| HUANG Zhanliang,BAI Xianting,PAN Jisheng,YAN Qiusheng.Influence of Process Parameters on Immersed CMP Assisted by DC Dielectrophoresis of Sapphire Wafers[J],53(18):144-155 |
| Influence of Process Parameters on Immersed CMP Assisted by DC Dielectrophoresis of Sapphire Wafers |
| Received:January 02, 2024 Revised:March 05, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.18.012 |
| KeyWord:dielectrophoresis chemical mechanical polishing sapphire wafer process parameters polishing pad effective number of abrasives processing effect |
| Author | Institution |
| HUANG Zhanliang |
School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou , China |
| BAI Xianting |
School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou , China |
| PAN Jisheng |
School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou , China |
| YAN Qiusheng |
School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou , China |
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| Abstract: |
| The extensive utilization of sapphire is attributed to its exceptional physical and chemical properties, as well as its outstanding optical performance. Currently, the prevalent method for surface processing of sapphire chips is chemical mechanical polishing, which involves creating a softening layer through chemical reactions on the workpiece's surface and subsequently removing it using free abrasives to enhance the machining efficiency. However, the centrifugal effect resulting from the rotational motion of both the workpiece and polishing disc during the processing process hampers efficient utilization of added abrasive in titration. The electrophoretic effect exploits the dielectric polarization phenomenon in a non-uniform electric field to induce particle motion, thereby facilitating the controlled displacement of abrasives. To enhance the processing efficiency of CMP, this study proposed an immersion-based method for direct current electrophoretic-assisted chemical mechanical polishing by synergistically integrating the negative electrophoresis effect and chemical mechanical polishing. According to the processing principle, an experimental device was constructed for submerged direct current electrophoresis-assisted chemical mechanical polishing. Single-factor polishing experiments were conducted to investigate the adaptability of access voltage, workpiece and polishing disc speed, swing displacement speed, polishing time, and type of polishing pad based on the influencing factors of electrophoretic effect in sapphire chip fabrication. Meanwhile, the contact model of abrasive, workpiece, and polishing pad was established in the machining process, accompanied by the development of an electrophoretic control model for abrasive. The impact of electrophoretic effect on abrasive control in immersion polishing was thoroughly analyzed. The experimental results demonstrated that electrophoretic effects significantly enhanced the chemical mechanical polishing (CMP) performance of sapphire wafers, leading to a remarkable increase in material removal rate (MRR) by 99.97% at 2 000 V. Moreover, the surface roughness Ra was reduced by 24.47%. Notably, a noticeable reduction in surface scratches was observed. Increasing the rotational speed of both the workpiece and polishing disc, as well as the eccentric displacement speed, initially enhanced but subsequently diminished both the material removal rate (MRR) and surface roughness (Ra) during polishing. This phenomenon arose due to the generation of centrifugal force and fluid flow resulting from the relative motion between the workpiece and polishing disc, which disrupted the abrasive aggregation while also facilitating their renewal. By utilizing polishing pads with grooves, the electrophoretic effects could effectively regulate the presence of free silica on the surface, leading to enhanced polishing efficiency in comparison to non-grooves pads and achieving a more refined surface texture. The electrophoretic effect enabled better control of free silica on the slotted polishing pad, resulting in enhanced polishing efficiency compared with non-slotted pads and achieving a smoother surface. Notably, the polyurethane polishing pad (SH) exhibited superior performance. Finally, employing an input voltage of 2 000 V, a workpiece and polishing disc rotational speed of 80 rpm in the same direction, a swing speed of 60 mm/min, and utilizing a precision polishing pad, sapphire chips were subject to a processing duration of 90 min. This resulted in achieving an impressive material removal rate of 8.645 nm/min while ensuring the surface remained unblemished with an exceptional surface roughness Ra value measuring at merely 0.953 nm. |
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