Capability of particle inspection on patterned EUV mask using model EBEYE M

Abstract

According to the road map shown in ITRS [1], the EUV mask requirement for defect inspection is to detect the defect size of sub- 20 nm in the near future. EB (Electron Beam) inspection with high resolution is one of the promising candidates to meet such severe defect inspection requirements. However, conventional EB inspection using the SEM method has the problem of low throughput. Therefore, we have developed an EB inspection tool, named Model EBEYE M※. The tool has the PEM (Projection Electron Microscope) technique and the image acquisition technique with TDI (Time Delay Integration) sensor while moving the stage continuously to achieve high throughput [2]. In our previous study, we showed the performance of the tool applied for the half pitch (hp) 2X nm node in a production phase for particle inspection on an EUV blank. In the study, the sensitivity of 20 nm with capture rate of 100 % and the throughput of 1 hour per 100 mm square were achieved, which was higher than the conventional optical inspection tool for EUV mask inspection [3]-[5]. Such particle inspection is called for not only on the EUV blank but also on the patterned EUV mask. It is required after defect repair and final cleaning for EUV mask fabrication. Moreover, it is useful as a particle monitoring tool between a certain numbers of exposures for wafer fabrication because EUV pellicle has not been ready yet. However, since the patterned EUV mask consists of 3D structure, it is more difficult than that on the EUV blank. In this paper, we evaluated that the particle inspection on the EUV blank using the tool which was applied for the patterned EUV mask. Moreover, the capability of the particle inspection on the patterned EUV mask for the hp 2X nm node, whose target is 25 nm of the sensitivity, was confirmed. As a result, the inspection and SEM review results of the patterned EUV masks revealed that the sensitivity of the hp 100 nm Line/Space (LS) was 25 nm and that of the hp 140- 160 nm Contact Hole (CH) was 21 nm. Therefore, we confirmed that particle inspection on the patterned EUV mask using Model EBEYE M could be available for the EUV mask of the hp 2X nm node. In the future, we will try to inspect the production mask of the hp 2X nm node, and try to confirm the performance for the EUV mask of the hp 1X nm node.