Jens Hahn

Litho resist rework influences on Cu metal layer patterning with TiN-hard mask

The use of TiN-Hard masks for Cu metal layer patterning has become a common technique for trench first metal hard mask (TFMH) back end of line (BEOL) integration schemas. Resist rework influences the chemical and physical behavior of the TiN hard mask and therefore the final result of the dual damascene etch process in terms of critical line dimension (CD) and trench taper determining the electrical metal sheet resistance. Within this paper, the effects of three different resist rework strip procedures on subsequent TiN hard mask and dual damascene etching, using O2, H2N2 and H2O plasma processes, are compared. Furthermore, the interaction of the rework process with the CD tuning capabilities in dual damascene etch are evaluated. Summarizing the data, a stable process flow for wafers with and without resist rework is shown, eliminating litho CD rework offsets, resulting in metal trench processing with tight geometrical and electrical distributions.

Novel metallization scheme using nitrogen passivated Ti liner for AlCu-based metallization

In many fabs for quarter micron and below technologies a stack consisting of Ti/TiN/AlCu/TiN or Ti/AlCu/TiN is being used for metallization. A new approach for metal stack deposition of 0.25 micrometers and beyond, utilizing hew design rules, has been used for DRAM processes. The novel metal deposition process uses an insitu nitrogen purge directly after deposition of bottom Ti to achieve a passivation of the Ti with a thin nitride before deposition of AlCu. This novel approach has been compared to standard metallization stacks consisting of Ti/AlCu/TiN and Ti/TiN/AlCu/TiN.