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14 May 2007 Optimal photomask printability using interactive OPC with a new calibration methodology
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Proceedings Volume 6607, Photomask and Next-Generation Lithography Mask Technology XIV; 66071P (2007)
Event: Photomask and Next-Generation Lithography Mask Technology XIV, 2007, Yokohama, Japan
The achievement of current critical feature sizes of 65nm and near future sizes of 45nm and 32nm using 193nm wavelength requires many innovations. A "correction" of a mask design is only as good as its ability to be printed. A new method to account for the various aspects of the lithographic systems has been developed and implemented. It includes a very fast computation of the latent image in the resist including immersion (of water or any other fluid), BARC, a variety of illuminators, acid production and diffusion as well as reaction that delivers soluble resist concentration after PEB (Post Exposure Bake). This goal is achieved by solving the Maxwell equations followed by the reaction-diffusion system typical of currently used chemically amplified resists. Then the printable contour on the printed micrographs (SEM) is extracted and placed on each plane in the resist in order to select the best representative of the process. A sophisticated optimization methodology has been developed and implemented so all parameters are calibrated to yield optimal imaging. The imaging and the corresponding processing are obtained at machine accuracy. Once the simulation system is properly calibrated, becoming a true representative of the imaging in the specific manufacturing environment, the design's hierarchy is modified according to the proximity of each polygon on the wafer. This process enables defect detection and OPC to be done on the modified hierarchy and avoids the need to flatten the design resulting in much faster processing, indeed one that can now be performed on a laptop. OPC using the combination of the "proximity analysis" and the printability simulation is carried out in a few simple steps. Imaged is accomplished in the resist and the printable contour is extracted. The contour is compared to the design and the "CDLOSS" is obtained. The design is segmented according to the proximity details and a movement assignment is determined. This algorithm completes the first iteration. The process is repeated until it achieves the required tolerance or exits with "unable to correct" if OPC fails. The final result is returned to the design-stream in its place in the hierarchy. This OPC system is very fast, stable, and accurate. Explicit examples are given in the figures presented below.
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Eytan Barouch and Stephen L. Knodle "Optimal photomask printability using interactive OPC with a new calibration methodology", Proc. SPIE 6607, Photomask and Next-Generation Lithography Mask Technology XIV, 66071P (14 May 2007);

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