High frequency characteristics of Cu/Ta/hydrogen silsesquioxane (HSQ) system and the effects of NH3 plasma treatment on the electrical properties for hydrogen silsesquioxane

In this paper we use the Cu/Ta/HSQ interconnect structures for high frequency characteristics. Then, ammonia (NH₃) plasma is employed for the nitridation of HSQ. The effects of NH₃ plasma treatments on the high frequency characteristics (100 MHz to 20 GHz) of the interconnect structure Cu/Ta/HSQ are discussed. Among various specimens in this study, the smallest insertion loss is 1.97 dB/mm at 20 GHz for the 400degC- annealed Cu/Ta/HSQ(NH₃-plasma-treated for 50 sec). Appropriate NH3-plasma bombardment helps to form a thin SiN_x barrier layer which prevents the diffusion of oxygen without increasing the dielectric constant of the Cu-HSQ interconnect system. The dielectric constant of HSQ decreases and then increases with the increase of NH₃ plasma treatment time and a minimum dielectric constant of 2.2 is obtained after 50 sec NH₃ plasma treatment. Finally, the crosstalk noises among all specimens were measured and the FOM was used to evaluate all specimens.