Reliability improvement of SiOC etch with trimethylsilane gas passivation in Cu damascene interconnects

摘要

A method of forming a SiCOH etch stop layer in a copper damascene process is described. A substrate with an exposed metal layer is treated with H₂ or NH₃ plasma to remove metal oxides. Trimethylsilane is flowed into a chamber with no RF power at about 350° C. to form at least a monolayer on the exposed metal layer. The SiCOH layer is formed by a PECVD process including trimethylsilane and CO₂ source gases. Optionally, a composite SiCOH layer comprised of a low compressive stress layer on a high compressive stress layer is formed on the substrate. A conventional damascene sequence is then used to form a second metal layer on the exposed metal layer. Via Rc stability is improved and a lower leakage current is achieved with the trimethylsilane passivation layer. A composite SiCOH etch stop layer provides improved stress migration resistance compared to a single low stress SiCOH layer.