Progress in extreme ultraviolet mask repair using a focused ion beam

The key challenge in extreme ultraviolet (EUV) mask defect repair is to avo id or limit the damage to the sensitive reflective multilayer (ML) stacks o n the mask substrate and repair <55 nm mask defects. Our EW mask design emp loys an oxide buffer layer between the ML and the absorber to protect the M L during repair. We have developed both opaque and clear EUV mask defect re pair processes using focus ion beam (FIB) based gas-assisted etching (GAE) and ion-induced deposition. The process has been successfully demonstrated on our TIN baseline mask by 10x EUV print tests of 100 nm resist lines/spac es. More importantly we have assessed the current FIB tool performance capa bility and compared it with the general requirements for repairing the EUV mask for the 70 nm lithography node. The characterization includes minimum "effective" beam size, etch selectivity, and edge placement precision. We d iscussed the required improvements and future directions in repair tool res earch and development in order for the mask repair technology to keep pace with lithography scaling in future generations. (C) 2000 American Vacuum So ciety. [S0734-211X(00)06606-3].