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Marangoni drying is widely employed in integrated circuit manufacturing to remove water from the wafer surface. The organic vapor blown at the meniscus induces a strong Marangoni effect, which strips the entrained water film induced by the wafer's withdrawal from a deionization water bath, and realizes ultra-clean drying of the wafer. The present work implements a numerical investigation of the terminal residual film and free surface flow in the water entrainment region during Marangoni drying based on a trans-scale model containing the thin water film, meniscus, and bulk region. The results show that the terminal thickness of the water film is 30 nm, which approximately agrees with the previous experimental and numerical results. In addition, the stagnation point moves away from the thin film region compared with that of wafer withdrawn in the absence of the Marangoni effect. The magnitude of free surface velocity in the thin film region after drying depends only on the withdrawal velocity, and is irrelevant to the Marangoni number. The analyses of the entrained water film thinning and surface flow provide useful guidance about controlling the drying process. [ABSTRACT FROM AUTHOR]

Highlights • Wafer drying using thermal Marangoni effect is modelled and investigated. • Entrained water film on wafer is thinned tenfold by Marangoni stress. • Evaporation suppresses interfacial temperature rise and weakens Marangoni effect. • Film thinning and Marangoni convection in air improve the evaporative flux. • Heat source, thermal conductivity and wafer thickness affect the drying effect. Abstract Marangoni drying induced by organic vapor is an important process in integrated circuit manufacturing to obtain an ultra-clean surface, but its application is limited by the utilization of flammable vapor. Thermal Marangoni drying induced by a temperature gradient is a safe and environmentally friendly technology. However, the regulation of thermal Marangoni-driven flow is complicated, and current understanding of the thermal Marangoni drying mechanism is inadequate. In this work, we present a coupled model of thermal Marangoni drying that combines the two-phase flow, heat transfer, and water vapor transfer in air. The evolution of entrained water film thickness, dynamics of Marangoni-driven flow, and evaporative cooling are numerically simulated. The results show that the achieved minimum residual thickness of the entrained water film is thinned more than tenfold compared with that of the wafer withdrawn without the thermal Marangoni effect. The temperature rise and Marangoni stress grow dramatically in the film and meniscus at the initial time, and then they remain as almost invariant after achieving the dynamic equilibrium between the heating and evaporative cooling. The convective water vapor transfer in air and the reduction of entrained water film thickness improve the evaporative flux, which in turn suppresses the increase in the thermal Marangoni effect until the dynamic equilibrium is attained. Furthermore, the higher heat source, lower wafer thermal conductivity and smaller wafer thickness can enhance drying performance. The investigation of drying dynamics will contribute to a comprehensive understanding of the thermal Marangoni drying process and provide guidance to its industrial applications. [ABSTRACT FROM AUTHOR]

With the rapid development of high-energy laser system, thick silicon mirror, as an important optical component to reflect laser, is required to have a surface with micron-level flatness, which poses significant challenges to silicon mirror manufacture process. Fine rotation grinding (FRG) is a typical efficient method for silicon mirror manufacture. A geometric model is developed in this paper to research silicon mirror surface figure control mechanism in FRG process. The model demonstrates the relationship between the grinding spindle obliquity and the mirror surface figure. From an application perspective, the relationship between the spindle obliquity and the spindle dial gauge indication is further presented. Based on this model, a MATLAB program is designed to give a series of simulation results for researching spindle adjustment regularity and getting the most ideal spindle obliquity. Besides, several grinding experiments are carried out. The simulation and experiment results are in good agreement, and a silicon mirror surface with the flatness of less than 2 μm is achieved. The proposed grinding geometric model can provide an actual guide for grinding spindle adjustment to control the surface figure of silicon mirror. [ABSTRACT FROM AUTHOR]

In this study, a specially designed carrier with a one-zone pneumatic loading system that uses a thick copper disk as the workpiece was developed. Comparative studies of the fluid pressure and workpiece orientation between the disk and wafer carriers during chemical mechanical polishing were conducted. The results reveal that the copper disk leans down toward the leading edge and produces a negative-dominated (approximately 70%) fluid pressure, which differs from the multi-zone carrier but agrees with other studies in which the fluid pressure is measured from the disk side. Different balancing statuses and wedged gaps are formed in these two structures. [ABSTRACT FROM AUTHOR]

The abrasive effect of particles is one of the basic mechanical actions in chemical mechanical polishing (CMP). In this paper, numerical simulations of particle sliding trajectories are performed to examine the influence of the kinematic parameters on the polishing uniformity of typical rotary-type CMP equipment. The trajectory simulations are carried out based on the kinematic analysis. The results reveal that the speed ratio \alpha and the period ratio kT0, which represent the coupling relationships among the three basic motions of CMP, are the two major factors affecting the trajectory distribution. Further, a trajectory density parameter is proposed to quantitatively evaluate the global uniformity of the trajectory distributions and to optimize the kinematic parameters for better uniformity. The statistical results of the trajectory density analysis reveal that the trajectory of the wafer edge is denser than that of the wafer central area. To obtain better trajectory uniformity, some particular values of \alpha and kT0, that is, \alpha=1 and kT0=1, which imply that the basic motions have a special coupling relationship, should be excluded; the preferred kinematic parameter values for CMP are \alpha=0.91\--0.93 and kT0=5\--7. This paper provides a basic guide to the kinematic parameter settings of CMP. [ABSTRACT FROM AUTHOR]

Abstract: A novel in-situ wafer bending/orientation measurement system, cooperated with our previous developed fluid pressure mapping system, was developed for 12-inch chemical mechanical polishing (CMP) equipment. Wafer bending and wafer orientation are studied for copper wafer sliding against the IC1000 pad. The results reveal a micron level wafer bending, and a slight wafer pitch angle of 10−5 degree. Both the wafer pitch angle and interfacial fluid pressure increase with the speed till a critical speed and then decrease. The convergent-dominated wedged gap caused by the convexly bended, trailing edge pitched wafer gives a reasonable explanation to the positive-dominated fluid pressure. [Copyright &y& Elsevier]

In this paper, the effect of slurry injection position on removal rate and nonuniformity was experimentally investigated on a 300-mm polisher developed by the authors, and the effect of slurry injection position on slurry fluid pressure distribution during polishing was also measured by a novel in situ fluid pressure measurement system integrated in the polisher. In situ pad conditioning was employed in all experiments. The results showed that removal rate, nonuniformity, and fluid pressure distribution were influenced dramatically by the slurry injection position. The slurry injection position determines the slurry distribution, and therefore, the removal rate profile and fluid pressure distribution were affected. [ABSTRACT FROM AUTHOR]

Highlights: [•] Wafer bending and fluid pressure are measured during 12-inch multi-zone CMP. [•] Multi-zone carrier has zone-loading effect on wafer bending. [•] Zone pressure configuration affects wafer bending and fluid pressure. [•] Convexly-bended wafer generates the largest fluid pressure due to a suitable wedged gap. [•] Higher edge zone pressure contributes to concave bending and lower fluid pressure. [Copyright &y& Elsevier]

In this paper, the kinematic analysis and numerical calculation are used to discuss the effect of the kinematic parameters on the final polishing result of typical rotary chemical-mechanical polishing (CMP) equipment. The relative velocity distribution and the sliding distance distribution are calculated based on the kinematic analysis. Especially, the coupling relationships between the kinematic parameters are investigated and discussed. And two parameters of the sliding distance nonuniformity (SDNU) and the sliding distance nonuniformity within concentric circles (SDNU\-cc) are proposed and calculated to evaluate the global uniformity of the sliding distance and to reveal the coupling relationships between the kinematic parameters. The results suggest that the relative velocity distribution and the sliding distance distribution are significantly affected by the coupling effects of the basic motions of CMP system; the SDNU is mainly affected by parameter \alpha, which represents the coupling relationship between the rotary motions of the wafer carrier and the polishing platen; the SDNU\-cc is mainly affected by parameter kT{0}^{\prime}(\alpha kT0), which represents the coupling relationship between the reciprocating motion and the rotary motion of the wafer carrier; \alpha\approx 1 and \alpha kT0>2 are proper for better polishing uniformity in real CMP process. [ABSTRACT FROM PUBLISHER]

The wafer backside grinding process has been a crucial technology to realize multi-layer stacking and chip performance improvement in the three dimension integrated circuits (3D IC) manufacturing. The total thickness variation (TTV) control is the bottleneck in the advanced process. However, the quantitative analysis theory model and adjustment strategy for TTV control are not currently available. This paper developed a comprehensive simulation model based on the optimized grinding tool configuration, and several typical TTV shapes were obtained. The relationship between the TTV feature components and the spindle posture was established. The linear superposition effect of TTV feature components and a new formation mechanism of TTV shape were revealed. It illustrated that the couple variation between the two TTV feature components could not be eliminated completely. To achieve the desired wafer thickness uniformity through a concise spindle posture adjustment operation, an effective strategy for TTV control was proposed. The experiments on TTV optimization were carried out, through which the developed model and TTV control strategy were verified to play a significant role in wafer thickness uniformity improvement. This work revealed a new insight into the fine control method to the TTV optimization, and provided a guidance for high-end grinding tool and advanced thinning process development. [ABSTRACT FROM AUTHOR]

The n-type semiconductor SnO2 with a wide band gap (3.6 eV) is massively used in gas-sensitive materials, but pure SnO2 still suffers from a high operating temperature, low response, and tardy responding speed. To solve these problems, we prepared small-sized pure SnO2 using hydrothermal and freeze-drying methods (SnO2-FD) and compared it with SnO2 prepared using a normal drying method (SnO2-AD). The sensor of SnO2-FD had an ultra-high sensitivity to NO2 at 100 °C with excellent selectivity and humidity stability. The outstanding gas sensing properties are attributed to the modulation of energy band structure and the increased carrier concentration, making it more accessible for electron exchange with NO2. The excellent gas sensing properties of SnO2-FD indicate its tremendous potential as a NO2 sensor. [ABSTRACT FROM AUTHOR]

The ultra-precision grinding technology based on a workpiece self-rotational principle is extensively used for silicon wafer thinning in the chip post-processing. Nevertheless, owing to the random nature of diamond grains and the unique machining manner of rotating components, accurate prediction and real-time monitoring of grinding forces remain a significant challenge in wafer self-rotational grinding (WSRG) process. This work establishes an improved theoretical model and builds a novel in-situ measurement system to analyze and detect the grinding force. Firstly, the motion trajectory and contact condition of diamond grains are explored. The grain–workpiece interactions are divided into rubbing, plowing, cutting and brittle stages. Secondly, the grinding force prediction model is proposed, which considers the combined effects of grain wear, grain randomness characteristics, brittle-to-ductile transition, elastic rebound, strain rate and grinding marks. Moreover, piezoelectric force sensors are employed to build the in-situ measurement system. The developed system is proven to simultaneously measure grinding forces online with continuous and stable output in the x , y and z directions. The impacts caused by feed rate, wheel speed and wafer speed are further revealed. Experimental results are consistent well with predicted ones, demonstrating a high prediction accuracy of the proposed grinding force model. Finally, a new index, namely the processing factor, is introduced to calculate the subsurface damage depth and residual stress for various machining parameters. This work not only enhances the understanding of predicting and measuring grinding force, but also provides a new method to evaluate the subsurface defects in brittle material grinding. [Display omitted] • Establish a prediction model of grinding force in wafer self-rotational grinding. • Consider the effect of grain wear, grain size, elastic rebound and brittle fracture. • Build an in-situ measurement system to monitor triaxial grinding force in real time. • Introduce processing factor to evaluate subsurface damage depth and residual stress. [ABSTRACT FROM AUTHOR]

In the field of advanced packaging, large-size silicon wafers are usually thinned by ultra-precision grinding technology relying on the process of workpiece self-rotation. However, the damage caused by mechanical material removal deteriorates the wafer surface flatness and die strength, while its atomic-scale formation principle has yet to be revealed. This work explores the ductile deformation and subsurface damage evolution mechanism of silicon wafer during the ultra-precision grinding process. Some grinding tests are first conducted using different diamond wheels. The surface topography and energy dispersive spectroscopy (EDS) mapping of ground wafers are measured by scanning electron microscope (SEM). The phase transition properties of the ground silicon wafer are confirmed via Raman spectrum. Next, the specimen of groove cross-section is fabricated and its morphology is examined via transmission electron microscopy (TEM) to analyze the subsurface damage characteristics. The subsurface defects at the atomic scale, involving amorphous layer, dislocations, stacking faults and lattice distortions, are observed. Due to its controllable load and similarity of the cutting motion, nanoscratch is utilized for investigating the influence of abrasive interactions on subsurface deformation during the grinding process. Thus, a series of multiple nanoscratch tests are performed in both varied and constant force modes. The material removal behaviors under different scratching conditions are illustrated. This work provides a fundamental understanding of developing a high-efficiency and low-damage thinning method for 12-inch silicon wafers. [Display omitted] • Subsurface damage evolution mechanism is revealed in wafer self-rotation grinding. • Atomic-scale defects, involving amorphous layer and stacking faults, are observed. • Nanocrystal structure and high-pressure phase transition are found in damaged zone. • Material removal behavior of multiple nanoscratch is studied for monocrystal silicon. [ABSTRACT FROM AUTHOR]

Transparent conductive electrodes (TCEs) are indispensable components of various optoelectronic devices such as displays, touch screen panels, solar cells, and smart windows. To date, the fabrication processes for metal mesh‐based TCEs are either costly or having limited resolution and throughput. Here, a two‐step surface energy‐directed assembly (SEDA) process to efficiently fabricate high resolution silver meshes is introduced. The two‐step SEDA process turns from assembly on a functionalized substrate with hydrophilic mesh patterns into assembly on a functionalized substrate with stripe patterns. During the SEDA process, a three‐phase contact line pins on the hydrophilic pattern regions while recedes on the hydrophobic non‐pattern regions, ensuring that the assembly process can be achieved with excellent selectivity. The necessity of using the two‐step SEDA process rather than a one‐step SEDA process is demonstrated by both experimental results and theoretical analysis. Utilizing the two‐step SEDA process, silver meshes with a line width down to 2 µm are assembled on both rigid and flexible substrates. The thickness of the silver meshes can be tuned by varying the withdraw speed and the assembly times. The assembled silver meshes exhibit excellent optoelectronic properties (sheet resistance of 1.79 Ω/□, optical transmittance of ≈92%, and a FoM value of 2465) as well as excellent mechanical stability. The applications of the assembled silver meshes in touch screen panels and thermal heaters are demonstrated, implying the potential of using the two‐step SEDA process for the fabrication of TCEs for optoelectronic applications. [ABSTRACT FROM AUTHOR]

A parabolic velocity field is proposed to get the minimum required rolling force in hot rolling process, the equal area yield criterion is used to calculate the plastic deformation power, the collinear vector inner product method is used to get friction power, the analytical equation of strip rolling power functional is obtained, and the required rolling force was calculated by minimizing the power functional. Meanwhile, the location of neutral point, shape factor, and stress state coefficient are discussed. The accuracy of the proposed theoretical model is examined through comparing with the experimental measured ones and online measured ones, it shows good agreement, the relative error of rolling force is less than 9.1%, and the proposed model is considered to be effective in hot tandem rolling process. [ABSTRACT FROM AUTHOR]

Clean, alternative energy sources, especially fuel cells, are gradually attracting global attentions while the produced toxic nitrogen dioxide (NO 2) is a greatly hazardous chemical impacting their energy efficiencies. Metal oxide semiconductors (MOS) hold significant promise as NO 2 sensors. However, intensive humidity interaction intensifies signal drifts and reliable response inhibitions under variable humidity conditions. In this study, we present a novel approach to address this issue by engineering in-situ F-doped NiO nanocomposites (NiOF x) decorated on ZnO snowflakes achieved through decomposition modulation of ZnOHF precursors. The optimized NO 2 sensor demonstrates unparalleled humidity-independence across a wide operating temperature range with prime sensitivity, low detection limit and rapid response/recovery. Matrix algorithm is also implemented in highly precise NO 2 identification under complicated atmospheric and humid conditions. Mechanism studies based on temperature programmed desorption (TPD), quasi in-situ X-ray photoelectron spectroscopy (Quasi in-situ XPS) reveal that F− dopants facilitate interfacial electron transferring and inhibit oxygen activity. In-situ diffuse reflectance infrared Fourier transform spectroscopy (In-situ DRIFTS) demonstrates that hygroscopic NiO and electronegative F− synergistically obstruct hydroxyl adsorptions on sensing materials. The innovative approach offers a promising solution for enhancing moisture resistance of MOS sensors for real-time NO 2 concentration monitoring in fuel cells and provides valuable insights into anti-humidity mechanisms. [Display omitted] • In-situ ZnO-NiOF x nanocomposites were hydrothermally synthesized. • The optimized sensor exhibits humidity-independence in NO 2 detections. • The enhanced oxygen activity induced by NiO causes the weak humidity tolerance. • Quasi in-situ XPS reveals humidity-immune effect of F− under high temperatures. • In-situ DRIFTS measurements verify the anti-interference NO 2 sensing mechanism. [ABSTRACT FROM AUTHOR]

• Novel Ni atomic clusters decorated yolk-shell In 2 O 3 was successfully constructed. • The sensor achieves high response (454.62), fast (1/3 s), ppb-level NO 2 detection. • Reaction dynamics confirm promoted spontaneous NO 2 reactions by atomic Ni. • In-situ DRIFTS measurements reveal NO 2 reaction pathways and rapid detections. • FEM simulation explores the promoted NO 2 diffusion kinetics by yolk-shell feature. Highly sensitive, sophisticated and rapidly responding/recovering NO 2 sensors are of a pressing demand across various modern applications. However, traditional metal oxide semiconductors (MOSs), such as In 2 O 3 , often grapple with issues such as diminished sensitivity and tardy responding/recovering. To address these challenges, we present a novel, simultaneous enhancement strategy centered around Ni atomic clusters (Ni AC) integrated into In 2 O 3 yolk-shell microspheres. This innovative structural and compositional design not only enhances NO 2 adsorption thermodynamics but also improves kinetics reacting rate. The optimized heterostructured Ni AC -In 2 O 3 exhibits exceptional NO 2 sensing performances with high response (454.62 to 10 ppm NO 2), instantaneous responding/recovering dynamics (1/3 s), and an impressively ultra-low detection limit (1 ppb) at 200 ℃. Reaction kinetics calculation, finite element method (FEM) simulations and further validation through In-situ diffuse reflection infrared Fourier transform spectroscopy (In-situ DRIFTS) and temperature-programmed desorption (TPD) analyses confirms the accelerated NO 2 adsorption/desorption dynamics, enhanced NO 2 dissociation and trace-concentration NO 2 molecule capturing capability attributed to Ni AC. Considering these merits, The fabricated Ni AC -In 2 O 3 ensures high-precise, instantaneous, ppb-level NO 2 detections. [ABSTRACT FROM AUTHOR]

[Display omitted] • Water reduces the deposition rate of the nanoparticles on the substrate. • Water increases the initial adhesion between the chemisorption nanoparticles and the substrate. • Water acts as a lubricating layer, accelerating the desorption of interfacial chemical bonds and mitigating damage to the Si substrate. • H 2 O 2 pretreatment of the substrate resultes in more negative surface charge. • H 2 O 2 pretreatment impedes particle deposition due to the increase of electrostatic repulsion and hydrophilicity of substrate surface. • H 2 O 2 pretreatment increases the probability of Si-O-Si bond formation, thus raising the removal difficulty of chemisorption nanoparticles. The cleaning of silicon wafer surfaces in the integrated circuits manufacturing has not yet been studied at the atomic scale, making it difficult to optimize. In this study, the atomistic mechanism of nanoparticle movement during the cleaning process of the substrate after chemical mechanical polishing (CMP) was investigated using ReaxFF reactive molecular dynamics simulations. The redeposition and removal processes of the silica nanoparticles on the Si (1 0 0) substrate with different ambient humidity and substrate state were simulated. Results indicated that water generally plays a positive role in cleaning process, preventing the silica nanoparticles from approaching the substrate and promoting the fracture of interfacial chemical bonds, and it also mitigates the substrate damage caused by particle removal. Aqueous H 2 O 2 influences the substrate state by increasing the oxidizability and hydroxylation level of the substrate surface, which changes the interaction force between the substrate and the nanoparticles, thus impacting particle redeposition process. Additionally, the peroxide facilitates the formation of Si–O–Si bonds and inhibits the removal of the nanoparticles. This work provides atomistic insights into the wafer cleaning process, which is of great significance for the solution design. [ABSTRACT FROM AUTHOR]

As a universal machining method, wafer self-rotational grinding is applied to obtain a planar surface with high processing accuracy. However, the wheel spindle vibration significantly deteriorates the wafer flatness but is rarely studied. This paper primarily focuses on the impacts caused by wheel spindle vibration on the surface topography of ground wafer. Firstly, a mathematical model is proposed to analyze the dynamic behaviors of wheel spindle, involving radial, axial and tilting movements. The dynamic response and frequency characteristics of vibration-induced errors are presented. Then, a surface formation model is developed, taking grinding kinematics, grain size randomness, vibration-induced error and overlapping effect into account. Two kinds of patterns, i.e., waviness along circumferential direction and waviness along mark direction, are observed from the simulated wafer surface. Moreover, their wavelengths are calculated to explore the effect of grinding parameters and vibration frequency on waviness features. Finally, grinding tests are performed under different machining conditions, as well as the spindle vibration signal and wafer topography are measured. The obtained waviness characteristics are consistent well with those in simulation. In addition, the variation of surface roughness under different vibration parameters is further revealed. This work is expected to provide new insight into the machined error prediction and wafer flatness improvement considering the dynamic performance of wheel spindle. [Display omitted] • Dynamic behaviors of wheel spindle in time domain and frequency domain are studied. • Build a modeling framework to reveal a surface formation mechanism of ground wafer. • The impacts of grain size randomness and vibration-induced error are considered. • Consistent waviness features are observed on measured and simulated wafer surfaces. [ABSTRACT FROM AUTHOR]

Accurate calculation of the heat source in the roll gap during the cold rolling process is the basis for a well-designed coolant system, which is particularly important for reducing roll wear and improving the flatness quality of strip steel. Although many established numerical models have high precision when calculating the work roll temperature, complex modeling processes and large calculation times result in the inability to predict the work roll temperature quickly for the application of automatic control systems. Therefore, the authors developed a new analytical heat source model to calculate the axial temperature distribution of the work roll in the cold rolling process. First, according to the deformation characteristics of strip cold rolling, the deformation zone is divided into a plastic zone and two elastic zones, and the length of each deformation zone is calculated considering the effect of tension. Then, the friction heat generated in the elastic zone is calculated. Second, new exponential velocity and corresponding strain-rate fields satisfying kinematically admissible conditions are proposed to calculate the deformation heat and friction heat generated in the plastic zone. Finally, the work roll temperature prediction model is established by contemplating the heat source of the roll gap, emulsion heat transfer, air cooling, and contact heat transfer with the intermediate roll. By repeatedly optimizing the weighted coefficient d of intermediate principal shear stress on the yield criterion, the maximum error between the calculated results and the actual measured cold roll temperature data was reduced to 3.1%. The effects of the reduction ratio, rolling speed, and resistance to deformation on the deformation heat and friction heat are discussed, and the variation of temperature field of the work roll with time is analyzed quantitatively. [ABSTRACT FROM AUTHOR]

Silicon wafers are commonly thinned employing an ultra-precision grinding machine based on a workpiece self-rotational principle. The diamond grains, stochastically located on the grinding wheel surface, remove the workpiece material and generate a difference in the size and shape of undeformed chips. However, an in-depth understanding of the grain-workpiece interaction randomness in wafer thinning process and its link with surface roughness has not been revealed yet. In this paper, a new index, i.e., undeformed chip width, is first proposed to analyze and describe the stochastic characteristics in material removal process as well as predict the surface roughness of ground wafer. The grinding wheel morphology is constructed by the random operation for grain size and position. Then, a 2D topography generation model is established to calculate the undeformed chip width. The non-uniform distribution characteristics of undeformed chip width under different grinding conditions are further analyzed. Finally, the relation between undeformed chip width and surface roughness of ground wafer is presented. The correctness of developed models is verified using a series of grinding experiments. • A ground wafer undeformed chip modeling framework from a micro scale is proposed. • A wheel morphology is reconstructed by random operation for grain size and position. • An undeformed chip width is defined to describe random properties in material removal. • A regression model of surface roughness in wafer self-rotational grinding is derived. [ABSTRACT FROM AUTHOR]

The ultra-precision grinding technology based on the workpiece self-rotational principle has been extensively employed to obtain a high surface accuracy and material removal rate during the wafer thinning process. However, no estimation methods and prediction models are currently available for the surface topography of ground wafers, especially considering the material removal characteristics between the grain and silicon. This paper proposed a novel three-dimensional topography modeling framework from a micro-scale perspective to reveal the material removal and surface generation mechanism underlying the wafer self-rotational grinding process. First, the wheel morphology was reconstructed via the random operation for grain position and size, while the combined effects of plastic side flow, elastic spring back and brittle fracture were quantized according to the elasticity theory principle. Then, a new method was developed to calculate the profile height of the wafer topography using kinematic transformation. The groove angle and surface roughness were used to characterize the wafer surface topography. The findings were consistent with the simulation results and validated the correctness of the model. The simulation model was used to examine the impact of the grain size and grinding parameters on the wafer surface topography, while the degree of influence was further evaluated according to the change rate of the groove density curve. This work provided new insights into the material removal behavior during wafer self-rotational grinding and optimized the grinding parameters to obtain a smoother surface. [Display omitted] • Develop a novel model framework at micro-scale for ground wafer surface topography. • Reveal a deformed mechanism considering rebound, plastic flow and brittle fracture. • Reconstruct a wheel morphology by the random operation for grain size and position. • Derive an analytic expression of groove surface caused by the grain cutting motion. • Analyze the kinematic overlapping effect of grain trajectory in surface generation. [ABSTRACT FROM AUTHOR]

Highlights: [•] This study aimed to maximize the material removal rate and minimize the within wafer non-uniformity simultaneously. [•] The design of experiment approach was used to optimize the process parameters for CMP of a 12-inch wafer. [•] Confirmation tests indicated that MRR of 6551Å/min and WIWNU of 4.72% can be obtained using the optimum combination. [ABSTRACT FROM AUTHOR]

The effect of reheat temperature on continuous cooling bainite transformation in a low carbon microalloyed steel was investigated using a dilatometer based on welding thermal simulation process. The variation of microstructure was analyzed in detail by means of optical microscope and transmission electron microscope (TEM). The results showed that the morphology of the main microstructure changes from polygonal ferrite to granular bainite with increasing reheat temperature at a given lower cooling rate. For the higher cooling rate, the microstructure is predominantly lath bainite irrespective of the reheat temperature. The specimens with the relatively fine austenite grain size have the lowest bainite start and finish temperatures among the simulated sub-zones of heat affected zone, which is consistent with the result of the bainite lath width size observed using the TEM. Meanwhile, although the prevailing type of impingement mode of transformation is anisotropic growth impingement for all heat treatment processes, the reheat temperature has some influence on the maximum transformation rate and effective activation energy of bainite transformation. [ABSTRACT FROM AUTHOR]

Abstract: Microstructural variation in high strength low carbon bainitic steel weldment was investigated in detail by means of optical microscope, transmission electron microscope and scanning electron microscope equipped with electron backscattered diffraction. The results showed that the welded joint has various microstructures such as acicular ferrite, coarse granular ferrite and fine polygonal ferrite. The martensite–austenite (MA) constituent has a variable structure in each sub-zone, which includes fully martensite and fully retained austenite. Meanwhile, the fine grained heat affected zone has higher content of retained austenite than the welded metal (WM) and coarse grained heat affected zone (CGHAZ). The orientation relationship between retained austenite and product phases in the WM and CGHAZ is close to Kurdjumov–Sachs relationship. However, the polygonal ferrite in the fine grained HAZ has no specific orientation relationship with the neighboring retained austenite. The toughness of the coarse grained region is much lower than that of the WM because the coarse bainite contains many large MA constituents to assist the nucleation of microcracks and coarse cleavage facet lowers the ability to inhibit the crack propagation. [Copyright &y& Elsevier]

Martensite-austenite (M-A) constituent formed during welding is generally recognized as an important factor to decrease the toughness of welded joint. In this article, the morphology and chemical composition of M-A constituent in the low carbon bainitic steel welded joint was analysed in detail by means of optical microscope, transmission electron microscope and scanning electron microscope with electron probe microanalysis. The experimental results show that the M-A constituent formed in the different sub-zones presents different morphologies and different amounts. The maximum amount of M-A constituent occurs in the coarse grained heat affected zone (HAZ). It is evident that the carbon atoms segregate on the M-A constituent and carbon concentration on the slender M-A constituent is higher than that on the massive M-A constituent. Meanwhile, the distribution profile of silicon on the M-A constituent shows an obvious inhomogeneity. Most of M-A constituents have a twinned structure and/or a high dislocation density. According to impact testing results, the crack initiation energy in the HAZ specimens deteriorates significantly because the large M-A constituent can assist the formation of cleavage crack. On the other hand, the coarse prior austenite grain in the HAZ lowers the crack propagation energy. [ABSTRACT FROM AUTHOR]

Abstract: The correlation of microstructural characteristics and toughness of the simulated coarse grained heat affected zone (CGHAZ) of low carbon bainitic steel was investigated in this study. The toughness of simulated specimens was examined by using an instrumented Charpy impact tester after the simulation welding test was conducted with different cooling times. Microstructure observation and crystallographic feature analysis were conducted by means of optical microscope and scanning electron microscope equipped with electron back scattered diffraction (EBSD) system, respectively. The main microstructure of simulated specimen changes from lath martensite to coarse bainite with the increase in cooling time. The deterioration of its toughness occurs when the cooling time ranges from 10 to 50s compared with base metal toughness, and the toughness becomes even worse when the cooling time increases to 90s or more. The MA (martensite–austenite) constituent is primary responsible for the low toughness of simulated CGHAZ with high values of cooling time because the large MA constituent reduces the crack initiation energy significantly. For crack propagation energy, the small effective grain size of lath martensite plays an important role in improving the crack propagation energy. By contrast, high misorientation packet boundary in coarse bainite seems to have few contributions to the improvement of the toughness because cleavage fracture micromechanism of coarse bainite is mainly controlled by crack initiation. [Copyright &y& Elsevier]

Vertical rolling is an important technique used to control the width of continuous casting slabs in the hot-rolling field. Accurate prediction of vertical rolling force is a core point maintaining rolling-mill equipment. Owing to the limitation of the algorithm in use, the prediction accuracy of most vertical rolling force models based on the energy method can only reach more than 10%. Therefore, it is challenging to optimize the rolling-force model to improve prediction accuracy. An innovative approach for optimizing the calculation of vertical rolling force with a unified yield criterion is presented in this paper. First, the maximal width of a dog-bone region is determined by the slip-line method, and the dog-bone shape is described using a sine-function model. Second, the velocity and corresponding strain-rate fields satisfying kinematically admissible conditions are proposed to calculate the total power of the vertical rolling process. Finally, the analytical solution of the rolling force and the dog-bone-shape model is obtained by repeatedly optimizing the weighted coefficient b of intermediate principal shear stress on the yield criterion. Moreover, the effectiveness of the proposed mechanical model is verified by measured data in the strip hot-rolling field and other models' results. Results show that the prediction accuracy of the vertical rolling force model can be improved by optimizing the value of b. Then, the impacts of reduction rate, initial thickness, and friction factor on dog-bone shape size and vertical rolling force are discussed. [ABSTRACT FROM AUTHOR]

Realizing nitrogen dioxide (NO 2) detections based on semiconductor-based gas sensors with high tolerance to humidity conditions is deemed to be a long-term challenge. To independently acknowledge the physiosorbed-water influence mechanism on semiconductor-based sensors, hydrophobic zeolitic imidazolate framework-8 (ZIF-8) covered chemisorbed-oxygen-nonexistence zinc hydroxyfluoride (ZnOHF) snowflake-like nanorod bundles are synthesized for NO 2 detections with non-hindrance of interfering gases and high humidity in our work. Gas-sensing testing results display that the 0.6ZIF-8/ZnOHF-based gas sensor provides an optimum NO 2 response of 12.1–10 ppm NO 2 at the operating temperature of 200 ℃ with excellent NO 2 selectivity. As the relative humidity (RH) increases from 20% RH to 80% RH, the response of the 0.6ZIF-8/ZnOHF sensor shows a marginal fluctuation of only 13%, exhibiting outstanding anti-humidity characteristics towards NO 2 detections, the outperformed NO 2 selectivity and humidity tolerance of which are greatly attributed to the unique band structures of ZnOHF and the surficial hydrophobic treatment by ZIF-8, which is further validated via In-situ diffuse reflection infrared Fourier transform spectroscopy (In-situ DRIFTS) and electronic structure analyses. Humidity impact on ZnOHF poses a persuasive evidence for establishing the separate physiosorbed water interfering mechanism on semiconductors. This work endows a perspective on optimizing humidity tolerance for semiconductor-based sensors at low operating temperature. • Snowflake-like ZIF-8/ZnOHF was synthesized via an in-situ chemical process. • Hydroxyl-independent humidity-interfered behaviors were identified of ZnOHF. • Optimized ZIF-8/ZnOHF sensor exhibits excellent anti-humidity NO 2 sensitivity. • In-situ Fourier Transform infrared spectra verify the anti-humidity mechanism. [ABSTRACT FROM AUTHOR]

We report for the first time using pure cobaltous tungstate (CoWO 4) as an efficient ethanol sensor by controlling the Co3+-Co2+ redox couple in CoWO 4. The prepared Co x WO 4 has a flower-like structure self-assembled by a mesoporous microbelt. Moreover, the Co x WO 4 sensor with a Co3+/Co2+ ratio of 38.9% exhibits a high response (42.9–100 ppm ethanol), fast response/recovery time (11/13 s), low detection limit (0.42 ppm), as well as remarkable short-term and long-term repeatability. Notably, the Co x WO 4 sample maintains a constant response value over a wide range of humidity (30–90 RH%), manifesting its good anti-humidity properties. The outstanding sensing performance is owing to the Co3+-Co2+ redox couple, high surface area and moderate porosity of the obtained samples. The self-transforming of the Co3+-Co2+ redox couple contributes to the formation of absorbed oxygen (O 2 -), oxygen vacancies and the reduction of the band gap, which is a crucial factor in improving the sensing properties of Co x WO 4. • Pure cobalt tungstate was used for the first time as an efficient ethanol sensor. • The sensor shows a fast response/recovery time and low detection limit. • The self-transforming of Co3+-Co2+ redox on the surface is also a crucial factor. [ABSTRACT FROM AUTHOR]

Printable organic electronics are attractive owing to its high throughput and easy fabrication. Traditional coating methods (such as inkjet printing) are liquid‐solid contact‐based that deposit liquid solutions onto solid surfaces. Film quality is limited by surface energy of target surfaces and surface tension of the solvents. Furthermore, these printing methods are challenging to directly fabricate films on non‐flat or curved surfaces owing to the fluidity of liquid solution drops. In this work, a water transfer printing method that is solid‐solid contact‐based and assisted by Van der Waals force is reported. Nanometer‐thick films can be deposited on various surfaces: both high‐ and low‐surface energy, both flat and non‐flat surfaces. Water plays two roles: 1) as the transfer medium substrate and providing weak adhesion force between water and the transferred film; 2) high surface tension of water providing room to create surface tension gradient and producing Marangoni force to unfold the crumpled nanometer‐thick films. Electronic and optoelectronics on wrinkled skin and curved surfaces are demonstrated with this water transfer printing method. [ABSTRACT FROM AUTHOR]

In advanced semiconductor packaging, silicon wafers are typically thinned to tens of microns in thickness using ultra-precision grinding techniques, and the cutting speed greatly determines their surface integrity. However, an in-depth understanding of fundamental material removal mechanism considering the strain rate effect has not been revealed yet. This paper systematically explores the impact of cutting speed on the penetration depth, subsurface damage characteristics and scratch-induced stress field for monocrystal silicon material. First, nanoscratch tests in varied-load and constant-load modes are performed under different scratch speeds on the silicon specimen surface. The surface morphology of generated groove is observed to identify its brittle and plastic features. Next, the geometric relationship and contact pressure between the indenter and workpiece during the scratching process are analyzed. A theoretical penetration depth model is developed considering scratch speed, indenter tip radius and elastic recovery. The corresponding parameters are solved via the particle swarm optimization algorithm and agree very well with the experimental data. Then, the subsurface damage under different scratch speeds is measured by a transmission electron microscope. The atomic scale lattice defects are presented, involving the amorphous layer, stacking faults and phase transformation. Finally, a scratch-induced stress field model is established to interpret the distortion degree variation in damaged regions with scratch speed. The distribution of stress components in the scratch region is presented. [Display omitted] • Reveal Si material removal behavior under different cutting speeds by nano-scratch. • Derive a penetration depth model for Si scratch considering strain rate effect. • Observe lattice defects close to an atomic scale in subsurface damage area via TEM. • Present the distribution variation of stress component with changed scratch speed. [ABSTRACT FROM AUTHOR]

Ultra-precision thinning technology using workpiece self-rotational grinding followed by chemical mechanical polishing (CMP) is extensively applied in the integrated circuit manufacturing process, which enables to obtain large size ultra-thin silicon wafers with high material removal rate and low damage layer thickness. However, an in-depth understanding of the influence caused by ground surface topography on material removal mechanism in silicon CMP process has not been revealed yet. This work systematically investigates the contact characteristics of the wafer-pad interface and corrosion behaviors of the ground silicon wafer immersed in polishing solution. Firstly, some silicon wafers are ground using different wheels and subsequently polished. The material removal depth during the whole CMP process is measured. Then, the intrinsic model of polishing pad is determined via mechanical property tests. A finite element method is adopted to evaluate the contact status, displacement distortion and stress distribution at the contact region between pad and ground wafer surface. Moreover, the chemical reaction mechanism between ground silicon wafer and polishing solution is revealed by utilizing X-ray photoelectron spectroscopy and electrochemical analysis. The influence of wafer surface topography on corrosion resistance in CMP process is illustrated. Finally, corresponding experimental results are explained from an atomic scale by a ReaxFF reactive molecular dynamics simulation model. This presented study demonstrates the corrosion promotion principle of ground silicon wafer in CMP process. [Display omitted] • Effects of the ground silicon wafer topography on CMP process is characterized. • Contact state, distortion and stress distribution at wafer-pad interface are shown. • Corrosion behaviors of ground wafers immersed in polishing solution are analyzed. • Chemical reaction for α − Si in aqueous •OH environment is revealed by a MD model. [ABSTRACT FROM AUTHOR]

With its merits of excellent electrical properties and chemical durability, monocrystal silicon has been widely used as the substrate material in photovoltaic and integrated circuit fields. However, surface and subsurface damages caused by the machining process significantly reduce the chip life and the impacts of anisotropy remain poorly understood. Herein, this study employs nanoscratch tests to explore the anisotropy dependence on material removal and deformation mechanism for monocrystal silicon. Nanoscratch tests, under varied and constant load modes, are first carried out on a silicon surface along different crystal orientations. The surface morphologies of generated groove are observed to identify the surface crack system and depict the material removal behaviors. Then, a transmission electron microscope is applied to analyze the subsurface damage characteristics of deformation regions along different scratch directions. The results present the lattice defects close to the atomic scale, such as amorphous layer, stacking faults and phase transformation, and reveal the damage evolution mechanism considering material anisotropy. In addition, a molecular dynamics simulation model of monocrystalline silicon scratch is developed to expose the diversity of dislocation and stress distribution along different crystal orientations. This work provides a theoretical basis for realizing efficient and precise machining of anisotropic hard-brittle materials. [Display omitted] • Material removal behavior of Si is revealed along various crystal orientations. • Brittle–ductile transition and penetration depth are distinct due to anisotropy. • Atomic scale lattice defects are observed in damage area along [100] and [110]. • The damage features induced by compressive and shear stresses are analyzed. • [100] direction is more favorable to obtain a lower thickness of the damaged area. [ABSTRACT FROM AUTHOR]

This work described the manufacture of hot rolled X100 pipeline steels at the laboratory based on thermomechanically controlled processing (TMCP) and high-temperature processing (HTP) concepts. Continuous cooling phase transformation was assessed by dilatometric tests for both steels. Microstructures were characterized using optical and electron microscopes to elaborate the evolution of mechanical properties with process parameters. The main microstructures for both steels were changed from granular bainite to lath bainite/martensite or acicular ferrite with increasing cooling rate. However, the TMCP steel always had lower transformation critical temperatures than the HTP steel. After hot rolling, the TMCP steel with predominantly acicular ferrite showed more excellent mechanical properties than the HTP steel with mainly granular bainite. In this sense, the combined addition of Mo and low Nb is superior to high Nb content for the alloy design of X100 pipeline steel. The optimum performance of TMCP steel can be obtained using the following process parameters: 820 °C finish rolling temperature, 460 °C final accelerated cooling temperature, and 25 °C/s cooling rate. The statistical analysis of precipitates showed that their type, morphology, and size distribution were similar for both steels, implying that the effect of high Nb content seems not to be exploited completely in as-rolled HTP steel. [ABSTRACT FROM AUTHOR]

The microstructures of high strength bainitic steel weldments were characterized, and their hydrogen permeability was investigated by the electrochemical permeation technique. The effective diffusion coefficient in the welded joint increases with heat input, while the hydrogen concentration at the sub-surface decreases with increasing heat input, mainly due to coarsening grain and inclusion sizes. Compared with as-welded specimens, the tempered membranes have lower effective diffusion coefficient and higher density of hydrogen traps due to newly formed carbides acting as hydrogen trapping sites that are derived from the decomposition of martensite-austenite constituents. These were further confirmed by the partial permeation technique. [ABSTRACT FROM AUTHOR]

The automatic width control of the strip that is used in vertical rolling is a key issue in the hot strip rolling process. It is the first time that the internal deformation power and the friction power are obtained by using angular bisector yield criterion and Pavlov projection principle in the vertical rolling. At the same time, the shear power is determined by use of the integral mean value theorem. Then the vertical rolling force and shape parameters are obtained by minimizing the total power functional. The relative error of rolling forces is less than 8.29 % compared with those measured on-line in a hot strip rolling plant. Moreover, the formula forms of the three powers mentioned above are greatly simplified and improved. [ABSTRACT FROM AUTHOR]

Multi-pass submerged arc welding was performed on the HSLA steels using multi-microalloyed electrodes in the present work, and three different heat input processes were employed to investigate the microstructure evolution and corresponding mechanical properties of weldments. The emphasis was placed on studying the influence of microstructure aspects on impact toughness of weld metal and HAZ with different heat inputs to reveal fracture micromechanism and to optimize the welding system. According to the experimental results, the acceptable welding parameters were ascertained for the studied steel to obtain a good balance of high strength and toughness welded joint. The optimal range of size distribution of non-metallic inclusion formed in the weld metal was determined and the essential causes of deteriorated HAZ toughness were revealed. [ABSTRACT FROM AUTHOR]

Abstract: A three-dimensional velocity field for plate rolling is proposed by global weighted method. Then, using the field and linear MY (mean yield) criterion, the power functional of internal deformation for plate rolling is analyzed. The collinear vector inner product is used in the friction power functional. Ultimately, analytical solution of total power functional is obtained. By minimizing the power functional, the rolling force and torque, as well as the stress effective factor are obtained. The calculated results by the solutions of rolling torque and force are compared with those of experimental ones. Good agreement is found and the maximum error percentage between them is less than 15.5%. [Copyright &y& Elsevier]

A new linear yield criterion, referred to as geometrical approximation (GA) yield criterion, is proposed in this paper. On the π-plane in Haigh Westergaard stress space, its locus is an equilateral and non-equiangular dodecagon which has the largest approximation to the Mises locus in geometry. Also, its specific plastic work is deduced and applied to the limit analysis of circular plate under uniformly distributed load. Classical yield experimental data are adopted to validate the proposed criterion. It shows that the GA yield criterion can well fit the classical experimental data for different ductile metals. Application of the deduced specific plastic work to the limit analysis of a circular plate shows that the GA-based analytical results are higher than the Tresca results and closely match the Mises numerical results. [ABSTRACT FROM AUTHOR]

Abstract: Analytical solution of limit load for a defect-free pipe elbow is obtained under internal pressure using GM (geometric midline), in which the strain hardening effect has been taken into account. The limit load is a function of ratio of thickness to radius t 0/r 0, strain hardening exponent n, curvature influence factor m and ultimate tensile strength. Comparison with FE and analytical results of other investigators was performed. Although the limit loads calculated by GM criterion are little higher than the traditional analytical results, the GM results are in good agreement with FE results. Besides, the effect of different criteria, strain hardening exponent, ratio of thickness to radius, as well as curvature influence factor on the limit loads are also discussed systematically. [Copyright &y& Elsevier]

In recent years, a variety of film thickness measurement techniques for copper chemical mechanical planarization (CMP) are subsequently proposed. In this paper, the eddy-current technique is used. In the control system of the CMP tool developed in the State Key Laboratory of Tribology, there are in situ module and off-line module for measurement subsystem. The in situ module can get the thickness of copper film on wafer surface in real time, and accurately judge when the CMP process should stop. This is called end-point detection. The off-line module is used for multi-points measurement after CMP process, in order to know the thickness of remained copper film. The whole control system is structured with two levels, and the physical connection between the upper and the lower is achieved by the industrial Ethernet. The process flow includes calibration and measurement, and there are different algorithms for two modules. In the process of software development, C++ is chosen as the programming language, in combination with Qt OpenSource to design two modules' GUI and OPC technology to implement the communication between the two levels. In addition, the drawing function is developed relying on Matlab, enriching the software functions of the off-line module. The result shows that the control system is running stably after repeated tests and practical operations for a long time. [ABSTRACT FROM AUTHOR]

Highlights: [•] An eddy current measurement system for Cu thickness in CMP was established. [•] The nano-scale sensitivity under large lift-off distance was reached by optimizing. [•] The differential method for signal processing avoids the drift of system. [Copyright &y& Elsevier]

Abstract: The relationship between martensite–austenite (MA) constituent and cleavage crack initiation in the heat affected zone of a low carbon bainitic steel was investigated according to welding simulation and instrumental Charpy impact testings. The results showed that with increasing heat input, the toughness of the specimen deteriorates and the MA constituent size increases gradually. The MA constituent can assist the formation of microcrack by interface debonding mechanism. According to the classical Griffith theory, the calculation size of Griffith crack is consistent with the width size of the MA constituent under most circumstances, indicating that the decrease in the crack initiation absorbed energy is mainly attributed to coarse MA constituent. [Copyright &y& Elsevier]