论文信息 - Mask CD control (CDC) using AIMS as the CD metrology data source

Mask CD control (CDC) using AIMS as the CD metrology data source

It has been previously demonstrated that wafer CD uniformity can be improved via an ultrafast laser system. The system provides local CD Control (CDC) by writing inside the bulk of photomasks. Intra-field CD variation correction has been implemented effectively in mask-shops and fabs based on CD-SEM and Scatterometry (Optical CD or OCD) as the CD data source. Using wafer CD data allows correction of all wafer field CD contributors at once, but does not allow correcting for mask CD signature alone. For mask shops attempting to improve CDU of the mask regardless of the exposure tool, it is a better practice to use only mask CD data as the CD data source. In this study, we investigate the use of an aerial imaging system AIMSTM45-193i (AIMS45) as the mask CD data source for the CDC process. In order to determine the predictive value of the AIMS45 as input to the CDC process, we have created a programmed CD mask with both 45nm and 65nm node L/S and hole patterns. The programmed CD mask has CD errors of up to 20nm in 2.5nm steps (4X). The programmed CD mask was measured by AIMS45, defining the CDU map of the programmed CD mask. The CDU data was then used by Pixer CDC200TM to correct the CDU and bring it back to a flat, almost ideal CDU. In order to confirm that real CDU improvement on wafer had been achieved, the mask was printed before and after CDC on an immersion scanner at IMEC and results of pre and post CD data were compared.

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