Feasibility Study of Matched Machine Overlay Enhancement toward Next Generation Device Development

In this study, we proposed the concept of high order field-by-field correction for Matched Machine Overlay (MMO) error minimization and we have validated it through experiments. Because scanners have unique grid fingerprint, MMO value between machines is higher than the one of Single Machine Overlay (SMO). In some cases, the localized grid distortion mainly contributes to the MMO value. However, this localized grid distortion cannot be flatten by a normal correction method such as 10-parameter correction. Until now, in order to flat the localized grid distortion, ultimate correction capability can be realized by combining 6-parameter field-by-field correction and intra-field high order correction methods. However 6-parameter could be not enough to follow the diversity of local distortion. In this study, for further improvement of MMO, high order field-by-field correction capability was investigated and the results were compared. Base on simulation, we found that the field-by-field correction was a successful way to lower the MMO value of EUV vs. ArF immersion scanners. By experimental demonstration, it showed that field-by-field correction was more effective to correct localized grid distortion and the gain via high order model was about 0.5 nm. These results will be helpful to achieve the MMO specification for the next generation device.