scholarly journals Analysis of Correlation between Pad Temperature and Asperity Angle in Chemical Mechanical Planarization

2021 ◽  
Vol 11 (4) ◽  
pp. 1507
Author(s):  
Seonho Jeong ◽  
Kyeongwoo Jeong ◽  
Jinuk Choi ◽  
Haedo Jeong
Keyword(s):  
Chemical Mechanical Planarization ◽  
Micro Ct ◽  
Polishing Process ◽  
Contact State ◽  
Contact Points ◽  
Conditioning Process ◽  
Device Integration ◽  
Asperity Angle ◽  
Ct Analysis ◽  
Semiconductor Fabrication

Chemical mechanical planarization (CMP) is a technology widely employed in device integration and planarization processes used in semiconductor fabrication. In CMP, the polishing pad plays a key role both mechanically and chemically. The surface of the pad, consisting of asperities and pores, undergoes repeated cycles of glazing induced by polishing followed by the recovery of roughness by a conditioning process applied during CMP. As a polymer material, the pad also experiences thermal expansion from changes in temperature. Such changes can be expressed in terms of surface roughness values, but these do not fully capture the actual changes to the pad surface. In this study, the change in pad temperature occurring during CMP was analyzed with regard to its effect on the asperity angle, and the influence on CMP outcome was assessed. The changes in the surface asperities according to the steady-state pad temperature were evaluated using various measurement methods. The change in pad roughness was characterized in terms of the asperity angle, and the contact state predicted according to temperature were validated by measuring the contact perimeter, the number of contact points, and related values. Through Scanning Electron Microscope (SEM) and micro-CT analysis, it was confirmed that in the continuous polishing process and the conditioning process, the changes in asperity angle due to changes in pad temperature affect the polishing outcome.

Micro‐CT analysis of the Lisfranc complex reveals higher bone mineral density in dorsal compared to plantar regions

2021 ◽  
Author(s):  
Melissa R. Requist ◽  
Yantarat Sripanich ◽  
Tim Rolvien ◽  
Amy L. Lenz ◽  
Alexej Barg
Keyword(s):  
Bone Mineral Density ◽  
Bone Mineral ◽  
Micro Ct ◽  
Mineral Density ◽  
Ct Analysis

scholarly journals A Micro-Computed Tomography Comparison of the Porosity in Additively Fabricated CuCr1 Alloy Parts Using Virgin and Surface-Modified Powders

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1995
Author(s):  
Mirko Sinico ◽  
Suraj Dinkar Jadhav ◽  
Ann Witvrouw ◽  
Kim Vanmeensel ◽  
Wim Dewulf
Keyword(s):  
High Energy ◽  
High Energy Density ◽  
Micro Ct ◽  
Micro Computed Tomography ◽  
Powder Bed ◽  
Metallurgical Defects ◽  
Ct Analysis ◽  
Ct Data ◽  
Surface Modified ◽  
Fusion Pores

Recently, the use of novel CuCr1 surface-modified powder for reliable laser powder-bed fusion (LPBF) manufacturing has been proposed, enabling a broader LPBF processing window and longer powder storage life. Nevertheless, virgin CuCr1 powder is also LPBF processable, on the condition that a high-energy density is employed. In this work, we compare two dense specimens produced from virgin and surface-modified CuCr1 powder. Furthermore, a third sample fabricated from surface-modified powder is characterized to understand an abnormal porosity content initially detected through Archimedes testing. Utilizing high-resolution micro-CT scans, the nature of the defects present in the different samples is revealed. Pores are analyzed in terms of size, morphology and spatial distribution. The micro-CT data reveal that the virgin CuCr1 dense specimen displays keyhole pores plus pit cavities spanning multiple layer thicknesses. On the other hand, the sample fabricated with the surface-modified CuCr1 powder mainly contains small and spherical equi-distributed metallurgical defects. Finally, the CT analysis of the third specimen reveals the presence of a W contamination, favoring lack-of-fusion pores between subsequent LPBF layers. The LPBF melting mode (keyhole or conductive), the properties of the material, and the potential presence of contaminants are connected to the different porosity types and discussed.

Velocity control algorithm in glass polishing based on the cubic NURBS curve

2017 ◽  
Vol 232 (4) ◽  
pp. 685-696 ◽  
Author(s):  
Junzhao Han ◽  
Wenhua Chen
Keyword(s):  
Control Algorithm ◽  
Linear Acceleration ◽  
Control Points ◽  
Velocity Control ◽  
Polishing Process ◽  
Nurbs Curve ◽  
Weighting Factors ◽  
Final Velocity ◽  
Contact Points ◽  
Glass Polishing

To limit velocity fluctuations and to achieve a controllable jerk value in a glass polishing process, a new velocity control algorithm is proposed based on nonuniform rational B-splines (NURBS). The key of this algorithm is replacing the traditional linear acceleration–deceleration with flexible NURBS acceleration–deceleration. Based on the linear acceleration–deceleration algorithm, the control points of the NURBS curve are confirmed, and the final velocity of the polishing wheel center is solved using the Preston equation. With jerk continuity and limitations of the servo system, nonlinear equations are constructed, and the weighting factors corresponding to the control points are obtained. Cubic velocity control equations can be derived from the obtained feature parameters, which include the final velocity, control points, weighting factors and knot vectors. Based on the proposed NURBS acceleration–deceleration algorithm, a fourth-order Runge–Kutta formula was used to obtain the initial points, and the Milne–Hamming equation was used to predict and correct the next point. The predictor-corrector interpolation algorithm for parametric trajectory was implemented during the polishing process. The experimental results indicate that the proposed approach guarantees limited fluctuations of the relative velocity at contact points and ensure smoother velocity changes at dangerous points.

scholarly journals Analysis of Porous Structure in Autoclaved Materials Modified by Glass Sand

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 408
Author(s):  
Anna Stepien
Keyword(s):  
Computed Tomography ◽  
Building Materials ◽  
Micro Ct ◽  
Structure Building ◽  
Acoustic Insulation ◽  
Ct Analysis ◽  
Glass Sand ◽  
Aerated Concrete ◽  
Wall Construction ◽  
Dominant Phase

This paper describes the use of glass sand in the production of autoclaved bricks. Traditional autoclaved materials consist of SiO2, CaO, and H2O. The purpose of the tests is to analyze the possibility of using glass sand in autoclaved materials and to determine their properties and durability. Depending on the structure, building materials can have porosities ranging from 0% (glass, metals) to over 90% (thermal insulation materials such as aerated concrete). Porosity of materials is directly related to the strength of materials and their density, and further to the thermal and acoustic insulation properties of products used especially for external wall construction, i.e., bricks, concrete, and aerated concrete. This type of silicate brick is formed at a temperature of 203 °C, therefore the dominant phase forming the microstructure is tobermorite, in contrast to the C-S-H phase, which dominates in concretes and which is characterized by a larger specific surface. The nature of pores, their number, appearance and arrangement in the material can be studied using computer techniques (SEM, XRD, computed tomography, porosimetry). Computed tomography (micro-CT analysis) showed that the number of voids in the material modified by glass sand is about 20% in relation to the weight of the product. The density of the product with glass sand was determined to be 2.2 kg/dm3.

Spatial Kinematic Analysis of Threaded Fastener Assembly

2005 ◽  
Vol 128 (1) ◽  
pp. 116-127 ◽  
Author(s):  
Stephen Wiedmann ◽  
Bob Sturges
Keyword(s):  
Design Space ◽  
Compliant Mechanisms ◽  
Contact Point ◽  
Three Dimensional ◽  
Vertical Movement ◽  
Initial Contact ◽  
Geometric Problem ◽  
Intelligent Sensor ◽  
Contact State ◽  
Contact Points

Compliant mechanisms for rigid part mating exist for prismatic geometries. A few instances are known of mechanisms to assemble screw threads. A comprehensive solution to this essentially geometric problem comprises at least three parts: parametric equations for nut and bolt contact in the critical starting phase of assembly, the possible space of motions between these parts during this phase, and the design space of compliant devices which accomplish the desired motions in the presence of friction and positional uncertainty. This work concentrates on the second part in which the threaded pair is modeled numerically, and contact tests are automated through software. Tessellated solid models were used during three-dimensional collision analysis to enumerate the approximate location of the initial contact point. The advent of a second contact point presented a more constrained contact state. Thus, the bolt is rotated about a vector defined by the initial two contact points until a third contact location was found. By analyzing the depth of intersection of the bolt into the nut as well as the vertical movement of the origin of the bolt reference frame, we determined that there are three types of contacts states present: unstable two-point, quasi-stable two-point, stable three point. The space of possible motions is bounded by these end conditions which will differ in detail depending upon the starting orientations. We investigated all potential orientations which obtain from a discretization of the roll, pitch, and yaw uncertainties, each of which has its own set of contact points. From this exhaustive examination, a full contact state history was determined, which lays the foundation for the design space of either compliant mechanisms or intelligent sensor-rich controls.

scholarly journals Insights from in vivo micro‐ CT analysis: testing the hydraulic vulnerability segmentation in Acer pseudoplatanus and Fagus sylvatica seedlings

2018 ◽  
Vol 221 (4) ◽  
pp. 1831-1842 ◽  
Author(s):  
Adriano Losso ◽  
Andreas Bär ◽  
Birgit Dämon ◽  
Christian Dullin ◽  
Andrea Ganthaler ◽  
...  
Keyword(s):  
Fagus Sylvatica ◽  
Acer Pseudoplatanus ◽  
Micro Ct ◽  
Hydraulic Vulnerability ◽  
Ct Analysis

Single‐staged implant placement using the bone ring technique with and without membrane placement: Micro‐CT analysis in a preclinical in vivo study

2019 ◽  
Vol 31 (1) ◽  
pp. 29-36 ◽  
Author(s):  
Ken Nakahara ◽  
Maiko Haga‐Tsujimura ◽  
Kensuke Igarashi ◽  
Eizaburo Kobayashi ◽  
Benoit Schaller ◽  
...  
Keyword(s):  
In Vivo Study ◽  
Micro Ct ◽  
Implant Placement ◽  
Ct Analysis

scholarly journals Micro CT Analysis on the Correlation of a Cervical Defect and the Reparative Dentin in Human Permanent Teeth

2010 ◽  
Vol 30 (2) ◽  
pp. 129-135
Author(s):  
Shoichi HIGASHI ◽  
Mitsuori MAYAHARA ◽  
Tetsuo KODAKA ◽  
Kaoru EGAWA ◽  
Masanori NAKAMURA ◽  
...  
Keyword(s):  
Permanent Teeth ◽  
Micro Ct ◽  
Reparative Dentin ◽  
Ct Analysis
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