Location-specific Processing Research Articles

Laser Powder Bed Fusion Parameter Selection via Machine-Learning-Augmented Process Modeling

Laser powder bed fusion additive manufacturing (AM) is a highly active research area in the materials and manufacturing community, driven by promises of reduced lead time, increased design flexibility, and potentially location-specific process control. However, a complex processing space counters these benefits and results in difficulties when attempting to develop process parameter sets across different component geometries and subgeometries. We develop a procedure for coupling physics-based process modeling with machine learning and optimization methods to accelerate searching the AM processing space for suitable printing parameter sets. We demonstrate the approach first on simple geometries that vary in size to show the methodology and then on a more complicated geometry to show the benefit of locally tailored process parameters on component processing history.

Does orthographic processing emerge rapidly after learning a new script?

Orthographic processing is characterized by location-invariant and location-specific processing (Grainger, 2018): (1) strings of letters are more vulnerable to transposition effects than the strings of symbols in same-different tasks (location-invariant processing); and (2) strings of letters, but not strings of symbols, show an initial position advantage in target-in-string identification tasks (location-specific processing). To examine the emergence of these two markers of orthographic processing, we conducted a same-different task and a target-in-string identification task with two unfamiliar scripts (pre-training experiments). Across six training sessions, participants learned to fluently read and write one of these scripts. The post-training experiments were parallel to the pre-training experiments. Results showed that the magnitude of the transposed-letter effect in the same-different task and the serial function in the target-in-string identification tasks were remarkably similar for the trained and untrained scripts. Thus, location-invariant and location-specific processing does not emerge rapidly after learning a new script; instead, they may require thorough experience with specific orthographic structures.

Novel inverse heat transfer technique for estimation of properties and location-specific process parameters of roof-mounted solar PV plants

Accurate quantification of properties and location-specific process parameters of roof-mounted solar PV power plants are essential for design and development of the power plant as well as for operation and maintenance and capacity improvement/reclaim of the power plant. In this work, a novel inverse heat transfer technique based on an efficient optimization method, Salp Swarm Algorithm (SSA), has been used to estimate the unknown properties and process parameters. This methodology uses limited on-site plant recorded data and consumes relatively less computational and experimental resources. Numerical and experimental analysis is carried out for representative periods and for representative days. The observed results indicate that the location-specific process parameters can be estimated with reasonable accuracy and these results can be used to estimate the module temperature which in turn is used for accurate estimation of power generated using temperature coefficients and healthiness of the system. The proposed methodology is simple to implement, uses only limited experimental data and is recommended for studies aimed towards estimating the unknown properties and process parameters.

Mirror, Mirror for Us All

Love them or hate them, Disney theme parks have become some of the most culturally significant locations of collective memory of the American experience. Rather than focus, as most discussion has, on whether this should be viewed as “good” or “bad,” this essay seeks to lay a groundwork for understanding how Disney parks gained their cultural authority. In doing so it will suggest that public historians could benefit from framing the interaction between history and the public at Disney parks as a location-specific process by which the public and a corporation are engaged in a cultural ritual of transforming historical fact into the national narrative.

Zoning additive manufacturing process histories using unsupervised machine learning

Metal additive manufacturing (AM) is currently a highly active area of research within the materials processing and manufacturing community, owing to the promises of lower lead time, increased design flexibility, and location-specific process control. These benefits are balanced by a typically complex processing space, resulting in difficulties when attempting to generalize process-structure relationships across different component geometries. We develop a procedure for reducing the overall complexity of a representation of the AM processing space using techniques from time series analysis and dimensionality reduction. This procedure is highly generic and applicable to a variety of time sequenced signals. We then utilize this reduced feature space as input to a cluster analysis, producing zoned maps of process history. We apply the approach to several canonical geometries, describe its overall utility, and discuss the implications of the resulting zonings in terms of the underlying digital process.

Spatial negative priming: Location or response?

In tasks requiring a response to the location of a target stimulus (for example, reaching), responses often are slower to a location that was recently occupied by an irrelevant distractor stimulus. In most demonstrations of this "spatial negative priming" (SNP), there is a 1-to-1 correspondence between possible stimulus locations and possible responses. As such, it is ambiguous whether the effect is due to a location-specific processing delay or to inhibition of a response. In the present experiment, subjects were required to press a key corresponding to the ordinal position of a target O in one of four locations, ignoring a distractor X appearing in another location. Location markers were widely or narrowly spaced, such that the inner two locations of wide displays corresponded to the outer two locations of narrow displays (hence, requiring different responses). SNP occurred when a target appeared at the location of a recent distractor, regardless of whether the response was associated with the distractor. In contrast, no SNP occurred for a target sharing the same response as a distractor, but in a different location. The results strongly support a location-specific, rather than response-specific, locus of SNP.

(Invited) Combined Gas Cluster Ion Beam (GCIB) and Chemical-Mechanical Planarization (CMP) Process for Replacement Metal Gate (RMG) Application

The introduction of high-k metal gate (HK/MG) stack has enabled the resumption of Moore’s Law at the 45/32nm nodes, when the conventional Poly/SiON gate stacks failed to meet the required scaled-down performance targets. Despite the well demonstrated benefits such as reduced gate leakage, HK/MG integration scheme itself brings about new challenges in Si-based semiconductor process technologies. Among them, the most critical and stringent step is RMG CMP, which is tasked to deliver gate height uniformity within the range of a few nanometers on all chips across the entire 300mm wafer for 14nm technology nodes and beyond. Conventional approaches to CMP planarity and uniformity often include the optimization of carrier zone pressure, platen/carrier rotation, slurry flow, conditioning sweep profileetc. Advances in CMP equipment technologies have also enabled new possibility such as multi-zone carrier pressure control through APC for within-wafer non-uniformity (WiWNU) reduction. Another widely-adopted approach is to rely on the high-selectivity of slurries to “stop dead” on the final layer of interests (e.g., tungsten in the case of RMG) without creating excessive local topography due to oxide erosion. While all the above approaches prove effective to certain degree, they are, by nature, wafer-level to sub wafer-level processes. As a consequence, it is difficult for them to differentiate between dies locally, for example, and correct the non-uniformity accordingly to the range of a few nanometers. In this contribution, an alternative planarization scheme for RMG is presented to enable nano-scale gate height uniformity control across all dies on 300mm wafers. The new scheme begins with conventional high-selectivity CMP process (pass-1 W-CMP) to remove overburden and polish the gate height down to a few nanometers thicker than the final target, followed by all-die gate height measurement on all wafers. Then the gate height data are fed forward to a GCIB tool, where location-specific process (LSP) takes place to trim the oxide down to a pre-determined target, die by die, through high-energy raster ion beam with high oxide-to-tungsten selectivity. This is followed by a final tungsten touch-up CMP process with high tungsten-to-oxide selectivity to level off the protruded metal patterns and drive the gate height to final target. Applied to SOI-based deep-trench (DT) and FINFET integrated wafers based on 14nm ground rule, the new RMG planarization scheme above demonstrates supreme gate height uniformity. Gate height WiWNU reduces continuously from ~ 2.95% post pass-1 W-CMP to 1.85% post GCIB, and to 1.51% post T/U CMP. The 3sigma of gate height across all dies on 300mm wafers is less than 3nm. The underlying mechanism to achieve nano-scale planarity and uniformity control by this new planarization method will be discussed.

A Combined Gas Cluster Ion Beam (GCIB) and Chemical-Mechanical Polish (CMP) Planarization Scheme for Tungsten Replacement Metal Gate (W-RMG)

Conventional approaches to CMP planarity and uniformity often include the optimization of carrier zone pressure, platen/carrier rotation, slurry flow, conditioning sweep profile etc. Advances in CMP equipment technologies have also enabled new possibility such as multi-zone carrier pressure control through APC for within-wafer non-uniformity (WiWNU) reduction. Other widely-adopted approaches include the use of high-selectivity of slurries to “stop dead” on the final layer of interests without creating excessive local topography due to oxide erosion. While all the above approaches prove effective to certain degree, they are, by nature, wafer-level to sub wafer-level processes. As a consequence, it is difficult for them to differentiate between adjacent chips locally, for example, and correct the non-uniformity to the range of a few nanometers across the wafer as required by RMG module for 22 nm technology nodes and beyond. In this contribution, a novel planarization scheme for RMG is presented to enable nano-scale gate height uniformity control across all dies on 300 mm wafers. The new scheme begins with conventional high-selectivity CMP process (pass-1 W-CMP) to remove overburden and polish the gate height down to a few nanometers thicker than the final target, followed by all-chip gate height measurement on all wafers. Then the gate height data are fed forward to a GCIB tool, where location-specific process (LSP) takes place to trim the oxide down to a pre-determined target, chip by chip. This is followed by a final tungsten touch-up CMP process with high tungsten-to-oxide selectivity to level off the protruded metal patterns and drive the gate height to final target.

Spatial Negative Priming: Location or Response?

In tasks requiring a response to the location of a target stimulus (for example, reaching), responses often are slower to a location that was recently occupied by an irrelevant distractor stimulus. In most demonstrations of this spatial negative priming (SNP), there is a 1-to-1 correspondence between possible stimulus locations and possible responses. As such, it is ambiguous whether the effect is due to a location-specific processing delay or to inhibition of a response. In the present experiment, subjects were required to press a key corresponding to the ordinal position of a target O in one of four locations, ignoring a distractor X appearing in another location. Location markers were widely or narrowly spaced, such that the inner two locations of wide displays corresponded to the outer two locations of narrow displays (hence, requiring different responses). SNP occurred when a target appeared at the location of a recent distractor, regardless of whether the response was associated with the distractor. In contrast, no SNP occurred for a target sharing the same response as a distractor, but in a different location. The results strongly support a location-specific, rather than response-specific, locus of SNP.

Measurement of the intrinsic mass transfer coefficient for CO2 dissolution in brine

A full-factorial designed experiment was completed to quantify the effect of temperature, wet CO2 density and brine Na–Ca–Cl salinity on the liquid-side mass transfer coefficient kL for the dissolution of CO2 into brine. The range of experimental conditions corresponds to those relevant to the surface dissolution approach to geologic storage of anthropogenic CO2.The measured range of kL was from 0.015 to 0.056cm/s. An empirical correlation was developed for kL as a function of temperature to wet CO2 density and NaCl salinity. Greater temperature and smaller NaCl salinity increase kL. There is an interaction effect between temperature and wet CO2 density, which increases or decreases kL depending on the value of each. CaCl2 salinity does not have a statistically significant effect on kL.Wet CO2 density was used as an independent variable, in the place of pressure, since it was found to play a critical role in the onset of gas entrainment. Geologic storage of CO2 via the surface dissolution method requires different operating conditions for different applications. Importantly, since the composition of brine varies between locations, the dependency of kL on NaCl salinity allows for location specific process design.

Mechanisms of Visuospatial Attention: Evidence from Event-related Brain Potentials

A series of experiments are reviewed that studied mechanisms underlying visuospatial attention by measuring the influence of attentional selectivity on event-related brain potentials (ERPs). The results are interpreted within a theoretical framework developed by LaBerge (1995)and LaBerge and Brown (1989). Spatial attention can have an effect on occipital P1 and N1 components in trial-by-trial cueing situations, which indicate a spatially selective modulation of processing in the VI-IT pathway. However, this effect is strongly attenuated when unattended locations are potentially relevant, suggesting that early attentional modulations within the ventral stream are optional rather than obligatory. A distinct parietal negativity (Nd1) that is elicited in cued attention tasks is assumed to reflect the existence of a transient location expectation gradient within the posterior parietal cortex (PPC). This effect is not present in sustained attention situations. The factthatthis effectis also observed with auditory stimuli suggests that this spatially selective PPC activity is modality-unspecific. Attentional selectivity in multi-stimulus arrays is reflected by the N2pc component, which may indicate location-specific processing modulations in the ventral pathway that are contingent upon an initial feature analysis.