ATOMIC LAYER EPITAXY OF COPPER ON TANTALUM

The decreasing size and increasing complexity of the components in fut ure microelectronics devices present a great challenge in the developm ent of new deposition techniques. One method for the deposition of sem iconductor materials which has gen erated considerable interest is ato mic layer epitaxy (ALE). This method has been shown to yield films wit h excellent step coverage and high conformity, even on very complex sh aped substrates. In this paper we report, for the first time, the depo sition of copper using the ALE technique. The films were deposited on tantalum substrates using copper(I) chloride as the precursor and hydr ogen as the reducing agent. The films were found to be polycrystalline and practically free from texture. They were also very low in chlorin e contamination and possessed a rather rough surface morphology. An in itial fast substrate reduction, yielding a film thickness of approxima tely 300 Angstrom, was observed, the rate determining step being the r eaction of hydrogen with the adsorbed copper chloride. The activation energy for this step was estimated to be 80 kJ mol(-1).