Mask manufacturers are facing major reticle metrology challenges, driving the need for cost‐effective solutions that provide tighter registration specifications and on‐device registration qualification. E‐beam mask writers’ local registration error may have a critical impact on the error contribution of the reticles to wafer overlay, as it is very local and most likely is not revealed with standard quality control schemes and sampling. The reticle error signatures are, of course, writing‐strategy‐dependent, but may also be caused by residual deflector alignment issues, thus leading to a very local but potentially critical non‐correctable overlay error on the wafer. Since the e‐beam writer strategy does not differ significantly between ArFi masks and EUV masks, we expect a similar error signature for both mask types. We will present data which demonstrates local registration errors that can be correlated to the writing swathes of state‐of‐the‐art e‐beam writers and multi‐pass strategies, potentially leading to systematic device registration errors versus design of close to 2nm. Furthermore, error signatures for local charging and process effects are indicated by local registration measurements resulting in systematic error, also on the order of 2nm. A unique measurement methodology, Local Registration Metrology, is presented that allows for dense sampling of reticle dies to characterize the local e‐beam registration error. Several thousand sites in a region of interest with length and width of a few hundred microns are measured. LMS IPRO metrology algorithms enable parallel registration measurement of all individual sites for fast and accurate metrology. High throughput allows completion of Local Registration measurement within a few minutes instead of exceeding a day of measurement time with conventional registration metrology strategies. This capability enables mask users to add local registration quality control to ensure the local wafer pattern placement error contribution by a mask is within the acceptable tolerance. In addition, based on the results of Local Registration Metrology, e‐beam mask writer corrections via feed forward can now be developed to significantly reduce local overlay error on wafer caused by the reticles.

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Klaus-Dieter Roeth, Hendrik Steigerwald, Runyuan Han, Oliver Ache, and Frank Laske, "Fast local registration measurements for efficient e-beam writer qualification and correction: EMLC18 Best Paper (Conference Presentation)," Proc. SPIE 10810, Photomask Technology 2018, 108100A (Presented at SPIE Photomask Technology + Extreme Ultraviolet Lithography: September 17, 2018; Published: 12 October 2018); https://doi.org/10.1117/12.2506286.5848036899001.