Abstract
As the ULSI circuits are scaled down, the linewidth and spacings between metal interconnect also are made smaller, transmission delay is primarily caused by the parasitic resistance and capacitance(RC) along the metallic lines. There are two principle methods of reducing the transmission delay. The first method is to replace the aluminum wires with copper interconnects which offer lower resistivity and high resistance to electromigration. The second method is to use a lower dielectric constant material as the inter-metal dielectric. In addition, owing to the severe depth of focus(DOF) budget in deep sub-micron lithography, chemical mechanical polishing(CMP) is the only enabling technique known to achieve global planarization. For this reason, the characteristics of low dielectric constant material after chemical mechanical polishing(CMP) process must be researched in the future. In this thesis, one of the most promising low-k materials, hydrogen silsesquioxane (HSQ) from Dow Corning Inc., is made study on its intrinsic properties, thermal stability, chemical mechanical polishing HSQ and the impact of copper. In this study, the thermal stability of HSQ is about at 450 ℃. As for the feasibility for integrated HSQ with copper interconnects, we also have found that dielectric properties are easily degraded resulted from the copper diffusion into HSQ film. On the other hand, the characteristics of post-CMP HSQ show the leakage current and low dielectric constant are increased due to the damage during CMP process. In this work, we applied difference plasma treatments such as H2, NH3 plasma to low-k HSQ. Experimental results show that the resistance of HSQ to copper diffusion also is effectively enhanced. Furthermore, plasma treatments can restore the dielectric properties of HSQ after CMP process to a similar state of as-cured HSQ. These improvements are due to the formations of hydrogen-contained and thin nitride layer on the HSQ film. The inert-passivation layer effectively prevent HSQ from moisture uptake and copper diffusion.