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Resolution enhancement technologies (RET), such as optical proximity correction (OPC) help us develop sub-
100nm technology node by using photolithography equipments and materials for 130nm photolithographic process.
Because the resolution of scanner and materials has arrived almost at their limit, small patterns below resolution limit are
more sensitively affected by very small tolerance of various factors which were not considered by major process
parameters such like lens flare, reticle haze, reticle critical dimensional (CD) errors, etc. As patterning small ones under
resolution limit directly means large MEEF (mask error enhancement factor) in photo process, reticle CD errors are
actually magnified on wafer. Therefore, reticle CD errors should be tightly controlled when we try to define small
patterns under resolution limit.
As the feature size shrinks down, the importance of OPC model accuracy grows up for the purpose of ensuring
high pattern fidelity. In conventional process of OPC model generation, we don't concern how mask database CDs are
exactly matched with real reticle CDs, since the specification of reticle CD is enough tight to ignore CD variation on the
reticle such as 1-dimensional CD difference, linearity CD uniformity. But in the process with large MEEF, OPC model
with incorrect CD information of reticle has a bad influence to prediction pattern fidelity.
In this paper, we describe the effect of reticle CD errors on the OPC model accuracy. To quantify that effect, we
compared two cases of OPC model generation. One is making OPC model by using mask database CDs themselves, the
other is by using mask real CDs in 110nm node for poly and metal 1 (damascene) layers. As a consequence of the test,
we can achieve the accuracy OPC model calibrated with reticle CD errors which better predicts wafer CDs and 2-
dimensional images than the model, calibrated by original database CDs.
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