Patent ID: 6355567
Filing Date: 2002-03-12
Classification: H01L

Abstract:
A process for forming a retrograde opening in a film, comprising the steps of;(a) forming a film having: (1) a top, (2) bottom, and (3) characteristic that varies in the same sense from the top of the film to the bottom of the film; (b) applying a first etchant to anisotropically etch an opening in the film extending downward from the top of the film; and (c) applying a second etchant: (1) to isotropically etch the opening in the film, and (2) having a composition based on the characteristic of the film to produce further etching of the film at a first etch rate at a lower portion of the opening that is greater than a second etch rate at a higher portion of the opening resulting in a tapered retrograde opening having a top width and a bottom width greater than the top width.