Analytical formula for inductance of metal of various widths in spiral inductors

This paper presents an analytical formula for the inductance of an inductor with the layout of variable metal width, based on the quasistatic approximation. Experimental results indicate that the analytical formula is feasible. A layout with metal whose width increases monotonously from the inner turn has a higher Q value than other configurations of the metal with the same inductance. This information will be of help in designing high-performance inductors for RF integrated circuit applications.