Method of back end of line metal via process

A method of a back end of line metal via process, at least comprising:

• step 1:
• providing a first material layer, covering the first material layer with a second material layer, and etching the second material layer to form a via and a trench longitudinally communicating with the via;
• step 2:
• forming a TiN barrier layer on an inner surface of the trench and on an inner surface of the via;
• step 3:
• forming a Co seed layer on a surface of the TiN barrier layer;
• step 4:
• fully filling the via with Co by means of electrochemical deposition;
• step 5:
• forming a TiN hard mask layer over the Co on the bottom of the trench;
• step 6:
• removing the Co seed layer on sidewalls of the trench;
• step 7:
• removing the TiN hard mask layer on the bottom of the trench;
• step 8:
• covering the sidewalls and bottom of the trench with a TaN/Ta barrier layer;
• step 9:
• covering the TaN/Ta barrier layer with a liner layer;
• step 10:
• growing a Cu seed layer over the liner layer in the trench;
• and
• step 11:
• filling the trench with Cu by means of electrochemical deposition, and performing top planarization.