Line Width Roughness Research Articles

Approaching Angstrom-Scale Resolution in Lithography Using Low-Molecular-Mass Resists (

Resists that enable high-throughput and high-resolution patterning are essential in driving the semiconductor technology forward. The ultimate patterning performance of a resist in lithography is limited because of the trade-off between resolution, line-width roughness, and sensitivity; improving one or two of these parameters typically leads to a loss in the third. As the patterned feature sizes approach angstrom scale, the trade-off between these three metrics becomes increasingly hard to resolve and calls for a fundamental rethinking of the resist chemistry. Low-molecular-mass monodispersed metal-containing resists of high atom economy can provide not only very high resolution but also very low line-width roughness without sacrificing sensitivity. Here we describe a modular metal-containing resist platform (molecular mass <500 Da) where a molecular resist consists of just two components: a metal and a radical initiator bonded to it. This simple system not only is amenable to high-resolution electron beam lithography (EBL) and extreme ultraviolet lithography (EUVL) but also unites them mechanistically, giving a consolidated perspective of molecular and chemical processes happening during exposure. Irradiation of the resist leads to the production of secondary electrons that generate radicals in the initiator bonded to metal. This brings about an intramolecular rearrangement and causes solubility switch in the exposed resist. We demonstrate record 1.9-2.0 nm isolated patterns and 7 nm half-pitch dense line-space features over a large area using EBL. With EUVL, 12 nm half-pitch line-space features are shown at a dose of 68 mJ/cm2. In both of these patterning techniques, the line-width roughness was found to be ≤2 nm, a record low value for any resist platform, also leading to a low-performance trade-off metric, Z factor, of 0.6 × 10-8 mJ·nm3. With the ultimate resolution limited by instrumental factors, potential patterning at the level of a unit cell can be envisaged, making low-molecular-mass resists best poised for angstrom-scale lithography.

7.4 nm linewidth Pt nanowires by electron-beam lithography using non-chemically amplified positive-tone resist and post-exposure bake

Abstract 7.4 nm linewidth Pt nanowires were demonstrated on SiO2/Si substrates via electron-beam lithography using a non-chemically amplified positive resist ZEP520A and post-exposure bake (PEB) treatment. The effect of the PEB treatment conditions on the nanowires’ characteristics was investigated. As the PEB temperature and time increased, a decrease in the mean linewidth and an improvement of the line-width (line-edge) roughness of the nanowires were observed. Pt nanowires with an ultrafine linewidth of 7.4 nm were successfully fabricated using the optimal condition of 100 °C for 2 min, verifying the effectiveness of PEB for fabricating sub-10 nm linewidth robust metal nanowires.

A Cyclic Etching Process Using HFE-347mcc3 as a Lower-GWP Alternative to Perfluorocarbons for High-Aspect-Ratio SiO2 Features

As circuits continue to integrate at higher levels, the critical dimensions of DRAM and 3D-NAND are decreasing, leading to an increase in aspect ratios of various features such as contact holes and via holes in DRAM, and channel holes of stack layers in 3D-NAND. This trend has made the process of etching high-aspect-ratio SiO2 features more challenging. To achieve this, it is necessary to satisfy specific conditions including high selectivity to the mask or the underlayer film and the anisotropic etch profiles.Perfluorocarbons (PFCs) such as CF4 and c-C4F8 are commonly used for SiO2 etching. PFCs form a thicker steady-state fluorocarbon film on Si than SiO2, leading to high SiO2/Si selectivity. In addition, PFCs enable anisotropic etching since a passivation layer is formed on the sidewall, preventing lateral etching of the sidewall by chemical etchants.However, PFCs are a representative greenhouse gas with a high global warming potential (GWP) compared to CO2, causing significant adverse effects on global warming. Therefore, there have been efforts to reduce greenhouse gas emissions, such as setting goals for greenhouse gas reduction by each country through the Paris Agreement in 2015. Semiconductor manufacturers have also committed to reducing greenhouse gas emissions per silicon substrate area by 30% compared to 2010. In this regard, various studies are being conducted to develop a SiO2 etching process using alternative materials with lower GWP than PFCs. Fluorinated ethers and fluorinated alcohols are potential substitutes due to their low GWPs and short lifetimes. For example, heptafluoropropyl methyl ether (HFE-347mcc3) has a GWP of ~530 and an atmospheric lifetime of 5.2 years, significantly lower than those of PFCs.During etching of SiO2, the mask is susceptible to damage and corrosion by ions, resulting in various pattern deformations such as bowing, necking, and striation. These deformations adversely affect the miniaturization of the DRAM structure by reducing the process margin between holes and have a negative influence on the electrical characteristics of the device, such as contact resistance, line edge roughness, and line width roughness.To prevent these pattern deformations, the cyclic etching process that repeats the passivation layer deposition step and SiO2 pattern etching step was devised. A fluorocarbon film is deposited on the mask to protect it, then SiO2 is etched. The fluorocarbon film is deposited again to reinforce the mask and damaged fluorocarbon film during the etching process, and then SiO2 etching step is repeated to achieve the high-aspect-ratio SiO2 features.In this study, the cyclic etching process was conducted using HFE-347mcc3 as a lower-GWP alternative to PFCs to etch SiO2 contact holes. The effect of the duration of each step on the etch profile was investigated by adjusting the duration of the deposition and etching steps. This work demonstrated the feasibility of using HFE-347mcc3 as a lower-GWP alternative to PFCs for cyclic etching of SiO2 contact holes to obtain anisotropic etch profiles.

Novel process integration flow of germanium-on-silicon FinFETs for low-power technologies

Germanium channel FinFET transistors process integration on a silicon substrate is a promising candidate to extend the complementary metal–oxide–semiconductor semiconductor roadmap. This process has utilized the legacy of state-of-art silicon fabrication process technology and can be an immediate solution to integrate beyond Si channel materials over standard Si wafers. The fabrication of such devices involves several complicated technological steps, such as strain-free epi layers over the Si substrate to limit the substrate leakage and patterning of narrow and sharp fins over germanium (Ge). To overcome these issues, the active p-type germanium layers were grown over n-type germanium and virtual substrates. The poly ((4-(methacryloyloxy) phenyl) dimethyl sulfoniumtriflate) was utilized as a polymeric negative tone e-beam resist for sub-20 nm critical dimensions with low line edge roughness, line width roughness, and high etch resistance to pattern p-Ge fins to meet these concerns. Here, the devices use the mesa architecture that will allow low bandgap materials only at the active regions and raised fins to reduce the active area interaction with the substrate to suppress leakage currents. This paper discusses the simple five-layer process flow to fabricate FinFET devices with critical optimizations like resist prerequisite optimization conditions before exposure, alignment of various layers by electron beam alignment, pattern transfer optimizations using reactive ion etching, and bilayer resist for desired lift-off. The Ge-on-Si FinFET devices are fabricated with a width and gate length of 15/90 nm, respectively. The devices exhibit the improved ION/IOFF in order of ∼105, transconductance Gm ∼86 μS/μm, and subthreshold slope close to ∼90 mV/dec.

Chemically Amplified Molecular Glass Photoresist Regulated by 2-Aminoanthracene Additive for Electron Beam Lithography and Extreme Ultraviolet Lithography.

2-Aminoanthracene was used as a nucleophilic additive in a molecular glass photoresist, bisphenol A derivative (BPA-6-epoxy), to improve advanced lithography performance. The effect of 2-aminoanthracene on BPA-6-epoxy was studied by electron beam lithography (EBL) and extreme ultraviolet lithography (EUVL). The result indicates that the additive can optimize the pattern outline by regulating epoxy cross-linking reaction, avoiding photoresist footing effectively in EBL. The EUVL result demonstrates that 2-aminoanthracene can significantly reduce line width roughness (LWR) for HP (Half-Pitch) 25 nm (from 4.9 to 3.8 nm) and HP 22 nm (from 6.9 to 3.0 nm). The power spectrum density (PSD) curve further confirms the reduction of roughness at medium and high frequency for HP 25 nm and the whole range of frequency for HP 22 nm, respectively. The study offers useful guidelines to improve the roughness of a chemically amplified molecular glass photoresist with epoxy groups for electron beam lithography and extreme ultraviolet lithography.

Effects of photoacid generator decomposition on dissolution kinetics of poly(4-hydroxystyrene) in tetraalkylammonium hydroxide aqueous solutions

For the advancement of lithography, the resist materials and processes are the most critical factors. In particular, the process of developing resist materials is important in reducing the line width roughness and stochastic defects. In this study, a quartz crystal microbalance method was used to investigate the dissolution dynamics of poly(4-hydroxystyrene) (PHS) films containing triphenylsulfonium nonaflate (TPS-nf) in tetraalkylammonium hydroxide (TAAH) aqueous solutions. The time required for dissolution increased with the alkyl chain length of TAAH. The dissolution rate of PHS films increased with UV irradiation dose for tetramethylammonium hydroxide and tetraethylammonium hydroxide developers, whereas the dissolution time increased for the tetrabutylammonium hydroxide developer. For the tetrapropylammonium hydroxide developer, the dissolution time of PHS films without postexposure baking (PEB) slightly decreased with UV irradiation, whereas that with PEB increased. Both the surface free energy of PHS films and the molecular size of TAAH are considered to affect dissolution kinetics.

Novel hexameric tin carboxylate clusters as efficient negative-tone EUV photoresists: high resolution with well-defined patterns under low energy doses.

Synthesis of two novel tin carboxylate clusters (RSn)6(R'CO2)8O4Cl2 is described, and their structures have been characterized by X-ray diffraction. These clusters have irregular ladder geometry to form very smooth films with small surface roughness (RMS <0.7 nm) over a large domain. EUV lithography can be used to resolve half pitches (HPs) in the order of 15-16 nm with line width roughness (LWR = 4.5-6.0 nm) using small doses (20-90 mJ cm-2). Cluster 1 (R = n-butyl; R'CO2 = 2-methyl-3-butenoate) contains only a radical precursor and cluster 2 (R = vinyl, R'CO2 = 2-methylbutyrate) bears both a radical precursor and an acceptor; the latter is much better than the former in EUV and e-beam photosensitivity. For these clusters, the mechanisms of EUV irradiation have been elucidated with high resolution X-ray photoelectron spectroscopy (HRXPS) and reflective Fourier-transform infrared spectroscopy (FTIR). At low EUV doses, two clusters undergo a Sn-Cl bond cleavage together with a typical decarboxylation to generate carbon radicals. The n-butyl groups of cluster 1 are prone to cleavage whereas the vinyl-Sn bonds of species 2 are inert toward EUV irradiation; participation of radical polymerization is evident for the latter.

Sequential Brush Grafting for Chemically and Dimensionally Tolerant Directed Self-Assembly of Block Copolymers

We report a method for the directed self-assembly (DSA) of block copolymers (BCPs) in which a first BCP film deploys homopolymer brushes, or "inks", that sequentially graft onto the substrate's surface via the interpenetration of polymer molecules during the thermal annealing of the polymer film on top of existing polymer brushes. By selecting polymer "inks" with the desired chemistry and appropriate relative molecular weights, it is possible to use brush interpenetration as a powerful technique to generate self-registered chemical contrast patterns at the same frequency as that of the domains of the BCP. The result is a process with a higher tolerance to dimensional and chemical imperfections in the guiding patterns, which we showcase by implementing DSA using homopolymer brushes for the guiding features as opposed to more robust cross-linkable mats. We find that the use of "inks" does not compromise the line width roughness, and the quality of the DSA as a lithographic mask is verified by implementing a robust "dry lift-off" pattern transfer.

Grazing-Incidence Soft-X-ray Scattering for the Chemical Structure Size Distribution Analysis in EUV Resist

In extreme ultraviolet lithography (EUVL), it is required to develop EUV resist which has low line width roughness (LWR) for the further miniaturization of circuit pattern. In order to reduce LWR, it is necessary to analyze and control the chemical-components spatial distribution in the resist thin film. We have reported that the measurement of chemical-components spatial distribution in the resist thin film coated on the Si3N4 membrane using the method of the transmission-mode resonant soft X-ray scattering (RSoXS). In this study, in order to analyze the chemical-structure-size distribution in the resist thin film on a Si wafer under similar condition adapted to the resist-coating actual process, we examined the grazing-incidence RSoXS (GI-RSoXS). A chemically amplified resist (CAR) and a non-CAR were spin-coated on silicon wafers, which had varied film thickness of 20, 50, and 100 nm. The scattering profile of each sample was measured at the incident photon energy of 280 and 296 eV. As a result, it is suggested that the chemical-structure-size distribution in the resist thin films depends on the resist film thickness. It is confirmed that the GI-RSoXS method is very effective to evaluate the chemical-structure-size distribution of resist thin films.

Atomically Flat, 2D Edge-Directed Self-Assembly of Block Copolymers.

Nanoscale shape engineering is an essential requirement for the practical use of 2Dmaterials, aiming at precisely customizing optimal structures and properties. In this work, sub-10-nm-scale block copolymer (BCP) self-assembled nanopatterns finely aligned along the atomic edge of 2D flakes, including graphene, MoS2 , and h-BN, are exploited for reliable nanopatterning of 2D materials. The underlying mechanism for the alignment of the self-assembled nanodomains is elucidated based on the wetting layer alternation of the BCP film in the presence of intermediate 2D flakes. The resultant highly aligned nanocylinder templates with remarkably low levels of line edge roughness (LER) and line-width roughness (LWR) yield a sub-10-nm-wide graphene nanoribbon (GNR) array with noticeable switching characteristics (on-to-off ratio up to ≈6 × 104 ).

Role of landing energy in e-beam metrology of thin photoresist for high-numerical aperture extreme ultraviolet lithography

BackgroundLithography advancements require to resist layer thickness reduction, essential to cope with the low depth of focus (DOF) characteristic of high numerical aperture extreme ultraviolet lithography (HNA EUVL). However, such a requirement poses serious challenges in terms of resist process metrology and characterization, as patterns in thin resist suffer from low contrast, which may affect the performance of the edge detection algorithms used for image analysis, ultimately impacting metrology.AimInvestigate e-beam imaging using low landing energy (LE) settings as a possible way to address the thin resist film metrology issues.ApproachA low-voltage aberration-corrected SEM developed at Carl Zeiss is to image three thin resist thicknesses and two different underlayers, at various LE and number of frames. All images are analyzed using MetroLER software, to extract the parameters of interest [mean critical dimension (CD), line width roughness (LWR), and linescan signal-to-noise ratio (SNR)] in a consistent way.ResultsThe results indicate that mean CD and LWR are affected by the measurement conditions, as expected. Imaging through LE unravels two opposing regimes in the mean CD estimate, the first in which the mean CD increases due to charging and the second in which the mean CD decreases due to shrinkage. Additionally, the trend between LE and linescan SNR varies depending on the stack.ConclusionWe demonstrated the ability of low-voltage aberration-corrected SEM to perform thin-resist metrology with good flexibility and acceptable performance. The LE proved to be an important knob for metrology of thin resist.

Near-field infrared nanoscopic study of EUV- and e-beam-exposed hydrogen silsesquioxane photoresist

This article presents a technique of scattering-type scanning near-field optical microscopy (s-SNOM) based on scanning probe microscopy as a nanoscale-resolution chemical visualization technique of the structural changes in photoresist thin films. Chemical investigations were conducted in the nanometer regime by highly concentrated near-field infrared on the sharp apex of the metal-coated atomic force microscopy (AFM) tip. When s-SNOM was applied along with Fourier transform infrared spectroscopy to characterize the extreme UV- and electron-beam (e-beam)-exposed hydrogen silsesquioxane films, line and space patterns of half-pitch 100, 200, 300, and 500 nm could be successfully visualized prior to pattern development in the chemical solutions. The linewidth and line edge roughness values of the exposed domains obtained by s-SNOM were comparable to those extracted from the AFM and scanning electron microscopy images after development. The chemical analysis capabilities provided by s-SNOM provide new analytical opportunities that are not possible with traditional e-beam-based photoresist measurement, thus allowing information to be obtained without interference from non-photoreaction processes such as wet development.

Scaling and readiness of underlayers for high-numerical aperture extreme ultraviolet lithography

With the introduction of high-numerical aperture (NA) extreme ultraviolet (EUV) lithography, the thickness of layers in the lithographic stack will scale owing to reduced depth of focus and etch budget. The consequence of thinning down underlayers for EUV lithography has been scarcely investigated. In here, we assessed the readiness of nine state-of-the-art underlayers, spin-on and dry deposited, in thickness series down to 4 nm nominal. Preliminarily, the coating quality of these underlayers was evaluated. Thickness uniformity across 300 mm wafer ranged from about ±0.5 nm to < ± 0.05 nm depending on the coating technique employed. Surface roughness of the underlayers varied from as much as 0.63 nm to as low as 0.062 nm but was not impacted by thickness scaling. Film density and total surface energy varied by <10 % with thickness. EUV lithography of dense lines/spaces arrays of pitch 28 nm was carried out using a positive tone chemically amplified photoresist. Dose-to-size and exposure latitude changed by < ± 5 % when thickness of underlayer was decreased. Failure free process was at most 1 nm smaller for thinner underlayer than it was for the thinnest version of each type. The unbiased linewidth roughness increased consistently but limitedly (<5 % ) when thinner underlayers were used, mainly due to a reduction in the correlation length. By calculating the power spectral density of the blanket underlayer we can pinpoint this effect to a reduction of correlation length of the underlayer own surface roughness. Finally, Z-factor calculations demonstrated that overall photoresist performance depended more significantly on the specific underlayer type (±12.6 % ) than it did on underlayer thickness (±8 % ). All these results indicate that most of underlayers investigated had limited impact on the properties as well as the patterning performance when scaling in view of high NA EUV.

A Study on the Resolution and Depth of Focus of ArF Immersion Photolithography.

In this study, the resolution and depth of focus (DOF) of the ArF immersion scanner are measured experimentally according to numerical aperture (NA). Based on the experiment, the theoretical trade-off relationship between the resolution and depth of focus can be confirmed and k1 and k2 are extracted to be about 0.288 and 0.745, respectively. Another observation for a problem in small critical dimension realization is the increase in line width roughness (LWR) according to mask open area ratio. To mitigate the trade-off problem and critical dimension variation, the photoresist thickness effect on depth of focus is analyzed. Generally, the photoresist thickness is chosen considering depth of focus, which is decided by NA. In practice, the depth of focus is found to be influenced by the photoresist thickness, which can be caused by the intensity change of the reflected ArF light. This means that photoresist thickness can be optimized under a fixed NA in ArF immersion photolithography technology according to the critical dimension and pattern density of the target layer.

(Digital Presentation) Influence of Fin Width Modulation on Nanoscale FinFET

ABSTRACT In the present research work, the influence of Fin width thickness variation on the electrical performance parameters have been performed for the FinFET device. Various Fin angle (i.e., θ) have been considered to analyze the effect of Fin thickness variations. All the analyzed results have been compared with the ideal FinFET (i.e., θ = 0) device to observe the effect of angle variation on threshold voltage (VTH), Transconductance (gm), Gate current (IG) and Drain Induced Barrier Lowering (DIBL). In addition, the impact of Fin width thickness variations has been used to realize the inverter Voltage Transfer Characteristics (VTC). The characteristics comparison reveals that including the effect of Fin width improves the device performance of FinFET devices. INTRODUCTION The FinFET device has been considered as a future candidate for VLSI circuit design and manufacturing. Compared with planar technology, the FinFET device shows reduced Short Channel Effects (SCEs) and improved electrostatic control. However, device variability poses a severe threat to downscaling FinFET dimensions in the nanoscale regime because non-uniformity has a significant influence on short-channel devices [1, 2]. In the fabrication of FinFET devices, the effect of the nonrectangular Fin shape must be carefully considered because the Fin thickness of the fabricated FinFET differs from the ideal shape. It is found that it is difficult to achieve a perfect rectangular Fin shape due to Line Edge Roughness (LER) and Line Width Roughness (LWR) [3]. In previous research works, authors considered the variations introduced in the vertical direction of the Fin while ignoring the fact that Fin width fluctuates in the lateral direction too [4]. This lateral Fin fluctuation introduces significant errors during performance parameter analysis. Therefore, this present research work focused on fluctuations in the Fin in the lateral direction. Here, the effects of non-uniformity on electrical performance parameters such as VTH, gm, IG and DIBL have been analyzed and compared with the ideal FinFET device. Furthermore, the impact of these variations is incorporated into the realization of inverter VTC characteristic. DEVICE DESIGN AND RESULT ANALYSIS Fig. 1(a) shows the full 3D view of the FinFET device. The doping concentration of the Source/Drain (S/D) region is maintained at 1×1020 cm-3 . Here, channel thickness (Tsi ) and gate oxide thickness (tox ) are 8 nm and 1 nm, respectively. Titanium Nitride (TiN) metal has been employed as the gate electrode because TiN shows low resistivity, high melting, thermal stability, and compatibility with the standard CMOS process [5]. To analyze the effects of fin width variation on the performance parameters of FinFET, the non-uniformity has been shown in Fig. 1(b). Here, Tsi fluctuations are approximated as a linear slope, making an angle (θ) to X-axis in the range of -70 to 70 to exaggerate the width variation effects. A Positive angle means the drain area is more significant compared to the source area and vice versa. Fig. 2 displays the VTH and DIBL variations against the Fin width variation. It has been realized that for Fin thickness variation from -70 to +70 there is a shift in threshold voltage (VTH ) of 6.12% and 4.08%, respectively. However, it is also observed that the non-uniform Fin width improves the DIBL for the FinFET device. This is due to the modulation of the effective S/D area with the channel region. CONCLUSIONS AND FUTURE ASPECTS The effect of Fin width thickness variation is increasing as the feature size of the FinFET device reduces. This work realized that the linear variation in the overall Fin width thickness introduces comparable variations in electrical performance parameters for FinFET device. For instance, there is a significant improvement in DIBL for Fin thickness variation from -70 to +70 because these variations are directly correlated to the Fin thickness reduction. These insights will allow technologists and designers to capture a valid performance characteristic for Fin width variations effects to meet future design challenges in the nanometer regime. REFERENCES [1] A Khakifirooz, IEEE Trans. Elect. Dev., vol. 55(6), pp. 1401-1408, 2008.[2] RS Rathore, IEEE 4th International Conference on Signal Processing, Computing and Control (ISPCC), Solan, 2017, pp. 377-380.[3] RS Rathore, Superlattices and Microstructures, vol. 113, pp. 213-227, 2018.[4] X Wu, IEEE Trans. Elect. Dev., vol. 52(1), pp. 63-68,2005.[5] AR Brown, IEEE Trans. Elect. Dev., vol. 54(11), pp. 3056-3063, 2007. Figure 1

Shape and Roughness Extraction of Line Gratings by Small Angle X-Ray Scattering: Statistics and Simulations

Since 2010, a lot of progress was done concerning Small Angle X-ray Scattering (SAXS) extraction capabilities for dimensional control of line gratings. In this paper, we summarize the general methodology, including transmission (T-)SAXS experimental setup, and extract the line shape and roughness in line gratings. We describe step by step the full data treatment to extract the pitch, critical dimension (CD), line shape and roughness, focusing on the Line Width Roughness (LWR) extraction through a Power Spectral Density (PSD) analysis. The reliability of the extraction by T-SAXS is evaluated thanks to different extractions, comparison to TEM cross-section and analyses of count statistic in case of line roughness.

Macrocycle Network-Aided Nanopatterning of Inorganic Resists on Silicon

Inorganic resists have emerged as promising candidates in semiconductor industries to realize sub-10 nm node technology. However, controlling vertical shrinkage of resist films during the pattern development process, particularly for ultralow thin film applications, is among the highly pressing limitations of inorganic resists along with pattern roughness and poor resist shelf-life characteristics. Tin-based clusters and small molecules have been recently introduced as resist materials. They possess a high absorption coefficient and fast solubility transitions under irradiation exposure. As we investigated, n-butylstannoic acid (BTA) showed ∼38% vertical shrinkage when its film was exposed with deep ultraviolet photons (DUV, ∼254 nm) and could pattern features of ∼120 nm. We hypothesized and experimentally validated an approach that provided control on shrinkage issues, along with improving its patterning potential to sub-15 nm regime. In our approach, BTA was embedded into a polyhydroxy organic host matrix composed of noria (water-wheel-like macrocycle) derivatives. The rigid molecular cage structure and photo-inert nature of noria (N-Me) were utilized as the host matrix that apprehended the inorganic resist material within its intermolecular space. Ultrathin films (∼20 nm) were coated on silicon, and various nanofeatures including 10 nm lines, meshlike grids with 10 nm width, complex patterns, and so forth were patterned using electron beam and helium ion beam lithography. Most importantly, we were able to drastically reduce the vertical shrinkage to ∼13% with respect to initial thickness, which substantiates the potential of our hypothesis. We also noticed good shelf-life (6 months), good etch resistance, and low line edge roughness (LER)/line width roughness (LWR) for the developed resist composition.

Large-Area Superconducting Nanowire Single-Photon Detectors for Operation at Wavelengths up to 7.4 μm.

The optimization of superconducting thin-films has pushed the sensitivity of superconducting nanowire single-photon detectors (SNSPDs) to the mid-infrared (mid-IR). Earlier demonstrations have shown that straight tungsten silicide nanowires can achieve unity internal detection efficiency (IDE) up to λ = 10 μm. For a high system detection efficiency (SDE), the active area needs to be increased, but material nonuniformity and nanofabrication-induced constrictions make mid-IR large-area meanders challenging to yield. In this work, we improve the sensitivity of superconducting materials and optimize a high-resolution nanofabrication process to demonstrate large-area SNSPDs with unity IDE at 7.4 μm. Our approach yields large-area meanders down to 50 nm width, with average line-width roughness below 10%, and with a lower impact from constrictions compared to previous demonstrations. Our methods pave the way to high-efficiency SNSPDs in the mid-IR band with potential impacts on astronomy, imaging, and physical chemistry.

(Digital Presentation) Extending the Application of Capacitively Coupled Plasma Etching Tools to the Front-End-of-Line Fin-Cut Etching Process for FinFET Mass Production

As FinFET scales down to advanced technology nodes, Self-aligned Quadruple Patterning (SaQP) scheme is widely deployed for Fin formation, where two mandrels (MD1 and MD2) and corresponding mandrel spacers (MD1SP and MD2SP) are patterned for accurate CD transferring. The Fin-cut etching process of the MD2SP Cutting is very critical for the patterning of the Standard Cell and the SRAM patterns. This work studies the application of the Front End of Line (FEoL) MD2SP Cutting process in both inductively coupled plasma (ICP) and capacitively coupled plasma (CCP) etchers. The mismatch between the two tools is observed and discussed in detail. For CCP tools, a degradation of line width roughness (LWR) and increase of critical dimension (CD) loading between dense and isolated patterns are observed. Compared with the ICP etchers, the CCP etchers have lower plasma dissociation and stronger physical bombardment of ions. Furthermore, it is harder to control the plasma density and directionality separately. To increase CCP tool applications in FEoL processes, we introduce a Silicon coating process to modify the photoresist (PR) during the CCP etching to harden the surface of the PR and enhance the LWR performance. Furthermore, the application of atomic layer etching (ALE) technology ensures the CD loading between the dense and isolated patterns. With the application of our study, we can broaden the application of CCP tools in FEoL for FinFET mass production.

Multiple regression analysis of postdevelop unbiased line width roughness and etch resistance for high-accuracy estimations of postetch pattern roughness

As device scaling continues, development of photoresists with low pattern roughness and high sensitivity has become challenging. One obstacle that delays the material development process is the discrepancy between postdevelop and postetch pattern roughness, where a photoresist with high postdevelop patterning performance shows poor postetch pattern roughness. Herein, we demonstrate that pattern roughness after a nontrim etch process can be accurately estimated by a multiple regression analysis of a power spectral density (PSD) variable of postdevelop roughness and an etch resistance parameter of resins. The nontrim etch process here refers to an etch condition which leads to increased pattern roughness. Unbiased line width roughness (LWR) shows the highest correlation with postetch LWR among postdevelop roughness PSD variables. An etch resistance parameter also correlates well with postetch roughness. A multiple regression analysis reveals that the contributions of postdevelop unbiased LWR and etch resistance to the postetch LWR are 59% and 41%, respectively. Based on the calculated contributions, postetch LWR is estimated with a high accuracy (R2 > 0.93). This estimation method allows for an efficient material screening at a lithography level without assessing postetch patterning performance, thus the process of material development could be accelerated.