Papers by Keyword: Pad

Abstract: A multi-material, multi-layer dome structure is proposed for desigining futuristic body protection pads that will address a safety issue prominent among the population of elderly people, patients, industry workers, military personnel, and sport players. Those people are prone to be subjected to blunt impacts due to falls, bullets, and blast waves, which can result in serious injuries, early death, and extremely high medical costs. Protector pads can effectively reduce impact force and prevent injuries in high-risk individuals. However, most currently available protection pads are bulky, heavy, or rigid. Therefore, new body protectors need to be developed to satisfy the requirements of wearing comfort, ease of fitting, ensured protection, and cost-effectiveness. Out of many different design ideas generated, the most promising ones were identified through an evaluation process based on various criteria such as performance, comfort, and manufacturability. One of those designs utilizes a dome-shaped top layer and thin fabric membrane component that is very strong in tension but flexible in bending. Such structure will make the pads excellent in dissipating shock energy by diverting normal impact force to lateral direction and minimizing the force directly transmitted to the weakest body parts. Through finite element analyses, the best combinations of materials and components were identified. The selected pad structure was optimized for light-weight and flexibility while keeping excellent resistance to the compression. The thickness of the shell element and the overall thickness of the whole pad were optimized for the same level of deflection and stress as other simple shell pads. The results showed that the dome-shaped structure could be a useful component of effective body protection pads through optimal combination of various materials and layers.

Abstract: Chemical-mechanical polishing (CMP)-a perspective technology in fabrication of micro-and nanoelectronics elements, devices and systems. The development of models of CMP processes remains to be the actual problem. It is pointed out that known CMP models do not account for the features of chemical and mechanical mechanisms of interaction of active fluid and particles with a polished surface as well as an interaction of a viscoelastic pad with the surface. A description of the elementary acts of such interaction are absent in the available models. On the base of the analytical review of the current state of the theory and problems of (CMP) modeling some approaches were suggested to the problem accounting for the complex of the phenomena of different scales determining the polishing rate such as diffusion of slurry into the surface layer and restriction of time of chemical treatment of the surface by a rough pad being under the action of a mechanical load. A model of the CMP process was developed. Within the framework of this model a dependence of the polishing rate on the loading parameters was derived. The dependence generalizes the empirical Preston law.

Abstract: In a chemical mechanical polishing (CMP) process, the removal rate is affected by the actual contact conditions between the wafer and the polishing pad. The polishing pad is one of the most important consumable materials: when the wafer is polished, the pad surface asperity changes. Further, the polishing pad surface asperity has a substantial influence on the actual contact conditions. Therefore, measurement and quantitative evaluation methods for the pad surface asperity have been proposed by various research institutes. We have developed a novel measurement and quantitative evaluation method for polishing pad surface asperity based on contact image analysis using an image rotation prism. We have proposed four effective evaluation parameters: the number of contact points, the contact ratio, the maximum value of the minimum spacing of the contact points, and the half-width of the peak of the spatial Fast Fourier transform (FFT) result of a contact image. This paper discusses the change in the polishing pad surface asperity measured by the proposed evaluation parameters in serial batch polishing tests. In particular, this research focused on the relationships between the proposed evaluation parameters and the removal rate, which change with an increase in the number of serial batch polishing tests. As a result, linear correlations were found between the evaluation parameters and the removal rate.

Abstract: Blend fuel of corn stalk and coal was made in a series of blend ratios with corn stalk mass percent ranging from 10 to 90%. Several data were gotten by proximate analysis with considering indexes of volatile matter, fixed carbon, sulfur content, heat value and ash. The regression equations of the data were gotten through regression analysis for the relationship between blend ratios of corn stalk(BRCS) and proximate analysis data(PAD)．The result showed that there was linear relation between PAD of the blend fuel and BRCS, and linear equation slope absolute value of volatile matter, fixed carbon, sulfur content, heat value and ash were 8.49,7.64,5.45,4.85,3.97, respectively. Volatile matter content increased with the increase of BRCS, and other PAD was opposites. Variation rate and variation tendency of the blend fuel PAD was gotten through proximate analysis and fitted equation, and some references may be provided for utilization of blend fuel of biomass and coal.

Abstract: Due to the continual improvement of CMP technologies, and the need for polishing delicate wafers at high speed, graphite impregnated pads (GiP) dressed by brazed organic dia mond disks (BODD) can double the throughput of wafer-pass at the reduced cost of ownership (CoO). The increased polishing rate is due to the act of nano graphite particles that absorb slurry. The nano graphite particles coated with chemical and abrasive can achieve high removal rate without causing scratches on the wafer. In addition, nano graphite particles do not stick to wafer surfaces, so they can be cleaned easily. BODD can uniquely dress GiP to create slurry channels so the pore free pad is not bottlenecked by slurry supply. This paper also demonstrated the low stress polishing by applying ultrasound during the CMP process.

Abstract: Chemical mechanical polishing (CMP) has been widely accepted in modern integrated circuit (IC) industries and hard disk manufacturing processes, to insure wafer surface with high level of global and local planarity required. In CMP process, temperature rise has two-edged influences: temperature-rise accelerates the chemical activity and the motion of nano-particles contained in the slurry through which material removal ratio (MRR) is enhanced; the other side of the same coin is, however, that it will soften the pad surface and subsequently reduce the MRR. Furthermore, it is found that temperature-rise would cause agglomeration of nano-particles, which would cause the wafer surface defect. The net effects of temperature thus should be under investigation with scrutiny. In an attempt to study the temperature variation and influencing rule, in this paper we firstly establish the flow equation considering pad roughness, coupling the energy equation on the basis of thermodynamics. Then, by taking numerical simulation which is carried out to give out the temperature distribution of conventional CMP process. The results show that temperature-rise in the CMP process is very minor. The research will surely shed some lights on the mechanism of CMP and lay a feasible foundation for possible future utilization.

Abstract: Chemical mechanical polishing (CMP) is a widely adopted technique to achieve high level of global and local planarity required in modern integrate circuit (IC) industries, wherein the pad properties weigh heavily on the final performance. A preliminary two-dimensional wafer-scale flow model for CMP is presented considering the roughness, the elasticity, as well as the porosity of the pad. Numerical simulations were conducted to show the slurry flow features’ variations due to pad parameters change. The results show that the porosity of the pad is conducive to slurry delivering, and small porous parameter will lead to prominent increase of load capability, accounting for larger material removal rate (MRR) whilst the elasticity of the pad has a more complex influence. The rough surface carries additional fluid in the valleys of the polishing pad thereby provide some chemical reactions. The model will shed lights on the mechanism of CMP process, which is for a long time considered as a difficult circle to square.

Abstract: Temperature rise has two-edged influences on chemical mechanical polishing (CMP) process: temperature-rise facilitates the chemical activity and the motion of the nano particles contained in the slurry through which material removal ratio (MRR) is enhanced; to the other side of the same coin, however, it will soften the pad surface and subsequently reduce the MRR. Thus the research on temperature distribution of CMP process will be conducive to discovering the mechanism of polishing, and acquiring stable MRR and improving surface quality. With the help of the knowledge of tribology, hydrodynamics, and thermodynamics, flow equation considering the temperature variation in the fine step of CMP process, wherein high surface quality is the main concern and usually operates in contact free state, is set up, based on which the temperature field in contact is investigated in detail by taking advantage of the simulation technique, and the heat energy production and transition relations are obtained. Due to the slurry used, a small viscous heating effect is acknowledged by simulated results, and the temperature rise is negligible in contact-free flows, which is very conducive to the promotion of the final polished wafer/disk surfaces. The research will surely shed some lights in the mechanism of CMP and lay a feasible foundation for possible future utilization.

Abstract: Chemical mechanical polishing (CMP) is a widely used technique to achieve high level of global and local planarity required in modern integrate circuit (IC) industries and hard disk manufacturing process, etc., which pleas for concentrate researches. The main purpose of the present research is in an attempt to express the counterintuitive experimental aftermath: the ‘negative’ pressure, i.e., a suction force occurred in conventional commercial CMP process. A preliminary two tiers wafer-scale flow model for CMP is presented considering the roughness as well as the elasticity of the bulk pad substrate. Numerical simulations were conducted to elucidate the contact pressure and flow pressure distributions. The results show that a divergence region appears near the leading edge, which contributes to the suction pressure. A stress-richened area near the edges will give rise to over polishing. The research aftermaths agree well with the experiments, that validate the proposed analysis to some extend. This will shed lights on the mechanism of CMP process, which for a long time is considered as a black art where empirical or semi-empirical data are dependent upon to optimize the CMP parameters.

Abstract: Chemical mechanical polishing (CMP) is a widely used technique to achieve high level of global and local planarity required in integrate circuit (IC) areas, which pleas for concentrate researches. A preliminary wafer-scale flow model for CMP is presented considering the roughness as well as the porosity and compressibility of the pad. Pressure distributions for three kinds of pad roughness: cosine shape, two-scale cosine shape and actual roughness were given with the help of numerical simulation by solving the corresponding two-dimensional slurry flow model. Pressure fluctuations and peaks can be seen from the results. The model predictions will be conducive to the removal rate and mass transport computation. The research is a qualitative one and will pave the way for further explorations of mechanisms of CMP process.