TABLE OF CONTENTS In this chapter we focus on the design and layout of passive devices. In particular we will emphasize the realization of inductors and capacitors in a integrated circuit process. We begin the discussion with a simple loop inductor. Since the loop is a core building block for more complicated structures, we will spend more time on this structure. By using loops in series and parallel, we can build spirals, solenoids, and other more complex structures. The design and layout of transformers for ICs builds on this background and is covered in detail in Chapter 10. Finally, we cover the design of MIM capacitors in an IC process.
A loop or ring inductor is a natural inductor structure because we can cut the loop at any point to introduce the leads into the inductor, as shown in Fig. 6.1. Since the structure is planar, it can be easily incorporated onto a PCB or integrated circuit. A circular loop is approximated in an IC process with a polygon. [1] In an IC process allowing only Manhattan geometries, or orthogonal interconnect angles, then a rectangular loop inductor is a good choice. Intuitively, the inductance is a function of the loop area A since by the mean value theorem
The resistance, though, depends on the perimeter of the loop. Thus, to maximize the Q of the structure, we should utilize a shape with maximum area to perimeter. It is well...
