Pattern Placement Research Articles

Three dimensional flow of liquid transfer between a cavity and a moving roll

Gravure printing is one of the most promising technologies for high volume production of printed electronics and microscale films and devices. The characteristics of the printed pattern, i.e. ink volume, resolution and pattern placement (registration), are directly related to the fluid mechanics of the liquid transfer process from a cell to a substrate wrapped around a rotating roll; the liquid transfer is mainly controlled by free surfaces and dynamic contact lines. Most of the available analyses are restricted to axisymmetric flows, at which the relative motion between the cavity and the substrate is greatly simplified. Recent results have shown that the use of the complete description of the relative motion in a roll-to-roll process is critical to obtain accurate results on the amount of liquid that is transferred to the substrate. In this work we present an extension of the model describing liquid transfer from a groove to a substrate in a R2R process in order to consider the liquid transfer from a small individual cell; to this end we solve a full 3D free surface flow with moving contact lines. The results show that the liquid transfer dynamics is governed by two different characteristic time scales, one is associated with the contact line motion and the other with liquid filament breakup. Both are dependent on the capillary number. The predictions show how the volume, registration and shape of the printed dot varies with operating conditions and liquid properties. These predictions could be helpful in designing high precision printing operations.

A Process for Topographically Selective Deposition on 3D Nanostructures by Ion Implantation.

Area-selective atomic layer deposition (AS-ALD) is attracting increasing interest because of its ability to enable both continued dimensional scaling and accurate pattern placement for next-generation nanoelectronics. Here we report a strategy for depositing material onto three-dimensional (3D) nanostructures with topographic selectivity using an ALD process with the aid of an ultrathin hydrophobic surface layer. Using ion implantation of fluorocarbons (CFx), a hydrophobic interfacial layer is formed, which in turn causes significant retardation of nucleation during ALD. We demonstrate the process for Pt ALD on both blanket and 2D patterned substrates. We extend the process to 3D structures, demonstrating that this method can achieve selective anisotropic deposition, selectively inhibiting Pt deposition on deactivated horizontal regions while ensuring that only vertical surfaces are decorated during ALD. The efficacy of the approach for metal oxide ALD also shows promise, though further optimization of the implantation conditions is required. The present work advances practical applications that require area-selective coating of surfaces in a variety of 3D nanostructures according to their topographical orientation.

Creation of guiding patterns for directed self-assembly of block copolymers by resistless direct e-beam exposure

We present an approach for the creation of guiding patterns to direct the self-assembly of block copolymers. A neutral layer of a brush polymer is directly exposed by electrons, causing the cross-linking of the brush molecules, and thus changing its local affinity. The advantage relies on the achievable resolution and the reduction of the process steps in comparison with deep UV and conventional electron beam lithography, since it avoids the use of a resist. We envision that this method will be highly valuable for the investigation of high-chi directed self-assembly materials and complex guiding pattern designs, where pattern placement and resolution are becoming critical.

Development of pallet pattern placement strategies in robotic palletisation

Purpose – This paper presents an investigation on the development of different pattern placement strategies in robotic palletisation of box packages in the packaging industry with practical implementations for one, two, four and five block patterns with the aim of improving the operational efficiency in robotic palletisation. Design/methodology/approach – The work involves considering the gripper design and maximum number of picks and various process parameters that affect the robotic implementation of pallet patterns and develops a methodology to form different patterns for a given pallet size. Findings – The proposed methodology represents an efficient approach for pallet pattern implementation and results in reduced number of placements required for a given number of boxes per layer and reduced time for palletisation. Originality/value – The paper introduces a novel technique for pallet loading problem (PLP) considering the physical aspects and restrictions encountered when using the robot and the gripper size to generate the pattern on the pallet. Traditional solutions of PLP do not consider these aspects in pattern placements.

A new general approach for solving the self-calibration problem on large area 2D ultra-precision coordinate measurement machines

The manufacturing of flat panel displays requires a number of photomasks for the placement of pixel patterns and supporting transistor arrays. For large area photomasks, dedicated ultra-precision writers have been developed for the production of these chromium patterns on glass or quartz plates. The dimensional tolerances in X and Y for absolute pattern placement on these plates, with areas measured in square meters, are in the range of 200–300 nm (3σ). To verify these photomasks, 2D ultra-precision coordinate measurement machines are used having even tighter tolerance requirements. This paper will present how the world standard metrology tool used for verifying large masks, the Micronic Mydata MMS15000, is calibrated without any other references than the wavelength of the interferometers in an extremely well-controlled temperature environment. This process is called self-calibration and is the only way to calibrate the metrology tool, as no square-meter-sized large area 2D traceable artifact is available. The only parameter that cannot be found using self-calibration is the absolute length scale. To make the MMS15000 traceable, a 1D reference rod, calibrated at a national metrology lab, is used. The reference plates used in the calibration of the MMS15000 may have sizes up to 1 m2 and a weight of 50 kg. Therefore, standard methods for self-calibration on a small scale with exact placements cannot be used in the large area case. A new, more general method had to be developed for the purpose of calibrating the MMS15000. Using this method, it is possible to calibrate the measurement tool down to an uncertainty level of <90 nm (3σ) over an area of (0.8 × 0.8) m2. The method used, which is based on the concept of iteration, does not introduce any more noise than the random noise introduced by the measurements, resulting in the lowest possible noise level that can be achieved by any self-calibration method.

Z-correction, a method for achieving ultraprecise self-calibration on large area coordinate measurement machines for photomasks

High-quality photomasks are a prerequisite for the production of flat panel TVs, tablets and other kinds of high-resolution displays. During the past years, the resolution demand has become more and more accelerated, and today, the high-definition standard HD, 1920 × 1080 pixels2, is well established, and already the next-generation so-called ultra-high-definition UHD or 4K display is entering the market. Highly advanced mask writers are used to produce the photomasks needed for the production of such displays. The dimensional tolerance in X and Y on absolute pattern placement on these photomasks, with sizes of square meters, has been in the range of 200–300 nm (3σ), but is now on the way to be <150 nm (3σ). To verify these photomasks, 2D ultra-precision coordinate measurement machines are used with even tighter tolerance requirements. The metrology tool MMS15000 is today the world standard tool used for the verification of large area photomasks. This paper will present a method called Z-correction that has been developed for the purpose of improving the absolute X, Y placement accuracy of features on the photomask in the writing process. However, Z-correction is also a prerequisite for achieving X and Y uncertainty levels <90 nm (3σ) in the self-calibration process of the MMS15000 stage area of 1.4 × 1.5 m2. When talking of uncertainty specifications below 200 nm (3σ) of such a large area, the calibration object used, here an 8–16 mm thick quartz plate of size approximately a square meter, cannot be treated as a rigid body. The reason for this is that the absolute shape of the plate will be affected by gravity and will therefore not be the same at different places on the measurement machine stage when it is used in the self-calibration process. This mechanical deformation will stretch or compress the top surface (i.e. the image side) of the plate where the pattern resides, and therefore spatially deform the mask pattern in the X- and Y-directions. Errors due to this deformation can easily be several hundred nanometers. When Z-correction is used in the writer, it is also possible to relax the flatness demand of the photomask backside, leading to reduced manufacturing costs of the plates.

BLAS

Increasing the degree of parallelism and reducing the overhead of garbage collection (GC overhead) are the two keys to enhancing the performance of solid-state drives (SSDs). SSDs employ multichannel architectures, and a data placement scheme in an SSD determines how the data are striped to the channels. Without considering the data access pattern, existing fixed and device-level data placement schemes may have either high GC overhead or poor I/O parallelism, resulting in degraded performance. In this article, an adaptive block-level data placement scheme called BLAS is proposed to maximize the I/O parallelism while simultaneously minimizing the GC overhead. In contrast to existing device-level schemes, BLAS allows different data placement policies for blocks with different access patterns. Pages in read-intensive blocks are scattered over various channels to maximize the degree of read parallelism, while pages in each of the remaining blocks are attempted to be gathered in the same physical block to minimize the GC overhead. Moreover, BLAS allows the placement policy for a logical block to be changed dynamically according to the access pattern changes of that block. Finally, a parallelism-aware write buffer management approach is adopted in BLAS to maximize the degree of write parallelism. Performance results show that BLAS yields a significant improvement in the SSD response time when compared to existing device-level schemes. In particular, BLAS outperforms device-level page striping and device-level block striping by factors of up to 8.75 and 7.41, respectively. Moreover, BLAS achieves low GC overhead and is effective in adapting to workload changes.

Graphene as discharge layer for electron beam lithography on insulating substrate

Charging of insulating substrates is a common problem during Electron Beam lithography (EBL), which deflects the beam and distorts the pattern. A homogeneous, electrically conductive, and transparent graphene layer is used as a discharge layer for EBL processes on insulating substrates. The EBL resolution is improved compared with the metal discharge layer. Dense arrays of holes with diameters of 50 nm and gratings with line/space of 50/30 nm are obtained on quartz substrate. The pattern placement errors and proximity effect are suppressed over a large area and high quality complex nanostructures are fabricated using graphene as a conductive layer.

Measurement sensitivity and resolution for background oriented schlieren during image recording

Background oriented schlieren (BOS) visualization technique is examined by means of optical geometry. Two most important results are the calculation of the sensitivity and spatial resolution of a BOS system, which allows for the determination of the experiment design space. A set of relations that characterize the performance of a BOS measurement is given, with emphasis on the design of background pattern and spatial placement of optical components.

MODELING THE IMPACT OF SPATIAL STRUCTURE ON GROWTH DYNAMICS OF INVASIVE PLANT SPECIES

Invasive nonindigenous plant species can have potentially serious detrimental effects on local ecosystems and, as a result, costly control efforts often have to be put in place to protect habitats. An example of an invasive problem on a global scale involves the salt marsh grass species from the genus Spartina. The spread of Spartina anglica in Europe and Asia has drawn much concern due to its ability to convert coastal habitats into cord-grass monocultures and to alter the native food webs. However, the patterns of invasion of Spartina species are amenable to spatially-explicit modeling strategies that take into account both temporal and spatio-temporal processes. In this study, an agent-based model of Spartina growth on a simulated mud flat environment was developed in order to study the effects of spatial pattern and initial seedling placement on the invasion dynamics of the population. The spatial pattern of an invasion plays a key role in the rate of spread of the species and understanding this can lead to significant cost savings when designing efficient control strategies. We present here a model framework that can be used to explicitly represent complex spatial and temporal patterns of invasion in order to be able to predict quantitatively the impact of these factors on invasion dynamics. This would be a useful tool for assessing eradication strategies and choosing optimal control solutions in order to be able to minimize future control costs.

Numerical Simulation of Boundary Condition Dependence of Mask Pattern Placement Error by Finite Difference Method in Steady State

A photomask for semiconductor device production faces serious problems related to the thermal displacement of the mask pattern during exposure. During mask exposure, pattern placement error occurs in the mask. The minimization of thermal in-plane displacement is needed. To estimate thermal displacement, a model based on the three-dimensional steady-state thermal theory and two-dimensional in-plane stress theory was proposed by the finite difference method. Three types of boundary condition, that is, a free edge, a fixed edge, and a combination of a free edge and a fixed edge were investigated to minimize mask pattern placement error. Quantitative relations of the boundary condition and thermal displacement were clarified. It was found that the fixed edge minimizes pattern placement error caused by thermal expansion. Moreover, the combination of the free and fixed edges indicated the directionality of the placement error distribution.

Pattern Placement Accuracy in Block Copolymer Directed Self-Assembly Based on Chemical Epitaxy

The realization of viable designs for circuit patterns using the dense features formed by block copolymer directed self-assembly (DSA) will require a precise and quantitative understanding of self-assembled feature registration to guiding templates or chemical prepatterns. Here we report measurements of DSA placement error for lamellar block copolymer domains indexed to specific lines in the surface chemical prepattern for spatial frequency tripling and quadrupling. These measurements are made possible by the use of an inorganic domain-selective prepattern material that may be imaged upon polymer removal after DSA and a prepattern design incorporating a single feature serving as an in situ registration mark that is identifiable by pattern symmetry in both the prepattern and resulting self-assembled pattern. The results indicate that DSA placement error is correlated with average prepattern line width as well as prepattern pitch uniformity. Finally, the magnitude of DSA placement error anticipated for a uniform, optimized prepattern is estimated.

USE OF SINGLE LAYER CONCRETE ARMOUR UNITS AS TOE REINFORCEMENT

Detailing and optimization of the toe reinforcement is presented as a case study from the construction of the 5.2km long main breakwater for the new Colombo South Harbour in 18m water depth. During the breakwater design the environmental constraints on supply of large rock armour were recognized, and CORE-LOC™ single layer concrete armour units were selected for the primary armour protection. During construction, supply of relatively small quantities of 8-12t rock for use in the toe reinforcement became an issue, and use of CORE-LOC™ units placed on the flat rock armour apron as an alternative to rock armour toe reinforcement was investigated and implemented. This use is unusual as there is no in-plane compression between units as found when they are placed on the slope. A site based prototype scale trial was conducted to evaluate placing method and criteria, and an "alternate opposing cannon† pattern placement, in rows going seaward from the primary armour, was successful. Packing density and unit spacing is the same as for the primary armour. Hydraulic stability of this alternative toe reinforcement was verified in 2D physical hydraulic model testing.

The optimum design of power distribution for pressurized water reactor

The aim of this work is to develop a two-level optimization method for designing the optimum initial fuel loading pattern and burnable poison placement in pressurized water reactors. At the lower level, based on the fuel loading pattern (LP) optimized by backward diffusion calculation theory, Pontryagin’s maximum principle is employed to investigate the optimum arrangement of burnable poison (BP) that can generate the lowest radial power peaking factor (PPF). At the upper level a multi-objective problem (MOP), with LP and BP as two objective functions, is proposed by coordinate the interrelationship of LP and BP, and optimized by non-dominated sorting genetic algorithm (NSGA-II). The results of optimum designs called ‘Pareto optimum solutions’ are a set of multiple optimum solutions. After sensitivity analysis is performed, the final optimum solution which is chosen based on a typical VVER-1000 reactor reveals that the method could not only save the fuel consumption but also reduce the PPF in comparison to published data.

フエ王宮宮殿建築・太和殿における柱&#x9AF9;飾技術の復原的研究

The focus of this paper is reconstruction study of painting pattern analyze between columns and flat plan of “Thai Hoa” palace. At 1st is characterized by dragon head and extremities, classified into two type water in the mouth or not. 2nd,dragon head and tail take the symmetry axis of the body is wrapped in a spiral pattern is arranged. 3rd,when considering dragon pattern placement, the building borders the central axis plan is placed symmetrically. Dragon is one of the highest prestige, overlapping pattern of spiral structure and symmetry, suggest that the concept of spatial correlation and building decoration.

Placement Sequence Methodology in Pallet Pattern Formation in Robotic Palletisation

The Pallet Loading Problem (PLP) in packaging industry usually deals with generating optimal pallet patterns of placing boxes on a rectangular pallet. For a given pattern, the boxes can be placed in different set of sequences each affecting efficiency and productivity of robotic palletisation. Therefore, getting an optimal pallet pattern does not guarantee an optimal pattern placement strategy. Therefore, there is a need to develop a methodology that considers the palletisers physical characteristics and limitations in robotic palletising systems. This paper presents development of a methodology to determine the placement sequence in robotic pallet pattern formation with the aim of improving the operational efficiency in robotic palletisation.

An Algorithm to Determine Placement Sequence in Robotic Pallet Pattern Formation

In automated manufacturing palletising operations, the Pallet Loading Problem (PLP) usually deals with generating optimal pallet patterns of placing boxes on a rectangular pallet. For a given pattern, the boxes can be placed in different set of sequences each affecting efficiency and productivity of robotic palletisation. Therefore, merely getting an optimal pallet pattern does not guarantee an optimal pattern placement strategy. Very few published literature is available to address this problem, and so there is a need to develop a methodology that considers the palletisers physical characteristics and limitations in robotic palletising systems. This paper presents development of an algorithm to determine the placement sequence in robotic pallet pattern formation with the aim of improving the operational efficiency in robotic palletisation.

Simulation Study of Sub-10 nm Pattern Formation Using Diblock Polymer Directed Self-assembly

Because top-down approaches, such as the extreme ultraviolet technique and high-index fluidbased immersion ArF lithography, may cover one or two generations, lithography technology for scaling down feature size to sub-10-nm is becoming more complex. The directed self-assembly technology of block copolymers is one candidate for next-generation lithography. In this paper, a directed self-assembly lithography process for block copolymers is modeled and simulated on a molecular scale to solve the challenges associated with directed self-assembly technology. Sub-10nm patterns can be formed by using precise pattern placement of a conventional ‘top-down’ optical lithography with the well-defined nanostructure and self-healing properties of ‘bottom-up’ block copolymer self-assembly. Simulation results matched the experiment results.

Bit patterned media based on block copolymer directed assembly with narrow magnetic switching field distribution

Electron-beam (E-beam) directed assembly, which combines the long-range phase and placement registration of e-beam lithography with the sharp dot size and spacing uniformity of block copolymer self assembly, is considered highly promising for fabricating templates that meet the tight magnetic specifications required for write synchronization in bit patterned media magnetic recording systems. In our study, we show that this approach also yields a narrower magnetic switching field distribution (SFD) than e-beam patterning or block copolymer self-assembly alone. We demonstrate that the pattern uniformity, i.e., island diameter and placement distributions are also important for achieving tight magnetic SFDs.

Atomic precision lithography on Si

Lithographic precision is as or more important than resolution. For decades, the semiconductor industry has been able to work with ±5% precision. However, for other applications such as micronanoelectromechanical systems, optical elements, and biointerface applications, higher precision is desirable. Lyding et al. [Appl. Phys. Lett. 64, 11 (1999)] have demonstrated that a scanning tunneling microscope can be used to remove hydrogen (H) atoms from a silicon (100) 2 × 1 H-passivated surface through an electron stimulated desorption process. This can be considered e-beam lithography with a thin, self-developing resist. Patterned hydrogen layers do not make a robust etch mask, but the depassivated areas are highly reactive since they are unsatisfied covalent bonds and have been used for selective deposition of metals, oxides, semiconductors, and dopants. The depassivation lithography has shown the ability to remove single H atoms, suggesting the possibility of precise atomic patterning. This patterning process is being developed as part of a project to develop atomically precise patterned atomic layer epitaxy of silicon. However, significant challenges in sample preparation, tip technology, subnanometer pattern placement, and patterning throughput must be overcome before an automated atomic precision lithographic technology evolves.