A method includes forming a first conductive spiral and a second conductive spiral of a spiral inductor coupled to a substrate. The second conductive spiral overlays the first conductive spiral. A first portion of an innermost turn of the spiral inductor has a first thickness in a direction perpendicular to the substrate. The first portion of the innermost turn includes a first portion of the first conductive spiral and does not include the second conductive spiral. A second portion of the innermost turn includes a first portion of the second conductive spiral. A portion of an outermost turn of the spiral inductor has a second thickness in the direction perpendicular to the substrate. The second thickness is greater than the first thickness. The portion of the outermost turn includes a second portion of the first conductive spiral and a second portion of the second conductive spiral.