Characterization of high-density micromachined interconnects

Silicon micromachining is used to locally reduce the substrate height of large diameter wafers in order to maintain single-mode microstrip propagation. Effective dielectric constant and attenuation are shown up to 45 GHz for a 50-ohm microstrip line that is printed across a thick (400 μm) and thin (100μm) silicon area. Discontinuity effects for the dielectric and conductor show lower reflection (-10dB above 15 GHz) and smoother transmission characteristics for the abrupt conductor transition compared to the tapered one. Loss performance of the reduced height interconnects are comparable to full height constant thickness designs and interconnect densities as high a factor of 4 can be achieved.