Capability of model EBEYE M for EUV mask production

Abstract

According to the ITRS Roadmap [1], within a few years the EUV mask requirement for defect will be detection of defect size of less than 25 nm. Electron Beam (EB) inspection is one of the candidates to meet such a severe defect requirement. EB inspection system, Model EBEYE M※1, has been developed for EUV mask inspection. Model EBEYE M employs Projection Electron Microscope (PEM) technique and image acquisition technique to acquire image with Time Delay Integration (TDI) sensor while the stage moves continuously [2]. Therefore, Model EBEYE M has high performance in terms of sensitivity, throughput and cost. In a previous study, we showed the performance of Model EBEYE M for 2X nm in a development phase whose sensitivity in pattern inspection was around 20 nm and in particle inspection was 20 nm with throughput of 2 hours in 100 mm square [3], [4]. With regard to pattern inspection, Model EBEYE M for High Volume Manufacturing (HVM) is currently under development in the production phase. With regard to particle inspection, Model EBEYE M for 2X nm is currently progressing from the development phase to the production phase. In this paper, the particle inspection performance of Model EBEYE M for 2X nm in the production phase was evaluated. Capture rate and repeatability were used for evaluating productivity. The target set was 100% capture rate of 20 nm. 100% repeatability of 20 nm with 3 inspection runs was also set as a target. Moreover, throughput of 1 hour in 100 mm square, which was higher than for Model EBEYE M for 2X nm in the development phase, was set as a target. To meet these targets, electron optical conditions were optimized by evaluating the Signal-to-Noise Ratio (SNR). As a result, SNR of 30 nm PSL was improved 2.5 times. And the capture rate of 20 nm was improved from 21% with throughput of 2 hours to 100% with throughput of 1 hour. Moreover, the repeatability of 20 nm with 3 inspection runs was 100% with throughput of 1 hour. From these results, we confirmed that Model EBEYE M particle inspection mode could be available for EUV mask production.