Photolithographic method and apparatus employing a polychromatic mask

A photolithographic method and associated apparatus are provided that permit three-dimensional structures to be defined in a photoresist coating in such a manner that multi-level structures can be formed which have constant width at different depths within the photoresist coating. The photolithographic method and apparatus may permit such three-dimensional structures to be defined within a photoresist coating with the use of a single polychromatic mask and, optionally, a micro-lens array. By designing the polychromatic mask to have a plurality of regions that selectively pass and block respective wavelengths of light, the photoresist coating can be selectively illuminated with light have different wavelengths. As a result of the optical absorption characteristics of the photoresist coating, the different wavelengths of light propagate to different depths within the photoresist coating, thereby defining multi-level microstructures therein.