Papers by Keyword: Polishing Pad

Abstract: This research aims to study the properties of polishing pads made from polyurethane mixed with rice husk fiber for use in chemical mechanical polishing (CMP) of sapphire. After cleaning and sizing, the rice husk fiber was modified using hydrochloric acid (HCl). Then, both unmodified and modified rice husk fibers were mixed with polyurethane at ratios of 7.5, 10, and 12.5 phr to form polishing pads. The hardness and polishing performance of these pads in sapphire CMP were then tested. The experimental results showed that polishing pads from rice husk fiber could be successfully formed and remained stable. The natural fibers were evenly distributed across the contact surface of the pads. The hardness of polishing pads from rice husk fiber was smaller than conventional polishing pad (SUBA800) in range of 40.5–47.5%. Polishing results revealed that pads made from polyurethane mixed with unmodified and modified rice husk fiber achieved the highest material removal rates (MRR) of 94.2% and 64.7%, respectively, compared to the conventional pad. These results indicate that both types of fibers able to be used as a material for manufacturing polishing pads for adding value and reducing the waste from the agricultural.

Abstract: Extremely low expansion glass ceramics are widely used in integrated circuit (IC), liquid crystal display (LCD) lithography, high-precision measurement and astronomy, due to their excellent mechanical properties and chemical stability at higher temperatures. Nevertheless, the extremely low expansion glass ceramics are hard-to-machine materials due to their hard-brittle nature, resulting in cracking, chipping and scratching induced in conventional machining. This leads to higher surface roughness, and is not qualified for high-performance devices. In this study, surface roughness of 0.447 and 4.904 nm are achieved for R_a and peak-to valley (PV), respectively with a measurement area of 70×53 μm² after chemical mechanical polishing (CMP). Firstly, the glass ceramic wafers are lapped using silicon carbide (SiC) abrasives on a cast-iron plate. After lapping, the wafers are polished by CeO₂ slurry in a sequence of 3 μm and 500 nm in diameter, and polyurethane and floss pads are used correspondingly. Finally, CMP is employed on the glass ceramic wafers. Floss pad and silica slurry are used in CMP in an alkaline solution with a pH value of 8.5. After CMP, the wafers are cleaned and dried by deionized wafer and compressed air, respectively.

Abstract: 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.

Abstract: Polishing process is a primary technique for planarization of material surface in manufacture fabrication. The pad structure and its material properties are important to determine the polish rate and planarity that can be achieved by the polishing process. Besides, the pad conditioning is used to regenerate the surface of the polishing pad surface by breaking up the glazed areas. Because the polishing and pad conditioning mechanism is inadequately understood and because higher levels of pad polishing performance are desired, the investigation of experiment becomes more important.In this paper, a high precision polishing machine has established. With an improved design, a test rig can be easily used to simulate the polishing, pad conditioning process and acquire the signals of temperature. The temperature of test pads (i.e. Rodel IC1000A, Rodel IC 1000B and Opetech SB 660) is measured during polishing and pad conditioning process. For the self-design test rig, its surface temperature is measured by T-type thermocouples screwed behind the polishing (or conditioning) interface of the carrier. The experimental results provide a temperature index to end-point-detection and contribute to understanding of the mechanism on polishing pads.

Abstract: Chemical mechanical polishing/ planarization (CMP) is a key technology for fabricating high-efficient semiconductor devices, and the CMP characteristics (removal rate and accuracy, etc.) is depended on the various consumables represented by slurry, polishing pad and dresser used in the CMP process. Currently, in the pad, there are many studies that have pointed the evaluation methodology and the correlation between the pad surface asperity and the CMP characteristics. On the other hand, the dresser is one of the most important consumables because the dresser can control the pad surface asperity, and the diamond grains electrodeposited dresser (diamond dresser) is frequently used. One drawback point of the diamond dresser is that the dressing performance declines owing to the deterioration of the diamond grains. Previously, we have developed a novel flexible fiber dresser that would ensure high performance and longer life of tools, and we have reported the fundamental characteristics by the flexible fiber dresser compared with that of the diamond dresser. In this paper, we will show the results of tool life evaluation of the flexible fiber dresser using a contact image analysis method. As a result, the flexible fiber dresser can be continuously used over 35 hours. Furthermore, the result of having examined the stability of the removal rate of a silicon wafer is reported. Therefore, we found that the flexible fiber dresser is one of the most effective dressing methods for the polishing pad.

Abstract: According to the shortcomings of the traditional free abrasive chemical mechanical polishing (CMP), in recent years, the fixed abrasive chemical mechanical polishing (FA-CMP) technology is proposed. It is a new planarization technology developed on the basis of the traditional CMP. Pad is an important and dispensable part in FA-CMP. The cost and quality of FA-CMP pad are determined by the preparation technology. In order to study the FA-CMP pad of the low cost and high quality, in this paper, by reading a lot of literature, 5 kinds of preparation technology of FA-CMP pad are analyzed. Study results will provide some reference for further designing and manufacturing the FA-CMP pad.

Abstract: Diamond conditioners, or dressers, are commonly used to dress polishing pads that are applied to the chemical mechanical polishing of silicon wafers for integrated circuits. Although the diamond conditioner has regular distribution diamond grits, they differ in shape and can be oriented differently because the shape of diamond grits is generally cubo-octahedral. Therefore, the dressing behaviors on the polishing pad are unpredictable. In this work, the fundamental characteristics of dressing are investigated by a single crystal diamond with various shapes (each resulting in point-cutting, line-cutting, and face-cutting), a rake angle of-50°, and cutting faces in the (100) and (111) planes. For the purpose of analysis, plowing ratio is defined as the sum of the areas of the two side ridges divided by the groove area. This ratio can be used to evaluate the contribution of plowing and cutting actions from the dressing. Experimental results reveal that a groove with ridges on both side walls is formed as the diamond is moved over the pad. The profile of the scratch correlates with the shape of the diamond. In summary, cutting dominates when point-cutting is responsible for the dressing. On the contrary, plowing plays a major role with respect to line-cutting. The cutting action tends to dominate when the dressing is completed by face-cutting a (111) plane. Alternatively, the wear tends to be dominated by the plowing action if the dressing is conducted via face-cutting a (100) plane.

Abstract: Considering the grit aggregation of fixed abrasive and the environmental pollution of free abrasive machining tools, a kind of ultra-fine abrasive polishing pad was fabricated by means of sol-gel technology. The effects of drying method, gel reaction time, sodium alginate concentration and pad thickness which determine the property of the polishing pad were respectively investigated. And the polishing pad fabricated under the optimized condition was utilized to polish silicon wafer on a nano-polishing machine to evaluate the tool performance.

Abstract: Some technologies of ultra-precision single-plane polishing and lapping devices, including spindle section, polishing pad, cooling system, dressing system and pressurization system are discussed. The development trends of ultra-precision single-plane polishing and lapping devices are also analyszed as more controllable, integrated and high-precision in the future.

Abstract: In this work, we developed a computational fluid dynamics (CFD) model to simulate the slurry flow between the wafers and pad during the chemical mechanical polishing (CMP) process under a multiple-wafer configuration. A serial of simulations were carried out to visualise slurry flow and explore the effects of the process variables concerned on the flow velocity and pressure distributions beneath the wafers. Through the model and simulation, the flow field characteristics were obtained and analyzed under different operating conditions. The results can provide an insight into a fundamental understanding of the slurry flow behaviours under the multiple-wafer configuration and some useful implications for the selection of practical polishing variables.