Patent attributes
A method for forming an arbitrary pattern of sub-micron contact holes in a substrate using a combination of interferometric photolithography and optical photolithography with a non-critical mask. The substrate is covered with a photosensitive material and is exposed by a standing wave interference pattern produced by the superposition of two coherent laser beams. Then the substrate is rotated through 90° and exposed by the same pattern. The double exposure produces a regular array of sub-micron unexposed regions which are all potentially holes if developed. The photosensitive material is then covered by a non-critical photomask and a standard light source is used to exposed those areas of the photosensitive material containing unwanted holes. Upon final development, the desired pattern is obtained.
