Deep trench etch and clean process technology for CU/SiOC passive device

A critical process issue was revealed in the process to integrate passive device with Cu/Low- k backend of line technology. To improve on chip inductor performance in the region of radio frequency, thick inductor Cu spiral line (>2 μm) was used to reduce inductor series resistor. In Cu single Damascene process technology, deep trench etch is one of the essential process steps. It was found that dry etching of 2-μm-deep inductor trench in SiOC low- k dielectric film in C 4F 8/N 2/Ar chemistry introduced a large amount of polymer along sidewalls. Commonly used amine-based semi-aqueous chemical wet cleaning after photoresist strip is incapable of removing them. Rather, this chemical treatment alone caused swelling and partial peeling of polymers from the dielectric sidewalls. The polymer residues can have adverse effects on Cu filling process and electrical performance of Cu conductors and inductors. Moreover, they impose risks to the device reliability. In this paper, we discuss the development of a new cleaning process that can effectively remove the stubborn polymers.