A novel model of hydrogen plasma assisted chemical vapor deposition of copper

Abstract

A new distributed parameter model of a capacitively coupled rf hydrogen discharge including a copper precursor has been developed, from the first three moments of the Boltzmann equation. The model predicts the concentrations and fluxes of (1) the positive ions H +, H 2 + and H 3 + (2) the electrons and (3) atomic hydrogen, under the conditions that produce low resistivity copper films with the precursor Cu(II) hexafluoroacetylacetonate (Cu(HFA) 2). Since Cu(HFA) 2 is consumed predominantly at the wafer, an analytical model also has been derived to estimate the concentration distribution of Cu(HFA) 2 in the reactor, as a function of the operating conditions. Copper is formed on the wafer via a surface reaction between the adsorbed precursor and atomic hydrogen, that is produced in the plasma by the dissociation of molecular hydrogen. The hydrogen plasma model has been coupled with the precursor transport model using a rate expression that reflects the PACVD surface reaction mechanism, to explain the experimental observations and suggest process windows for high copper deposition rates and film purity. New data were taken and are reported here to test the model definitively.