Thermodynamic and experimental study of Cu-LPCVD by reduction of copper chloride

Copper thin films have been deposited on (100) silicon substrates covered by a refractory metal film (W, Cr) via low pressure chemical vapor deposition (LPCVD) using Cu3Cl3 as a precursor. Synthesis of the halide occures via chlorination of copper by Cl2. According to thermodynamic calculations, the chlorination efficiency may be controlled by the temperature of the chlorination chamber (T1) and the chlorine flow rate. For T1 > 450°C copper chloride deposition rates in excess of 1 μm/min can be obtained. Deposition is performed “in situ” on individual 4 inch Si wafers heated by halogen lamps up to 500°C. The copper formation results from the reduction of Cu3Cl3 by hydrogen and starts at temperatures as low as 250°C. The morphology, composition and properties of the deposited layers are strongly dependent on the wafer temperature and reactor total pressure. In this paper, we present a thermodynamic analysis of copper chlorination and of the chemical reactions involved in the LPCVD of copper by reduction of copper chloride together with an overall description of the results obtained so far with this new process.