摘要:
In order to introduce megasonic into chemical-mechanical polishing and improve polishing effect, the influence of megasonic vibrations on the flow of slurry was discussed. The axial amplitude on the working surface of polishing head was measured, and the megasonic-induced flow of slurry was also investigated experimentally.Meanwhile, the megasonic vibrations of polish head and the megasonic-induced flow field of slurry were calculated, and then the mechanism of megasonic-induced flow of slurry was investigated theoretically. The test results indicate that the frequency is 1. 7 MHz, and the amplitude of the working surface decreases and oscillates along the radial direction with the maximal value of 70 nm in the center. The experiments of megasonic-induced flow indicate that the megasonic vibrations enable the slurry pour out of the cells of polishing pad, and the amount of slurry pouring off increases with time but the flux decreases gradually to zero. This experimental result can be understood by megasonic-induce flow field. The axial amplitude on the working surface is distributed along radial direction as Bessel functions, with the result that the megasonic-induced flow field can be characterized by a function of time and coordinates. The fluctuations and the difference of the flux of slurry at different positions lead to the flow of the slurry among different regions. The megasonic-induced flow of slurry can effectively increase the utilization of slurry and improve the polishing effect.%为了将兆声引入化学机械抛光,进一步提高抛光效率,深入研究了化学机械抛光中兆声对抛光液流动的影响.首先测试抛光头工作表面的轴向振幅,再观察兆声致抛光液流动现象,最后对抛光头中声场和兆声致流场进行理论分析.利用流体力学理论分析讨论兆声致抛光液流动的机理.测试结果表明:抛光头工作表面振动频率为1. 7 MHz,振幅沿径向减小并伴有振荡,中心处最大振幅接近70 nm,这与计算结果基本一致.兆声致抛光液流动实验表明:兆声能有效激励抛光液使其从抛光垫微孔中涌出,涌出量逐渐增大,但流量逐渐减小,渐近至零.这一结果可由兆声致流场给出解释:兆声振子表面轴向振幅被贝赛尔函数调制,这种振动沿轴向传至抛光液,产生随坐标和时间变化的流场;流量随时间的涨落和不同区域间的流量差,造成抛光液在抛光垫微孔间交互流动.可见,这种兆声致抛光液流动,能有效提高抛光液利用率、改善抛光效果.