Study of ADI (After Develop Inspection) on Photo Resist Wafers Using Electron Beam (Ⅲ): Novel Method for ADI on Metal Hard Mask by Penetration Contrast

摘要

We proposed a model for highly sensitive detection of residue defects in electron beam defect inspection of photo resist patterns on a metal hard mask and verified the principle of that model. When there are photo resist residue defects on the bottom anti-reflective coating (BARC), the thickness of total organic layer is thicker at the defect pattern than in areas where there is no residue. The model proposed here focuses on this increase in layer thickness. The landing energy of the primary electrons allows electron penetration to the under layer (TiN) in the patterns where there is no defect (thin layer), but does not allow such penetration in the defective patterns (thick layer). In that landing energy region, SEM image contrast differs according to the primary electron penetration or non-penetration in the non-defective patterns and in the defective patterns. This method detects defects according to the contrast change (penetration contrast method). The principle of this model (i.e., the penetration contrast method) is verified in this report. The behavior of the defect that caused with the variation of an actual exposure condition was compared with this method and without this method. This method was also applied for quantitative detection of defects considered to be caused by dose amount of lithography process. This method was shown to be clearly effective in ADI for the metal hard mask.