Performance of EBeyeM for EUV mask inspection

Abstract

According to the ITRS Roadmap, the EUV mask requirement for 2X nm technology node is detection of defect size of 20 nm. The history of optical mask inspection tools involves continuous efforts to realize higher resolution and higher throughput. In terms of productivity, considering resolution, throughput and cost, we studied the capability of EUV light inspection and Electron Beam (EB) inspection, using Scanning Electron Microscope (SEM), including prolongation of the conventional optical inspection. As a result of our study, the solution we propose is EB inspection using Projection Electron Microscope (PEM) technique and an image acquisition technique to acquire inspection images with Time Delay Integration (TDI) sensor while the stage is continually moving. We have developed an EUV mask inspection tool, EBeyeM, whole design concept includes these techniques. EBeyeM for 2X nm technology node has the following targets, for inspection sensitivity, defects whose size is 20 nm must be detected and, for throughput, inspection time for particle and pattern inspection mode must be less than 2 hours and 13 hours in 100 mm square, respectively. Performance of the proto-type EBeyeM was reported. EBeyeM for 2X nm technology node was remodeled in light of the correlation between Signal to Noise Ratio (SNR) and defect sensitivity for the proto-type EBeyeM. The principal remodeling points were increase of the number of incident electrons to TDI sensor by increasing beam current for illuminating optics and realization of smaller pixel size for imaging optics. This report presents the performance of the remodeled EBeyeM (=EBeyeM for 2X nm) and compares it with that of the proto-type EBeyeM. Performances of image quality, inspection sensitivity and throughput reveal that the EBeyeM for 2X nm is improved. The current performance of the EBeyeM for 2X nm is inspection sensitivity of 20 nm order for both pattern and particle inspection mode, and throughput is 2 hours in 100 mm square for particle inspection mode.