Patent ID: 7101806

Claim:
A method for forming semiconductor structures, the method comprising the steps of: (a) forming a first plurality of deep trenches, wherein forming each trench of the first plurality of deep trenches includes the steps of: (i) providing a semiconductor substrate, (ii) forming a hard mask layer on top of the semiconductor substrate, (iii) etching a hard mask opening in the hard mask layer so as to expose the semiconductor substrate to the atmosphere through the hard mask layer opening, wherein the step of etching the hard mask opening comprises the step of etching a bottom portion of the hard mask opening according to a first set of etching parameters, (iv) etching a deep trench in the substrate via the hard mask opening; and (b) determining a first yield of the first plurality of deep trenches; and (c) if the first yield of the first plurality of deep trenches is not within a pre-specified range of a target yield, forming a second plurality of deep trenches, wherein each trench of the second plurality of deep trenches is formed by using steps (a)(i) through (a)(iv), except that the step of etching the bottom portion of the hard mask opening is performed according to a second set of etching parameters, wherein the second set of etching parameters are adjusted from the first set of etching parameters such that, for each trench of the second plurality of deep trenches, a side wall of the bottom portion of the hard mask opening is more vertical than that corresponding to a trench of the first plurality of deep trenches, wherein the second set of etching parameters are adjusted from the first set of etching parameters such that, for each trench of the second plurality of deep trenches, the step of etching the bottom portion of the hard mask opening has a lower degree of anisotropy than that associated with the a trench of the first plurality of deep trenches.