Toshiyuki Enomoto

Improving Anti-Adhesion in Cutting of Aluminum Alloy by Micro Stripe Texture – Considering Texture Combination

In cutting of aluminum alloys, one of the most serious problems is chip adhesion to cutting tool surface, often leading to tool failure, above all, in dry cutting. To address this problem, we adopted surface engineering approach, namely, a functionalization of tool surfaces by textures. In our previous research, we have developed the DLC-coated cutting tool with nano/micro-textured surfaces and the cutting tool with micro stripe textured surface formed using femtosecond laser technology. Face-milling experiments on aluminum alloys showed that the nano/micro-textured surface suppresses the genesis of adhesion at the atomic level. On the other hand, it was found that micro stripe texture prevents chip adhesion from growing larger even in dry cutting conditions. In this study, a cutting tool with new textured surface combined nano/micro texture and micro stripe texture was developed in order to further improve anti-adhesiveness in cutting of aluminum alloys. As a result, it was confirmed that the combined texture brings excellent anti-adhesion compared to the previously developed tools.

Improving Tool Wear Resistance in Steel Cutting by Textured Surface and its Mechanism

In the cutting processes, improvements of anti-adhesive properties and wear resistance of cutting tools are strongly required for increasing a cutting tool life. In order to meet these requirements, we adopted surface engineering approach, namely, a functionalization of tool surfaces by textures. In our previous researches, we have developed two types of cutting tool with textured surface, namely, cutting tool with nano/micro textured surface and cutting tool with micro stripe textured surface, in the hopes of improving anti-adhesive properties in cutting of aluminum alloys. As a result, we have clarified that the developed tools significantly decrease chip adhesion on the tool surface by a series of face milling experiments for aluminum alloys. In this paper, the previously developed tools with textured surfaces were applied to the cutting of steel material (S53C) and the wear resistances of the textured surfaces were evaluated. As a result, it was found that the micro stripe texture improves the wear resistance significantly. Moreover, the mechanism of improving wear resistance by the textured surface was also discussed.

New Evaluation Method of Polishing Pad Property for Estimating Edge Roll-Off of Silicon Wafer

With the ever-growing demand for further increase in the integration density of semiconductor devices, silicon wafers as the substrates for most devices are required to be extremely flat. In particular, it is strongly required to suppress edge roll-off, which seriously deteriorates the surface flatness near the wafer edge during polishing process in the final stage of the wafer manufacturing. In this study, we investigate the properties of polishing pads required for decreasing edge roll-off and propose the evaluation method of the properties. Polishing experiments with silicon wafers and evaluation tests for polishing pads reveal that the proposed method can estimate the obtained edge surface flatness.

Investigation of a Polishing Pad and a Carrier Film for Decreasing Edge Roll Off of Workpiece

Demand for diminishing edge roll off of workpiece has rapidly increased, especially in polishing silicon wafers and glass disks. However, the conventional polishing technologies cannot meet the demand. To address this problem, the influence of carrier film properties and that of polishing pad properties on the stress distribution near the workpiece edge were investigated using finite element methods. Based on the analytical results, double-layered polishing pads having an extra-fine fiber thin layer and a hard polymer layer were developed. Polishing experiments on silicon wafers and glass plates showed that the developed polishing pads achieved high finishing efficiency and extremely flat surface near the edge.

Achieving High Flatness of Workpiece Edge Shape by Considering Polishing Pressure

In recent years, the achievement of further high flatness of workpiece edge shape is strongly required in mirror finishing. Especially, the edge roll off of silicon wafers as the substrates of semiconductor devices is demanded to decrease in the polishing process for raising the yield of IC chips. Many theoretical and experimental analyses for the edge roll off generation have been already done to meet the demand. The analyses, however, cannot fully account for the obtained edge shape in actual polishing. Concretely, the influence of the polishing pressure as one of the key polishing conditions on the edge roll off has not been clarified. In this study, the influence of the polishing pressure on the edge shape was investigated by the polishing experiments and the edge roll off generation analyses using the model based on the viscoelasticity of the polishing pad, which was proposed in the previous study. And it was revealed that an appropriate polishing pressure is needed to be set for achieving high flatness of workpiece edge shape with the consideration of the properties of applied polishing pads.

Achievement of High Flatness of Large Diameter Silicon Wafer in Double-Sided Polishing: Optimization of Polishing Conditions Considering Relative Motion Direction

Silicon (Si) wafers are the most commonly used substrates for manufacturing semiconductor devices. The design rule is miniaturized, and the chip size is increasing to improve the degree of the device integration. Then Si wafer is required to be manufactured with the higher flatness and larger diameter to meet above demands. The double-sided polishing is widely adopted as the finishing process of the wafer manufacturing, because the wafers with the good surface quality and flatness can be obtained economically. However, the polishing technology has serious problems: It is very difficult to set the appropriate conditions for stably polishing the Si wafer and wearing the pad to the high flatness. In our previous work, the optimization of the polishing conditions with the theoretical calculation was conducted, however, the calculation did not consider the relative motion direction having large influence on polishing behaviours. In this study, the optimizing method considering the relative motion direction was newly developed, and it was revealed that the calculation results corresponded well with the experimental results. Furthermore, it was found that the time-fluctuation of the wafer flatness was larger in the case of the wafer having taper shape, compared to that having convex shape in the calculation.© 2009 ASME

The Edge Roll Off Generation Mechanism in Polishing by Considering the Viscoelasticity of Polishing Pads

Recently, the achievement of further high flatness of workpiece edge shape is strongly required in mirror finishing. Especially, the edge roll off of silicon wafers as the substrates of semiconductor devices is demanded to decrease in the polishing process for raising the yield of IC chips. Many theoretical and experimental analyses of the edge roll off generation have been already done and the polishing methods for suppressing the roll off have been proposed to meet the demand. The analyses, however, cannot fully account for the obtained edge shape in actual polishing and the problem about the roll off remains. In this study, the generation mechanism of the edge roll off based on the viscoelasticity of polishing pad was newly proposed. The mechanism considered the horizontal and vertical relative static and dynamic motion between the pad and the workpiece. Moreover, the non-contact viscoelasticity measurement instrument was originally developed to evaluate the viscoelasticity of the polishing pad precisely. A series of polishing experiments for silicon wafers revealed that the edge shape, which was induced from the edge roll off generation mechanism and the measured viscoelasticity of the polishing pad, corresponded well with the obtained edge shape.Copyright