Method of forming double pattern in a structure

A semiconductor structure, comprising:

• a substrate;
• and
• a double patterned positive photoresist layer disposed over the substrate, wherein the double patterned positive photoresist layer is formed by:
• forming a positive photoresist layer over the substrate;
• forming a negative photoresist layer on the positive photoresist layer;
• performing an exposure process to form a first exposure region in the positive photoresist layer and a second exposure region in the negative photoresist layer, wherein the second exposure region having a second width is located on the first exposure region having a first width, and the first exposure region and the second exposure region have a same central axis according to the exposure process, and wherein the first width is less than the second width;
• performing a negative-tone development process to remove portions of the negative photoresist layer outside of the second exposure region to form one or more first openings to expose the positive photoresist layer;
• etching the positive photoresist layer along the one or more first openings to form one or more second openings through both the negative photoresist layer and the positive photoresist layer;
• removing the second exposure region of the negative photoresist layer;
• and
• performing a positive-tone development process to remove portions of the positive photoresist layer in the first exposure region to form the double patterned positive photoresist layer.