Lithographic technique for patterning a semiconductor device

Abstract

A method of forming a patterned resist layer on a semiconductor substrate is described. The substrate is coated with a resist layer and placed on a substrate stage within a projection printer. The projection printer includes a radiation source that emits a radiation wave having a predetermined wavelength, a lens having a predetermined numerical aperture, and a reticle having an opaque section and a transparent section. The projection printer has a resolution that is a function of the wavelength and the numerical aperture. The resist layer is exposed to a radiation pattern formed at the surface of the resist layer when the radiation wave passes through the reticle. The radiation pattern includes a radiative area lying beneath the transparent section and a substantially radiation-free area lying beneath the opaque section. All dimensions of the radiation pattern at the surface of the resist layer are no less than the resolution. A portion of the substantially radiation-free area prevents a significant amount radiation from reaching a first region in the resist layer during all of the exposure. The first region has a pair of opposite edges. Spaced-apart second regions in the resist layer are exposed by the radiative area during the exposure. A resist pattern is formed where a second region lies immediately adjacent to the first region at an opposite edge and another second region lies immediately adjacent to the first region at the other opposite edge. The opposite edges are formed at different times and the distance between the opposite edges are less than the resolution.