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The dissociative photoionization of phenyl triflate (C6H5OSO2CF3), a neutral photoacid generator used in photolithography, was investigated in a gas phase experiment employing extreme ultraviolet (EUV) synchrotron radiation at 92 eV and photoelectron–photoion coincidence detection. The interaction of EUV photons with the molecule leads almost exclusively to dissociation, which is dominated by a sequential fragmentation mechanism, in which SO2, CF3, CO, and C2H2 are lost. For lithographic purposes, the lack of the observation of a fragment that could serve as a precursor for the formation of triflic acid means that the effective photoacid generator concentration in a photoresist is reduced, impacting its patterning performance in EUV lithography. A better understanding of the dissociative photoionization of photoresist components and proxies thereof can provide a crucial handle that guides the design of photoresists for the upcoming technology nodes with ever decreasing feature sizes for more powerful computer chips. [ABSTRACT FROM AUTHOR]

The identification of core technologies is a basic and important task in technology planning practice. We propose a limit citation network based on social network analysis and use the core–periphery structure to identify core patents. Then a case study is used to verify the feasibility of the methods. The results are: We obtain 994*994 co-citation matrix to identify core technologies in the EUVL and its network has an apparent core/periphery structure. The EUVL technology network has 123 core patens and 871 periphery patents. Seven core technologies are identified through the core network visualisation of connections between core patents. There are ten companies at a main position of the EUVL core technologies patentee network, of which AMAT has a strong presence, ASML and AGC play an important role. Most companies tend to pay attention to several technology domains, and one core technology area perhaps is the focus of many companies. The limit citation network improves the accuracy of network analysis results and could be used as a basis network model for analysis in some certain technology area. The identification of core technologies and main patentees on EUVL can help companies to accurately positioning the core technology and find the potential business partners. [ABSTRACT FROM AUTHOR]

The photochemical acid generation is refined from the first principles of quantum electrodynamics. First, we briefly review the formulation of the quantum theory of light based on the quantum electrodynamics framework to establish the probability of acid generation at a given spacetime point. The quantum mechanical acid generation is then combined with the deprotection mechanism to obtain a probabilistic description of the deprotection density directly related to feature formation in a photoresist. A statistical analysis of the random deprotection density is presented to reveal the leading characteristics of stochastic feature formation. [ABSTRACT FROM AUTHOR]

High-power lasers play an important role in modern science, industry, and medicine. A significant milestone was reached on 5 December 2022, when Inertial Confinement Nuclear Fusion (ICF) achieved scientific breakeven, releasing more energy than the input laser energy. Additionally, Extreme Ultraviolet Lithography (EUVL) has enabled the development of microchips with 3 nm process nodes, marking a leap in semiconductor technology. These examples, together with the recent achievement of 10 PW (1015 W) laser output, herald remarkable advancements in technology and science. Laser systems are broadly classified based on their operating regimes into two main categories: Continuous Wave (CW) operation, where the laser is continuously pumped and emits a steady beam of light, and the pulsed regime, in which the laser produces single or multiple pulses at various repetition rates. This review will primarily focus on pulsed laser systems, exploring their various types and recent technological advancements. [ABSTRACT FROM AUTHOR]

Extreme ultraviolet lithography (EUVL) is a leading technology in semiconductor manufacturing, enabling the creation of high-resolution patterns essential for advanced microelectronics. This review highlights recent progress in inorganic metal-oxide-based photoresists, with a focus on their applications in EUVL. The unique properties of zinc-based, tin–oxygen, and IVB group inorganic photoresists are examined, showcasing their enhanced chemical reactivity and precise patterning capabilities. Key advancements include the development of zinc oxide and tin oxide nanoparticles, which demonstrate significant improvements in photon absorption and solubility under extreme ultraviolet exposure. Additionally, the review delves into the photochemical reactions of tin–oxygen clusters and the influence of various ligands on film density and cross-linking. The findings suggest that these inorganic photoresists not only improve photolithographic performance but also hold potential for broader applications, such as pyroelectric infrared sensors and 3D printing. Future research directions are outlined, including the optimization of process parameters, the exploration of new ligand and metal combinations, and the evaluation of the environmental benefits of inorganic photoresists over traditional organic ones. These advancements are poised to further enhance the resolution and patterning capabilities required for next-generation semiconductor devices. [ABSTRACT FROM AUTHOR]

Particle-caused reticle defects contribute to a profound effect on the final integrated circuit (IC) yield, posing a significant technological challenge in extreme ultraviolet (EUV) lithography. This study employs the direct simulation Monte Carlo method to simulate the rarefied flow field within the EUV scanner reticle mini environment, investigating the influence of the rarefied flow field on particle behavior based on a bidirectional coupled gas-solid two-phase model. Simulation results demonstrate that the flow field induces the formation of a "particle inhibition zone" at high flow rates. Consequently, the "stopping distance" of particles released from the reticle masking blade surface remains consistently around 4 mm, and the residual rate of small particles (100 nm) is only 1.4%. The flow field control within the EUV scanner reticle mini environment can effectively mitigates the risk of particle-caused damage to the reticle surface while maintaining internal cleanliness. [ABSTRACT FROM AUTHOR]

The photochemical acid generation is refined from the first principles of quan-tum electrodynamics. First, we briefly review the formulation of the quantum theory of light based on the quantum electrodynamics framework to establish the probability of acid generation at a given spacetime point. The quantum mechanical acid generation is then combined with the deprotection mecha-nism to obtain a probabilistic description of the deprotection density directly related to feature formation in a photoresist. A statistical analysis of the ran-dom deprotection density is presented to reveal the leading characteristics of stochastic feature formation.

Synchrotron light sources can provide the required spatial coherence, stability and control to support the development of advanced lithography at the extreme ultraviolet and soft X-ray wavelengths that are relevant to current and future fabricating technologies. Here an evaluation of the optical performance of the soft X-ray (SXR) beamline of the Australian Synchrotron (AS) and its suitability for developing interference lithography using radiation in the 91.8 eV (13.5 nm) to 300 eV (4.13 nm) range are presented. A comprehensive physical optics model of the APPLE-II undulator source and SXR beamline was constructed to simulate the properties of the illumination at the proposed location of a photomask, as a function of photon energy, collimation and monochromator parameters. The model is validated using a combination of experimental measurements of the photon intensity distribution of the undulator harmonics. It is shown that the undulator harmonics intensity ratio can be accurately measured using an imaging detector and controlled using beamline optics. Finally, the photomask geometric constraints and achievable performance for the limiting case of fully spatially coherent illumination are evaluated.

The six‐degree‐of‐freedom (6‐DOF) micromotion mechanism is a key component in extreme ultraviolet (EUV) projection lithography objectives to compensate for wavefront aberration and ensure performance stability. It is required to have high precision and high reliability. A 6‐DOF mirror micromotion mechanism of an EUV lithography objective lens with Stewart configuration is proposed, and based on the RPY (Roll‐Pitch‐Yaw) angular rotation method and the second‐type Lagrange method, the kinematic and dynamic models of the mechanism are constructed to realize the decoupling of the mechanism's kinematics and the solution of the driving force. Comparative verification with finite element transient analysis shows that the response value of the dynamic model and the finite element method (FEM) differs by 4.8% in a specific posture. A hybrid optimization method, combining genetic algorithms and particle‐swarm optimization (GA‐PSO), was proposed to optimize the structural parameters of the initial design of the motion outriggers in a micromotion mechanism. The results demonstrate a 15.1% reduction in maximum driving force, significantly enhancing outrigger driving smoothness. [ABSTRACT FROM AUTHOR]

Photoresists are fundamental materials in photolithography and are crucial for precise patterning in microelectronic devices, MEMS, and nanostructures. This paper provides an in-depth review of recent advancements in positive photoresist research and development, focusing on discussion regarding the underlying mechanisms governing their behavior, exploring innovative fabrication techniques, and highlighting the advantages of the photoresist classes discussed. The paper begins by discussing the need for the development of new photoresist technologies, highlighting issues associated with adopting extreme ultraviolet photolithography and addressing these challenges through the development of advanced positive-tone resist materials with improved patterning features, resolution, and sensitivity. Subsequently, it discusses the working mechanisms and synthesis methods of different types and subtypes of photoresists, starting from non-chemically amplified, organic, and inorganic–organic hybrid photoresists and progressing to dry film resists, with an emphasis on the upsides of each. The paper concludes by discussing how future research in the field of lithography—prioritizing concerns related to environmental impacts, improved photoresist material and properties, and utilization of advanced quantum technology—can assist with revolutionizing lithography techniques. [ABSTRACT FROM AUTHOR]

Perfluorododecyl iodide (I-PFC12) is of interest for area-selective deposition (ASD) applications as it exhibits intriguing properties such as ultralow surface energy, the ability to modify silicon's band gap, low surface friction, and suitability for micro-contact patterning. Traditional photolithography is struggling to reach the required critical dimensions. This study investigates the potential of using I-PFC12 as a way to produce contrast between the growth area and non-growth areas of a surface subsequent to extreme ultraviolet (EUV) exposure. Once exposed to EUV, the I-PFC12 molecule should degrade with the help of the photocatalytic substrate, allowing for the subsequent selective deposition of the hard mask. The stability of a vapor-deposited I-PFC12 self-assembled monolayer (SAM) was examined when exposed to ambient light for extended periods of time by using X-ray photoelectron spectroscopy (XPS). Two substrates, SiO2 and TiO2, are investigated to ascertain the suitability of using TiO2 as a photocatalytic active substrate. Following one month of exposure to light, the atomic concentrations showed a more substantial fluorine loss of 10.2% on the TiO2 in comparison to a 6.2% loss on the SiO2 substrate. This more pronounced defluorination seen on the TiO2 is attributed to its photocatalytic nature. Interestingly, different routes to degradation were observed for each substrate. Reference samples preserved in dark conditions with no light exposure for up to three months show little degradation on the SiO2 substrate, while no change is observed on the TiO2 substrate. The results reveal that the I-PFC12 SAM is an ideal candidate for resistless EUV lithography. [ABSTRACT FROM AUTHOR]

Synchrotron light sources can provide the required spatial coherence, stability and control to support the development of advanced lithography at the extreme ultraviolet and soft X-ray wavelengths that are relevant to current and future fabricating technologies. Here an evaluation of the optical performance of the soft X-ray (SXR) beamline of the Australian Synchrotron (AS) and its suitability for developing interference lithography using radiation in the 91.8 eV (13.5 nm) to 300 eV (4.13 nm) range are presented. A comprehensive physical optics model of the APPLE-II undulator source and SXR beamline was constructed to simulate the properties of the illumination at the proposed location of a photomask, as a function of photon energy, collimation and monochromator parameters. The model is validated using a combination of experimental measurements of the photon intensity distribution of the undulator harmonics. It is shown that the undulator harmonics intensity ratio can be accurately measured using an imaging detector and controlled using beamline optics. Finally, the photomask geometric constraints and achievable performance for the limiting case of fully spatially coherent illumination are evaluated. [ABSTRACT FROM AUTHOR]

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State-of-the-art extreme ultraviolet lithography requires the use of ultrathin photoresists (or resists) due to pattern stability concerns and reduced depth of focus of the extreme ultraviolet lithography scanners. Current resists for extreme ultraviolet lithography are less than 50 nm thick. These ultrathin resists further complicate pattern transfer as unintended plasma-induced damage during dry etching is more pronounced. A better understanding of the interaction of plasma species with ultrathin resists is critical for enabling pattern transfer of sub-10 nm features. Here, we study the impact of vacuum ultraviolet photons, argon ions, and argon plasma on a 40 nm thick polymethylmethacrylate film. Using a deuterium lamp, an industrial ion beam etch tool, and an industrial inductively coupled plasma etch tool, we exposed the polymer to photons, ions, and plasma, respectively. The exposed samples were then analyzed for chemical and physical changes using different characterization techniques. It was observed that the vacuum ultraviolet photons interact with the entire bulk of polymer film, while the ions only affect the surface and subsurface region. The photon exposed samples formed smaller polymer fragments at low exposure doses and further started to cross-link at high doses. In contrast, the ion modification leads to carbonization of only the top few nanometers of the polymer film, leaving the bottom bulk intact. The plasma exposed sample showed changes characteristic to both vacuum ultraviolet photons and ions and their synergism. It was stratified with a 1.34 ± 0.03 nm thick ion-caused carbonized layer on top of a 13.25 ± 0.12 nm photon-induced cross-linked layer. By studying the impact of plasma photons on ultrathin polymethylmethacrylate, we were able to establish a baseline for a testing methodology that can be extended to novel ultrathin resist platforms. [ABSTRACT FROM AUTHOR]

Tin contamination of the collector mirror surface remains one of the crucial issues of EUV (Extreme Ultraviolet) sources, directly impacting the availability of the tool. Hydrogen plasma-based tin removal processes employ hydrogen radicals and ions to interact with tin deposits to form gaseous tin hydride (SnH4), which can be removed through pumping. An annular surface wave plasma (SWP) source developed at the University of Illinois—Urbana Champaign is integrated into the cone and perimeter of the collection mirror for in situ tin removal. The SWP is characterized by high ion and radical densities, low electron temperature, and local generation where etching is needed. This method has the potential to significantly reduce downtime and increase mirror lifetime. Radical probe measurements show hydrogen radical densities in the order of 1019 m−3, while Langmuir probe measurements show electron temperatures of up to 6 eV and plasma densities on the order of 1017–18 m−3. The generated ions are essential to the tin cleaning and have sufficiently low energy to cause no damage to the collector capping layer. Tin etch rates of up to 270 nm/min were observed in a variety of experimental conditions, including various powers, pressures, flowrates, and temperatures. The high etch rates demonstrated in this study exceed the expected contamination rate of the EUV source. [ABSTRACT FROM AUTHOR]

Extremely low probability stochastic defects are becoming a major concern in extreme-ultraviolet (EUV) lithography due to the discrete/probabilistic nature of photons, photo- and secondary electrons, reactions, and (macro-) molecular dissolutions. We introduce minimum complete models for stochasticity in EUV exposed resist films and predict the ultimate resolution of EUV lithography from a stochasticity viewpoint. Principal component analysis (PCA) is applied to three-dimensional chemo-physical event distributions in pattern-exposed resist films calculated by a fully coupled Monte Carlo simulation combined with discrete development/etching models. It expresses variabilities in the event distributions as linear combinations of the principal components (eigen-distributions), each of which reflects correlated reactions and clustering of (macro-) molecules. It successfully explains the fluctuations in local pattern edges and their material/process dependencies. Large size event distribution data are generated using the principal components, and stochastic defects are detected in the generated data. This virtual defect generation and inspection explains the observed probabilities and structures of stochastic defects. Thus, PCA provides general and universal representations for reaction stochasticity in resist films exposed by EUV lithography. It predicts that the ultimate resolution of EUV lithography in terms of stochasticity is limited by photoelectron/secondary electron scattering/diffusion or by photo-reaction density around the optical limit of 8 nm. [ABSTRACT FROM AUTHOR]

Effective cleaning of tin contamination on the collecting mirrors in extreme ultraviolet source is one of the key techniques to improve throughput and cost performance of extreme ultraviolet lithography. Hydrogen radicals produced in hydrogen plasma that is induced by wideband extreme ultraviolet radiation are expected to be utilized for in situ tin contamination cleaning in extreme ultraviolet sources. In this Letter, we clarified absolute density and cleaning ability of the hydrogen radicals produced by intense extreme ultraviolet pulse through ground state population density measurement by laser-induced fluorescence technique. The experimentally obtained radical parameters coincided well with simulation results and collisional radiative model. It was found that the extreme ultraviolet induced plasma was in quasi-steady state with abundant amount of hydrogen radicals in ground state. Further, it was found that the in situ tin contamination cleaning in extreme ultraviolet lithography source would become more practical with increase in operational parameters, such as extreme ultraviolet emission intensity, gas pressure, and radical production cross section. [ABSTRACT FROM AUTHOR]

This paper offers a comprehensive overview of the polyhedral oligomeric silsesquioxane (POSS) and POSS-based composites within the realm of photoresist resin. The study involves a systematic exploration and discussion of the contributions made by POSS across various lithographic systems, with specific emphasis on critical parameters such as film formation, sensitivity, resolution, solubility, and edge roughness. These lithographic systems encompass X-ray lithography (XRL), deep ultraviolet nanoimprint lithography (DUV-NIL), extreme ultraviolet lithography (EUV), and guided self-assembled lithography (DSA). The principal objective of this paper is to furnish valuable insights into the development and utilization of POSS-based photoresist materials in diverse lithographic contexts. [ABSTRACT FROM AUTHOR]

Ultrafine semiconductor fabrication by lithography has undergone a significant transition from deep ultraviolet (DUV) to extreme ultraviolet (EUV) processes, which presents new challenges. Specifically, the damage caused to components utilized in an EUV system, such as multilayer mirrors, reticles, and pellicles within lithography equipment, owing to EUV-induced H2 plasma, is a critical issue that directly affects the process yield and equipment lifespan. To address these issues, it is crucial to establish an environment similar to that of EUV-induced plasma and develop a method to evaluate the resulting damage. Accordingly, an evaluation method is developed for assessing the material damage caused by hydrogen radicals and ions in inductively coupled H2 plasma. In these systems, the electron density ranged from 5 × 108 to 3.5 × 1010 cm−3, the electron temperature ranged from 1 to 4 eV, and the ion energy ranged from several to tens of eV; these conditions closely align with the environment of an EUV-induced H2 plasma. The damage to Mo2C, a potential EUV pellicle material, is quantitatively analyzed by measuring the fraction of the pore area and examining the chemical characteristics after exposing the samples to various plasma conditions, including electron density, gas pressure, and exposure time. [ABSTRACT FROM AUTHOR]

Nickel (Ni) and its alloys are important multifunctional materials for the fabrication of integrated circuits, as either the absorber for the extreme ultraviolet lithography masks and/or interconnect metals at the nanometer scale. However, these applications require that Ni to be patterned controllably, selectively, and anisotropically—requirements that can only be met with a plasma based atomic layer etch (ALE) process. In this work, a plasma-thermal ALE approach is developed to pattern Ni, utilizing a nitrogen plasma to form NixN at the surface, formic acid (FA) vapor to selectively remove the NixN layer, and a low-energy Ar+ sputter process to remove carbon residue left by the FA prior to the subsequent nitridation step. This three step ALE process was shown effective to etch Ni with a rate of 1.3 ± 0.17 nm/cycle while maintaining surface smoothness. [ABSTRACT FROM AUTHOR]

One of the critical issues in lithography using extreme ultraviolet (EUV) light is tin contamination of the EUV collector mirrors in the tin-based LPP-EUV light source. The contamination can be removed by the reaction of tin atoms with hydrogen radicals producing stannane (SnH4), which is gaseous at the normal temperature. Hydrogen radicals can be produced from hydrogen molecules through photo-dissociation and photo-ionization induced by broadband radiation emitted from the EUV light source. In this work, an efficient production of hydrogen radical using vacuum ultraviolet (VUV) light emitted from laser-produced high-Z plasma is experimentally demonstrated. A two-dimensional radiation hydrodynamic simulation, coupled with photoionization and photo-dissociation cross sections, also shows the efficient hydrogen radical production by increased VUV light emission, as observed in the experiment. [ABSTRACT FROM AUTHOR]

A cyclic azimuthal shearing interferometer is devised for optical testing with a single-snapshot detection of surface asymmetry. A dove prism is used for azimuthal shearing of the wavefront, while a polarization-pixelated camera is adopted to capture four phase-shifted interferograms at once to calculate the wavefront gradient. Quantitative analysis is made subsequently using Zernike polynomials so as to identify relevant aberration components. The measurement point density turns out far higher than conventional Shack-Hartmann wavefront sensors, providing the potential of efficient real-time measurements for off-axis reflective optical systems intended for adaptive correction of EUV lithography and space telescopes. [ABSTRACT FROM AUTHOR]

Laser-spot-location detection technology based on photodetectors is widely used in the aerospace, medical, military and communication fields. However, most of the current research focuses on continuous laser detection in the visible and near-infrared bands, and the real-time high-precision position detection of a long-wave infrared pulsed laser is lacking. In this paper, a spot-position detection system based on a four-quadrant detector is designed for a 10.6 μm CO2-driven laser in extreme ultraviolet light source, and a second-order extended error compensation algorithm based on a Gaussian-spot model is proposed. Finally, the algorithm is verified and analyzed experimentally by a spot-position detection system under both focusing and defocusing conditions. The experimental results show that the root-mean-square error, maximum absolute error and average absolute error of the second-order error compensation algorithm are significantly reduced compared with the traditional algorithm, and the detection accuracy of the spot-position is better than 9 μm. The above results show that this spot-position detection system has obvious advantages and high accuracy, which can realize the high-precision real-time detection of a laser's spot position to obtain accurate spot position information, provide feedback adjustments for subsequent beam pointing control, and provide a theoretical basis for the beam pointing stability of the extreme ultraviolet light source system. [ABSTRACT FROM AUTHOR]

We demonstrate the possibility of manufacturing Be-based ultrathin films with high transmission at wavelengths of 11.4 and 13.5 nm. For free-standing films of Be and Be-based multilayer structures (Si/Be, ZrSi2/Be, Be/BexNy, Zr/Be, Ru/Be, Mo/Be), we determine the thresholds of the absorbed power at which over a short period (tens of minutes) of vacuum annealing, initially sagging free-standing films became visibly stretched over the hole. Of the film structures tested here, the Be/BexNy structure (with beryllium nitride interlayers) showed the highest threshold for the absorbed power (1 W/cm2). However, due to the low strength of this structure, ZrSi2/Be, Mo/Be, and Be films seem to be more promising for the manufacture of a full-size pellicle. Long-term vacuum annealing of Mo/Be and Be ultrathin films showed that they could withstand 24 hours of vacuum heating at an absorbed power density of 0.2 W/cm2 (film temperature 250°C) without noticeable changes in EUV transmission or sagging of films. With comparable transmission (~83% at 13.5 nm and ~88% at 11.4 nm), a multilayer Mo/Be structure with a thickness of 30 nm appears to be preferable, as it shows less brittleness than a monolayer Be film with a thickness of 50 nm. [ABSTRACT FROM AUTHOR]

We demonstrate the efficient generation of extreme ultraviolet (EUV) light from laser-produced plasma (LPP) driven by 2 μm wavelength laser light as an alternative for 10 μm CO2 gas LPP currently employed in EUV lithography machines for high-volume manufacturing of semiconductor devices. High conversion efficiencies of laser light into "in-band" EUV photons up to 5.0% are achieved by homogeneously heating the plasma that is laser-generated from preshaped tin microdroplet targets. Scaling the laser pulse duration, spot size, and intensity yields a high in-band EUV energy output of up to 12.5 mJ. The EUV emission source size is studied under a similar parameter range and is shown to match typical etendues of EUV optic columns. Our findings make 2 μm LPP a particularly promising candidate to power future EUV nanolithography. [ABSTRACT FROM AUTHOR]

The laser–produced plasma extreme ultraviolet (LPP–EUV) source is the sole light source currently available for commercial EUVL (extreme ultraviolet lithography) machines. The plasma parameters, such as the electron temperature and electron density, affect the conversion efficiency (CE) of extreme ultraviolet radiation and other critical parameters of LPP–EUV source directly. In this paper, the optical emission spectroscopy (OES) was employed to investigate the time–resolved plasma parameters generated by an Nd:YAG laser irradiation on a planar tin target. Assuming that the laser–produced tin plasma satisfies the local thermodynamic equilibrium (LTE) condition, the electron temperature and electron density of the plasma were calculated by the Saha–Boltzmann plot and Stark broadening methods. The experimental results revealed that during the early stage of plasma formation (delay time < 50 ns), there was a significant presence of continuum emission. Subsequently, the intensity of the continuum emission gradually decreased, while line spectra emerged and became predominant at a delay time of 300 ns. In addition, the evolution trend of plasma parameters, with the incident laser pulse energy set at 300 mJ, was characterized by a rapid initial decrease followed by a gradual decline as the delay time increased. Furthermore, with an increase in the incident laser pulse energy from 300 mJ to 750 mJ, the electron temperature and electron density of laser–produced tin plasma exhibiting a monotonically showed increasing trend at the same delay time. [ABSTRACT FROM AUTHOR]

In extreme ultraviolet (EUV) lithography, tin droplets evaporate and subsequently coat various surfaces including the collector mirrors. To clean off the tin, a hydrogen plasma is often used, but as a result, an unstable by-product, stannane (SnH4) is formed. The physicochemical characteristics of this gas, its formation in a plasma process, and its interaction with various materials have not been explored and understood completely. Here, the electron ionization mass spectrum of SnH4 is presented. All ten natural abundance isotopes were observed experimentally for each fragment, i.e., Sn+, SnH+, SnH2+, and SnH3+. Density functional electronic structure theory was used to calculate the optimized ground state geometries of these gas phase species and their relative stabilities and helped explain the absence of SnH4+ in the observed signals. The density of the liquid, its cracking pattern, and the surface morphology of its deposits were examined. The surface of the deposited tin film resulting from the decomposition and subsequent oxidation was characterized by x-ray photoelectron spectroscopy. The main species found at the surface were metallic tin and tin (II) oxide (SnO). The detailed characterization of stannane should help correctly identify it in EUV lithographic processes and develop approaches in the future to mitigate its decomposition and redeposition on the collector mirrors or vacuum chamber walls. [ABSTRACT FROM AUTHOR]

The characterization of scanning tip morphology is crucial for accurate linewidth measurements. Conventional rectangular characterizers are affected by lateral distortion caused by the nonlinearities in AFM scanning, leading to errors between the actual characterization results and the true values. In this study, we innovatively developed self-traceable two-dimensional nano-gratings using chromium atomic deposition technology and extreme ultraviolet interference lithography. We used this structure as a characterizer for conducting scanning tip characterizations.This paper analyzed the periodic stability of the grating sample during scanning and corrected the lateral distortion of atomic force microscopy (AFM) at scan scales of 0.5 µm and 1 µm based on its self-traceable characteristics. Additionally, we extracted the angle information of the scanning tip in the X direction and Y direction within a scan scale of 0.5 µm. The results demonstrate that the two-dimensional grating sample exhibited excellent periodic stability during scanning. The characterization errors for the tip's X direction and Y direction angles are within ±2°, showing high consistency. This study highlights that self-traceable two-dimensional grating samples have the capability for in situ bidirectional characterization of tip information, providing a creative solution for the development of new-style tip characterizers. [ABSTRACT FROM AUTHOR]

Photoresists are fundamental materials in photolithography and are crucial for precise patterning in microelectronic devices, MEMS, and nanostructures. This paper provides an in-depth review of recent advancements in positive photoresist research and development, focusing on discussion regarding the underlying mechanisms governing their behavior, exploring innovative fabrication techniques, and highlighting the advantages of the photoresist classes discussed. The paper begins by discussing the need for the development of new photoresist technologies, highlighting issues associated with adopting extreme ultraviolet photolithography and addressing these challenges through the development of advanced positive-tone resist materials with improved patterning features, resolution, and sensitivity. Subsequently, it discusses the working mechanisms and synthesis methods of different types and subtypes of photoresists, starting from non-chemically amplified, organic, and inorganic–organic hybrid photoresists and progressing to dry film resists, with an emphasis on the upsides of each. The paper concludes by discussing how future research in the field of lithography—prioritizing concerns related to environmental impacts, improved photoresist material and properties, and utilization of advanced quantum technology—can assist with revolutionizing lithography techniques.

Nanotransfer printing (nTP) is one of the most promising nanopatterning methods given that it can be used to produce nano-to-micro patterns effectively with functionalities for electronic device applications. However, the nTP process is hindered by several critical obstacles, such as sub-20 nm mold technology, reliable large-area replication, and uniform transfer-printing of functional materials. Here, for the first time, a dual nanopatterning process is demonstrated that creates periodic sub-20 nm structures on the eight-inch wafer by the transfer-printing of patterned ultra-thin (<50 nm) block copolymer (BCP) film onto desired substrates. This study shows how to transfer self-assembled BCP patterns from the Si mold onto rigid and/or flexible substrates through a nanopatterning method of thermally assisted nTP (T-nTP) and directed self-assembly (DSA) of Si-containing BCPs. In particular, the successful microscale patternization of well-ordered sub-20 nm SiOx patterns is systematically presented by controlling the self-assembly conditions of BCP and printing temperature. In addition, various complex pattern geometries of nano-in-micro structures are displayed over a large patterning area by T-nTP, such as angular line, wave line, ring, dot-in-hole, and dot-in-honeycomb structures. This advanced BCP-replicated nanopatterning technology is expected to be widely applicable to nanofabrication of nano-to-micro electronic devices with complex circuits. [ABSTRACT FROM AUTHOR]

The tin-oxo cage ([R12Sn12O14(OH)6]2+) is an excellent photoresist candidate in extreme ultraviolet lithography (EUVL). Photoionization that leads to plenty of photoelectrons and secondary electrons is an inevitable process upon irradiation by EUV light. The secondary electrons could cause electron blur and decrease the resolution of the photoresist. The utilization and improvement are limited owing to its poorly understood fundamental chemical process, such as exposure to EUV. In this study, the property of complexes (bare cage, binary complexes, and ternary complexes) formed by the combination of the cage and different counterions (methanesulfonate, tosylate, and triflate) was explored using density functional theory (DFT). Extended transition state-nature orbital of chemical valence (ETS-NOCV), charge decomposition analysis (CDA), and atomic dipole moment corrected Hirshfeld (ADCH) atomic charge analyses were carried out to characterize the interaction process (including ionization, electron attachment, and cleavage of the carbon–tin bond) and inherent mechanism. The number and species of counterions are closely associated with ionization and electron attachment; however, they show an inconspicuous effect on the carbon–tin bond energy. Meanwhile, tin free radical could be the reactivity site of ionization (and electron affinity). The activity of radical species is affected by counterions; this could be attributed to the changes in the charge density by diverse counterions, which could be an important factor in why the counterion affects the pattern. In addition, a superb linearity between the ADCH of tin free radical and IP/AP was found, which indicate that the atomic charge could be a simple and reliable substitution of complicated calculation for IP (or AP) to screen suitable counterions and improve the resolution of photoresist. [ABSTRACT FROM AUTHOR]

Continuing extreme downscaling of semiconductor devices, essential for high performance and energy efficiency of future microelectronics, hinges on extreme ultraviolet lithography (EUVL) and addressing associated challenges. One of such challenges is a need for improved EUV photoresists featuring simultaneously high sensitivity, resolution, and etch selectivity. Here, a new, positive‐tone, organic–inorganic hybrid EUV photoresist is demonstrated that delivers a high‐resolution EUVL and electron‐beam lithography (EBL) patterning capability combined with high sensitivity and etch resistance. The new resist, poly(methyl methacrylate) infiltrated with indium oxide (PMMA‐InOx), is synthesized via vapor‐phase infiltration (VPI), a material hybridization technique derived from atomic layer deposition. The weak binding of the gaseous indium precursor, trimethylindium, to the carbonyl group in PMMA allows the synthesis of hybrids with inorganic content distributed uniformly in the resist, enabling high EUVL and EBL sensitivities (18 mJ cm−2 and 300 µC cm−2, respectively) and high‐resolution positive‐tone EUVL patterning (e.g., 40 nm half‐pitch line‐space and 50 nm diameter contact hole patterns) with high Si etch selectivity (>30–40). The low exposure doses required to pattern the PMMA‐InOx hybrid resist, high etch resistance, and processing strategies, which are developed, can pave the way for using infiltration‐synthesized hybrid thin films as reliable positive‐tone EUV photoresists for future semiconductor patterning. [ABSTRACT FROM AUTHOR]

Variants of the structures of free-standing films with a high transmittance coefficient at a wavelength of 13.5 nm, which were developed for use in the projection of extreme ultraviolet (EUV) lithography as protective and filtering elements, are considered. Our attention is focused on the most problematic—in terms of manufacturing and the requirements on their characteristics—ultrathin free-standing films (pellicles), which are installed in front of the mask (photomask) in modern EUV scanners and serve to protect the surface of the mask from contamination. The main approaches used to manufacture ultrathin free-standing large-aperture films are compared. A brief review of the research on the development of high transmittance pellicles at a wavelength of 11.2 nm, which may become an operating wavelength for future EUV lithography, is given. [ABSTRACT FROM AUTHOR]

Abstract Continuing extreme downscaling of semiconductor devices, essential for high performance and energy efficiency of future microelectronics, hinges on extreme ultraviolet lithography (EUVL) and addressing associated challenges. One of such challenges is a need for improved EUV photoresists featuring simultaneously high sensitivity, resolution, and etch selectivity. Here, a new, positive‐tone, organic–inorganic hybrid EUV photoresist is demonstrated that delivers a high‐resolution EUVL and electron‐beam lithography (EBL) patterning capability combined with high sensitivity and etch resistance. The new resist, poly(methyl methacrylate) infiltrated with indium oxide (PMMA‐InOx), is synthesized via vapor‐phase infiltration (VPI), a material hybridization technique derived from atomic layer deposition. The weak binding of the gaseous indium precursor, trimethylindium, to the carbonyl group in PMMA allows the synthesis of hybrids with inorganic content distributed uniformly in the resist, enabling high EUVL and EBL sensitivities (18 mJ cm−2 and 300 µC cm−2, respectively) and high‐resolution positive‐tone EUVL patterning (e.g., 40 nm half‐pitch line‐space and 50 nm diameter contact hole patterns) with high Si etch selectivity (>30–40). The low exposure doses required to pattern the PMMA‐InOx hybrid resist, high etch resistance, and processing strategies, which are developed, can pave the way for using infiltration‐synthesized hybrid thin films as reliable positive‐tone EUV photoresists for future semiconductor patterning.

Exploiting advanced patterning strategies and materials to achieve smaller sizes and higher precision is urgently and constantly pursued. In this work, to suppress the radiolytic low-energy secondary electron diffusion and accompanying unpredictable defects, we demonstrate a patterning control strategy to realize high-precision nanoscale fabrication through a quenching mechanism and achieve significant resolution and roughness enhancement in ∼10 nm patterning. [Display omitted] Nanopatterning is a well-established approach to fabricating nanostructures in electronics and optics, and exploiting patterning strategy to achieve smaller feature sizes and higher precision is urgently and constantly pursued. State-of-the-art extreme ultraviolet lithography and electron beam lithography have proven to produce smaller sizes. However, for such energetic radiation-based approaches, the serious diffusion behavior of the radiolytic low-energy secondary electrons will result in unpredictable defects in the unexposed matrix, limiting the ultimate resolution and hindering its potential in sub-10 nm patterning. Herein, we report significant progress in high-resolution patterning via suppressing of residues caused by secondary electron diffusion, and 10 nm line-space nanostructures are achieved by utilizing a free radical quencher in patterning a highly sensitive zirconium-containing photoresist. Lithography evaluation combined with theoretical calculation reveals this novel radical quencher approach can effectively suppress undesired electronic excitation and ionization reactions, thereby significantly improving resolution and edge roughness. By inhibiting secondary electron-induced active species, this quenching mechanism is found to increase the onset dose and effectively narrow the energy deposition; thus improving the patterning contrast and facilitating the acquisition of straight lines with sharp edges. This work provides a new perspective on active species diffusion control for higher precision nanoscale fabrication. [ABSTRACT FROM AUTHOR]

[Display omitted] With the development of microelectronics, the demand for continuously miniaturized feature sizes has driven continuous progress in lithography technology. Extreme ultraviolet (EUV) lithography can directly pattern sub-20-nm half-pitch resolution, and it has emerged as the most promising nanoscale fabrication technology. However, the restricted brightness of the EUV light source and the limited reflectivity of multilayer mirrors impose new requirements for the sensitivity of photoresists. Furthermore, the high-resolution patterning characteristics of the EUV require resistive materials featuring smaller component sizes and higher etch resistance. Thus, the development of photoresists with new attributes of EUV remains a challenge. This review covers the evolution of EUV photoresists, including chemically amplified resists, non-chemically amplified polymer resists, molecular glass resists, and metal-containing resists, including the future development trends of EUV-sensitive materials. [ABSTRACT FROM AUTHOR]

Dynamic gas lock (DGL) is one of the central components of contamination control for extreme ultraviolet lithography, and airflow efficiency is a key parameter. In this paper, the principle of the DGL and airflow efficiency is described at first, then a set of experiments is carried out on a self-developed DGL experimental device. The results of the experiment show that the pressures of the project optics box and the wafer chamber do not influence the airflow efficiency of DGL. In addition, the airflow efficiency increases slowly with the total airflow, and the gradient gradually diminishes. With an increase in the total airflow from 1 to 3 Pa m3/s, the argon efficiency increases from 0.247 to 0.260, while the nitrogen efficiency increases from 0.251 to 0.264, which shows that the efficiency of argon is slightly smaller than that of nitrogen under the same conditions. Within the interesting range of argon gas flow, the maximum difference between theory and experiment is less than 6%, which is acceptable in engineering. The theoretical calculation method in this paper can be used to evaluate the airflow efficiency for engineering applications. It is concluded that the airflow efficiency of the DGL is almost independent of the pressures of the upper and lower sides. However, the total airflow and the gas species will change the airflow efficiency. [ABSTRACT FROM AUTHOR]

Defect control of extreme ultraviolet (EUV) masks using pellicles is challenging for mass production in EUV lithography because EUV pellicles require more critical fabrication than argon fluoride (ArF) pellicles. One of the fabrication requirements is less than 500 μ m transverse deflections with more than 88% transmittance of full-size pellicles (112 m m   × 145 m m ) at pressure 2 P a . For the nanometer thickness (thickness/width length ( t / L ) = 0.0000054) of EUV pellicles, this study reports the limitation of the student's version and shear locking in a commercial tool-based finite element method (FEM) such as ANSYS and SIEMENS. A Python program-based analytical-numerical method with deep learning is described as an alternative. Deep learning extended the ANSYS limitation and overcame shear locking. For EUV pellicle materials, the ascending order of transverse deflection was R u < M o S i 2 = S i C < S i N x < Z r S r 2 < p - S i < S n in both ANSYS and a Python program, regardless of thickness and pressure. According to a neural network, such as the Taguchi method, the sensitivity order of EUV pellicle parameters was P o i s s o n ' s   r a t i o < E l a s t i c   m o d u l u s < P r e s s u r e < T h i c k n e s s < L e n g t h . [ABSTRACT FROM AUTHOR]

Enabling extreme ultraviolet lithography (EUVL) as a viable and efficient sub-10 nm patterning tool requires addressing the critical issue of reducing line edge roughness (LER). Stochastic effects from random and local variability in photon distribution and photochemical reactions have been considered the primary cause of LER. However, polymer chain conformation has recently attracted attention as an additional factor influencing LER, necessitating detailed computational studies with explicit chain representation and photon distribution to overcome the existing approach based on continuum models and random variables. We developed a coarse-grained molecular simulation model for an EUV patterning process to investigate the effect of chain conformation variation and stochastic effects via photon shot noise and acid diffusion on the roughness of the pattern. Our molecular simulation demonstrated that final LER is most sensitive to the variation in photon distributions, while material distributions and acid diffusion rate also impact LER; thus, the intrinsic limit of LER is expected even at extremely suppressed stochastic effects. Furthermore, we proposed and tested a novel approach to improve the roughness by controlling the initial polymer chain orientation. [ABSTRACT FROM AUTHOR]

Area-selective atomic layer deposition (AS-ALD) is a coveted method for the fabrication of next-generation nano-electronic devices, as it can complement lithography and improve alignment through atomic scale control. Selective reactions of small molecule inhibitors (SMIs) can be used to deactivate growth on specific surface areas and as such enable AS-ALD. To investigate new applications of ASD, we need insight into the reactions of SMIs with a broad range of technology relevant materials. This paper investigates the reactions of aminosilane SMIs with a broad range of oxide surfaces and the impact on subsequent atomic layer deposition (ALD). We compare the reactions of two aminosilane SMIs, namely, dimethylamino-trimethylsilane (DMA-TMS) and hexamethyldisilazane (HMDS), with a hydroxylated SiO2 surface and the impact on subsequent ALD processes. The DMA-TMS reaction saturates faster than the HMDS reaction and forms a dense trimethylsilyl (TMS) layer with a higher TMS surface concentration. The higher TMS surface concentration yields better inhibition and higher selectivity during subsequent TiO2 ALD. We show that a wide range of surfaces, i.e., MgO, HfO2, ZrO2, Al2O3, TiO2 (TiN/TiOx), SiO2, SnO2, MoOx, and WO3 remain reactive after DMA-TMS exposure for conditions where SiO2 is passivated, indicating that DMA-TMS can enable AS-ALD on these surfaces with respect to SiO2. On these surfaces, DMA-TMS forms residual TMS and/or SiOxCyHz surface species that do not markedly inhibit ALD but may affect interface purity. Surfaces with lower, similar, and higher surface acidity than SiO2 all show less reactivity toward DMA-TMS, suggesting that surface acidity is not the only factor affecting the substrate-inhibitor interaction. Our study also compares a hybrid inorganic-organic SnOxCyHz and inorganic SnO2 material in view of their relevance as resist for extreme ultraviolet lithography. DMA-TMS can enable selective infiltration in SnOxCyHz, as opposed to selective deposition on SnO2, indicating tunable reactivity by bulk and surface composition. These insights into the reactivity of aminosilane SMIs may aid the design of new area-selective deposition processes, broaden the material space, and enable new applications. [ABSTRACT FROM AUTHOR]

In extreme ultraviolet (EUV) lithography, chemistry is driven by secondary electrons. A deeper understanding of these processes is needed. However, electron-driven processes are inherently difficult to experimentally characterize for EUV materials, impeding targeted material engineering. A computational framework is needed to provide information for rational material engineering and identification at a molecular level. We demonstrate that density functional theory calculations can fulfill this purpose. We first demonstrate that primary electron energy spectrum can be predicted accurately. Second, the dynamics of a photoacid generator upon excitation or electron attachment are studied with ab-initio molecular dynamics calculations. Third, we demonstrate that electron attachment affinity is a good predictor of reduction potential and dose to clear. The correlation between such calculations and experiments suggests that these methods can be applied to computationally screen and design molecular components of EUV material and speed up the development process.

In extreme ultraviolet (EUV) lithography, chemistry is driven by secondary electrons. A deeper understanding of these processes is needed. However, electron-driven processes are inherently difficult to experimentally characterize for EUV materials, impeding targeted material engineering. A computational framework is needed to provide information for rational material engineering and identification at a molecular level. We demonstrate that density functional theory calculations can fulfill this purpose. We first demonstrate that primary electron energy spectrum can be predicted accurately. Second, the dynamics of a photoacid generator upon excitation or electron attachment are studied with ab-initio molecular dynamics calculations. Third, we demonstrate that electron attachment affinity is a good predictor of reduction potential and dose to clear. The correlation between such calculations and experiments suggests that these methods can be applied to computationally screen and design molecular components of EUV material and speed up the development process.

Extreme ultraviolet lithography (EUVL) is widely employed in the electronics, automotive, military, and AI computing areas for IC chip fabrication. A pellicle is a thin and transparent membrane that protects a costly photomask, known as a reticle, during the EUVL process. The fabricated IC chip can be disastrous without a pellicle. When a particle lands on a photomask, it frequently results in a faulty pattern, which leads to chip failure and lower production yield. A nanometer‐thick graphite (NGF) has demonstrated tremendous potential for addressing optical, mechanical, thermal, and chemical criteria among potential pellicle materials such as carbon allotropes, Si, SiNx, and Si‐Mo‐Nb. This review summarizes current progress in NGF pellicles, including large‐scale material fabrication (up to 135 mm × 135 mm), transfer method for freestanding form, and practical characterization methods. Current significant challenges and future opportunities for NGF pellicles are also discussed in order to facilitate a critical transition from lab‐scale research to industrial‐scale implementation. [ABSTRACT FROM AUTHOR]