WET-DRY BILAYER RESIST

A method of patterning a substrate includes forming a multilayer photoresist stack on a substrate. The multilayer photoresist stack includes a dry photoresist layer, deposited by vapor deposition, over a wet photoresist layer deposited by spin-on deposition. A first relief pattern is formed in the wet photoresist layer by exposure to a first pattern of actinic radiation of a first wavelength and development of developable portions of the wet photoresist layer using a first development process. The first relief pattern uncovers portions of the dry photoresist layer. A second relief pattern is formed in the dry photoresist layer by exposure to a second pattern of actinic radiation of a second wavelength and development of developable portions of the dry photoresist layer using a second development process. The developable portions of the dry photoresist layer are defined by the second pattern of actinic radiation and the first relief pattern.