Patent ID: 7893479

Claim:
A semiconductor structure, comprising: a hard mask layer on a top substrate surface of a semiconductor substrate, said hard mask layer including a hard mask layer opening through which a portion of the top substrate surface is exposed to a surrounding ambient, wherein the hard mask layer comprises a pad oxide layer on the top substrate surface, a nitride layer on the pad oxide layer, a BSG (borosilicate glass) layer on top of the nitride layer, and an ARC (anti-reflective coating) layer on top of the BSG layer, wherein a BSG side wall surface of the BSG layer is exposed to the surrounding ambient through the hard mask layer opening, wherein an ARC side wall surface of the ARC layer is exposed to the surrounding ambient through the hard mask layer opening, wherein the BSG side wall surface and the ARC side wall surface constitute a top side wall surface, and wherein there exist two separate points A and B on the nitride side wall surface and two separate points C and D on the top side wall surface such that (i) the four points A, B, C, and D are coplanar, (ii) a plane going through the four points A, B, C, and D is parallel to a reference direction that is perpendicular to the top substrate surface, (iii) both the line segments AB and CD are perpendicular to the reference direction, and (iv) the line segments AB is longer than the line segments CD.