On the Planarization Mechanism of the Soft Pad Polishing：From Mechanical Property Characterization to Theoretical Modeling

• Main Authors: Yu hsuan, 林育萱
• Other Authors: Yeau-Ren Jeng
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/21890757431308537957

碩士 === 國立中正大學 === 機械工程所 === 96 === Soft pad polishing is a key technology for fine surface finish and planarization. Archaeological evidence suggests that the history of soft pad polishing dates back to the New Stone Age. In recent decades, there is a fast development of polishing technology and machine tools due to the drive for precision components and miniaturized devices. Consequently, the soft pad polishing is now used for a vast range of applications including precision machine components, optical devices and semiconductor wafers. Despite extensive research efforts over the last decade on the soft pad polishing, the mechanism for surface planarization remains elusive. This study aims to unveil the planarization mechanism during a soft pad polishing by a systematic approach combining an experimental testing that reflects the mechanical behavior of the polishing pad under different asperity heights with a surface contact model developed for the estimation of material removal rate. The study utilizes Nano Dynamic Mechanical Analysis (Nano DMA) technique to characterize the mechanical property of polishing pad under various conditions. The polishing pad is characterized under a fixed load with a range of dynamic loading to emulate the mechanical response of the soft pad in contact with asperities with different surface heights. Experimental results show that increasing dynamic loading leads to higher visco-elastic modulus of a soft pad irrespective of the fixed load. This findings suggests that visco-elastic modulus of a soft pad increases with higher surface asperity heights. The results for dry pads and wet pads show the same trend. However, the modulus of wet pads tends to be lower than that of dry pads. Furthermore, a micro-contact model is developed to describe the contact behavior among a pad, a work piece and a particle. Subsequently, this study establishes a material removal rate model that accounts for the micro contact behavior, amount of the polishing particle, and penetration depth of the particle. Finally, the model of material removal rate is used to calculate the material removal of different surface heights based on the mechanical property characterized with Nano DMA. The results show that different surface heights will approach to the same level after polishing. These findings reveal that the mechanical property of a soft pad is fundamental and pivotal for the planarization during polishing. This pioneering research proposes the first planarization mechanism for a soft pad polishing through a synergistic approach combining experimental characterization with theoretical modeling. The proposed mechanism provides a theoretical foundation for the selection and fabrication of a polishing pad, and set the guidelines for the design of the machine tool and the selection of operation parameters during polishing that cannot be achieved with empirical findings and phenomlogical approaches.