Michio Uneda

A study on combined vibration drilling by ultrasonic and low-frequency vibrations for hard and brittle materials

This research aims to improve machining accuracy concerning the method of drilling ceramics and other hard and brittle materials as well as to establish a drilling technology that would ensure high efficiency and longer life of tools. Specifically, the authors contrived a new drilling method that combines ultrasonic vibrations of a diamond core drill and low-frequency vibrations of the workpiece and produced a combined vibration drilling apparatus experimentally. In this paper, the combined vibration drilling apparatus is used for a series of experiments under different vibration conditions to examine the behavior of drilling force, drilled hole accuracy, and edge chipping on the drilled hole surface. In addition, the behavior of tools during combined vibration drilling are theoretically examined. As a result of these considerations, the authors found that combining ultrasonic and low-frequency vibrations is one of the most effective methods for drilling hard and brittle materials.

A Basic Study of the Behavior of Slurry Action at Multi-Wire Saw

The workpiece descent type multi-wire saw uses a slicer to di ce sil con wafers. This slicing method uses a cutting fluid mixed with abrasive grains, which is ca lled s slurry. The slurry is applied on the wire tool to be carried into the processing area. Therefore, t he adhesion conditions and the action of the slurry affect the slicing characteristics. In t his project, the relation between the slurry action and the slicing characteristics was studied. The processing mechanism of a multi-wire saw with a descending workpiece was investigated. Introduction The multi-wire saw is one of the processing methods to slice the larg -sized silicon ingot. This slicing method uses the water as cutting fluid mixed abrasive grains (sl urry). This slurry is supplied on the wire tool and carried in the processing area. The slurry amount whic h enters in the processing area changes owing to each adhesive conditions and actions of slurry. And, these slurry characteristics affect on slicing efficiency. Therefore, the authors mainly paid a ttentions to slurry actions on the wire tool of multiwire saw. This study aims to clear the processing mechanisms of multi-wire saw to descend the workpiece from the relation between slurry actions and sl icing characteristics. In this report, authors observed slurry actions by a high speed camera and slic ed the workpiece by using multi-wire saw. The influence between slurry actions and slicing characteristics (processing efficiency and wafer accuracy) was studied under one series of t he slicing conditions. As the results of slicing, it was clear that the film between the wire tools ha d considerably an influence on slicing efficiency and wafer accuracy. Experimental Apparatus and Method Figure 1 shows the mechanism of multi-wire saw to descend the workpi ece. The piano wire fed from new the wire bobbin is wound on the winder bobbin through the parts of seesaw, f our grooved rollers to guide the wire at the processing area. The wire tool repeats th motion of going and returning at the processing area. The slurry is supplied continuously and uniformly on the w ire of both sides of the workpiece. The supplied slurry at the processing area is collected in he slurry tank and it is re-used. After the processing, the processing efficiency and wafer accuracy are mea sured. Figure 2 shows the observation points of slurry actions. As the slurry actions on the wire change by each supplying conditions of slurry, the slurry actions during the slici ng process are observed by a high speed camera. There are three observation points. The point (A) is he slurry supplying point, the point (B) is the middle point between the slurry supplying point and edge of the workpiece, and the point (C) is the edge of the workpiece. Table 1 shows the main experimental conditions. Key Engineering Materials Online: 2003-04-15 ISSN: 1662-9795, Vols. 238-239, pp 89-92 doi:10.4028/www.scientific.net/KEM.238-239.89

Basic Study on Etching Selectivity of Plasma Chemical Vaporization Machining by Introducing Crystallographic Damage into Work Surface

Plasma chemical vaporization machining (PCVM) is a high-speed plasma etching method using atmospheric-pressure plasma. Although it does not leave an affected layer on the processed surface because of the small ion energy owing to the small mean free path of gas molecules, it is not suitable for planarization because of its isotropic etching. Thus, a combination of PCVM and a mechanical machining process is proposed. The convex parts of a substrate surface are considered to be affected by mechanical machining and are removed preferentially by PCVM. In this report, it is investigated whether etching rate of the affected layer becomes larger or not. As a result, it was found that the etching rate increased in the first 100 nm depth of the mechanically polished substrate, which corresponds to the thickness of the heavily damaged layer observed by cross-sectional transmission electron microscopy.

Evaluation of In-Plane Microdeformation Distribution Characteristics of Polishing Pad Surface

In the chemical mechanical polishing (CMP) of a Si wafer, the physical properties of the polishing pad affect the processing characteristics. There have been several studies on the evaluation of pad surface asperity. In this study, we investigate the fundamental characteristics of polishing pads by the digital image correlation (DIC) method from two viewpoints. It was found that the pad surface deforms owing to shrinkage. Moreover, there is a strong relationship between the in-plane microdeformation characteristics and the amount of material removed from the pad in the conditioning process. Since the DIC method can measure changes in pad surface conditions, it can be used to evaluate future CMP monitoring systems.

Effects of atmosphere and ultraviolet light irradiation on chemical mechanical polishing characteristics of SiC wafers

To establish a high-efficiency and high-quality polishing process by controlling the workpiece environment, a prototype chemical mechanical polishing (CMP) machine that can perform double-side CMP simultaneously in a sealed pressure chamber was developed. Using this new machine, polishing experiments on single crystalline silicon carbide (SiC) wafers were carried out. The results showed that applying a highly pressurized O2 gas and ultraviolet light irradiation were effective in SiC CMP.

Effect of Groove Pattern of Chemical Mechanical Polishing Pad on Slurry Flow Behavior

In chemical mechanical polishing (CMP), the slurry flow behavior on the polishing pad is very important both for improving polishing effectiveness and for reducing the slurry consumption. In this study, we aim to evaluate two types of CMP pad that have unique special groove patterns, slurry outflow and inflow pads, for controlling the slurry flow behavior. We describe the effect of the groove patterns on the slurry flow behavior observed using images recorded using a high-speed digital camera. The results of the study indicate several advantages of the proposed pads over the conventional pads from the viewpoint of slurry flow behavior.

Performance Evaluation Method of Chemical Mechanical Polishing Pad Conditioner Using Digital Image Correlation Processing

In chemical mechanical polishing (CMP), conditioning is generally used for the regeneration of the pad surface texture. Currently, the performance evaluation of conditioners depends on the users experience so that it is important to develop a novel quantitative evaluation method for conditioner performance. In this paper, we propose a novel evaluation method for conditioner performance using digital image correlation (DIC) processing. The proposed method can measure the in-plane micro-deformation distribution of the pad surface texture by conditioning. It is found that a pad surface deforms over 40 µm with conditioning and that the in-plane deformation value increases with a decrease in the mesh size of conditioner grains.

Effect of Pad Surface Asperity on Removal Rate in Chemical Mechanical Polishing

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.

Consideration of Femtosecond Laser-Induced Effect on Semiconductor Material SiC Substrate for CMP Processing

In this paper, lapped C-face of single crystal SiC wafer was irradiated by femtosecond laser. Chemical mechanical polishing (CMP) was then carried out to polish the irradiated SiC C-face. The authors compared the results of femtosecond laser-assisted CMP process. A white-light interferometer was used to investigate the surface morphology of the processed SiC substrate before and after laser irradiation. It was found that the material removal rate (MRR) of the irradiated substrate is about 3 times higher than that of the substrate not treated by femtosecond laser. In addition, lower surface roughness was realized after femtosecond laser assisted CMP process.

Long life mechanism on a flexible fiber conditioner in CMP

A flexible fiber conditioner was developed as a surface reference conditioning tool in CMP (Chemical Mechanical Planarization) process. The conditioner keeps contact force of each fiber edge constant to the pad by making use of fiber bending effect. In this paper, the running test was evaluated using the flexible fiber conditioner. The result indicated that the fiber conditioner achieved long life polishing rate and cutting rate in spite of round shape of fiber edge by fiber edge wear. The long life mechanism was verified in terms of a rake angle of a cutting edge of fiber edge. It was verified that the fiber conditioner continues to roughen the pad surface due to small negative rake angle and small cutting width.