Device-quality copper using chemical vapor deposition of β-diketonate source precursors in liquid solution

Device-quality copper films were produced by chemical vapor deposition from copper(II) β-diketonate precursors using a liquid delivery approach. This liquid delivery method exploits the high solubility of copper(II) β-diketonate precursors in selected solvents, such as isopropanol and ethanol, to provide highly accurate, reproducible, and controllable flow rates of precursor and solvent mixtures to the reaction zone. The approach was successfully employed to produce high-quality copper files from predetermined mixtures of bis(hexafluoroacetylacetonato) copper(II) and ethanol or isopropanol. Plasma-assisted chemical vapor deposition (PA-CVD) was used with substrate temperatures of 160-170°C, reactor working pressures of 1.0-1.7 Torr, hydrogen flow rates between 500 and 1200 cc/min, and hydrogen plasma power density ranging from 0.13 to 0.25 W/cm². The films were subsequently characterized by Rutherford backscattering spectroscopy, cross-section SEM (scanning electron microscopy), and a four-point resistivity probe. These studies indicated that the films thus grown were pure, dense, highly uniform, and displayed resistivities of 1.7-1.9 μΩ cm. Films produced on patterned test structures exhibited conformal step coverage and complete hole and via fill. Growth rates over large-area substrates were around 250 Å/min for via filling.