Process for damascene structure with reduced low-k damage
Embodiments described herein generally provide methods for reducing undesired low-k damages during a damascene process using a sacrificial dielectric material and optionally a barrier/capping layer. In one embodiment, a damascene structure is formed through a sacrificial dielectric material deposited over a dielectric base layer. The damascene structure is filled with a suitable metal such as copper. The sacrificial dielectric material filled in trench areas between the copper damascene is then removed, followed by a barrier/cap layer which conformally or selectively covers exposed surfaces of the copper damascene structure. Ultra low-k dielectric materials may then fill the trench areas that were previously filled with sacrificial dielectric material. The invention prevents the ultra low-k material between the metal lines from exposing to various damaging processes during a damascene process such as etching, stripping, wet cleaning, pre-metal cleaning or CMP process.
1. A method for forming a semiconductor structure, comprising:
depositing a sacrificial dielectric material over a dielectric base layer;
forming a damascene feature definition into the sacrificial dielectric material and the dielectric base layer;
conformally forming a barrier layer on exposed side wall and bottom surfaces of the damascene feature definition, wherein the barrier layer is a tantalum/tantalum nitride (Ta/TaN) bilayer;
conformally forming a seed layer on the barrier layer, wherein the seed layer comprises a copper-manganese (CuMn) alloy;
subjecting the copper-manganese (CuMn) alloy with a thermal treatment process in an oxidizing atmosphere so that a portion or all of manganese within the CuMn alloy is oxidized to form a self-forming manganese oxide (MnO x ) layer;
filling the damascene feature definition with a conductive material, wherein the conductive material is formed on the seed layer;
removing the entire sacrificial dielectric material located in trench areas between the filled damascene feature definition;
selectively depositing a passivating layer on a top surface of the conductive material, wherein the passivating layer comprises cobalt or a cobalt alloy; and
filling the trench areas with an ultra low-k dielectric material having a dielectric constant less than about 3,
wherein the thermal treatment process is performed before the removing the entire sacrificial dielectric material.