Coherent multiple imaging by means of pupil plane filtering

Miklos Erdelyi; Armen Kroyan; Karoly Osvay; Zsolt Bor; William L. Wilson Jr.; Michael C. Smayling; Frank K. Tittel

doi:10.1117/12.354393

26 July 1999 Coherent multiple imaging by means of pupil plane filtering

Miklos Erdelyi, Armen Kroyan, Karoly Osvay, Zsolt Bor, William L. Wilson Jr., Michael C. Smayling, Frank K. Tittel

Proceedings Volume 3679, Optical Microlithography XII; (1999) https://doi.org/10.1117/12.354393
Event: Microlithography '99, 1999, Santa Clara, CA, United States

Abstract

A resolution enhancement technique suitable for Deep-UV microlithography based on coherent multiple imaging (CMI) will be described. We showed recently that a Fabry-Perot etalon inserted between the mask and the projection lens in an optical stepper is able to simultaneously enhance the resolution and depth of focus of an aerial image. Since the multiple images of the mask pattern created by the etalon are added together coherently, the final image profile is very sensitive to the initial phase conditions. It is possible to simulate this coherent multiple imaging techniques using a simulation model which either superimposes separate output electric fields or by applying an appropriate transmission-phase pupil plane filter in the simulator. The first approach, however, requires a modification of the simulation software which allows output of the electric field profile, while the second approach can be used with a conventional commercial lithography simulator. In this paper computer simulations for isolated and extended contact hole arrays are used to demonstrate that the CMI method can enhance resolution by 18 percent while maintaining or even increasing the DOF of the aerial image. It is also shown that the high intensity side lobes generated by the filter nc abe eliminated by means of a phase shifting mask or by reducing the spatial coherence of the illumination source. The optimum value of spatial coherence was found to be 0.28. In this case the side lobes disappear, and the intensity of the main peaks doubles. The impact of this technique on image intensity is also discussed.

Citation Download Citation

Miklos Erdelyi, Armen Kroyan, Karoly Osvay, Zsolt Bor, William L. Wilson Jr., Michael C. Smayling, and Frank K. Tittel "Coherent multiple imaging by means of pupil plane filtering", Proc. SPIE 3679, Optical Microlithography XII, (26 July 1999); https://doi.org/10.1117/12.354393

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