Mask roughness contribution to wafer edge placement error

Andreas Frommhold; Joern-Holger Franke; Tatiana Kovalevich; Eelco Van Setten; Vidya Vaenkatesan

doi:10.1117/12.2658332

28 April 2023 Mask roughness contribution to wafer edge placement error

Andreas Frommhold, Joern-Holger Franke, Tatiana Kovalevich, Eelco Van Setten, Vidya Vaenkatesan

Proceedings Volume 12494, Optical and EUV Nanolithography XXXVI; 1249408 (2023) https://doi.org/10.1117/12.2658332
Event: SPIE Advanced Lithography + Patterning, 2023, San Jose, California, United States

Abstract

We study the effect of phase variability as an aspect of mask roughness that could contribute to Edge Placement Error (EPE) on the wafer. Phase variability in the diffracted light arises through non-specular reflection from rough surfaces or local thickness variation of the ruthenium capping layer. This leads to a speckle pattern in the aerial image intensity. Simulations were performed using representative values of mask rms and correlation length from literature and rough absorber contours extracted from mask images. The aim was to identify how such a contribution manifests in the lithographic performance of a 44 nm pitch L/S pattern. In simulation, this type of mask roughness leads to increased CD and pattern placement variability in defocus, local best focus shifts and Bossung tilts. Measurements with AIMS EUV of the pattern on reticle showed similar effects in the aerial image. Finally, we gauge the impact on-wafer by isolating the systematic variability through focus for two illuminations, one sensitive to speckle and another insensitive one.

Conference Presentation

Citation Download Citation

Andreas Frommhold, Joern-Holger Franke, Tatiana Kovalevich, Eelco Van Setten, and Vidya Vaenkatesan "Mask roughness contribution to wafer edge placement error", Proc. SPIE 12494, Optical and EUV Nanolithography XXXVI, 1249408 (28 April 2023); https://doi.org/10.1117/12.2658332

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