Patent ID: 9601341
Date: 2017-03-21
CPC Classifications: H01L

Claim:
1. A method of forming a feature in a substrate including the steps of: forming a mask structure over the substrate and directly on an upper surface, wherein the forming of the mask structure comprises forming a mask layer directly on the upper surface and forming an aperture through the mask layer such that a portion of the upper surface is circumscribed by an edge of the mask layer delimiting a bottom of the aperture and said portion of the upper surface is exposed via the aperture, and subsequently forming re-entrant structure that constricts access via the aperture to said portion of the upper surface by defining a re-entrant opening that is within the bounds of and is narrower in a horizontal direction than the aperture as viewed in plan; subsequently etching the substrate through the re-entrant opening using a cyclic etch and deposition process that forms, in the underlying structure, a feature having a maximum critical dimension (CD) in said horizontal direction which is smaller than the CD of the aperture in said horizontal direction; and removing the mask structure.