The study on Integration of Low Dielectric Constant Material Hydrogen Silsesquiox(HSQ) and Copper
|關鍵字:||低介電常數材料;low dielectric constant material;low k;HSQ|
Hydrogen silsesquioxane (HSQ) is one of the most intensively studied low-k materials concerning both its basic properties as well as integration-related issue. The dielectric constant of HSQ is about 2.8. Also, copper is paid much attention for its lower resistivity and higher anti-electromigration capability comparing with Al. In this thesis, the reaction of low-k HSQ film and copper were investigated by using metal-insulation-semiconductor (MIS) capacitor. In addition, the different plasma treatments (H2 and NH3) were applied on HSQ films instead of conventional barrier layer for enhancing the resistance of HSQ film to copper diffusion. The structure of HSQ was significantly changed after subjected to a further thermal annealing. The bonding of Si-H was broken and the porosity of the HSQ film was decreased. Moreover, the degradation of dielectric properties due to copper diffusion in the HSQ film was severe after a high temperature annealing. These eventually caused the increase of the leakage current and dielectric constant. By applying the plasma post-treatments on HSQ, however, leakage current and dielectric constant were decreased with increasing treatment time when compared with those of untreated HSQ. For the H2-plasma treatment, the hydrogen radicals could recover the broken Si-H bonds and form a passivation layer at the surface of the HSQ film. This would maintain the porous structure and prevent low-k HSQ from moisture uptake and copper attack. Accordingly, both leakage current and dielectric constant were significantly decreased. On the other hand, NH3-plasma treatment provided nitrogen to form a thin SiNx layer at the surface of HSQ film. The thin SiNx layer was inert and also effectively blocked moisture uptake and copper diffusion into HSQ. Electrical characteristic measurements and material analyses were also consistent with our inference. In addition, the experimental results indicated that the plasma post-treatments (H2 and NH3) are effective methods in enhancing the barrier properties of HSQ for copper penetration into HSQ.