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 SiNx 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.