Nano-machining repair tool plays an important role in the current 65 nm node photomask repair. It removes defects mechanically with nanometer sized diamond tip with high accuracy and low damage using high accuracy AFM data. The repair performance of nano-machining repair system largely depends on the diamond tip whose aspect ratio decides the minimum reparable feature size. As the device shrinks to 45 nm or 32 nm node, higher aspect ratio tip with weak structure is required. It is contradiction to the fact that more accurate edge placement and better repair slope is required in smaller node repair, because deflection or tip wear effect could happen in high aspect ratio tip. In this article, deflection and wear effect were investigated in single layer repair recipe using SEM and AIMSTM. Multilayer recipe which complements weak structure was estimated carefully, and some limits were discussed. Finally some requirements of nano-machining repair system for 45 nm node were presented.