Lowering the photoresist swing effect to increase the lithographic critical dimension uniformity: one step ahead in perfecting the dual Damascene module

Valentina Dall'Asta; Emma Litterio; Nicoletta Corneo; Bertrand Le-Gratiet; Tito Flavio Bellunato

doi:10.1117/12.2614005

25 May 2022 Lowering the photoresist swing effect to increase the lithographic critical dimension uniformity: one step ahead in perfecting the dual Damascene module

Valentina Dall'Asta, Emma Litterio, Nicoletta Corneo, Bertrand Le-Gratiet, Tito Flavio Bellunato

Author Affiliations +

Proceedings Volume 12055, Advances in Patterning Materials and Processes XXXIX; 120550W (2022) https://doi.org/10.1117/12.2614005
Event: SPIE Advanced Lithography + Patterning, 2022, San Jose, California, United States

Conference Poster

Abstract

Still acknowledged as a peculiarly challenging module, the Dual Damascene (DD) in via-first approach is constantly the object of an improvement effort, through many ways: I) testing new materials, II) tuning the coating/baking recipes and III) varying the scanner illumination conditions. The extensive characterization involved, in this case, a KrF 4-layer stack, in which the under-layer gained the role of both vias-filler and flattening material, thanks to the evaluation of many parameters like the introduction of a multi-bake route and the variation of the film thickness. The stack, customized to guarantee the etch feasibility, implied: the usage of a hard mask to allow the digging selectivity, a Bottom-Anti-Reflective-Coating (BARC) to avoid any back-reflection coming from the Silicon oxide substrate and the PhotoResist (PhR) on top. Evaluating different illumination modes, this study demonstrated how the tuning of the Numerical Aperture (NA) and of the σ values can be a feasible solution to decrease the swing effect entity; being it responsible, in most cases, for large dimensional variations when encountering small film thickness intra-die biases. Process Window (PW) and Depth of Focus (DoF) were analyzed thanks to the usage of properly designed test vehicles, to check the definition of the expected structural dimensions. This gave the opportunity to improve the Critical Dimension Uniformity (CDU), always remaining a key topic, especially when dealing with devices addressed to the automotive market.

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Valentina Dall'Asta, Emma Litterio, Nicoletta Corneo, Bertrand Le-Gratiet, and Tito Flavio Bellunato "Lowering the photoresist swing effect to increase the lithographic critical dimension uniformity: one step ahead in perfecting the dual Damascene module", Proc. SPIE 12055, Advances in Patterning Materials and Processes XXXIX, 120550W (25 May 2022); https://doi.org/10.1117/12.2614005

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