US Patent 7906275 Self-aligned spatial frequency doubling

In accordance with the invention, there are methods for self-aligned spatial frequency doubling in one dimension and also in two dimension. The method for self-aligned spatial frequency doubling in one dimension can include forming a film stack over a substrate, wherein the film stack comprises a photoresist layer and forming a one-dimensional periodic first pattern having a first pitch p on the photoresist layer using an optical exposure, wherein the first pitch p is at least smaller than twice the bandpass limit for optical exposures. The method can also include forming a second pattern using the first pattern by nonlinear processing steps, wherein the second pattern has a second pitch p2=p/2.