Design and fabrication of deep submicron CMOS technology compatible suspended high-Q spiral inductors

In this paper, deep submicron complementary metal-oxide-semiconductor (CMOS) process compatible high-Q suspended spiral on-chip inductors were designed and fabricated. In the design, the electromagnetic solver, SONNET, and the finite element program, ANSYS, were used for electrical characteristics, maximum endurable impact force, and thermal conduction simulations, respectively. Based on the design, suspended spiral inductors with different air cavity structures, i.e., diamond opening, circle opening, triangle opening, and full suspended with pillar supports were developed for various applications. Among these structures, the suspended inductor with pillar support possesses the highest Q_max (maximum of quality factor) of 6.6 at 2 GHz, the least effective dielectric constant of 1.06, and the lowest endurable impact force 0.184 Newton. On the other hand, the spiral inductor with diamond opening has a lowest Q_max of 4.3, the largest effective dielectric constant of 3.44 and highest endurable impact force 4 Newton. The former is suitable for station telecommunication applications in which the mechanical vibration is not a serious concern, while the latter can be used for mobile telecommunication applications subject to strong mechanical vibrations. Additionally, the conventional on-chip spiral inductor embraced by SiO₂ with a dielectric constant of 4 was prepared for comparison and found its Q_max is 3.8 at 1.2 GHz.