Evaluation of litho printability of DRAM contact hole patterns with various programmed defects

Abstract

As the photomask design rules continue to shrink towards 45nm and below, the defect classification criteria is becoming more challenging to be set accurately. Pattern fidelity issues and masks defects that were once considered insignificant or merely nuisances are now yield-limiting. On the other hand, there are still cases of small defects captured during reticle inspection but will not print on the wafer. In addition, in a production setting environment it is critical to ascertain quickly and efficiently the true lithographic effect of reticle defects in order to avoid yield and cycle time impacts.As a starting point, it is best to inspect the reticle at the highest sensitivity to find all defects and anomalies. From there, fast and efficient means to sort and prioritize defects are necessary for inspection operators' and engineers' convenience. Then, it is critical to model all the defects accurately for their lithographic impact. Finally, an accurate lithographybased set of reticle defect disposition criteria can be developed for the manufacturing process flow.The focus of this study is on contact or hole patterns since the issues regarding capture of defects on such patterns are typically more complex than the ones on line and space patterns. The intent is to assess and devise defect disposition criteria for contact hole layers utilizing KLA-Tencor's 5X6 DUV inspection system with both standard die-to-die and Litho2 algorithms and the Automated Mask Defect Disposition (AMDD) system. AMDD lithographic printability results will be compared to AIMS results and printed results on wafer.

Progressive growth and hard defect disposition integrated system for 65nm and 45nm ArF immersion lithography

“…Paper has shown that AMDD can give CD results that are consistent with AIMS after quantification and calibration of their image intensity difference [3,5]. AMDD is based on PROLITH, which is a CD calculation software using inspection image from KLA-Tencor Co. inspection tools.…”