"What you see is what you print": aerial imaging as an optimal discriminator between printing and non-printing photomask defects

Amir Sagiv; Shmoolik Mangan

doi:10.1117/12.793055

19 May 2008 What you see is what you print: aerial imaging as an optimal discriminator between printing and non-printing photomask defects

Amir Sagiv, Shmoolik Mangan

Author Affiliations +

Proceedings Volume 7028, Photomask and Next-Generation Lithography Mask Technology XV; 70281E (2008) https://doi.org/10.1117/12.793055
Event: Photomask and NGL Mask Technology XV, 2008, Yokohama, Japan

Abstract

Advanced photomasks for low-k₁ lithography, are prone to various defects sources: contamination, geometry, transmission, phase, etc. These defects exhibit a complex relation between the signal from an imaging detector and its print related impact, with important consequences for the performance of the detection scheme under nuisance-ubiquity conditions. We studied numerically several imaging schemes, with respect to their defect detection signal and its relation to the associated CD effect. We show that for actinic aerial imaging detection the signal is tightly correlated and linearly scaled with the induced CD variation regardless of defect source and location. Conversely, the correlation of non-actinic and/or non-aerial (high-resolution based) detection signal with printing effect is poor. Whereas the linear behavior characterizing aerial imaging is independent of the distribution of defect attributes, the statistics of non-aerial defect signal is shown to be highly sensitive to defect distribution. Such non-aerial detection schemes would generally have to compromise detection sensitivity in order to maintain a constant nuisance false alarm rate. Aerial imaging is therefore the optimal discriminator between printing and non-printing defects. The tight linear correlation between defect signal and CD effect in aerial inspection systems, allows for an optimized and effective mask inspection, suitable for all mask types and technologies. Specifically, we show here that such a tool allows a straightforward migration from 65nm node to 45nm and 32nm with double patterning, by tuning the detection threshold without being flooded by nuisance induced false alarms.

Citation Download Citation

Amir Sagiv and Shmoolik Mangan "What you see is what you print: aerial imaging as an optimal discriminator between printing and non-printing photomask defects", Proc. SPIE 7028, Photomask and Next-Generation Lithography Mask Technology XV, 70281E (19 May 2008); https://doi.org/10.1117/12.793055

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