A method of forming a semiconductor device includes forming a dielectric layer over a substrate, and curing the dielectric layer with a first curing process. The first curing process includes providing a first UV light source, filtering the first UV light source with a first filter, the first filter permitting a first electromagnetic radiation within a first pre-determined spectrum to pass through and blocking electromagnetic radiation outside the first pre-determined spectrum, and curing the dielectric layer with the first electromagnetic radiation of the first UV light source.