Search

Based on the bidirectional evolutionary structural optimization (BESO) method, the present article proposes an optimization method for a thermal structure involving design-dependent convective boundaries. Because the BESO method is incapable of keeping track of convection boundaries, virtual elements are introduced to assist in identifying the convection boundaries of the structure. In order to solve the difficult issue of element assignment under a design-dependent convection boundary, label matrixes are employed to modify the heat transfer matrix and the equivalent temperature load vector of elements over topology iterations. Additionally, the optimization objective is set to minimize the maximum temperature of the structure in order to deal with the objective reasonableness, and the p-norm method is then used to fit the objective function to calculate sensitivity. Finally, several cases, including 2D and 3D structures under various heat transfer boundary conditions, are provided to illustrate the effectiveness and good convergence of the proposed method.

Although concomitant nonalcoholic steatohepatitis (NASH) is common in chronic hepatitis B (CHB), the impact of viral factors on NASH and the outcome of CHB patients concomitant with NASH remain unclear. We aimed to investigate the outcomes of NASH in CHB patients receiving antiviral treatment.In the post-hoc analysis of a multicenter trial, naïve CHB patients receiving 72-week entecavir treatment were enrolled. We evaluated the biochemical, viral and histopathological responses of these patients. The histopathological features of NASH were also evaluated, using paired liver biopsies at baseline and week 72.A total of 1000 CHB patients were finally enrolled for analysis, with 18.2% of whom fulfilling the criteria of NASH. A total of 727 patients completed entecavir antiviral treatment and received the second biopsy. Serum HBeAg loss, HBeAg seroconversion and HBV-DNA undetectable rates were similar between patients with or without NASH (P0.05). Among patients with NASH, the hepatic steatosis, ballooning, lobular inflammation scores and fibrosis stages all improved during follow-up (all P0.001), 46% (63/136) achieved NASH resolution. Patients with baseline body mass index (BMI) ≥ 23 kg/mLower BMI and weight reduction but not virologic factors determine NASH resolution in CHB. The value of weight management in CHB patients during antiviral treatment deserves further evaluation.

The distribution and evolution of air in airliner cabins is an important basis for the study of cabin thermal environment and pollutant propagation. Due to the complex heat and mass transfer problems caused by forced and natural convection in a large-scale space, the accurate prediction of air distribution in airliner cabins still faces huge challenges. This study takes the cabin of the Airbus A320 as the research object. The accurate numerical simulation of the flow and heat transfer process in an airliner cabin under mixing ventilation mode was carried out using the Hybrid Thermal Lattice Boltzmann Method (HTLBM) combined with GPU (Graphics Processing Unit) acceleration technology, and the influence of human thermal plumes on air distribution and evolution characteristics in an airliner cabin was analyzed. The research shows that the human thermal plume changes the air distribution in the passenger cabin. The thermal plume slows down the jet attenuation, increases the energy exchange in the area near the passengers, and offsets the jet trajectory. The airflow self-locking effect is easier to form in the passenger breathing area, which increases the time for the flow field to develop into the steady state. The influence of human thermal plumes on the airflow distribution in the passenger cabin cannot be ignored.

Chronic hepatitis B (CHB) and liver fibrosis are associated with a high risk of hepatocellular carcinoma (HCC) development. We assessed whether entecavir (ETV) plus Biejia-Ruangan compound (BRC), an anti-fibrotic traditional Chinese medicine, can further reduce the risk of HCC in treatment-naïve Chinese patients with CHB and an Ishak fibrosis score of ≥3 points derived from our parent double-blind randomized placebo-controlled trial.After a 72-week comparison between ETV+BRC and ETV+placebo treatment, participants were eligible to enter an open-label treatment phase and were followed up every 6 months. The primary [secondary] endpoints were the incidence of HCC [liver-related deaths, non-HCC events, and non-liver-related deaths]. Modified intention-to-treat (mITT), intention-to-treat (ITT), and per-protocol (PP) populations were defined for the time-to-event analysis.A total of 1,000 patients were recruited; the median age was 42.0 years; 69.9% were male and 58.3% were HBeAg positive. In the mITT population, the 7-year cumulative incidence of HCC [liver-related deaths] was 4.7% [0.2%] for ETV+BRC, which was significantly lower than 9.3% [2.2%] for ETV monotherapy (p = 0.008 [p = 0.030]). Notably, ETV+BRC treatment yielded a lower incidence of HCC in those who did not achieve regression of fibrosis at week 72 than ETV monotherapy (p = 0.018). There were no differences in the other 2 secondary endpoints or safety profiles between the groups. Multivariable Cox proportional regression analysis, including the treatment allocation as a parameter, also demonstrated that ETV+BRC treatment was associated with a reduced incidence of HCC. The ITT and PP analyses showed consistent results.ETV plus BRC combination treatment could further reduce the risk of HCC and liver-related deaths in patients with CHB and advanced fibrosis or cirrhosis, which may have important clinical implications for HCC prevention.Patients with chronic hepatitis B virus infection are at an increased risk of developing liver cancer (specifically hepatocellular carcinoma [HCC]). While there are effective antiviral treatments that can suppress the virus in chronically infected patients, the risk of HCC remains. Herein, we show that adding a traditional Chinese medicine called Biejia-Ruangan compound to an antiviral reduced the risk of HCC in patients with chronic hepatitis B.

A new method for simultaneously reconstructing surface and internal transient temperature distributions in structures is presented by ultrasonic measurements. The principle of ultrasonic thermometry is based on temperature dependence of the velocity of ultrasonic wave (acoustic velocity) propagating through heated structures. Considering the bending effect of ultrasonic propagation path in non-uniform temperature field, an approach for predicting two-dimensional ultrasonic propagation path is developed using the Fermat theory. Combining the advantages of the ultrasonic pulse-echo measurements and an inverse analysis of thermo-acoustic coupling problem, a reconstruction algorithm is proposed to estimate two-dimensional surface and internal temperature fields. The presented approach is discussed in some detail and a number of examples are given as verification to demonstrate the feasibility and reliability of this method. The surface and internal temperature profiles determined by ultrasound agree well with the exact values. In addition, the influences of bending effect of wave propagation, measurement error of ultrasonic wave propagation time, number and position of measurement points on the reconstruction of temperature fields are analyzed in detail. It shows that the presented method is a promising means for high-accurately and nondestructively determining surface and internal transient temperature distributions in heated structures.

Objective. To explore the clinical value of the specific plasma cell detection and specific T lymphocyte detection test in diagnosing hypersensitivity caused by antituberculosis drugs. Methods. A total of 266 patients with pulmonary tuberculosis who developed hypersensitivity during the treatment of primary pulmonary tuberculosis in our hospital and 266 patients without hypersensitivity during the treatment of pulmonary tuberculosis in our hospital were selected as the control group. The admission time is from January 2013 to June 2020. The specific plasma cell test and specific T lymphocyte test were used as the criteria to determine which drugs induced hypersensitivity, and the diagnostic value of these two methods in the diagnosis of hypersensitivity induced by four first-line antituberculosis drugs (isoniazid (INH), ethambutol (EMB), rifampicin (RFP), and pyrazinamide (PZA)) was analyzed. Results. The sensitivity of the specific plasma cell test in the diagnosis of hypersensitivity induced by INH, EMB, RFP, and PZA was 63.42%, 51.20%, 47.81%, and 56.37%, respectively, and the specificity was 95.33%, 99.87%, 96.52%, and 99.99%, respectively. The sensitivity of the specific T lymphocyte test in the diagnosis of hypersensitivity induced by INH, EMB, RFP, and PZA was 66.47%, 52.88%, 49.91%, and 58.54%, respectively, and the specificity was 97.28%, 99.99%, 98.38%, and 100.00%, respectively. Conclusion. The specific plasma cell test and specific T lymphocyte test have high specificity in the diagnosis of hypersensitivity caused by antituberculosis drugs, and the specific T lymphocyte test is better than the specific plasma cell test. It is of great significance to guide the clinical application of antituberculosis drugs.

Background The clinical manifestations and factors associated with the severity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections outside of Wuhan are not clearly understood. Methods All laboratory-confirmed cases with SARS-Cov-2 infection who were hospitalized and monitored in Guangzhou Eighth People’s Hospital were recruited from January 20 to February 10. Results A total of 275 patients were included in this study. The median patient age was 49 years, and 63.6% had exposure to Wuhan. The median virus incubation period was 6 days. Fever (70.5%) and dry cough (56.0%) were the most common symptoms. A decreased albumin level was found in 51.3% of patients, lymphopenia in 33.5%, and pneumonia based on chest computed tomography in 86%. Approximately 16% of patients (n = 45) had severe disease, and there were no deaths. Compared with patients with nonsevere disease, those with severe disease were older, had a higher frequency of coexisting conditions and pneumonia, and had a shorter incubation period (all P Conclusions Most of the patients infected with SARS-CoV-2 in Guangzhou, China are not severe cases and patients with older age, male, and decreased albumin level were more likely to develop into severe ones.

As feature resolution and process variations continue to shrink for new nodes of both DUV and EUV lithography, the density and number of devices on advanced semiconductor masks continue to increase rapidly. These advances cause significantly increased pressure on the accuracy and efficiency of OPC and assist feature (AF) optimization methods for each subsequent process technology. To meet manufacturing yield requirements, significant wafer retargeting from the original design target is often performed before OPC to account for both lithographic limitations and etch effects. As retargeting becomes more complex and important, rule-table based approaches become ineffective. Alternatively, modelbased optimization approaches using advanced solvers, e.g., inverse lithography technology (ILT), have demonstrated process window improvement over rule-based approaches. However, model-based target optimization is computationally expensive which typically limits its use to smaller areas like hotspot repairs. In this paper, we present results of a method that uses machine-learning (ML) to predict optimal retargeting for line-space layers. In this method, we run ILT co-optimization of the wafer target and process window to generate the training data used to train a machine learning model to predict the optimum wafer target. We explore methods to avoid ML model overfitting and show the ML infrastructure used to integrate ML solution into a manufacturable OPC flow. Both lithographic quality and runtime performance are evaluated for an ML enabled retargeting flow, an ILT flow and a simple rule table flow at advanced node test cases.

Memory cells and access structures consume a large percentage of area in embedded devices so there is a high return from shrinking the cell area as much as possible. This aggressive scaling leads to very difficult resolution, 2D CD control and process window requirements. As the scaling drives lithography even deeper into the low-k1 regime, cooptimization of design layout, mask, and lithography is critical to deliver a production-worthy patterning solution. Computational lithography like Inverse Lithography Technology (ILT) has demonstrated it is an enabling technology to derive improved solutions over traditional OPC as reported in multiple prior publications. In this paper, we will present results of a study on advanced memory cell design optimization with Cell-Level ILT (CL-ILT) where significant design hierarchy can be retained during ILT optimization. Large numbers of cell design variations are explored with automatically generated patterns from ProteusTM Test Pattern Generator (TPG). Fully automated flows from pattern generation to mask synthesis with ILT, data analysis and results visualization are built on ProteusTM Work Flow (PWF) for exploring a fully parameterized design space of interest. Mask complexity including assist features (AF) types, rule or model based, and main feature segmentation are also studied to understand the impact on wafer lithographic performance. A heatmap view of results generated from this design exploration provides a clear and intuitive way to identify maximum design limits of memory cells. Comparison of results from ILT and traditional OPC will be presented as well with both wafer and simulation data.

Aircraft icing is a complex phenomenon involving flow, heat transfer, and phase transition, and the in-flight accretion of ice on aerodynamic surfaces presents a significant threat to the performance and safety of aircraft. The icing conditions have not only significant influence on the macroscopic morphology, physical and mechanical properties of the ice, but also great influence on the microstructure of icing characteristics. Fine prediction of icing process is an important foundation for assessing the impact of icing on aerodynamic characteristics and flight performance, and developing the aircraft icing protection system. Focusing on the microstructural features of aircraft icing, a phase-field method is developed for simulating the crystallization of supercooled water, and the influence of supercooling degree on crystal growth is investigated in this work. Based on the combination of icing tunnel experiment and microscopic image recognition, the relationship between the supercooling degree and nucleation rate of icing is obtained. Based on the phase-field method, the numerical simulation method for the prediction of microstructural features of aircraft icing is developed, and the microstructural evolution of icing under different supercooling conditions is analyzed. The results indicate that the phase-field method can predict the microstructural features effectively under supercooled conditions, which will be beneficial to understand the evolution mechanisms of aircraft icing and provide important basis for the characterization of icing features from qualitative to quantitative. The results are intended to illustratively show the potential of the phase-field model in computing and analyzing complex pattern formations in icing process, which will lay the foundation for fine prediction of aircraft icing.

This paper deals with the surface thermochemical effects on TPS-coupled aerothermodynamics in hypersonic Martian gas flow. An interface condition with finite-rate thermochemistry was established to balance the three-dimensional Navier-Stokes solver and TPS thermal response solver, and a series of coupled simulations of chemical non-equilibrium aerothermodynamics and structure heat transfer with various surface catalycities were performed for hypersonic Mars entries. The analysis of surface thermochemistry reveals that the surface chemical reactions have great contribution to aerodynamic heating, and the temperature-dependence of finite-rate catalysis highly influences the evolution of the coupling aerodynamic heating in the coupling process. For fixed free stream parameters with proper catalytic excitation energy, a “leap” phenomenon of the TPS-coupled heat flux with the coupling time appears in the initial stage of the coupling process, due to the strong thermochemical effects on the TPS surface.

Surface chemical effects have great influence on the prediction of hypersonic nonequilibrium aerodynamic heating, and they are particularly complex in a dissociated carbon–oxygen environment for th...

Aerodynamics, aerothermodynamics and thermal protection system response in high-enthalpy and high-speed flow is heat transfer with interface effects in nature. Modelling and simulation of these phenomena are of vital significance to ensure high-speed flight thermal safety. The heat transfer phenomena related with gas-surface interaction, interface heterogeneous reactions and microstructure morphology in high-enthalpy and high-speed flow were summarized. The modelling of interface effects and the corresponding coupling algorithms for computational fluid dynamics (CFD) and related approaches were reviewed. Recent research activities for interface problems in high-enthalpy and high-speed flow at China Aerodynamics Research and Development Center were discussed. They mainly focus on practical solutions of computational fluid dynamics with viscous wall boundary conditions, multi-zone coupling for fluid-thermal interaction and cross-scale algorithms of CFD coupled with smaller scale theoretical approaches. Finally, further perspectives about heat transfer with interface effects were proposed, including mesoscale experimental verification, interface cross-scale modelling and accuracy/uncertainty of coupling algorithms.

The anisotropic micro-structure of fiber will lead to the macroscopic anisotropic properties of fiber reinforced composites in both heat transfer and mechanical strength. However, few experimental studies have be made on the anisotropic heat transfer properties of fiber reinforced composites. In this study, the anisotropic thermal conductivities of two-dimensional (2D) plain woven and twill woven carbon-fiber/epoxy composites are measured at different temperature with the one-dimensional (1D) steady-state method, transient plane source (TPS) method and transient hot wire method, respectively. The out-of-plane thermal conductivity and in-plane thermal conductivity at the temperature ranging from −45 °C to 160 °C are obtained and comparisons are made among the three methods. The results show that all the three methods can be used to measure the anisotropic thermal conductivity of fiber/epoxy woven composites. Both the out-of-plane thermal conductivity and in-plane thermal conductivity of carbon-fiber/epoxy woven composites increase with temperature, and the in-plane thermal conductivity is approximately four times as high as the out-of-plane thermal conductivity for the plain woven composites. Compared with the results of 1D steady-state method, the max deviations of TPS method and hot wire method are 18.1% and 17.1%, respectively. The sources of error that leading to the deviations are also discussed.

Background: HBeAg-positive chronic infection is a unique phase of chronic hepatitis B virus (HBV) infection. Current guidelines advise against starting antiviral treatment for HBeAg-positive chronic hepatitis B virus (HBV) infection patients, some data suggest treating such patients may reduce the risk of hepatocellular carcinoma. We aimed to explore whether these patients can have evident histological liver injury (EHLI), and develop a non-invasive model for identifying EHLI in such patients. Method: We assessed whether HBeAg-positive chronic HBV infection patients can have EHLI defined by Ishak fibrosis stage ≥3 and/or histologic activity index ≥ 9 in a prospective multicenter study. Logistic and Lasso regression was used to select the optimal predictors. We used Akaike information criterion, discrimination improvement, net reclassification improvement to develop and validate models predicting EHLI risk in training cohort and two external validation cohorts. Findings: Of these 336 patients met the inclusion criteria, 181(54%) were HBeAg-positive chronic HBV infection, of whom 60 patients (33%) had EHLI, the proportion of significant fibrosis was higher than that of significant inflammation (33% vs. 8%, P

The difficulties involved in ramping EUV lithography to volume manufacturing have highlighted the critical task of understanding process, layout design and device interactions, and also of optimizing the overall product integration to reduce undesirable interactions. In this paper, we demonstrate mask synthesis methods that using rigorous EUV lithography models together with inverse lithography technology (ILT) for EUV process window and CD control improvement. To enable this new capability, we have linked the broad EUV physical effect modeling capability of our rigorous lithography simulator, Sentaurus Lithography (S-Litho), with our highly flexible production proven ILT mask synthesis solution (Proteus ILT). This new combined capability can take advantage of the wide range of EUV modeling capabilities including rigorous electromagnetic mask/substrate modeling. The advantages of using S-Litho rigorous simulation for ILT optimization is further benefited from significant speed enhancements using new high performance EUV mask 3D capabilities. ILT has been extensively used in a range of lithographic areas for DUV and EUV including logic hot-spot fixing, memory layout correction, dense memory cell optimization, assist feature (AF) optimization, source optimization, complex patterning design rules and design-technology co-optimization (DTCO). The combined optimization capability of these two technologies therefore will have a wide range of useful EUV applications. We will highlight the specific benefits of the rigorous DUV and EUV ILT functionality for several advanced applications including resist profile optimization for resist top- oss and resist descumming and process window improvement.

Hypersonic aircrafts and aero-engine combustion chambers both generate non-equilibrium and high-enthalpy flows and bring complex material-relied heat convection performance. The convective heating prediction is difficult due to unknown surface thermal state, leading to poor usability of wall temperature correlation method (WTCM). This paper aims at improving WTCM for convective heating prediction in chemically reacting flows through coupling computation of catalysis on thermal protection materials. Modified WTCM for chemically reacting flows accounts for two distinct physical events driven by temperature gradient and species reaction, which follow the Fourier’s and Fick’s laws, respectively. Preliminary validation testing demonstrates the feasibility of the modified WTCM to rapidly evaluate aerodynamic heating with limited deviation. The current research provides essential technical support for the evaluation and design of hypersonic aircrafts and aero-engine combustion chambers.

Hypersonic carbon dioxide reacting gas-surface interaction occurs on the heat shield of high-speed Mars entry capsules, which has great influences on the heat transfer characteristics. Based on hypersonic reacting flow solver with complex surface thermochemistry, the hypersonic chemical non-equilibrium flow with oxygen/carbon gas mixture was numerically simulated, and the interaction between non-equilibrium flow and surface reactions was numerically analyzed to reveal the mechanism of aerodynamic heating from surface thermochemistry. Numerical results of catalytic effects show that the near-wall thermochemical behaviors are essentially dominated by the near-wall diffusion and chemical reactions. Various surface reactions alter the flow structure in the boundary layer, and generate different aerodynamic heating patterns. Results from ablating simulations indicate that the ablating surface can induce additional near-wall diffusion and injection energy though their influence on the thermal boundary layer structure is neglectably small. The modeling of reacting gas-surface interaction can be of benefit to promoting the fidelity and precision of aerodynamic heating with complex surface thermochemistry.

Despite the large difficulties involved in extending 193i multiple patterning and the slow ramp of EUV lithography to full manufacturing readiness, the pace of development for new technology node variations has been accelerating. Multiple new variations of new and existing technology nodes have been introduced for a range of device applications; each variation with at least a few new process integration methods, layout constructs and/or design rules. This had led to a strong increase in the demand for predictive technology tools which can be used to quickly guide important patterning and design co-optimization decisions. In this paper, we introduce a novel hybrid predictive patterning method combining two patterning technologies which have each individually been widely used for process tuning, mask correction and process-design cooptimization. These technologies are rigorous lithography simulation and inverse lithography technology (ILT). Rigorous lithography simulation has been extensively used for process development/tuning, lithography tool user setup, photoresist hot-spot detection, photoresist-etch interaction analysis, lithography-TCAD interactions/sensitivities, source optimization and basic lithography design rule exploration. ILT has been extensively used in a range of lithographic areas including logic hot-spot fixing, memory layout correction, dense memory cell optimization, assist feature (AF) optimization, source optimization, complex patterning design rules and design-technology co-optimization (DTCO). The combined optimization capability of these two technologies will therefore have a wide range of useful applications. We investigate the benefits of the new functionality for a few of these advanced applications including correction for photoresist top loss and resist scumming hotspots.

Background: Non-invasive evaluation for liver fibrosis is of great clinical interest and value, but current models fail to accurately stage and differentiate each stage of liver fibrosis, especially in patients with chronic hepatitis B (CHB), and never taking off to be used clinically. Methods: This multicenter, prospective study used unbiased penalized logistic regression, assessed 30 variables referencing to histologic fibrosis stage in a large training cohort (n=800), and established simpler novel non-invasive program score (SNNPS). An independent validation cohort (n=400) was used to validate the SNNPS. Finally, a mobile program was then developed for one-step detailed calculation of certain hepatic fibrosis staging. Findings: Five variables-liver stiffness measurement (LSM), platelet counts, age, serum hyaluronic acid and spleen diameter, were identified as independent predictors for fibrosis stage and developing SNNPS that has AUCs of 0.893, 0.897, and 0.909 for significant fibrosis, advanced fibrosis, and cirrhosis, respectively. Using sub-models of SNNPS, S1 score ≤ 2.875 was 86% specific and 82% sensitive for mild fibrosis, S2 score ≤ 4.06 was 85% specific and 86% sensitive for significant fibrosis, and S3 score ≤ 4.402 or > 4.402 was 93% specific and 91% sensitive for advanced fibrosis or cirrhosis. In validation set, AUCs for significant fibrosis, advanced fibrosis, and cirrhosis were 0.904, 0.912, and 0.897, respectively. The SNNPS with highest LR and lowest LR- was significantly more specific and sensitive than AAR, APRI, LSM alone and Hepascore, and can be calculated via a mobile program in one-step. Interpretation: Using sophisticated mathematic modelling and a large multicenter study data developed and validated SNNPS that is superior to previously reported models, and can be easily calculated via mobile program to accurately diagnose various hepatic fibrosis stages in CHB patients in a wider range. Trial Registration Number: ClinicalTrials.gov. Identifier: NCT65418 Funding Information: National Major Science and Technology Special Project of China (2013ZX10005002). Competing Interest Declaration: The authors declare that there is no conflict of interest in this study Ethical Approval Statement: The study meets the requirements of Declaration of Helsinki, and protocol was approved by the ethics committee of each participating institution, and a written informed consent was obtained from all patients.

The Mars Science Laboratory (MSL) entry capsule has been designed as a lifting entry for sufficient deceleration and precise landing performance. This paper presents the static aerodynamics analysis of the MSL capsule in the hypersonic entry process for exploration mission to Mars. Hypersonic static coefficients were derived from fully three-dimensional computational fluid dynamics solutions with a specified effective specific heat ratio on a typical trajectory state. Aerodynamic performance analysis ascertains the trim characteristics and static stability of the capsule with respect to the center of gravity (CG) location. Analysis results obtained show that CG location determines the trim characteristics and the static stability, and certain CG radial and axial shift alters the lifting entry performance, so that proper aerodynamic configuration and inner equipment layout is needed for CG adjustment to satisfy the static aerodynamics requirements.

The 5nm and 7nm technology nodes will continue recent scaling trends and will deliver significantly smaller minimum features, standard cell areas and SRAM cell areas vs. the 10nm node. There are tremendous economic pressures to shrink each subsequent technology, though in a cost-effective and performance enhancing manner. IC manufacturers are eagerly awaiting EUV so that they can more aggressively shrink their technology than they could by using complicated MPT. The current 0.33NA EUV tools and processes also have their patterning limitations. EUV scanner lenses, scanner sources, masks and resists are all relatively immature compared to the current lithography manufacturing baseline of 193i. For example, lens aberrations are currently several times larger (as a function of wavelength) in EUV scanners than for 193i scanners. Robustly patterning 16nm L/S fully random logic metal patterns and 40nm pitch random logic rectangular contacts with 0.33NA EUV are tough challenges that will benefit from advanced OPC/RET. For example, if an IC manufacturer can push single exposure device layer resolution 10% tighter using improved ILT to avoid using DPT, there will be a significant cost and process complexity benefit to doing so. ILT is well known to have considerable benefits in finding flexible 193i mask pattern solutions to improve process window, improve 2D CD control, improve resolution in low K1 lithography regime and help to delay the introduction of DPT. However, ILT has not previously been applied to EUV lithography. In this paper, we report on new developments which extend ILT method to EUV lithography and we characterize the benefits seen vs. traditional EUV OPC/RET methods.

Many different advanced devices and design layers currently employ double patterning technology (DPT) as a means to overcome lithographic and OPC limitations at low k1 values. Certainly device layers with k1 value below 0.25 require DPT or other pitch splitting methodologies. DPT has also been used to improve patterning of certain device layers with k1 values slightly above 0.25, due to the difficulty of achieving sufficient pattern fidelity with only a single exposure. Unfortunately, this broad adoption of DPT also came with a significant increase in patterning process cost. In this paper, we discuss the development of a single patterning technology process using an integrated Inverse Lithography Technology (ILT) flow for mask synthesis. A single pattering technology flow will reduce the manufacturing cost for a k1 > 0.25 full chip random contact layer in a memory device by replacing the more expensive DPT process with ILT flow, while also maintaining good lithographic production quality and manufacturable OPC/RET production metrics. This new integrated flow consists of applying ILT to the difficult core region and traditional rule-based assist features (RBAFs) with OPC to the peripheral region of a DRAM contact layer. Comparisons of wafer results between the ILT process and the non-ILT process showed the lithographic benefits of ILT and its ability to enable a robust single patterning process for this low-k1 device layer. Advanced modeling with a negative tone develop (NTD) process achieved the accuracy levels needed for ILT to control feature shapes through dose and focus. Details of these afore mentioned results will be described in the paper.

EUV lithography is viewed as a highly desirable technology for 5nm and 7nm node patterning cost reduction and process simplicity. However, for the 5nm and 7nm nodes EUV not only needs to function in a low-K1 resolution environment but has several new and complex patterning issues which will need accurate compensation by mask synthesis tools and flows. The main new issues are: long-range flare variation across the chip, feature dependent focus offsets due to high mask topography, asymmetry inducing shadowing effects which vary across the lens slit, significantly higher lens aberrations, illumination source changes (across the lens and with time) and new resist exposure mechanisms. These solutions must be successfully deployed at low K1 values and must be integrated together to create OPC/RET flows which have high resolution, high accuracy, and are fast to deploy. Therefore, the combined requirements of low-K1 resolution, full reticle correction accuracy and process window can be even more challenging than in current optical lithography mask synthesis flows. Advanced computational methods such as ILT and model-based SRAF optimization are well known to have considerable benefits in process window and resolution for low-K1 193 lithography. However, these methods have not been well studied to understand their benefits for lower-K1 EUV lithography where fabs must push EUV resolution, 2D accuracy and process window to their limits. In this paper, we investigate where inverse lithography methods can improve EUV patterning weaknesses vs. traditional OPC/RET. We first show how ILT can be used to guide a better understanding of optimal solutions for EUV mask synthesis. We then provide detailed comparisons of ILT and traditional methods on a wide range of mask synthesis applications.

New inverse methods such as model-based SRAF placement, model-based SRAF optimization, and full main + assist feature ILT are well known to have considerable benefits in finding flexible mask pattern solutions to improve process window and CD control. These methods have traditionally relied on compact models that are tuned to match resist measurements at a single z-height or slice. At this slice in the resist, some critical failure modes such as top loss and scumming are not detected. In this paper, we describe and present results for a methodology to extend ILT’s process window improvement capabilities, and to co-optimize mask patterns with awareness of the resist profile. These improvements are proven to reduce the risk of patterning failures at the bottom and top of critical resist features, which a typical mask correction process would not alleviate. Ideally, mask optimization would use a full rigorous TCAD resist model to guide the correction at multiple heights in the resist. However, TCAD models are significantly slower than compact models in simulations and ILT already has high computational requirements. Therefore, we have generated compact models which are fitted to the TCAD model resist profile data. We show the significant process window improvements obtained with this new resist 3D aware ILT methodology.

The objective of the study was to investigate the heat transfer characteristics of a phase-change energy storage unit for thermal management. Considering the conduction in the solid and natural convection in the liquid, a physical and mathematical model for heat transfer was formulated. The governing conservation equations were solved using the finite-volume method on fixed grids. An enthalpy-porosity method was used for modeling the melting phenomenon of a phase-change energy storage unit. The time and space movement of the phase front, the temperature distribution, and the heat dissipation rate have been analyzed based on the model. The influence of the unit geometry, heat source location, and types of phase-change materials on the thermal performance of the energy storage unit were investigated. The model and numerical method were evaluated by comparing the numerical predictions with the experimental results. There was found to be excellent agreement between the calculation and experiment, indicating that the numerical method for heat transfer simulation of a phase-change energy storage unit is accurate. The results from the analysis elucidate the thermal performance of the phase-change energy storage unit and will provide the basis for the design and optimization of thermal management systems.