Cu Single Damascene Integration of an Organic Nonporous Ultralow- $k$ Fluorocarbon Dielectric Deposited by Microwave-Excited Plasma-Enhanced CVD

An integration of an organic nonporous ultralow-k dielectric fluorocarbon (k = 2.2) deposited by microwave-excited plasma-enhanced CVD into Cu single damascene interconnects is developed in this paper. The changing of the chemical structure of the fluorocarbon was found after dry etching, which resulted in the degradation of electrical properties during the postetching cleaning process. A nitrogen plasma treatment was applied as a postetching process to minimize damage introduction to the fluorocarbon in the following damascene fabrication processes, and a line-to-line leakage current was significantly improved without the variance of effective dielectric constant (k_eff = 2.5) in Cu lines. In a thermal stress test at 350^°C after Cu-interconnect fabrication, no degradation of the Cu line resistance and line-to-line capacitance was found, which indicated a sufficient thermal stability of the fluorocarbon film in Cu single damascene interconnects. Therefore, this robust organic nonporous fluorocarbon film is considered as one of the promising candidates of ultralow-k dielectrics for high-performance Cu interconnects in the future.