| Summary: | 碩士 === 國立中山大學 === 機械工程研究所 === 86 === The aim of this thesis is to develop a new cylindric polishing process which is applied to the manufacture of bare wafer with large diameter.The wafer surface is required to be smooth, damage free, and flat.Among the steps of wafer manufacturing, the polishing process is adopted to remove the damaged layer of surface and produce a smooth surface with nano-scale of roughness.Nevertheless, it is the common difficulty for the current polishing methods to maintain or even improve the flatness of wafer surface. The cylindric polishing process developed in this thesis is to allow the polishing process to own not only the smoothing and damage removing abilities but also the flatness improving capability.The difficulty of producing a flat surface by polishing process mainly comes from the random essence of its machining behaviors. It is also due to the inability of easy adjustment of machining rate distribution on polishing pad. The cylindric polishing process is a type of floating polishing methods. Both the average motion and machining capability of abrasive particles are dominated by their sustained shear forces. This shear force is a result of velocity gradient in the slurry flow and depends on the lubricating condition between tool and wafer surface. As long as the lubricating condition is properly controlled, the particle motion (or distribution) and its machining capability will be regulated.Thus, the machining behaviors of the cylindric polishing process tend to be less random as compared to the non-floating polishing methods.In addition, the adjustment of machining rate distribution of this process can be easily reached by modifying the lubricating condition between tool and wafer surface. These specific features render the cylindric polishing process becoming a potential means to improve the flatness of wafer surface.Another feature of the cylindric polishing process is its relative insensitivity of machining behaviors to tool wear.It is because the lubricating condition of this process is little affected by tool wear due to its specific tool geometry.This advantage may allow this process to gain significant benefit in reducing the need of tool replacement. The contents of this thesis include a description of system design and a preliminary study of machining rate characteristics of this process. A machining principle and the elastohydrodynamic lubrication theory will be adopted to model the machining rate. The qualitative properties of machining rate under various lubricating conditions are investigated . Several sets of experiments are conducted to reveal the wear-resistance and high repeatability properties of the process and to examine the validity of qualitative analysis.
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