基于电化学的化学机械平坦化终点检测方法及实验研究

Chemical mechanical planarization (CMP) of copper is the essential process in IC fabrication. During a time control CMP process, Cu over-polishing or under-polishing often occur, which strongly enhances defaults such as residual, dishing and erosion. Therefore it requires a reliable method to identify the endpoint of the CMP process. However, the conventional endpoint detection (EPD) technology of CMP becomes imperfect as the feature sizes scaling down. And the demand for the EPD technology of copper CMP is getting high due to the rapid expansion of the IC manufacturing equipments technology in China. Ion selective electrode (ISE) technology is getting more mature and becomes more widespread application at present, and especially the successful development of the 300mm CMP equipment implies the time has come to explore the electrochemistry EPD method based on the ISE technology. The purpose of this project is to development and experiment study on the EPD of copper CMP based on an electrochemistry method. The major highlight of the project is to development a new EPD method which can be used for copper CMP, and the EPD system based on the new EPD method will be integrated to the 300mm CMP equipment which is developed by our team. This project not only can minimize the defaults and improve the yields, but also can enhance the independent innovation and rapid expansion of the IC manufacturing equipments technology in our country.

残留、碟型凹陷和腐蚀是铜互连CMP的主要缺陷，严重影响了芯片的良率。终点检测技术可准确预测抛光终点，避免欠抛或者过抛，进而有效减少残留等缺陷的发生。随着研究的深入，传统的终点检测方法已显粗糙。此外，国家IC制造装备技术的发展也对铜互连CMP终点检测提出了要求。离子选择电极（ISE）技术已发展成为较成熟的技术并已在众多领域得到了应用，尤其是300mm晶圆铜互连CMP样机的成功研制，使进一步探索基于ISE的电化学终点检测方法成为可能。本项目首次将ISE技术引入300mm晶圆铜互连CMP终点检测领域，研制可用于不同抛光液体系的ISE电位测定系统，研究CMP缺陷的产生机制以及相应的ISE响应特性，探讨CMP过程中ISE电位及其演化规律与CMP缺陷产生的内在关系，建立基于ISE电位及其演化规律的终点检测方法，进而发展基于ISE的电化学终点检测技术，为铜互连CMP终点检测提供新的技术手段和技术支持。

作为集成电路制造中广泛应用的全局平坦化技术，化学机械平坦化利用化学腐蚀和机械磨削的协同效应实现最佳的抛光效果。随着晶圆尺寸的持续增加，如何检测到可靠的CMP终点并实现可控平坦化尤为关键。本项目建立了CMP过程的ISE电位测量平台，提出了电机功率终点检测策略，搭建并完善了电涡流在线测量系统，实现了快速、稳定、高精度的CMP终点检测。系统深入地进行了铜的摩擦化学及电化学行为研究，揭示了协同缓蚀剂在阻挡层抛光过程中的腐蚀抑制机理，针对CMP缺陷开展了低下压力CMP的材料去除机理研究。通过上述研究的整合，搭建了CMP终点检测集成系统，并在TSV CMP工艺进行了应用。高均匀、低缺陷的TSV晶圆抛光结果表明，所搭建的系统对于CMP技术的发展具有非常重要的意义。