Patent ID: 7319067

Claim:
A method of simultaneously controlling ADI-AEI CD differences of openings having different sizes, wherein the openings are formed with the steps comprising: forming an anti-reflection coating (ARC) and a patterned photoresist layer on a material layer, wherein the patterned photoresist layer has therein a first opening pattern and a second opening pattern of different sizes; and using the photoresist layer as a mask to sequentially etch the ARC and the material layer to form, in the material layer, a first opening and a second opening respectively corresponding to the first and the second opening patterns, wherein a recipe of the etching makes the first opening smaller than the first opening pattern by a first size difference and makes the second opening smaller than the second opening pattern by a second size difference, and a difference between the first and the second size differences is a relative size difference, the method comprising: setting an etching parameter affecting the relative size difference at a first value in etching the ARC and at a second value different from the first value in etching the material layer.