Marangoni effect-based under-layer for a Dual Damascene via-first approach: a scalable solution to the unwanted photoresist swing effect

One of the main challenges of a Dual Damascene (DD) via-first process is the control of the Critical Dimensions (CDs) in the lithography of the trenches. The PhotoResist (PhR) thickness presents variations from the via arrays to the open areas, which cause the variation of CDs: the swing effect. The planarization of a DD via-first process is reported. A dual-layer solution is used to demonstrate the complete filling of deeply etched structures and the advanced planarization in a multilayer technique. The first material coating the substrate exhibits a Marangoni effect; the second material owns the same physico-chemical properties of the first one, except for the Marangoni properties. The Marangoni effect of the first coating produces a thicker film in the via array than in the open area, resulting in a negative Film Thickness (FT) bias. Then, the coating with second material is performed and having it standard planarization properties, a positive thickness bias occurs. The addition of these two coatings results in a thickness bias intra-die and on complex topographies, ranging from 0 nm to 30 nm across the wafer. Additionally, the similar physicochemical nature of these two planarization materials enables this dual layer system to be treated as a single homogeneous layer as far as the etching process is concerned. In the perspective of a KrF lithographic process, this dual-layer offers a planar substrate to be coated with the PhR and allows a strong reduction of the intra-die swing effect, providing a scalable solution.