Determination of deep hole structure for advanced semiconductor devices analyzed by transmission X-ray scattering

An etching process for high-aspect ratio (HAR) structure is one of key technologies in the recent semiconductor device fabrication. In the development and control of etching processes, it is very critical to evaluate depth, shape profile, and tilting. Critical dimension small angle X-ray scattering (CD-SAXS) is a powerful measurement technique to characterize such shape parameters of HAR structures. In this paper, we evaluated the measurement sensitivity of CD-SAXS for changing shape parameters (average CD, depth, side wall shape, tilting) of HAR holes using simulation results. The simulation results show that CD-SAXS has sufficient sensitivity to characterize shape parameters of HAR structures. We also demonstrated the performance of CD-SAXS by measurement of 1 mu m depth holes on the 300 mm wafer. As a result, we were able to obtain detailed hole profiles, distribution of average CD and tilt angle across the entire wafer.