Exposure Source Error and Model Source Error Impact on Optical Proximity Correction

Previous studies have quantified the impact of source error on wafer CDs in the presence of OPC. The studies found that when a 100% emitting source error is introduced into the OPC model, the corrected mask is minimally impacted through process when small errors are introduced on the source. However, as slightly larger errors are placed on the source used in the OPC mode, catastrophic failures are found. When the same errors are introduced to the exposure source when the mask is corrected with a perfect source, there is a significant through process CD variation in the system but there are no clearly catastrophic failures. The present study continues beyond the initial work to better understand the interaction between source errors and OPC. In this case, partial transmission and zero transmission errors are introduced into the study. The initial study found a CD bias and extra CD variation when the error was located in the transmissive area for the source error case. As the result of a previous study, these effects are thought to be due to scattered background illumination and pattern shift, respectively. These effects were not as readily observed in the mask error case. This study looks at the interaction of different errors in the source during both exposure and OPC generation to better understand the effects of source errors on the final pattern. A resulting analysis of study is presented. The analysis explains whether scattered background illumination and pattern shift are the mechanisms of the source effects. This can be concluded if the same effects can be generated in the mask error case using various source errors. The software methodology used to execute these studies is presented in detail.