脉冲磁场辅助磁性复合磨粒化学机械抛光技术及其加工试验研究

摘要

A polishing method assisted by an auxiliary pulse electromagnetic field was proposed, where the magnetic polymer microspheres/SiO2 composite abrasives were anchored on a smooth glass tool plate by the magnetic force,and the dependence between diameter of composite abrasives and morphology of tool plate was reduced.In polishing processes,the abrasives entered into the polishing area easily by mean of pulse electromagnetic force,and a high material removal rate was obtained.An electromagnet with contrapuntal structure was designed,and simulation calculations show that uni-form distributions of magnetic flux density and electromagnetic force are achieved.Force analyses in-dicate that the electromagnetic force can help the magnetic polymer microspheres enter the polishing area from near-polishing area,and material is polished by magnetic composite abrasives in two-body abrasion wear mechanism.Owing to the pulse electromagnetic force,magnetic composite abrasives is deposited and entered into polishing area easily without the occurrence of magnetic abrasives aggrega-tion.Experiments of polishing silica wafer,using a glass tool plate of Ra 1.1μm surface roughness and pulse electromagnetic field with a certain frequency and duty cycle,have shown the superior char-acteristics.The material removal rate is increased from 137 nm/min to 288 nm/min with the assis-tance of the electromagnetic field of 5 Hz frequency and 50% duty cycle,and the surface roughness of wafer is decreased from Ra 405 nm to Ra 0.641 nm.%提出一种脉冲磁场辅助新型磁性复合磨粒化学机械抛光技术。该技术利用磁性聚合物微球与Si O 2磨粒组成的复合磨粒抛光液,在脉冲磁场辅助作用下,实现磨粒尺寸对硬质抛光盘微观形貌依赖性小、磨粒易进入抛光区域、材料去除率较高的抛光。设计了“之暠字形的对位式结构电磁铁,模拟计算表明其磁感应强度沿抛光平面分布均匀,磁性微球受到的磁力一致性好。磁性微球在抛光系统中的受力分析表明：磁性微球受磁力作用时有利于复合磨粒从近抛光区进入抛光区,以二体磨损的方式去除加工表面；磁性微球不受磁力作用时,复合磨粒随抛光液的流动而移动,避免大量聚集形成磁链。以表面粗糙度Ra=1.1µm的硬质抛光盘进行硅片抛光试验,施加不同频率和占空比的脉冲磁场前后,硅片的去除率从137 nm/min提高到288 nm/min,频率5 Hz、占空比50%时获得最大值,硅片表面粗糙度由抛光前Ra=405 nm减小到Ra=0.641 nm。