Method of Double Patterning Lithography process Using Plurality of Mandrels for Integrated Circuit Applications

A method comprising:

• forming a mandrel layer over a target layer;
• patterning the mandrel layer to form a first opening in the mandrel layer, wherein the first opening has an I-shape and comprises:
• two parallel portions;
• and
• a connecting portion interconnecting the two parallel portions;
• forming spacers on sidewalls of the first opening, wherein the spacers fill an entirety of the connecting portion, and the two parallel portions are narrowed by the spacers;
• etching the mandrel layer to remove portions of the mandrel layer on opposite ends of the connecting portion to form a second opening and a third opening, wherein the second opening and the third opening are between the two parallel portions of the first opening;
• and
• extending the two parallel portions of the first opening, the second opening, and the third opening into the target layer.

A method comprising:

• forming a mandrel layer over a target layer;
• performing lithography-and-etching processes to pattern the mandrel layer, with remaining portions of the mandrel layer comprising a first mandrel, a second mandrel, and a third mandrel parallel to each other, with the second mandrel being between the first mandrel and the third mandrel;
• etching the second mandrel to cut the second mandrel into a fourth mandrel and a fifth mandrel, with an opening separating the fourth mandrel from the fifth mandrel;
• forming a blanket spacer layer over the first mandrel, the second mandrel, the fourth mandrel, and the fifth mandrel;
• and
• performing an anisotropic etching on the blanket spacer layer, wherein the opening is fully filled by a remaining portion of the blanket spacer layer.