Immersion scanner proximity matching using angle resolving scatterometry metrology

The fingerprint of optical proximity effect, OPE, is required to develop each process node's optical proximity correction (OPC) model. The OPC model should work equally well on exposure systems of the type on which the model was developed and of different type. Small differences in optical and mechanical scanner properties can lead to a different CD characteristic for a given OPC model. It becomes beneficial to match the OPE of one scanner to the scanner population in a fab. Here, we report on a matching technique based on measured features in resist employing either CDSEM or scatterometry. We show that angle resolving scatterometry allows improving the metrology throughput and repeatability. The sensitivity of the CD as a function of the scanner adjustments and the effect of scanner tuning can be described more precisely by scatterometry using an identical number of printed features for measurement. In our example the RMS deviation between the measured and the predicted tuning effect of scatterometry is 0.2 nm compared to 0.8 nm of CD-SEM allowing to set tighter matching targets.