Characteristics of Transmission Lines on Silicon-on-Metal and Silicon-on-Quartz

Abstract

In this paper, we describe the effect of silicon substrate thickness on the characteristics of transmission lines fabricated using complementary metal-oxide-semiconductor (CMOS) technology. The S-parameters of the transmission lines on silicon-onmetal (SoM) and silicon-on-quartz (SoQ) are measured. The inductance of a microstrip line on SoM decreases as silicon substrate thickness is reduced, while that on SoQ is nearly constant for various substrate thicknesses. This fact is explained by the magnetic energy of the electromagnetic wave stored in the microstrip lines. Moreover, the loss of the microstrip line on SoM decreases as substrate thickness is reduced owing to a decrease in dielectric loss. In contrast, the characteristics of coplanar waveguides on both SoM and SoQ are constant for various substrate thicknesses.

Effects of Eddy Current on Characteristics of Spiral Inductors on Silicon

“…For the next step, we calculate the energy difference ÁE and the energy loss E loss of the spiral inductor from the extracted model parameters in order to investigate the dependences of the energies of the inductor on SoM and SoQ on silicon substrate thickness. In our previous study, 5) the behaviors of the electromagnetic energy and energy loss simulated using a full-wave solver are similar to those of the energies and energy loss estimated using the extracted model parameters. Therefore, in this study, we discuss behaviors of electromagnetic energies and energy loss using the extracted model parameters.…”

“…We measured the S-parameters of the spiral inductors in two cases: silicon-on-metal (SoM) and silicon-on-quartz (SoQ). 5) One is the case of SoM where the samples are directly mounted on a metal plate connected to a DC ground. The cross-sectional view is the same view shown in Fig.…”

“…Although the potential at the backside of the silicon substrate is not necessarily the ground potential owing to the substrate resistivity and the quartz plate, an effective RF ground for transmission lines is located about 300 mm below the substrate surface. 5) Moreover, an electromagnetic wave with a higher frequency can propagate in the quartz plate through the silicon substrate. Hereafter, we refer to this case as SoQ.…”

“…In our previous study, 5) we investigated the effects of silicon substrate thickness on the characteristics of transmission lines mounted on a metal plate. The effect of substrate thickness on the inductance of a microstrip line is explained by the magnetic energy of the electromagnetic wave stored in the line.…”