Variable angle spectroscopic ellipsometry ͑VASE™͒ is used as a tool to characterize properties such as optical constant, thickness, refractive index depth profile, and pore volume fraction of single and bilayer porous low-k films. The porous films were prepared using sacrificial pore generator ͑porogen͒ approach. Two sets of porous films with open-and closed-pore geometries were measured. Three models were used for data analysis: Cauchy, Bruggeman effective medium approximation ͑BEMA͒, and graded layer. Cauchy, a well-known model for transparent films, was used to obtain thickness and optical constant, whereas BEMA was utilized to calculate the pore volume fraction from the ellipsometric data. The Cauchy or BEMA models were then modified as graded layers, resulting in a better fit and a better understanding of the porous film. The depth profile of the porous film implied a more porous layer at the substrate-film interface. We found 3%-4% more porosity at the interface compared with the bulk for both films. This work shows that VASE™, a nondestructive measurement tool, can be used to characterize single-and multigraded layer porous films quickly and effectively.
Through an electron beam evaporation process, silver nanoparticles (Ag-nps) were introduced into dielectric thin-films. Silver incorporation into the oxide films resulted in a distribution of insulating Ag-nps at a density of ~10^12 particles/cm^2. For these samples, an enhancement of about two fold in dielectric constant was observed in both Al2O3 and HfO2. We attribute the dielectric constant enhancement to the polarizability of metallic nanoparticles. The dipole moment of the Ag-nps increased the stack dielectric constant in a frequency dependent manner. Because of the inherent relaxation frequency of the Ag-np dipoles and space-charge polarization, the dielectric constant was more strongly enhanced at lower frequencies (down to 100 Hz) relative to higher frequencies (up to 1 MHz). Gate leakage currents remained comparable between the control and nanocomposite samples. The Ag-nps also produced a memory effect. Potential applications of these Ag-np based films in CMOS devices are discussed.
This research will address issues at the back-end-of-line in microelectronics fabrication, specifically the need for Low-k extendibility. The International Roadmap for Semiconductors (2005) suggested that interconnect insulation must be replaced with a material having an ultra-low dielectric constant (k) of less than 2.0 and can withstand rigorous current process integration. Creating porosity in the films produces kvalues as low (1.0) air.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.