Method For Creating A Fully Self-Aligned Via

A method of forming a self-aligned via, the method comprising:

• providing a substrate having a first insulating layer thereon, the first insulating layer having a top surface and a plurality of trenches formed along a first direction, the plurality of trenches having recessed first conductive lines extending along the first direction and having a first conductive surface below the top surface of the first insulating layer, the first insulating layer comprising ultra low-k and the recessed first conductive lines comprising copper or cobalt;
• forming a liner comprising tantalum on the recessed first conductive lines;
• forming a metal film comprising tungsten on the recessed first conductive lines and growing at least one pillar comprising tungsten oxide from the metal film on the recessed first conductive lines, the at least one pillar extending orthogonal to the top surface of the first insulating layer;
• depositing a second insulating layer on the first insulating layer, around the at least one pillar and on a top of the at least one pillar to form an overburden of the second insulating layer;
• planarizing the second insulating layer to remove the overburden of the second insulating layer and expose the top of the at least one pillar;
• selectively removing at least one of the pillars to form at least one opening in the second insulating layer, leaving at least one pillar on the recessed first conductive lines;
• removing the liner from the recessed first conductive lines using a base and hydrogen peroxide in a ratio of about 1:1 to about 5:1, wherein the base is selected from one or more of sodium hydroxide, potassium hydroxide, aluminum hydroxide, lithium hydroxide, rubidium hydroxide, cesium hydroxide, ammonium hydroxide, pyridine, trimethylamine (TMA), trimethylamine (TEA), or tetramethylammonium hydroxide (TMAH);
• depositing a third insulating layer through the at least one opening onto the recessed first conductive lines;
• etching the third insulating layer selectively relative to the second insulating layer to form at least one via opening to the recessed first conductive lines;
• and
• depositing a second conductive material in the at least one opening to form a via and second conductive lines, the first via connecting the recessed first conductive lines to the second conductive lines.