基于二维周期结构衍射的套刻测量技术研究

Research on Diffraction-Based Overlay Measurement Using Two-Dimensional Periodic Structure

基于衍射光探测的套刻测量技术(DBO)具备高分辨率、高精度及低的工具引起编差(TIS)等显著优点,已逐步取代传统基于成像的套刻测量技术(IBO),成为大规模集成电路22 nm及以下工艺技术节点所广泛采用的套刻测量方式。相较IBO技术,DBO技术面临的最大问题是标记成本高,测量时间长。IBO技术仅需使用单个标记测量x、y两个方向的套刻误差,而DBO则需要分别使用x、y两种方向的一维光栅实现测量,且每个方向至少需要2个标记。提出一种基于二维周期结构标记衍射光探测的套刻测量方法,使用严格耦合波分析(RCWA)算法建立标记衍射光的物理模型,通过分析该方法测量套刻的灵敏度、主要测量误差,验证该方法的可行性。二维DBO测量方法的应用,将使标记成本和测量时间比传统的DBO方法减少一半,显著降低DBO测量的成本并提高测量效率。

Diffraction based overlay （DBO） metrology has fully demonstrated its remarkable advantages in terms of high resolution, high precision and low tool-induced shift （TIS） and so on . DBO technologies have been gradually replaced the traditional image based overlay （IBO） technologies and have also been developed to address the overlay metrology challenges for 22 nm technology node and beyond. In comparison with IBO technologies, the biggest problems that DBO faces now are high mark costs and long measurement time. IBO only uses single pad for two-dimensional （2D） overlay errors measurement, while DBO should adopt one- dimensional gratings for measurement with x, y directions. Furthermore, at least two marks are needed for one direction measurement. We introduce 2D periodic structure based DBO technologies. The DBO physical model is established through rigorous coupling wave analysis （RCWA） program. The feasibility of this method is proved by means of analysis of the overlay measurement sensitivity and main measurement errors. The application of 2D DBO measurement technology can help to reduce the measurement time and mark cost by half. The DBO measurement cost will thus be dramatically lowered, and the measurement efficiency will be promoted.