Mask characterization for double patterning lithography

Bubke, Karsten; Kruif, Robert de; Peters, Jan Hendrik; Dusa, Mircea V.; Connolly, Brid

doi:10.1117/1.3023078

Cited by 7 publications

References 10 publications

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Wet cleaning of Ta-based extreme ultraviolet photomasks at room temperature

Park,

Choi,

Kim

2024

Nanotechnology

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Owing to the wavelength-dependent limits of the deep ultraviolet (DUV) exposure process, the semiconductor industry introduced extreme ultraviolet (EUV) lithography operating at a 13.5-nm wavelength. Traditional photomasks employ pellicles for protection; however, EUV-specific pellicles are not widely applicable to commercial processes, requiring the development of a EUV photomask cleaning method. In this study, a wet cleaning method for Ta-based EUV photomasks at room temperature was systematically examined in terms of key parameters, including the pattern step height, surface topography, and particulate count, via atomic force microscopy and X-ray reflectivity. Post sulfuric acid-hydrogen peroxide mixture (SPM) treatment, the photomask exhibited a stable step height, indicating minimal pattern degradation. Additionally, discernible alterations in the surface roughness and a decrease in particle count were observed, further indicating to the effectiveness of SPM-mediated cleaning. Conversely, following SC-1 treatment, while the pattern step height remained relatively unchanged, a notable increase in surface irregularities and macroscopic particulates was observed, suggesting a suboptimal cleaning efficiency of the SC-1 solution despite its potential for pattern structure preservation. Our room temperature wet cleaning method efficiently reduces wear-out and successfully eliminates contaminants, potentially prolonging the EUV photomask's productivity and durability.

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Wet cleaning of Ta-based extreme ultraviolet photomasks at room temperature

Park,

Choi,

Kim

2024

Nanotechnology

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Single-Mask Double-Patterning Lithography for Reduced Cost and Improved Overlay Control

Ghaida

Torres

Gupta

2011

IEEE Trans. Semicond. Manufact.

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Abstract-1 We propose shift-trim double patterning lithography (ST-DPL), a cost-effective double patterning technique for achieving pitch relaxation with a single photomask. The mask is re-used for the second exposure by applying a translational mask-shift. An additional non-critical trim exposure is applied to remove extra printed features. ST-DPL can be used to pattern critical layers and is very suitable for regular and gridded layouts, where redesign effort and area overhead are minimal. In this paper, the viability of ST-DPL is demonstrated through a design implementation at the poly and contacts layers in bidirectional layouts. Standard-cell layouts are constructed so as to avoid layout decomposition conflicts, which are found to be the limiting factor for the pitch relaxation that can be achieved with double-patterning (ST-DPL as well as standard DPL). 2× pitch relaxation being associated with a considerable area overhead, 1.8× pitch relaxation is achieved in our implementation while ensuring no layout decomposition conflicts and a small area overhead. Specifically, in comparison to layouts assumed to be feasible with a hypothetical single-patterning process, we observe virtually no area overhead when ST-DPL is applied to the poly layer (<0.3% cell-area overhead) and no more than 4.7% cellarea overhead when ST-DPL is applied at both the poly and contacts layers. The proposed method has many benefits over standard pitch-split double-patterning: (1) cuts mask-cost to nearly half, (2) reduces overlay errors between the two patterns, (3) alleviates the bimodal line-width distribution problem in double patterning, and (4) slightly enhances the throughput of critical-layer scanners.

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