniques, enabling patterning of highresolution feature sizes and driving innovation in the semiconductor industry. Traditional top-down lithography processes face challenges with EUV interference lithography, such as requiring precise incidence angles and specialized, expensive multilayer mirrors for nanostructure patterning. Colloidal nanosphere lithography offers an effective and inexpensive nearfield technique, utilizing self-assembled nanoparticles to create complex 2D and 3D nanostructures. However, existing work primarily uses UV lasers, limiting pattern resolution to above 100 nm. In this study, we propose using colloidal nanosphere lithography combined with a 30 nm wavelength EUV light source to pattern periodic geometric patterns. We describe the proposed system, which consists of a high harmonic generation source pumped by an ultrafast laser at wavelength of 30 nm. The beam shapes and characteristics are characterized and presented. Initial results demonstrate successful patterning using the colloidal assembly serves as a mask, achieving complex geometric patterns with sub-50 nm feature sizes. This work explores a low-cost and scalable approach to studying EUV light interaction through colloidal nanosphere assemblies for 3D nanostructure patterning.

The Laser-assisted Discharge-produced Plasma (LDP) EUV source is a system to generate EUV from discharged plasma triggered by laser on one electrode disc which is coated by tin film. The source has been proven as a highly reliable light source in EUVL high volume production. Also, LDP EUV source enables to generate high brightness with relatively larger EUV plasma, which benefits space stability as well as relatively larger plasma power. In this session, the following items will be presented. (1) LDP EUV source configuration and operation sequence. (2) LDP EUV source key performance (3) Stability Improvement (4) Reliability improvement. (5) Sample exposure application

In the scanner, various forces act on the EUV pellicle. Identifying the underlying causes of pellicle destruction is challenging, and the criteria for evaluating the lifetime of the pellicle are ambiguous. Therefore, it is essential to analyze the complex forces that affect the pellicle and investigate how they impact its durability. Particle defects, in particular, can significantly reduce the lifetime of the pellicle, leading to mechanical damage such as deformation or destruction. To investigate these effects, we examined how particle defects impact the pellicle in the scanner environment, classifying them based on the type of defect. We modeled a scenario involving mask stage acceleration and compared the impact of defect conditions on pellicles, considering the increased scanner speed of a high-NA scanner. The results show that the stress around the defect increases rapidly due to the acceleration of the pellicle after being deflected by gravity. The embedded defect shows the highest stress, which has the potential to decrease the lifetime of the pellicle due to repeated acceleration.

Underlayer is applied to suppress the pattern defects and improve the line width roughness (LWR) of photoresist in the extreme ultraviolet (EUV) lithography. The interaction between the underlayer and photoresist plays an important role in the dissolution behavior during the development, especially for the as-formed interfacial layer. In this research, the types of underlayer are changed by the polar and dispersion components of the surface free energy, and the influence of underlayer on the dissolution behavior during the development is revealed by the quartz crystal microbalance (QCM) method. Poly(4-hydroxystyrene) (PHS) is prepared as the photoresist (a dissolution agent). Tetramethylammonium hydroxide (TMAH) aqueous solution is utilized as the developer. The dissolution rate (attenuation rate) of photoresist is depended on the ratio of polar and dispersion component of underlayer. With the increased ratio, the dissolution rate first descends and then rises.

New resist materials are necessary to achieve higher resolution for the high NA EUV tools. The feature size shrinkage also increases the possibility of defect generation. Therefore, controlling defects remains essential. There are many factors in the lithography process that can contribute to the formation of defects in resist patterns. As a result, when testing the new resist material for patterning, there are more instances of pattern failures than successful ones. However, understanding pattern flaws can gain knowledge about the mechanism of defect generation. Based on the idea that exploiting the information in pattern failures can guide the resist resolution improvement, this study presents a novel method of interpreting patterns with defects based on an image recognition technology named Hough transformation. Approximate 2500 SEM images and part of corresponding simulation results were automatically analyzed. These results were then utilized to extract chemical information.

The ongoing shrinkage in minimum pitch has necessitated an even stricter and more restrictive error budget. Paradoxically, as the pitch decreases, image performances (e.g., NILS, image contrast) deteriorate, which necessitates compensation through dose adjustments, consequently resulting in thermal issues in the resist. Therefore, to meet the stringent requirements for the feature size, it is necessary to consider physical material properties such as deformation effects in dose optimization and overlay control. In this study, the systematic simulation on wafer heating have been explored to understand the deformation mechanism induced by EUV exposure. We found the thermal deformation as a significant factor leading to image fading and overlay errors. Furthermore, we discovered that deformation varied depending on the location in field-to-field, die-to-die, and within-slit. Particularly, the concentrated mechanical load at the edge domain intensified thermal stress. Additionally, through thermal-mechanical analysis based on the resist type, we explored the correlation between deformation and material properties. Our investigation revealed that the primary contributing factor is the dose energy rather than material properties.

Graphite is highly noteworthy for next-generation pellicles due to its high emissivity (>0.3), and Young's modulus (4.1 GPa) which provides high thermal and mechanical stability. The widely used graphite synthesis is chemical vapor deposition on thick metal catalyst, which involves several disadvantages such as hard to control of thickness uniformity and damage during wet-transfer processes. To overcome these problems, we propose a direct synthesis of graphite film(< 30 nm) on insulating substrate at low temperature about 500°C starting from the amorphous carbon (a-C) on catalyst metal film, which is named as graphite-metal induced crystallization of a-C (G-MICA). We finally demonstrate the formation of a graphite with uniform thickness below 30 nm on 8-inch SiN_x/Si wafer with an annealing at 500°C for 1 h. In order to reveal the origin of thickness uniformity of G-MICA, we closely observe the microstructure evolution of graphite as a function of annealing temperature (400~800°C) and time (0.25~180 min) using Cs corrected transmission electron microscopy. We believe that the nucleation of graphite starts to form at the interface between Ni and a-C and so vertical growth of graphite is limited by the thickness of Ni, which is somewhat differ from previously reports. To evaluate EUV characteristic, we removed the SiNx layer under the graphite through dry etching as thin as possible and made it in the form of a membrane. The G-MICA pellicle with thickness of 18 nm showed EUV transmittance of 88%, and emissivity of 0.3. Therefore, we confirmed the possibility of low-temperature G-MICA as a pellicle synthesis.

It has been reported that the good correlation in sensitivity and resolution between EUV exposure and EB exposure because of the similar mechanism of the photochemical-reaction in photoresists during exposure. However, in the early stages of EUV resist development, there are problems on the points of the cost and time-consuming to evaluate all EUV resist materials by EB exposure. Therefore, we investigated the possibility of using KrF exposure as the initial screening of EUV resists. If the correlation between KrF exposure, EB exposure and EUV exposure can be found, it will be possible to evaluate photoresists in a step-by-step manner, such as screening with KrF exposure first, followed by EB exposure, and finally EUV exposure in the initial evaluation stage. In this paper, we report on our investigations in the case of novolac resists, PHS chemically amplified resists, acrylic chemically amplified resists, and EUV polymer resists.