Comparative studies of physical and chemical properties of plasma-treated CVD low k SiOCH dielectrics

Abstract

The 0.13 μm technology uses Cu/low k materials for back-end-of-line (BEOL) process. In this paper, we studied and compared impact of etching and photoresist stripping (PRS) plasma on the physical and chemical properties of two CVD low k SiOCH films, Coral™ and Black Diamond™. They were treated with etching (C 4F 8/N 2/Ar) and O 2 or forming gas PRS plasma. The etching plasma did not cause Si–CH 3/Si–O degradation when compared to the PRS treatments. Forming gas PRS caused substantial –CH 3 loss and surface C depletion for both SiOCH films, especially for films treated with harsh processing conditions. O 2 PRS on low k films performed better than forming gas in terms of Δ k/ k 0, C depletion and stability of Si–CH 3/Si–O based on the k value comparison, surface and FTIR analyses. Moreover, soft O 2 PRS effectively removed C built-up on film surface after etching. The surface roughness and PRS etching rates of both films were also studied and compared. We had therefore successfully developed the soft O 2 plasma chemistry as a suitable PRS recipe for integration of Cu/CVD low k BEOL interconnects.