Method for providing an alignment diffraction grating for photolithographic alignment during semiconductor fabrication

Abstract

The use of a resist latent image alignment mark in lieu of using dedicated discrete alignment targets defined on a semiconductor wafer and the use of field oxide step heights for alignment during the fabrication of circuit devices are disclosed. A resist latent image alignment mark is formed in a layer of photoresist material and utilized to position a mask for exposing portions of the photoresist to a radiation source to pattern locations for active areas on a semiconductor substrate. A LOCOS isolation structure is then formed around the active areas. The isolation structure is formed such that the depth of the isolation structure is adjusted to a particular radiation source wavelength. The depth of the isolation structure can then be used as a diffraction grating for stepper alignment. Isolation structure height may also be used as a diffraction grating for stepper alignment.