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.