Patent ID: 8101092

Claim:
A method for controlling ADI-AEI CD difference ratio of openings having different sizes, wherein the openings are formed with the steps comprising: forming an etching resistive layer, a silicon-containing (Si-containing) material layer and a patterned photoresist layer on a target material layer in sequence, wherein the patterned photoresist layer has therein a first opening pattern and a second opening pattern with different sizes; and performing steps of etching the Si-containing material layer, the etching resistive layer and the target material layer in sequence to form a first opening and a second opening corresponding to the first opening pattern and the second opening pattern in the target material layer, wherein a difference between a size of the first opening and a size of the first opening pattern is the first dimension difference, a difference between a size of the second opening and a size of the second opening pattern is the second dimension difference, a ratio of the second dimension difference to the first dimension difference called an ADI-AEI CD difference ratio, wherein the size diameter of the first opening pattern is larger than that of the second opening pattern, the method comprising: performing a first etching step by using the patterned photoresist layer as a mask to transfer patterns of the patterned photoresist layer to the Si-containing material layer so as to form a patterned Si-containing material layer and generate a polymer layer on sidewalls of the patterned photoresist layer and the patterned Si-containing material layer; performing a second etching step by using the patterned photoresist layer, the patterned Si-containing material layer and the polymer layer as masks so as to at least remove an exposed portion of the etching resistive layer and form a patterned etching resistive layer; removing a portion of the target material layer by using the patterned etching resistive layer as an etching mask to form the first opening and the second opening in the target material layer; and obtaining a predetermined ADI-AEI CD difference ratio by adjusting etching parameters of the first etching step and/or those of the second etching step.