Maskless photolithography: Embossed photoresist as its own optical element

This letter demonstrates that features embossed on the surface of a layer of photoresist can direct UV light in the photoresist layer. These topographical features act as optical elements: they focus/disperse and phase shift incident light in the optical near field, inside the resist layer. A number of different surface topographies have been examined, which give 50–250 nm features after exposure and development. This method gives patterns of complex features over large areas, in a parallel process, that can then be transferred into silicon or metal. It provides a method for controlling the intensity of light inside a thin film of photoresist.