Effects of the Thin-Film Metal Ground Embedded in On-Chip Microstrip Lines

This letter studies the influence of embedded thin-film metallization layers, normally designed as ground planes, upon the dispersive characteristics of multilayer microstrip lines. The spectral domain approach is used to analyze the effects of the metallization thickness as a design parameter in two structures: the thin-film microstrip line and metal-insulator-metal-insulator line. Numerical results indicate that the thin metallization layer can excite the slow-wave mode and change significantly the dispersive characteristics. Moreover, at low frequencies a local minimal attenuation can be achieved with certain metallization thickness. Thus, it is necessary to take into account this thin-film metal ground to achieve reliable numerical simulation from dc to millimeter-wave frequencies