Liu Yuanhang, Tao Hongfei, Zhao Dewen, Lu Xinchun
State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China.
Materials (Basel). 2022 Jun 15;15(12):4230. doi: 10.3390/ma15124230.
The wafer backside grinding process has been a crucial technology to realize multi-layer stacking and chip performance improvement in the three dimension integrated circuits (3D IC) manufacturing. The total thickness variation (TTV) control is the bottleneck in the advanced process. However, the quantitative analysis theory model and adjustment strategy for TTV control are not currently available. This paper developed a comprehensive simulation model based on the optimized grinding tool configuration, and several typical TTV shapes were obtained. The relationship between the TTV feature components and the spindle posture was established. The linear superposition effect of TTV feature components and a new formation mechanism of TTV shape were revealed. It illustrated that the couple variation between the two TTV feature components could not be eliminated completely. To achieve the desired wafer thickness uniformity through a concise spindle posture adjustment operation, an effective strategy for TTV control was proposed. The experiments on TTV optimization were carried out, through which the developed model and TTV control strategy were verified to play a significant role in wafer thickness uniformity improvement. This work revealed a new insight into the fine control method to the TTV optimization, and provided a guidance for high-end grinding tool and advanced thinning process development.
晶圆背面磨削工艺一直是三维集成电路（3D IC）制造中实现多层堆叠和芯片性能提升的关键技术。总厚度变化（TTV）控制是先进工艺中的瓶颈。然而，目前尚无TTV控制的定量分析理论模型和调整策略。本文基于优化的磨削工具配置开发了一个综合仿真模型，并获得了几种典型的TTV形状。建立了TTV特征分量与主轴姿态之间的关系。揭示了TTV特征分量的线性叠加效应和TTV形状的新形成机制。结果表明，两个TTV特征分量之间的耦合变化无法完全消除。为了通过简洁的主轴姿态调整操作实现所需的晶圆厚度均匀性，提出了一种有效的TTV控制策略。进行了TTV优化实验，验证了所开发的模型和TTV控制策略在提高晶圆厚度均匀性方面发挥了重要作用。这项工作揭示了对TTV优化精细控制方法的新见解，并为高端磨削工具和先进减薄工艺的开发提供了指导。
