Paper PS-MoM1
Comparison Between Hybrid and Porous Dielectric Material (SiOCH) Integration Strategies for Interconnect Technologies

Monday, October 20, 2008, 8:20 am, Room 304

To reduce interconnect RC delays in the future, porous SiOCH materials (p-SiOCH) are introduced as low dielectric constant materials. However, the porosity brings serious issues such as an increased sensitivity to etch and ash plasma exposures generating significant changes in the film structural properties. These issues can be aggravated by the integration strategy. One interesting emerging solutions is the late porogen removal process in which the porosity is generated by a sacrificial carbon based porogen desorbed after patterning or chemical-mechanical polishing (CMP) steps. Such hybrid materials (SiOCH matrix and porogen) are expected to be less sensitive to plasma induced damages similarly than dense low k materials. Starting from a standard damascene integration scheme, we investigate the advantages and drawbacks of hybrid materials (h-SiOCH) compared to porous materials. Etch mechanisms in fluorocarbon (FC) plasmas, material modifications induced by etching, post etch wet cleans and CMP processes are studied. Experimental results show that etching must proceed in low polymerizing chemistries since both ellipsometry and X-ray photoelectron spectroscopy (XPS) indicate an increased fluorine and carbon concentrations on the surface and lower etch rates than with porous materials. These results are well correlated with the dense nature and the high carbon content of the hybrid material both attributed to the presence of porogens. After conventional post etch wet cleans (fluorhydric acid based), no modification of the hybrid material has been evidenced thanks to infrared analyses. The impact of CMP using Hg probe measurement and IR spectroscopy has also been studied. While porous materials are modified during CMP processes due to surfactant diffusion of the slurry trough the pores, no modification is observed with hybrid materials. We have finally performed a full metal integration process and investigated the impact of the porogen removal process on the copper lines integrity. Preliminary experiment shows that copper lines are impacted by the thermally UV-assisted treatment that generates copper line corrosion issues. A promising solution, that will be presented in this paper, consist in protecting the Cu lines by a CoWP self-aligned barrier deposition and a siliciuration-nitridation process.