| Measurement of the dielectric constant of thin film in the frequency range of gigahertz (GHz) to terahertz (THz) is crucial for future integrated circuit (IC) interconnect technology. This research focuses on the use of time domain terahertz pulse technology for such characterization. In particular, the goniometric phase shift of a reflected electro magnetic pulse as a function of incident angle has been established and used to determine dielectric constant in GHz to THz range.;A THz wave sent through a freestanding film is distorted by the interaction between the wave and the film. Time domain spectroscopy is used to measure the freestanding films with the sub-wavelength thicknesses by considering multireflections in detail. Low dielectric constant (low-kappa) films in particular, TeflonRTM, Parylene-N and polyimide have been measured to demonstrate of the usefulness of the technique.;Simulation of the goniometric time domain spectroscopic (GTDS) system capability demonstrates that the calculated waveform as a function of the angle of incidence agrees with the experimental results. A sharp phase flip at the Brewster angle occurs with the bare Si wafer while the phase change with the incident angle for a film on the substrate is relatively smooth. By applying curve fitting to the measured relaxation angle width and the phase different near the Brewster angle, we obtained the dielectric constant of Poly(arylether) (FLARE 2.0) (2.8 for a 3.3 mum film), parylene-N (2.5 for a 1.8 mum film), and TiO2 (47 for a 0.1 mum film) films on silicon wafers. The inaccuracy of GTDS technique is about 3% to 5%. |
