Research On Wafer Edge Polishing Based On Ultrasonic Vibration

In recent years, the semiconductor industry gets fast development. As the mainsemiconductor material of chip, the diameter of silicon wafer is constantly increasing and thequality of wafer edge had become increasingly important. Therefore, the precision machiningtechnology of wafer edge is focused with many researches.On the basis of ultrasonic vibration and chemical mechanical polishing（CMP）technology, the paper researches on wafer edge polishing based on ultrasonic vibration.Aiming at some problems in silicon wafer edge processing and manufacturing such as poorquality of edge surface and edge defects, according to wafer edge polishing the paper presentsa new method of wafer edge polishing that based on traveling wave ultrasonic vibration, andapplied it on wafer edge polishing. Based on rotating travelling wave and the elliptical motionof the surface formation principle in circular piezoelectric vibrator, wafer edge polishing toolof ultrasonic vibration is designed and transformed basing on the circular piezoelectricvibrator. Dynamic analysis of circular piezoelectric vibrator about vibration characteristicslike the amplitude, mode of vibration and natural frequencies are carried out using finiteelement analysis software ANSYS, then experimental tests are also finished, the result ofexperiments are consistent with the simulation. Basing on the working principle of edgepolishing tool and experiment, experimental system and its monitoring apparatus aredeveloped. Under the condition that vibrator just products vibration, macroscopicrotation-free motion between silicon wafer and polishing tool, wafer edge polishingexperiments are carried out. The results verify the feasibility of ultrasonic vibration polishing,surface roughness of wafer edge is reduced obviously and achieved the effect of polishing.Experimental research and analysis are carried out in detail aiming at polishing time andpolishing pressures which are important process parameters affecting the polishingexperiment. The results show that under the condition of ultrasonic vibration polishing, thebest values of polishing time and polishing pressures are existed and polishing pressureseffect is the maximum. The bevel of wafer edge is contacted with polishing tool completely inpolishing process, which provides a new research idea for wafer edge polishing.