Inspectability and Lithographic Effects of Reticle Defects Under Aggressive OPC Environment

Today, many IC manufacturers use OPC (Optical Proximity effect Correction) technique to obtain finer circuit geometries by adding serifs and jogs to conventional binary mask. Moreover, for endless device shrink in the absent of alternative lithography solution, successful below-half-wavelength lithography requires “much stronger OPC” which consisted of complicate patterns generated from the finer grid size of OPC software or many assist patterns to the main patterns. The mask industry, therefore, is now facing significant problems induced by both increasing write time and defect-like-small complicated OPC patterns. It is questionable that current inspection system could detect all the defect-sources as the aggressiveness of OPC is accelerated. It is not everything to detect small defect only. The direction of development of new reticle inspection tool should be directed by a smart strategy under such an aggressive environment. This paper details the lithographic effects under the 193nm wavelength and inspection sensitivity using newly developed DUV inspection system for various defects on OPC reticle. The relationship between lithographic effects and reticle inspection sensitivity was investigated according to the defect type, defect size, defect position and the aggressiveness of OPC. From this study the requirements of next generation inspection system would be clarified to necessitate good OPC mask manufacturing.