Chemical interaction between atomic-layer-deposited HfO2 thin films and the Si substrate

HfO2 thin films were deposited on Si wafers using an atomic layer deposition technique at temperatures ranging from 200 to 400 degreesC with HfCl4 as the precursor and H2O as the oxidant. The time-dependent interfacial-layer growth behavior was dependent on the deposition temperature. The interfacial layer grew with increasing deposition time at 200 degreesC. However, the film thicknesses decreased with increasing deposition time after reaching a certain maximum value at 300 and 400 degreesC due to the enhanced dissolution of SiOx into the growing films at these temperatures. Post-annealing at 800 degreesC under a N-2 atmosphere resulted in the precipitation of a Si-rich interfacial layer even for the initially interfacial layer free films. This had the effect of reducing the capacitance density of the films. (C) 2002 American Institute of Physics.