The ZEISS AIMS™ platform is well established as the industry standard for qualifying the printability of mask features based on the aerial image. Typically the critical dimension (CD) and intensity at a certain through-focus range are the parameters which are monitored in order to verify printability or to ensure a successful repair. This information is essential in determining if a feature will pass printability, but in the case that the feature does fail, other metrology is often required in order to isolate the reason why the failure occurred, e.g., quartz level deviates from nominal. Photronics-nanoFab, in collaboration with Carl Zeiss, demonstrate the ability to use AIMS™ to provide quantitative feedback on a given repair process; beyond simple pass/fail of the repair. This technique is used in lieu of Atomic Force Microscopy (AFM) to determine if failing post-repair regions are "under-repaired" (too little material removed) or "over-repaired" (too much material removed). Using the ZEISS MeRiT® E-beam repair tool as the test platform, the AIMS™ technique is used to characterize a series of opaque repairs with differing repair times for each. The AIMS™ technique provides a means to determine the etch depth based on through-focus response of the Bossung plot and further to predict the amount of MeRiT® recipe change required in order to bring out of spec repairs to a passing state.

Advanced IC fabs must inspect critical reticles on a frequent basis to ensure high wafer yields. These necessary requalification inspections have traditionally carried high risk and expense. Manually reviewing sometimes hundreds of potentially yield-limiting detections is a very high-risk activity due to the likelihood of human error; the worst of which is the accidental passing of a real, yield-limiting defect. Painfully high cost is incurred as a result, but high cost is also realized on a daily basis while reticles are being manually classified on inspection tools since these tools often remain in a non-productive state during classification.An automatic defect analysis system (ADAS) has been implemented at a 20nm node wafer fab to automate reticle defect classification by simulating each defect's printability under the intended illumination conditions. In this paper, we have studied and present results showing the positive impact that an automated reticle defect classification system has on the reticle requalification process; specifically to defect classification speed and accuracy. To verify accuracy, detected defects of interest were analyzed with lithographic simulation software and compared to the results of both AIMS™ optical simulation and to actual wafer prints.

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The ZEISS AIMS™ measurement system has been established for many years as the industry standard for qualifying the printability of mask features based on the aerial image. Typical parameters in determining the printability of a feature are the critical dimension (CD) and intensity deviations of the feature or region of interest with respect to the nominal. While this information is critical to determine if the feature will pass printability, it gives little insight into why the feature failed. For instance, determining if the failure occurs due to the quartz level deviating from that of the nominal height can be problematic.Atomic force microscopy (AFM) is commonly used to determine such physical dimensions as the quartz etch depth or height and sidewall roughness for verification purposes and to provide feedback to front end processes. In addition the AFM is a useful tool in monitoring and providing feedback to the repair engineers as the depth of the repair is one of the many critical parameters which must be controlled in order to have a robust repair process.In collaboration with Photronics nanoFab, we have previously shown the Bossung plot obtained from the AIMS™ aerial image of a feature can be used to determine if the quartz level of a repaired region is above or below the nominal value. This technique can further be used to extract the etch time associated with the nominal quartz height in order to optimize the repair process. The use of this method can be used in lieu of AFM, effectively eliminating the time and effort associated with performing additional metrology steps in a separate system. In this paper we present experimental results supporting the technique and its applicability.

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