Extreme Ultraviolet Lithography Research Articles

Anionic Photoacid Generator Bound Polymer Photoresists With Improved Performance for Advanced Lithography Patterning

ABSTRACTChemically amplified resist (CAR) has gained considerable attention in the realm of extreme ultraviolet lithography (EUVL) due to their exceptional photosensitivity, high resolution, and commercialization. This work presents the development of an anionic photoacid generator (PAG) bound polymer (PGM) photoresist composed of three rationally selected monomeric units: 2‐Phenyl‐2‐propyl methacrylate (PPMA), γ‐butyrolactone‐3‐yl methacrylate (GBLMA), and triphenyl sulfonium salt 1,1,2‐trifluorobutanesulfonate methacrylate (MTFBS‐TPS). Electron beam lithography (EBL) studies demonstrate that the PGM photoresist functions as a positive tone photoresist with commendable sensitivity (27.9 μC/cm2) and contrast (6.53). When compared under similar conditions, with equal amounts of PAG and identical processing, the PGM photoresist exhibited superior pattern fidelity, ease of handling, and higher line resolution (25 nm) relative to the triphenyl sulfonium triflate (TPS‐OTF) blend polymer (PG‐T) photoresist. This enhancement is probably caused by anionic PAG directly attaching to the polymer backbone, which mitigates acid diffusion during the post‐exposure baking (PEB) process. Moreover, the PGM photoresist obtained a pattern of 37.5 nm at 50 mJ/cm2 in the EUVL test. The positive tone resists were successfully applied for the fabrication of nanoscale patterns.

Development and optimization of metal silicide EUV pellicle for 400W EUV lithography

In the extreme ultraviolet lithography (EUVL) process, extreme ultraviolet (EUV) pellicles serve as thin, transparent membranes that shield the photomask (reticle) from particle contamination, thereby preserving photomask pattern integrity, reducing chip failure risks, and enhancing production yields. The production of EUV pellicles is highly challenging due to their mechanical fragility at nanometer-scale thicknesses and the need to endure the rigorous conditions of the EUVL environment, which include high temperatures and hydrogen radicals. Consequently, extensive research has been conducted on a variety of materials, such as carbon-based and silicon-based substances, for the development of EUV pellicles. This study explores the feasibility of implementing metal silicide (MeSix) pellicles for high-power EUVL applications. We successfully fabricated MeSixpellicles in two dimensions: a 10 mm × 10 mm sample and a full-size 110 mm × 144 mm pellicle. We then evaluated their optical, mechanical, thermal, and chemical properties, as well as their lifespan. The pellicles demonstrated over 90% transmittance and less than 0.04% reflectance. The films exhibited a deflection of 300μm under a 2 Pa differential pressure and an ultimate tensile strength exceeding 2 GPa. The thermal emissivity was measured at 0.3. Additionally, the durability of the pellicles was validated through exposure to 20,000 wafers using a 400 W EUV power (offline test: 20 W cm-2). The transmittance variations of the pellicles were evaluated by comparing the measurements obtained before and after exposure to 400 W EUV power.

Probability distribution-based method for aberration budgeting in EUV lithography

Extreme ultraviolet (EUV) lithography is one of the most indispensable technologies in semiconductor manufacturing for 7 nm and smaller technology nodes. However, many key parameters in the lithography system may deviate from target values, and there are extremely complex coupling effects among these parameters. Additionally, aberrations that far exceed expectations damage lithography results severely. These accidents pose significant challenges in achieving satisfactory lithography outcomes. To investigate the impact of aberrations coupled with multiple key parameters on lithography results, and to provide quantitative and precise direction for the research and development of lithography systems, this paper proposes a methodology of budget analysis of aberrations based on probability distribution. First, a rapid prediction model of lithography results is established by multilayer perceptron. Then, the lithography results under different parameter conditions are obtained according to the prediction model. Subsequently, the aberration combinations that meet lithography requirements are filtered out. Finally, the impact of each aberration on lithography results and their budget range can be determined according to the general distribution and joint probability distribution of aberrations coupled with multiple key parameters. For patterns commonly used in EUV single exposure at the 5 nm technology node, this paper finds that aberrations such as Z2 and Z4 exhibit significant impacts on lithography results under the coupling of multiple key parameters. Additionally, all the budget ranges of aberrations are obtained. Specifically, for example, Z2, Z4, and Z5, their budget ranges are -18∼15mλ, 10∼45mλ, 7∼43mλ, respectively. While items such as Z1 and Z27, their budget ranges are -40∼40mλ consistently. This method can obtain the impact and budget range of aberrations under the coupling of multiple key parameters in the lithography system quickly and accurately. It can provide a reliable guideline for aberration compensation and optimization, and the research and development of lithography systems. Moreover, the budget ranges obtained by this method can also serve as a clear indicator for aberration monitoring.

Comparison of Al- and Hf-based hybrid photoresists grown by molecular layer deposition for extreme ultraviolet lithography

The continued downscaling of electronic device dimensions requires the development of high-performance resist materials for advanced lithographic patterning. In this study, we examine Al-based hybrid “alucone” thin films grown by molecular layer deposition (MLD) for application to extreme ultraviolet (EUV) lithography and compare their resist properties with those of previously studied Hf-based MLD hybrid “hafnicone.” Both alucone films presented here—standard alucone and oxygen-rich alucone—are deposited using the precursors trimethylaluminum and ethylene glycol. Using electron-beam lithography as a proxy for EUV, we demonstrate that alucone behaves as a negative-tone resist capable of resolving line widths down to ∼20 nm. It is found that the sensitivity of oxygen-rich alucone is 4800 μC/cm2 using 0.125M HCl as the developer, whereas standard alucone is somewhat less sensitive. The resolution of alucone is higher than that of hafnicone, although the sensitivity is poorer. By performing x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, we investigate the degradation mechanism of standard alucone and compare this mechanism to that of hafnicone. We rationalize the observed differences in resist behavior between hafnicone and alucone by considering the oxophilicity of the metal atom in the respective thin films. This study provides a deeper understanding of the relationship between MLD film chemistry and irradiation responsiveness, which can help advance the optimization of resist materials for microelectronics fabrication.

Single‐Component High‐Resolution Dual‐Tone EUV Photoresists Based on Precision Self‐Immolative Polymers

AbstractElectron beam (EB) and extreme ultraviolet (EUV) lithography are advanced techniques capable of achieving sub‐10 nm resolutions, critical for fabricating next‐generation nanostructures and semiconductor devices. However, developing EUV photoresists that meet all demands for resolution, line edge roughness (LER), and sensitivity (RLS) remains a significant challenge. Herein, we introduce high‐performance photoresists based on single‐component self‐immolative polymers (SIPs) with inherent signal amplification via cascade degradation. These SIPs function as dual‐tone photoresists under both EB and EUV lithography, with performance primarily determined by the exposure dose. Lithographic evaluations show that discrete SIPs provide significant improvements over disperse counterparts, achieving higher resolution and reduced LER. Specifically, a discrete SIP with a DP of 12 produces a line‐space pattern with a resolution of approximately 18 nm and an LER of 1.8 nm, compared to 21 nm resolution and 2.5 nm LER for disperse SIPs. Additionally, these SIP‐based photoresists, enriched with aromatic structures, exhibit excellent etch resistance. The single‐component nature and potential to address the RLS trade‐off underscore the promise of discrete SIPs for EUV lithography.

High-resolution chemical patterns from negative tone resists for the integration of extreme ultraviolet patterns of metal-oxide resists with directed self-assembly of block copolymers

Extreme ultraviolet (EUV) lithography faces significant challenges in designing suitable resist materials that can provide adequate precision, while maintaining economically viable throughput. These challenges in resist materials have led to printing failures and high roughness in EUV patterns, compromising the performance of semiconductor devices. Integrating directed self-assembly (DSA) of block copolymers (BCPs) with EUV lithography offers a promising solution because, while the BCPs register to the EUV-defined chemical guiding pattern, the thermodynamically determined structures of the BCPs automatically rectify defects and roughness in the EUV pattern. Despite the superior resolution of metal-oxide EUV resists (MORs), their application to DSA is limited by the difficulty in converting them into chemical patterns that allow effective transfer of the rectified patterns of DSA films into inorganic materials. To address this challenge, this study introduces a novel strategy for fabricating chemical patterns using hydrogen silsesquioxane (HSQ), a high-resolution negative tone inorganic resist, as a model system for MORs. Initially, a sacrificial Cr pattern is generated from HSQ patterns via reactive ion etching. The sacrificial Cr pattern is converted into a chemical pattern by first grafting a water-soluble polyethylene oxide brush onto the substrate, then wet etching the Cr, and finally grafting nonpolar polystyrene brushes. Assembling polystyrene-block-poly(methyl methacrylate) on these patterns results in structures oriented and registered with the underlying pattern, achieving 24 nm full-pitch resolutions. This approach has the potential to integrate MOR patterns into the DSA process, thereby enabling the generation of high-quality sub-10 nm patterns with high-χ BCPs.

Research on Nanometer Precision Measurement Method of High Order Even Aspheres

Optical aspheres are demanded with extremely high precision to meet functional requirements in space telescopes, extreme ultraviolet lithography, and other modern large optical systems. The nano-precision fabrication of optical aspheres requires high-precision measurements to guide deterministic optical processing. Null test is the preferred method for high-precision measurements. Null optics are required to compensate for the incident wavefront in the null test of optical aspheres. However, wavefront aberrations caused by the transmission flat or transmission sphere of interferometer and null optics can limit measurement accuracy and need to be separated. A nano-precision measurement method is proposed for the even optical aspheres of high order in this paper. A computer-generated hologram is used as a null optic to realize a null test on optical aspheres. Mapping distortion correction is performed on the measurement results to ensure that the transverse coordinates of the measurement results correspond correctly to those of the test surface. Absolute testing is applied to separate the wavefront aberrations caused by the computer-generated hologram and interferometer optics. Finally, the results obtained by this method were used to guide deterministic optical processing, enabling the nano-precision fabrication of optical aspheres.

Actinic mask inspection for the era of high-numerical aperture extreme ultraviolet lithography

Actinic mask inspection for the era of high-numerical aperture extreme ultraviolet lithography

Tatian polynomial-based annular pupil wavefront optimization method for high-NA extreme ultraviolet lithography

The advanced technology node has an exact error tolerance. The effect of projection objective aberration on imaging cannot be neglected. In order to reduce the effect of aberration, considering the central obscuration of the high-NA extreme ultraviolet projection objective, we propose a Tatian polynomial-based annular pupil wavefront optimization (TBAPWO) method. An active pupil consisting of 64-term Tatian polynomials is incorporated into the imaging model. The suitable coefficients of the Tatian polynomials are solved using the gradient iteration method. The optimized active pupil can improve lithographic imaging quality. Simulation results show that the TBAPWO method can effectively reduce the pattern error of imaging by more than 30%, which indicates that the effect of aberration on imaging is controlled.

Challenges and limits to patterning using extreme ultraviolet lithography

Challenges and limits to patterning using extreme ultraviolet lithography

Research on Chip Manufacturing and Fault Detection Technology

In the wave of the digital era, the chip plays a key role in promoting the whole information technology revolution with its core position in the development of world science and technology. As the cornerstone of computing and data processing, the development of chips has promoted the progress of the entire technology field. The chip’s manufacturing is the key to determining the performance and computing power of the whole chip, and fault detection technology in the production process is an important part of determining the product’s quality and cost. Therefore, under the background of Moore’s law approaching the physical limit, how to ensure the yield of chip production while continuing to improve chip performance has become a major challenge for the chip manufacturing industry. Based on this, this paper summarizes the key manufacturing steps of the chip. The chip manufacturing technology is comprehensively sorted from design to silicon wafer manufacturing, photolithography, etching, ion implantation, and other processes. At the same time, the research direction of monocrystalline silicon manufacturing technology and the existing lithography technology are introduced, including optical lithography, extreme ultraviolet lithography, electron beam lithography, and so on. Fault detection technology in chip production has also been introduced. In addition, the chip manufacturing and fault detection technology introduced in this paper is summarized and its future development is prospected, which provides reference and inspiration for promoting the continuous progress of chip technology.

Rectification of extreme ultraviolet lithography patterns by directed self-assembly: a roughness and defectivity study

Rectification of extreme ultraviolet lithography patterns by directed self-assembly: a roughness and defectivity study

Diagnostics of tin droplet-based laser produced plasma by triple Langmuir probe

Laser produced plasma extreme ultraviolet light source, as the exposure light source for next-generation lithography, faces urgent challenges due to its low conversion efficiency and significant debris contamination. Using a triple Langmuir probe, we conducted a study on the parameters and kinetic characteristics of tin droplet-based laser produced plasma that serves as extreme ultraviolet light source. In this paper, we report a design of triple Langmuir probe circuit based on the BWL (Bulk Wirewound Low-value) sampling resistor, which ensures that high-frequency signals remain undistorted during acquisition. Utilizing the “shadowgraph” method, we calculated the average deflection angles of droplet debris jets under different alignment conditions. Combining the diagnostic results from the probe, we found that the alignment accuracy between the laser and droplet directly influences the parameters of plasma. The parameters and kinetic characteristics of plasma were also diagnosed and analyzed at different angles and distances by moving the probe. Employing the triple Langmuir probe, measurements and analyses of laser produced plasma parameters and kinetic characteristics were achieved, providing a convenient method for diagnosing extreme ultraviolet lithography light sources. This work also offers an effective basis for optimizing the light sources.

Study of mask error enhancement factor improvement with low-n absorber extreme ultraviolet lithography mask

Study of mask error enhancement factor improvement with low-n absorber extreme ultraviolet lithography mask

A comparative study of total and partial ionization cross sections, branching ratios and fragmentation patterns of XH4 (X = C, Si, Ge, Sn, Pb)

The formation and decomposition of SnH4 has been recently reported using electron ionization mass spectrometry (J. Am. Soc. Mass Spectrom. 35 (2024) 1523 and J. Vac. Sci. Technol. A 41 (2023) 063209) due to its importance in tin contamination cleaning in extreme ultraviolet lithography. A comprehensive understanding of the fragment patterns of SnH4 requires total and partial ionization cross sections of SnH4. However, there is limited availability of experimental and theoretical ionization data for SnH4. We report the electron-impact ionization fragmentation patterns of XH4 (X = C, Si, Ge, Sn, Pb) and should provide missing data, especially for SnH4 and PbH4. Total ionization cross sections are calculated using the Binary Encounter Bethe (BEB) method. Partial ionization cross sections and branching ratios are determined using mass spectrum data (MSD) and Huber et al’s method. Finally, we compare the calculated percentage abundances for the fragments of XH4 with experimental measurements.

Exploring the optimal combination of Ru/Ta bilayer mask stacks and illumination source shapes to mitigate mask 3D effects at high-NA extreme ultraviolet lithography.

The imaging performance of extreme ultraviolet (EUV) lithography is determined by the optical properties and thickness of the photomask absorber material and the illumination source shape. Optimizing the trade-offs between imaging metrics, such as normalized image log slope, telecentricity error, and best focus variation through pitch (collectively known as mask-3-dimensional (M3D) effects), is crucial to improve the throughput of the EUV lithography process. This study aims to optimize Ru/Ta bilayer photomask absorber stacks and illumination source shapes to mitigate M3D effects using mask diffraction analysis. It intends to raise questions about the conventional absorber reflectivity or induced phase shift-based approach.

Resolution enhancement for high-numerical aperture extreme ultraviolet lithography by split pupil exposures: a modeling perspective

Resolution enhancement for high-numerical aperture extreme ultraviolet lithography by split pupil exposures: a modeling perspective

Laser-produced plasma water-window x-ray source by continuous liquid bismuth jet.

We have demonstrated a continuous-operated water-window (WW) x-ray source using a regenerative liquid bismuth (Bi) jet for 120 min. A regenerative liquid Bi jet with a diameter of 35-40 µm was continuously injected into a vacuum. The number of photons per pulse was observed to be 3 × 1011 photons/sr and 4.2 × 1011 photons/sr at peak wavelengths of 4.1 nm and 4.3 nm, respectively, which arises from n = 4-n = 4 (Δn = 0) transitions, and 1.7 × 1011 photons/sr at a peak wavelength of 2.8 nm, which is attributed to n = 4-n = 5 (Δn = 1) transitions. The total number of photons emitted/pulse in the 2.3-4.4 nm range was 1012-1013 photons/(nm · sr) for 120 min. We also observed that the fast on spectra scales with the laser intensity according to the power of 0.4 of the laser intensity. These results suggest that the continuous regenerative liquid Bi jet operation could credibly provide future shorter wavelength extreme ultraviolet (EUV) lithography and x-ray microscopy source for biological imaging applications.

Current Progress of EUV Spectral Responsivity Calibration for EUV Lithography at CMS/ITRI

Abstract To support the development of advanced EUV lithography for the semiconductor industry in Taiwan, a calibration system for photodiodes’ spectral responsivity was established. The current system utilizes the synchrotron radiation light source and the method is traceable to PTB, Germany. The wavelength range is from 10 nm to 15 nm, including the most often used 13.5 nm. Several techniques were studied to compensate for light source fluctuation and to reduce the measurement uncertainty. The relative expanded uncertainty of the spectral responsivity calibration at 13.5 nm is 4.6 % (k=2). A wafer-type EUV radiant power meter designed to be used in EUV lithography chambers is being developed. Our goal is to develop simple and reliable methods for on-site EUV optical power measurement and dose estimation.

Modeling the hundreds-of-nanoseconds-long irradiation of tin droplets with a 2 µm-wavelength laser for future EUV lithography

Abstract The properties of an extreme ultraviolet (EUV) source driven by hundreds-of-nanoseconds-long laser pulses of λ laser = 2 µm wavelength are investigated through radiation-hydrodynamic simulations. We show that single-pulse irradiation of 30 µm-diameter tin droplets can generate in-band energies ∼ 30 mJ directed in the 2π sr solid angle subtended by the collector mirror, yielding energies ∼100 mJ produced from 45 µm-diameter droplets. Time-integrated in-band EUV emission profiles, generated by taking Abel transforms of the local net in-band emissivity, reveal EUV source sizes in the axial (laser) direction × radial direction of ∼600 (1000) × 100 (150) µm2 for 30 (45) µm-diameter droplets. We find that approximately 74% of the total in-band emission is produced during the first half of the total propulsion distance irrespective of droplet size or laser intensity. Furthermore, we propose a one-dimensional analytical propulsion model to qualitatively explain the simulated droplet trajectory and to predict the time taken for the droplet to vaporize. These findings offer motivation for the development of high-power EUV sources based on single-pulse, hundreds-of-nanoseconds-long irradiation of tin droplets.