Evaluation of defect repair of EUVL mask pattern using FIB-GAE method

We utilized a newly developed low acceleration voltage FIB (Focused Ion Beam) system and evaluated the process for repairing the absorber layer on EUVL mask. During the etching of the absorber layer, which is a step in conventional repair technique, a phenomenon of side-etching of Ta-nitride layer with XeF2 gas was observed. This phenomenon was considered to be caused by the isotropic etching of the Ta-nitride layer with XeF2 gas. We then added another gas for etching and evaluated the new process to prevent the side-etching of Ta-nitride layer. In this paper, we will report four evaluation results of EUVL mask pattern defect repair using FIB-GAE (Gas Assisted Etching). The first one is the problem of pattern topography after conventional repairing process and the reaction mechanism of gas assisted etching of Ta based absorber. The second evaluation result is addressed in two parts. One is the evaluation of a new gas assisted etching process that employs an additional gas that has an ability to control the etching rate of absorber layer. The second part addresses the repairing accuracy of EUVL mask pattern. The third is the basic etching performance e.g. etching rate of Ta based absorber, Cr based buffer, and Si based capping layer. The fourth and the last evaluation is the application of the newly developed gas assisted etching process on programmed bridge defect in narrow pitched L/S patterns.