• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.5
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• pp.385-389
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• 2003

There are four main components of the CMP process: polishing pad, slurry, elastic supporter, and pad conditioner. The polishing pad is an essential component to the reproducibility of polishing uniformity in CMP process. However, the polishing pad in recently using metal CMP raised the several points of high cost caused by the increase of cycle time and the many usage of slurry. It is necessary to develop the novel polishing pad which would lead the cost reduction by the higher pad life-cycle, minimized cycle time and lower slurry usage. The characteristics of polishing pad were studied on the effects of different sets of the Polishing pad, which can be applied to metal chemical mechanical polishing process for global planarization of multilevel interconnection structure. The main purpose of this experiment is cost reduction by the increase of pad life-time, the decrease of cycle time and the lower usage of slurry through the specific hard porous structured pad design. It is confirmed that the novel polishing pad made the slurry usage decrease to 60% as well as the pad life-time increase twice with the 25% improvement of removal rate. The polishing time could be decreased and it also helped the cycle time to diminish. It can be expected that this results will help both the process throughput and the device yield to be improved.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.2
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• pp.14-20
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• 2005

This paper describes a dwell time calculation algorithm for polishing tool path generation in the small toot polishing process of the axis-symmetrical lens. Generally dwell time control in the polishing machines means that small polishing tool stays for a dwell time at the specific surface position to get the expected polishing depth. Polishing depth distribution on an aspherical lens surface consists of the superposition of the local polishing depth at the each dwell position. Therefore, tool path generation needs each dwell time together with tool positioning data during the polishing tool movements on the aspherical lens surface. The linear algebraic equation of removal depth removal matrix and dwell time is formulated. Parametric effects such as the dwell d interval are simulated to validate the dwell time calculation algorithm.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1312-1315
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• 1996

Polishing work for a curved surface die demands simple and repetitive operations and requires much time while it also demands high precision. Therefore it is operated by skilled worker in handiwork. But workers avoid polishing work gradually because of the poor environments such as dust and noise. In order to reduce the polishing time and to alleviate the problem of shortage of skilled workers, researches for automation of polishing have been pursued in the developed countries such as Japan. In this research we develop a polishing robot with 2 degrees of freedom motion and pneumatic system, and attach it to machining center with 3 degrees of freedom to form an automatic polishing system which keeps the polishing tool vertically on the surface of die and maintains constant pneumatic pressure. The developed polishing robot is controlled by real time sliding mode control using DSP(digital signal processor). A synchronization between machining center and polishing robot is accomplished by using M code of machining center. A performance experiment for polishing work is executed by the developed polishing robot.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.783-786
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• 2000

For the development of a ultra-precision CMC polishing system including on-machine measurement system, we study a corrective polishing algorithm. We calculated unit removal profiles for various polishing tools and polishing tool positions. Using these results we simulate the corrective polishing process based on dwell time control. We calculate dwell time distributions and residual error of the polishing simulation method and the FFT calculation method. We got good dwell time distributions and small residual when we used the FFT calculation method. This results will be used for the optimization of corrective polishing process.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.1
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• pp.99-106
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• 2002

For the development of a ultra-precision CNC polishing system including on-machine measurement system, we study a corrective polishing algorithm. We calculated unit removal profiles for various flat type polishing tools and polishing tool positions. Using these results we simulate the corrective polishing process based on dwell time control. We calculate dwell time distributions and residual error of the polishing simulation method and the FFT calculation method. We test corrective polishing algorithm with an optical glass. The target removal shape is a sine wave that has amplitude 0.3 micro meters. We find this polishing process has a machining resolution of nanometer order and is effective for sub-micrometer order machining. This result will be used for the software development of the CNC polishing system.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.346-351
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• 1998

Cutting process has been automated due to progress of CNC and CAD/CAM, but polishing process has been only depended on experiential knowledge of expert. Polishing work for a curved surface die demands simple and repetitive operations but requires much time for its high precision. Therefore it is operated in the handiwork by skilled worker. However the workers intend to avoid gradually polishing work because of the poor environments such as dust and noise. In order to reduce the polishing time and solve the problem of shortage of skilled workers, it has been done some research for an automation of polishing. To automate the polishing process, a 2 axes polishing robot which is attached to a 3 axes machining center has been developed by our previous research. This automatic polishing robot is able to keep the polishing tool normal on the curved surface of die. Therefore its performance of polishing is improved because of always keeping the tool normal on the surface. In this paper, the smaller sized polishing robot is developed to improve polishing performance. And the controller for 2 axes polishing robot is developed. The controller is composed of TMS320C31 with high speed which is 40-ns instruction cycle time, RAM memory with 64K words, digital input with 64 bits, digital output with 32 bits, and D/A converter with 4 channels, which is 12 bits resolution. To evaluate polishing performance of this developed robot, polishing experiment for shadow mask was carried out.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.950-955
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• 2001

For the development of an ultra-precision CNC polishing system including on-machine measurement system, we study a corrective polishing algorithm. We analyze and test the unit removal profiles for a ball type polishing tool. Using these results we calculate dwell time distributions and residual errors for a target removal shape. We use the polishing simulation method and feed rate calculation method for the dwell time calculation. We test corrective polishing algorithm with an optical glass. The target removal shape is a sine wave that has amplitude 0.3 micro meters. We find this polishing process has a machining resolution of nanometer order and is effective for sub-micrometer order machining. This result will be used for the software development of the CNC polishing system.

• International Journal of Precision Engineering and Manufacturing
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• v.3 no.4
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• pp.43-53
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• 2002

Polishing a die that has free-form surfaces is a time-consuming and tedious job, and requires a considerable amount of high-precision skill. In order to reduce the polishing time and cope with the shortage of skilled workers, a user-friendly automatic polishing system was developed. The polishing system is composed of two subsystems, a three-axis machining center and a two-axis polishing robot. The system has five degrees of freedom and is able to keep the polishing tool in a position normal to the die surface during operation. A sliding mode control algorithm with velocity compensation was proposed to reduce tracking errors. Trajectory tracking experiments showed that the tracking error can be reduced prominently by the proposed sliding mode control compared to a PD (proportional derivative) control. To evaluate the polishing performance of the polishing system and to and the optimal polishing conditions, the polishing experiments were conducted.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.2
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• pp.267-274
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• 2010

Recently, the magnetorheological (MR) polishing process has been examined as a new ultra-precision polishing technology for mirror surface generation in many applications, such as aspheric lenses, biochips, micro parts, etc. This method uses MR fluids which contains micro abrasives as a polishing media, and can. It is possible to obtain nano level surface roughness under suitable process conditions, however, required polishing time is highly dependent on the applied pre-polishing methods due to its very small material removal rate. Thus, in this study, a combined polishing method is presented to reduce total polishing time for SUS304. First, the electropolishing (EP) method was applied to obtain fine surface roughness, and the MR polishing was followed. Surface roughness variations were investigated according to the process conditions. As the results of this study, it was possible to reduce total polishing time for SUS304 using the proposed combined polishing method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.743-747
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• 1997

Polishing work for a curved surface die demands simple and repetitive operations and requires much time while it also demands high precision. Therefore it is operated by skilled worker in handiwork. Howener workers avoid polishing work gradually because of the poor environments such as dust and noise. In order to reduce the polishing time and to alleviate the problem of shortage of skilled workers, researches for automation of polishing have been pursued in the developed countries. In the research, a polishing robot with 2 degrees of freedom motion attached to machining center with 3 degrees of freedom and pneumatic system forms an automatic polishing system which keeps the polishing tool vertically on the surface of die and maintains constant pneumatic pressure. A synchronization between machining center and polishing robot is accomplished by using M code of machining center. A rulled surface and shadow mask are polished by the developed polishing robot.