Method of Investigation of the Stress-Strain State of Surface Layer of Machine Elements from a Sintered Nonuniform Material

A microstructural model of surface layer of machine elements from a nonuniform material is developed. With using of this model a calculation scheme that includes basic structural elements is created. Each element is characterized by the following properties: density, elastic modulus, thermal conductivity, linear expansion coefficient and Poisson's ratio. A mathematical model of surface layer of machine elements from a sintered nonuniform material is formulated on the basis of solution of two-dimensional heat-conduction and elasticity problems by the finite-element method. The created algorithms for solution of these problems are used for formation of an automated system for thermal strength calculations. This system is surrounded with some original techniques which provide the investigation of the stress-strain state of surface layer of machine elements from a sintered nonuniform material.

Analysis of Structural Parameters for Unbonded Flexible Pipes

Due to the complex structure and nonuniform material of unbonded flexible pipes, an elastic thin-walled cylinder model and a helical steel strip model were established respectively to simulate different layers based on the specific structure form and parameters. Quasi-static incremental load was adopted to identify the structural parameters which had significant effects on the axial, radial and bending behavior of the pipes during the complex deformation. Sensitivity of these parameters were also analysed. The conclusion in this paper could provide guaidance for the design of unbonded flexible pipe.

Coffee Stain Ring Effect and Nonuniform Material Removal in Chemical Mechanical Polishing

When a drop of coffee dries on the counter-top, it leaves a dense, ringlike stain along its perimeter. Solids immersed in a drying drop will migrate toward the edge of the drop and form a solid ring. Such phenomena create ringlike stains and happen for a wide variety of surfaces, solvents, and solutes. It is referred to as the coffee stain ring effect. The phenomenon is caused by the outward microfluidic flow of the solute within the drop, which is driven by the evaporation of solvent. We show that the mechanism for the ring effect contributes to the nonuniform material removal in chemical mechanical polishing (CMP), specifically, at edges of blanket wafers causing the edge effect or at edges and corners of protrusive features on patterned wafers inducing the doming effect; metal dishing and dielectric erosion. By controlling the evaporation profile of the solvent in the slurry layer between the wafer surface and the polishing pad, such as making grooves or embedding the abrasive particles on the pad, or delivering the slurry from the bottom of the pad, one can improve the uniformity of material removal during the CMP process.

Modeling and Analyzing on Nonuniformity of Material Removal in Chemical Mechanical Polishing of Silicon Wafer

Chemical mechanical polishing (CMP) has already become a mainstream technology in global planarization of wafer, but the mechanism of nonuniform material removal has not been revealed. In this paper, the calculation of particle movement tracks on wafer surface was conducted by the motion relationship between the wafer and the polishing pad on a large-sized single head CMP machine. Based on the distribution of particle tracks on wafer surface, the model for the within-wafer-nonuniformity (WIWNU) of material removal was put forward. By the calculation and analysis, the relationship between the motion variables of the CMP machine and the WIWNU of material removal on wafer surface had been derived. This model can be used not only for predicting the WIWNU, but also for providing theoretical guide to the design of CMP equipment, selecting the motion variables of CMP and further understanding the material removal mechanism in wafer CMP.

Issues in High-ĸ Gate Stack Interfaces

We address current challenges in the fundamental understanding of physical and chemical processes that occur in the fabrication of the transistor gate stack structure. Critical areas include (1) the interface between bulk silicon and high-dielectric-constant (high-ĸ) insulators, (2) the interface between high-ĸ insulators and advanced gate electrodes, and (3) the internal interfaces that form within dielectric stacks with nonuniform material and structure compositions. We approach this topic from a fundamental understanding of bonding and electronic structure at the interfaces, and of film-growth kinetics in comparison with thermodynamics predictions. Implications for the dielectric/electrode interface with metallic gates and issues with integration will also be presented.