Method for manufacturing dual damascene structure with a trench formed first

A method for manufacturing dual damascene structure with a trench formed first, comprising the steps of:

• providing a substrate having a plurality of semiconductor devices;
• forming a first metal layer on the substrate;
• forming a first etching stop layer on the first metal layer;
• forming a dielectric layer on the first etching stop layer;
• forming a second etching stop layer on the dielectric layer;
• forming a first patterned photoresist layer on the second etching stop layer;
• forming a trench by etching though the second etching stop layer and stopping in the dielectric layer at a predetermined depth;
• filling with a sacrificial layer into the trench;
• planarizing the sacrificial layer;
• forming a second patterned photoresist layer on the sacrificial layer;
• forming a via by etching the sacrificial layer and the dielectric layer;
• removing the sacrificial layer and the second patterned photoresist layer;
• etching the first etching stop layer to expose the first metal layer;
• filling with a second metal layer;
• and
• planarizing the second metal layer.