45nm Mask Defect Printability Test

The introduction of immersion technology has pushed the feature size to 45nm and beyond. With the continued shrinkage of feature sizes, some advanced Resolution Enhancement Technologies (RET) such as alternating phase shift masks (Alt-PSM), Embedded attenuated phase shift lithography (EA-PSM), SRAF (sub-resolution assist feature), the polarization of the used light source and etc are popularly used in advanced immersion lithography. However, the RET technology also introduces more complexity in mask making and easily induces more printing defects on nm. It is always a hot topic what kind of mask defects can be tolerated not only for increasing mask throughput but also for cost reduction. Although the Aerial Image Measurement System (AIMS) can assess the printability behavior of mask defects, it is not realistic to rely on AIMS data only because the real defects are also dependent on the resist performance and etch behavior.In this paper, the printed defects related to a state-of-the-art immersion stepper scanner (ASML 1900Gi) are investigated by the inspection of different features with programmed defects. The printed defects, which exist on dense/ISO Line, dense/ISO trench, dense/ISO hole and SRAF are studied carefully. All results are not only very useful in understanding the origins of the observed defect printing mechanisms but also very helpful in setting up a defect acceptance criteria for mask making at 45nm or high node in immersion lithography. The conclusion of this project can greatly improve many problems in mask making, such as defect classification, defect lost issue and defect repair performance confirm.