Deposition of Copper Particles and Films by the Displacement of Two Immiscible Supercritical Phases and Subsequent Reaction

Copper (Cu) particles and films were produced by forming Cu(II) compound (Cu(hfac) 2 ·H 2 O) films on substrates using a displacement from two immiscible supercritical phases (DISP) technique followed by reducing the copper(II) compound films in hydrogen at 200 °C. Various surfaces including native oxide of silicon (SiO x ), titanium nitride (TiN), tungsten (W), and low-k dielectric materials such as Coral, JSR5109, and Silox were used as substrates. The nucleation and growth behavior of the Cu DISP process was evaluated over a range of reduction times (from 5 to 60 min) and copper(II) compound concentrations (0.5-3 wt %). At short reduction periods (5-15 min) or low Cu(II) compound concentrations (∼ 0.5 wt %), Cu particles ranging from 60 to 95 nm in diameter were produced. In contrast, at long reduction periods (45-60 min) and high concentrations (∼3 wt %), continuous Cu films with 220-450 nm in thickness were deposited on the substrates. A morphology transition from particle to film was observed at medium reduction period (∼30 min) or medium concentration range (∼1 wt %). High affinity of TiN to Cu nucleation and film formation leads to more dense and smooth films than Cu films deposited under similar conditions on SiO x . However, nucleation of Cu DISP is not very sensitive to the surface conditions of the substrates compared with Cu CVD (chemical vapor deposition). Chemical composition analysis of the Cu film on TiN and SiO x by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) revealed that highly pure Cu films were obtained from Cu DISP.