Advanced Materials Research Vol. 497

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: This study aims to develop the CMP pads that have new groove pattern as control the slurry flow. We have been proposed two type groove patterns as inflow type and outflow type. Here, it is well known that the slurry flow is remarkably important as both to use the slurry effectively and to reduction the slurry quantity consumed of CeO2 abrasive that is one of rare metals. This paper describes the effect of groove pattern on the slurry flow from the observation image with high-speed camera. In particular, the slurry flow is quantitatively visualized by digital image processing. As a result, the several advantages of both proposed inflow type and outflow type show from a view point of slurry flow compared to the conventional XY-groove pad and No-groove pad.

Abstract: Based on the hybrid combination of case-based reasoning and BP-neural network, process parameters intellectual decision strategy of function ceramics with high efficiency and precision chemical mechanical polishing (CMP) was proposed in this paper firstly. And then, referring to the technical manuals, experiences of engineering workers and experimental data, the process parameters database for function ceramics in CMP has been built with Microsoft software Access. On the basis of the above efforts, the process parameters intellectual decision support system for high efficiency and precision CMP of function ceramics has been developed by applying PowerBuilder software, which can realize the process parameters optimization, the surface roughness prediction and process parameters intellectual decision. Examples show that the prediction results are coincident with the experiments well.

Abstract: By applying chemical-mechanical polishing (CMP) technique to high precision processing of rotary surface workpieces of silicon nitride (_Si3N4) ceramic, a CMP experimental device was established on a numerical control (NC) jig grinder. The polyurethane wheel and nonwoven cloth wheel was adoped. The Ce_O2 abrasive was applied to configure the water base polishing solution. Using Taguchi robust design method, through S/N ratios and analysis of variance, the influence of slurry concentration, polishing wheel speed and polishing wheel feed rate on material removal rate (MRR) were analyzed. With the increase of polishing wheel speed and polishing wheel feed rate, the MRR decreased. There was a balance concentration leading to the largest MRR. The best process parameters were selected: the slurry concentration of 20%, polishing wheel speed of 6000r/min, polishing wheel feed rate of 2.29mm/min, The result showed the descending order of selected process parameters impacting on MRR was polishing wheel speed, polishing wheel feed rate and slurry concentration.

Abstract: In the chemical mechanical polishing process (CMP) ，the groove shape of polishing pad is one of the most critical elements that directly influences the quality and efficiency of CMP. This review paper describes the basic patterns of groove shape and that the patterns shape of polishing pad how to effect on quality and efficiency of CMP. The effect comparison between various sorts of groove shape and their effects on polishing is described. It is intended to help reader to gain a more comprehensive view on groove shape of polishing pad, and to be instrumental for research and development new groove shape of polishing pad for CMP.

Abstract: Elastic deformation machining is a new developing machining method for machining aspheric optical workpieces. Fracture property of glass plate under uniform pressure has important influence on the design of mould which is the key part of elastic deformation machining. In this study, to explore the fracture property of glass plate under uniform pressure, the deformation property of glass plate under uniform pressure is analyzed, a fracture experiment of glass plate using vacuum absorption is carried out on a self-developed “fracture testing system” and the values of critical vacuum degree is fit to Weibull distribution. Results show that fracture of glass plate under uniform pressure is comminuted, and for glass plate with depth of 1.95mm and diameter of 96mm, the relative safe value of maximum center offset of the mould’s profile is 0.5mm.

Abstract: Deformation behavior; Aspheric surface; Finite element method; Contact area Abstract. Elastic deformation machining is a novel processing method for aspheric surface. In the machining process, the workpiece will deform and be in contact with the molded surface once load is applied. In this paper, a finite element model was built with Abaqus/CAE package to predict the deformation behavior of glass plate and some significative conclusions were obtained. The numerical simulation results show that the contact area between the plate and the mold is increasing with different pressure. Once the required pressure value is determined exactly, the glass plate can be deform and completely contact with the mold. The deformed shape of glass plate will completely contact with the mold at pressure p=100kPa. These conclusions have the positive significance for the applying of elastic deformation machining.

Abstract: The contemporary aspects of ultra precision machining of Si3N4 with regards to enhanced productivity and precision demands is presented in this paper. This paper reviews the literature on machining technology of covering the history, Several machining methods of Si3N4 are discussed. By comparing their advantages and disadvantages, some beneficial conclusions, which have some guiding significance for the coming practical works, are reached.

Abstract: The experimental research on ultrasonic vibration assisted milling non-ablating carbon fibre reinforced carbon composite was carried out by employing uncoated tungsten carbide milling cutter, in order to reduce the machining cost and improve the surface quality of workpiece. According to the experimental results, the tool wear was reduced and the surface quality of milled carbon fibre reinforced carbon composite was improved. Compared to traditional milling method, the flank wear land was narrowed and it dominated by abrasive particles wear mechanism. The wear trace was even and wide, with width of 7-8μm; while the rake face was worn in the mode of adhesion wear mechanism. Most of carbon fibres were cut off directly and there were little fracture, pull-out and delamination; the matrix phase was removed nearly in hybrid of brittle and ductile regime and surface damage was small.

Abstract: We composed optical system which is made of two optical lenses, beam expander, and Laser Diode(LD). When the light from the LD pointed to the remote moving object, we optically aligned to achieve full power performance in the given angle range. We also reviewed optical design data with Light Tools, and measured some factors including LD cell, surface roughness and refringence. The result shows that the laser point source optical system displayed good uniform power shape, and the LD used for this experiment to be guaranteed superior output power performance compared to conventional specifications.