In-situ Contamination Thickness Measurement by Novel Resist Evaluation System at NewSUBARU

In this study, we evaluated the feasibility of incorporating elements with high extreme ultraviolet (EUV) absorption cross sections into chemically amplified photoresist (CAR) formulations to mitigate the sensitivity degradation characteristic of EUV lithography (EUVL), particularly in efforts aimed at reducing photon shot noise. We designed experiments to identify high-absorption elements that enhance the radiolysis of photoacid generators (PAGs) under EUV exposure. Bilayer stacks comprising a fluoroalkylated polymer overcoat doped with candidate elements atop an acid-labile polymer underlayer were exposed to EUV radiation, post-exposure baked, and developed. Varying the overcoat composition revealed that iodine (I) increased the underlayer's solubility, whereas tin (Sn) produced no comparable effect. Guided by this result, we synthesized an iodine-containing radiosensitizer, IOH-A, by introducing acid-cleavable acetal groups into iohexol, a radiocontrast agent used in computed tomography angiography. Incorporating IOH-A into CAR formulations, followed by compositional optimization, yielded a 2.6% improvement in sensitivity and a 12% reduction in line-edge roughness (LER) during EUVL patterning. These results demonstrate a practical strategy to relax the long-standing sensitivity-LER trade-off in EUVL using CARs and propose IOH-A as a promising design motif for next-generation CAR systems.

Background: Extreme ultraviolet (EUV) pellicles are affected by heat deformation due to energy absorption during EUV exposure. Defects can accelerate thermal deformation, thereby shortening pellicle lifetime. Aim: We compared the thermal stress and thermomechanical stability with different defects, focusing on the internal defects that occur during the fabrication of EUV pellicles. Approach: Pellicles resistant to high thermal stress can be fabricated based on mechanical properties. To evaluate this, we compared the mechanical stability based on robustness against thermal stress during exposure. Results: Our results show that external contaminants had a greater contribution than internal defects on the mechanical stability of pellicles. However, pellicles with internal defects exhibited increased thermal stress and decreased mechanical stability compared with defect-free pellicles during EUV exposure. Conclusions: Thermal stress is used as an indicator in most studies to predict pellicle lifetime, but evaluation of thermomechanical stability including thermal stress and mechanical durability is required because the material can break under low thermal stress depending on the mechanical properties, and pellicle defects can be a major cause of shortening the lifetime of pellicles.

Numerous investigations on extreme ultraviolet (EUV) resist outgassing have been performed using the pressure rise and gas chromatography mass spectrometry (GC–MS) method. However, the reliability of the results obtained with these methods has not been clearly discussed. In this paper, to analyze and verify the reliability of the resist outgassing results, de-protection reaction and photo acid generator's (PAG's) decomposing reaction in the resist film, which are viewed as the main source of resist outgassing, are investigated using the Fourier transform infrared spectroscopy (FT-IR). Analysis was performed on a resist film after EUV exposure, before post exposure bake (PEB). Based on the measured amount of de-protection reaction in the resist film, the amounts of resist outgassing released were calculated. It was found that the resist outgassing amount obtained through FT-IR was somewhere between those obtained using the pressure rise and GC–MS methods results. These similarities in the results substantiate the reliability of resist outgassing amounts obtained through these analysis methods.

We synthesized three type polymers 1) Poly hydroxyl-styrene (PHS resist). 2) hydroxyl-styrene methacrylate copolymer (Hybrid resist). 3) methacrylic acid tertiary aliphatic esters copolymer (Methacrylate resist). These polymers have been used in ArF, KrF lithography. Recently, these resists have been investigated to employ for Extreme ultra violet (EUV) lithography because absorption of EUV doesn’t depend on the molecular structure. But EUV has very higher energy than ArF, KrF and it is exceed ionization potential of resist materials. Thus, polymer behavior under the EUV exposure is different from ArF, KrF exposure. For analyzing difference between ArF, KrF and EUV, we conducted to exposed resist materials (PHS, Hybrid, Methacrylate resist) using electron beam (EB) radiation source. As the results, we observed PHS resist showed crosslinking behavior less than 5μ C/cm² , Hybrid resist showed cross-linking behavior more than 20μ C/cm², Methacrylate resist showed moderate main chain scission behavior less than 20μ C/cm² respectively.

Extreme ultraviolet (EUV) lithography is considered to be the most effective strategy for realize 7 nm generation manufacturing and beyond. A key factor for the realization of EUV lithography is the choice of EUV resist material that is capable of resolving below 15-nm half pitch with high sensitivity. Chemical Amplified Resist (CAR) using positive-tone development (PTD) is still one of the strongest candidates for EUV lithography. Recently, some researchers have reported concerns on the limitations in the performance of CAR materials. Consequently, there is a critical need for new chemistry and development of new resist materials. However, new resist materials still have lots of concerns for manufacturing, such like a non-CAR materials including metal resist. Therefore, CAR materials are still most important items for EUV lithography manufacturing. We’ve been developing negative-tone imaging (organic solvent development) with EUV exposure (EUV-NTI) for a long time. EUV-NTI has advantages for line-width roughness (LWR) due to their low swelling and dissolving smoothly. New EUV-NTI performances will be shown and also process condition progress will be updated. Also, the basic study will be reported, which is high absorption unit including materials for improving stochastic effect. We report herein recent progress of CAR materials, both positive-tone and negative-tone for EUV lithography.

Extreme ultraviolet (EUV) lithography uses 13.5 nm light to reach the sub-20 nm resolution. However, the process of pattern formation induced by this high-energy light is not well-understood. In this work, we provide an inorganic EUV photoresist with fluorescence properties by introducing a carbazole derivative as a ligand, and we study its effect on the patterning process. Using the fluorescence properties, changes in the emission of the material after EUV exposure could be tracked by means of spectroscopy and microscopy. The resist sensitivity was substantially reduced by the incorporation of the carbazole benzoate ligands, which is attributed to hole trapping and steric hindrance. After EUV irradiation of the resist films, infrared, UV-visible absorption, and fluorescence spectroscopies showed that the carbazole units were still mostly intact, although their fluorescence intensity was lowered. Our work shows that fluorescent labeling can provide relevant mechanistic insights in the patterning process of resists, potentially with a molecular resolution.

As Extreme ultraviolet (EUV) lithography technology shows promising results below 40nm feature sizes, TOKYO ELECTRON LTD.(TEL) is committed to understanding the fundamentals needed to improve our technology, thereby enabling customers to meet roadmap expectations. TEL continues collaboration with imec for evaluation of Coater/Developer processing sensitivities using the ASML Alpha Demo Tool for EUV exposures. The results from the collaboration help develop the necessary hardware for EUV Coater/Developer processing. In previous work, processing sensitivities of the resist materials were investigated to determine the impact on critical dimension (CD) uniformity and defectivity. In this work, new promising resist materials have been studied and more information pertaining to EUV exposures was obtained. Specifically, post exposure bake (PEB) impact to CD is studied in addition to dissolution characteristics and resist material hydrophobicity. Additionally, initial results show the current status of CDU and defectivity with the ADT/CLEAN TRACK ACT^TM 12 lithocluster. Analysis of a five wafer batch of CDU wafers shows within wafer and wafer to wafer contribution from track processing. A pareto of a patterned wafer defectivity test gives initial insight into the process defects with the current processing conditions. From analysis of these data, it's shown that while improvements in processing are certainly possible, the initial results indicate a manufacturable process for EUV.

Study on resist performance of chemically amplified molecular resists based on cyclic oligomers

Relying on reflective mask technology, extreme-ultraviolet (EUV) lithography is particularly vulnerable to mask substrate roughness. Previous research has shown mask roughness to play a significant role in printed line-edge roughness (LER). Here the analysis of mask-roughness effects is extended to printed contact-size variations. Unlike LER, illumination partial coherence is found to have little affect on the results for contacts that are near the diffraction limit. Analysis shows that, given the current state-of-the-art EUV mask, mask roughness has a significant effect on the process window for small contacts. The analysis also shows that a significant portion of the contact-size variation observed in recent 0.1-numerical-aperture EUV exposures can be attributed to the mask-roughness effect studied here.

Stacked Graphene Films The diagram illustrates the use of a pellicle made from a multilayer composite film, composed of layer-by-layer stacked graphene, for extreme ultraviolet (EUV) lithography. This graphene-based pellicle offers excellent optical transparency, mechanical strength, and thermal stability, ensuring superior protection for the photomask during EUV exposure and minimizing degradation or contamination. More information can be found in the Research Article by Yun Sung Woo, Byung Hee Hong, and co-workers (10.1002/adfm.202518685).

In this paper, the 'pattern formation' characteristics of a polyhydroxystyrene (PHS)-acryl hybrid extreme ultraviolet (EUV) resist was investigated using a high speed atomic force microscope. This analysis covers the dissolution or development, rinse and drying processes that are conventionally applied after EUV exposure and post exposure bake. As a result, it was found that during the development process, the EUV-exposed resist film exhibited swelling characteristics. This was assumed to be the effect of the balance / imbalance in dissolvability introduced by the hydrophobic acryl and hydrophilic PHS components of this hybrid resist. During the rinse process with de-ionized water, the critical dimension (CD) of the resulting line pattern after development was observed to increase with rinse time. This was attributed to a possible permeation of water into the resist line pattern causing the CD to swell. Lastly, for the drying process, the same line pattern CD was found to shrink similar to pre-rinse sizes and taper at the top edges. This suggests evaporation of the rinse water imbedded into the resist line pattern.

The following topics are dealt with: low-power electronics; Internet of Things; integrated circuit design; video coding; integrated circuit manufacture; CMOS integrated circuits; field programmable gate arrays; magnetic sensors; calibration; power consumption.

A new class of compounds, (5-alkylsulfonyloxyimino-5H-thiophen-2-ylidene)-2-methylphen yl-acetonitriles, characterized as non-ionic and halogen-free photoacid generators (PAG's) was developed. The compounds generate various kinds of sulfonic acids, such as methane, n-propane and camphor sulfonic acid under the g-line (436nm), i-line (365 nm) and Deep UV (DUV, 248 nm or shorter) exposure and are applicable for chemically amplified (CA) photoresists. The application-relevant properties of the compounds such as solubility in propylene glycol monomethyl ether acetate (PGMEA), UV absorption, thermal stability with or without poly(4-hydroxystyrene), storage stability in a neat form, sensitivity in some model resist formulations and dissolution inhibition efficiency during development process were evaluated. The compounds exhibit enough solubility in PGMEA, red-shifted UV absorption ($lamdamax: 405 nm), good thermal stability up to 140 C in a phenolic matrix, effective acid generation in terms of quantum yield in an acetonitrile solution and high sensitivity in negative tone and positive tone CA resist formulations, such as tert-butyl ester type and t-BOC type formulations, with g-line, i-line and DUV exposure. The photochemical decomposition reaction of the compound was also studied. Additionally a scanning electron microscope (SEM) photography as an application example of microlithography by the CA negative tone resist with the PAG is presented.

Optimizing the photochemistry in extreme ultraviolet (EUV) photoresists due to EUV exposures may enable faster, more efficient resists, leading to a greater throughput in manufacturing. Since the fundamental reaction mechanisms in EUV resists are believed to be due to electron interactions after incident 92 eV photons (13.5 nm) generate photoelectrons during ionization events, understanding how these photoelectrons interact with resist components is critical for optimizing the performance of EUV resists and EUV lithography as a whole. The authors will present an experimental method to measure the cross section of incident electron induced decomposition of three different photoacid generators (PAGs). To study the photoelectrons generated by the EUV absorption and measure their effect within resists, photoresists were exposed to electron beams at electron energies between 80 and 250 eV. The reactions between PAG molecules and electrons were measured by using a mass spectrometer to monitor the levels of small molecules produced by PAG decomposition that outgassed from the photoresist. This methodology allowed us to determine the number of PAG molecules decomposed per incident electron. By combining this result with the average penetration depth of an electron at a given energy, the cross sections of PAG molecules were determined for energies ranging between 80 and 250 eV. Comparing the cross sections of PAG molecules can provide insight into the relationship between chemical structure, reactivity to the electrons, and trends in cross section versus electron energy. This research is a part of a larger SEMATECH research program to understand the fundamentals of resist exposures to help in the development of new, better performing EUV resists.

Carbon contamination on extreme ultraviolet (EUV) multi-layer mirror is a seriously restrictive factor for lithography quality, chip output and life of lithography machine. In order to estimate the carbon contamination of EUV multi-layer and study the mechanism of carbon contamination deeply, an effective theoretical model of the carbon deposition on the multi-layer surface and experimental equipment for studying the carbon contamination are established. The theoretical model describes the transport of residual hydrocarbons to the irradiated area and the subsequent dissociation of the hydrocarbon by direct EUV radiation and secondary electron excitation, and indicates that the direct EUV radiation is the primary reason to dissociate the hydrocarbon, and makes the carbon deposited on the surface of multi-layer. Various carbon deposition states are simulated by the theoretical model, and some effective simulated results are obtained. Optical design scheme and structure design scheme of the experimental equipment are presented. The optical system includes two spherical multi-layer mirrors and a plane mirror multi-layer mirror. Ray trace and EUV intensity on sample are calculated, the light spot on sample is about Φ10mm and the EUV intensity is about 0.126mW/mm2. Structure of the experimental equipment includes adjusting mechanism of two spherical mirrors, rotary mechanism of plane mirror, alignment mechanism of EUV source, adjusting mechanism of sample, and so on. After testing, linear resolution and angle resolution of two spherical mirrors adjusting mechanism are 1μm and 5μrad respectively; linear displacement and linear resolution of sample adjusting mechanism are 50mm and 1μm respectively. The structure design scheme meets the requirement of the carbon contamination experiment.