In the preparation of Integrated Circuits (ICs), employing the Dual Damascene (DD) via-first approach, the fulfilling of extremely deep via and, in general, of highly etched structures, still remains a challenging task. Especially, if this is combined with the need to obtain a planar surface with a thickness bias proximal to zero between flat zones and highly via-rich parts of the die or deep trenches. Herein, we report a full analysis of the impact of the nature of solvent and polymer composing the Hard-Mask (HM) precursor on the filling of via and long trenches. The analysis is carried out by means of optical microscopy (OPT) and scanning electron microscopy (SEM) on standard silicon wafers processed with the HM, changing different variables; from the use of materials comprising different solvents and polymers with various C-contents, up to the variation of the coating parameters such as: the spin speed, the bake temperature and the primer vaporization step before dropping the via-filler material. Interestingly, the solvent is demonstrated to play a crucial role in the formation of macro-defectiveness on long deep trenches surrounded by a flat area: PropyleneGlycolMonomethylEtherAcetate (PGMEA) uniquely-based materials can bring to a peculiar halation-effect, partially avoided with the introduction of several pre-bake steps of the under-layer on a HexaMethylDiSilazane (HMDS)-presprayed Silicon surface.