Research On Multi-electrodes Piezoelectric Vibrator And Its Application In Megasonic Assisted CMP

Based on the theory of propagation of acoustic wave in multilayered medium, megasonic polishing vibrators are designed and produced in this paper. Silicon wafers are polished by megasonic assisted chemical mechanical polishing and traditional chemical mechanical polishing respectively, and both coarse polishing and precision polishing experiments are carried out. Firstly, the general formulas of propagation of acoustic wave in multilayered medium are presented, sound intensity transmissivity in double media layers and in three layers of media are analyzed. Secondly, a matching layer structure of polishing head and a solid liquid coupling polishing tool are calculated and designed, then, megasonic assisted chemical mechanical polishing(MA-CMP) are carried out by attaching them to traditional chemical mechanical polishing equipment. The results show that megasonic assisted chemical mechanical polishing is a feasible method to improve surface quality both in coarse polishing and precision polishing. In addition, aiming to eliminate coupling vibration and obtain uniform vibration amplitude of the disc plate piezoelectric vibrator, this paper puts forward a multiple electrodes piezoelectric vibrator to control vibration modes. A matching layer structure polishing vibrator with a multiple electrodes piezoelectric ceramic is produced. The first natural frequency of the thickness extension vibration disc plate piezoelectric vibrator is 1.7MHz. Using the multiple electrodes piezoelectric polishing vibrator to polish silicon wafers, both uniform polishing effects and improved material removal rate are obtained.