Spral Inductor Coupling on 0.25 μm Epitaxial CMOS Process

In this study, the degree of coupling between two adjacent inductors is examined. The inductors were implemented on a 0.25 μm epitaxial CMOS process. Coupling mechanisms considered in this study were magnetic coupling and substrate coupling. The amount of coupling is determined by measuring the S21 parameter between the inductors implemented. The effectiveness of several isolation structures reported in literature in reducing coupling between inductors was evaluated. These isolation structures include patterned ground shields and halo substrate contacts. From measured results, it is found that reducing magnetic coupling by implementing a diagonal configuration improves isolation by 5 dB. Furthermore, patterned ground shields are effective in improving the isolation between adjacent inductors.