Experimental study of the strong halation-effect of a fully PGMEAbased under-layer on a highly etched topography in the dual damascene via-first approach

摘要

In the preparation of Integrated Circuits (ICs), employing the Dual Damascene (DD) via-first approach, the fulfilling ofextremely deep via and, in general, of highly etched structures, still remains a challenging task. Especially, if this iscombined with the need to obtain a planar surface with a thickness bias proximal to zero between flat zones and highlyvia-rich parts of the die or deep trenches. Herein, we report a full analysis of the impact of the nature of solvent and polymercomposing the Hard-Mask (HM) precursor on the filling of via and long trenches. The analysis is carried out by means ofoptical 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 stepbefore dropping the via-filler material. Interestingly, the solvent is demonstrated to play a crucial role in the formation ofmacro-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 ofseveral pre-bake steps of the under-layer on a HexaMethylDiSilazane (HMDS)-presprayed Silicon surface.