Low Stress TiN as Metal Hard Mask for advance Cu-interconnect

摘要

As VLSI technology scaled down to 65nm-node and beyond, Black Diamond (BD) and BD Ⅱ are widely used as the dielectric in the Back End of the line (BEOL). The BD and BD Ⅱ are porous and soft, the CD (Critical Dimension) will distort and change after etch and line slant without enough support. In recent years, TiN Metal Hard Mask has been widely used as an effective approach to solve this issue due to its high hardness. However, with traditional PVD process (Physical Vapor Deposition), TiN film stress is very high causing a severe CD distortion and Cu line void. In this paper, A new PVD TiN process was developed and the film formation mechanism is studied based on TiN Metal Deposition (MD) diagram. Experiment results show chamber pressure, process Ar flow, sputter power and deposition rate during processing can affect TiN film stress. Low stress TiN film was introduced after optimization of these process parameters as Metal Hard Mask in order to avoid BD materials distortion and overcome Cu metal void formation.