抛光微区受限流体中磨粒接触状态和运动机制的研究

Nowadays, integrate circuit (IC) manufacturing is developing to 14nm and below 14nm process. Chemical mechanical polishing (CMP) technology is also approaching to its woking limit with the development of IC manufacturing. However, the microscopic removal mechanisms of material in the confined space during the CMP have not been understood completely. The confined space is consisted of the wafer, pad and slurry. This will restrict the further development of CMP technology. It is very difficult that the mechanism of abrasive contact and movement is studied directly by experiment at present because the CMP process is dynamic and transient. Therefore, in this project the CMP process including wafer, pad, abrasive and water will be studied with the help of molecular dynamics simulation(MD), assisted by experimental verification. The experiment will include abrasive scratch test, nanoabrasive microfluid jet test, and abrasive fluorescent tracing test, and so on. On the bais of the combination between the hydrodynamic effect and the solid contact effect, the friction lubrication status between wafer, slurry and pad will be confirmed on basis of the simulation. Then the contact status and movement mechanism of abrasive in the dynamic confined fluids between the wafer and pad will be analyzed. Finally, the comparison between the abrasive plough process and abrasive impact process during CMP will be studied on the basis of the scratch test and fluid jet test of the silicon wafer. Based on the results of this project research, the microscopic material removal mechanisms during CMP will be improved. And it is very helpful for the improvement and development of the CMP technology in the future.

随着集成电路制造向14纳米及其以下线宽发展，晶圆表面的平坦化指标已接近现有化学机械抛光(CMP )工艺的加工极限。但由于晶片(Wafer)、抛光垫(Pad)与抛光液(Slurry)所构成的抛光微区内，Wafer表面的微观材料去除机制等科学问题尚未解决，限制了CMP技术的提高。本项目将以分子动力学仿真为主要手段，以硅片表面磨粒划痕、纳米颗粒微射流、颗粒荧光示踪等实验结果为基础，建立包含Wafer、Pad、磨粒(Abrasive)和水膜的接近于CMP真实加工过程的分子动力学仿真平台。通过综合考虑流体动压因素和固体接触因素，揭示在Wafer、Pad和水所构成的动态受限流体内磨粒与Wafer、Pad的微观动态接触机制及磨粒的微观动态运动机制，阐明CMP材料去除过程中磨粒的犁削作用和冲击作用。该项目的实施将完善CMP微观材料去除机制的理论，促进CMP技术的进一步发展。

由于晶片(Wafer)、抛光垫(Pad)与抛光液(Slurry)所构成的抛光微区内，磨粒的微观材料去除机制等科学问题尚未解决，限制了目前化学机械抛光（CMP）技术的进一步提高。本项目主要通过建立包含Wafer、Pad、磨粒(Abrasive)和水膜的接近于CMP真实加工过程的分子动力学仿真平台，结合实验，进行CMP微观材料去除过程的研究。.研究结果表明：磨粒冲击作用下，不同膜厚的氧化膜与单晶硅基体结合强度的差异是导致基体原子飞离数呈现膜厚效应的主要原因，磨粒与Wafer之间粘着作用在材料去除过程中占据重要地位。据此，提出不同于传统Indentation-Sliding 模型的Contact-Penetration-Adhesion(CPA)CMP材料去除模型。之后，结合磨粒与表面之间的CMP加工过程中的真实接触面积在材料去除过程重要地位的研究结果，进一步提出了CMP过程中介孔磨粒的最优结构。 上述结果，不但合理解释了CMP中机械作用和化学作用的匹配机理，而且也为新型抛光技术和抛光液的研究提供了理论指导。同时，磨粒犁削过程的仿真研究，更进一步表明磨粒与Wafer之间粘着作用的重要性。综合上述结果，有望能最终揭示CMP材料去除机理。.此外，对于受限流体研究而言，随着载荷的增加，在分层现象和黏度增加共同作用下，单晶硅受限空间内的水膜的流动状态将由层流和湍流的混合状态过渡到单一的层流状态。同时，受限水膜边界滑移现象越发显著。 .而在射流冲击过程的仿真研究中发现，射流中团簇和基体之间的水膜完全固化及完全固化的保持，对基体损伤的形成具有决定作用，从而解释了实际磨粒水射流加工中存在合适的射流距离的现象，这为揭示FJP的材料去除机理打下了坚实基础。.最后，通过含有水膜的抛光垫纳米压痕仿真研究，发现随着含水量的增加，相对于干抛光垫而言，其弹性模量会先出现减小然后再上升的现象。上述现象与CMP的实验结果，以及生物材料的纳米压痕实验结果均吻合。相应受限水膜固化机制，对CMP材料去除过程以及生物材料的机械性能的研究，均有着重要意义。. 总之，该项目目前的研究结果，有望完善CMP微观材料去除机制的理论，促进CMP技术新工艺的开发。