Surface characterization of copper electroless deposition on atomic layer deposited palladium on iridium and tungsten

Iridium and tungsten refractory metals possess high melting points, hardness, and good electrical resistivity. Palladium has been recently deposited on W and Ir via atomic layer deposition and it is also an appropriate catalyst for the electroless deposition of copper. Palladium was deposited at 80 ± 5 °C with a PdII(hfac)2 sublimation temperature of 46.0 ± 0.5 °C using 13 sccm Ar as a carrier gas, and 105 sccm H2 as a reducing gas on Ir and W substrates for 150 cycles. The thickness of Pd was 20 and 30 Å on Ir and W substrates, respectively, with a low surface roughness. For the Cu electroless process, ethylenediamine-tetraacetic acid (EDTA) was used as a chelating agent, glyoxylic acid as a reducing agent, and additional chemicals such as polyethylene glycol and 2,2′dipyridine as surfactant and stabilizer respectively. Electroless Cu was undertaken at 60 °C with good adhesion to iridium and tungsten with Pd as a catalytic layer.