The effect of reduction atmospheres on the sintering behaviors of inkjet-printed Cu interconnectors

In order to overcome the serious problems posed by Cu ink, which include the strong tendency to the oxidation of Cu nanopowders, various reduction atmospheres were investigated. As a result, a resistivity of ∼4 μΩ cm was achieved in the Cu interconnectors sintered at 200 °C with a gaseous mixture of formic acid (HCOOH) and alcohol. As regards this sample, micrographs show the facet boundaries and an average grain size of ∼300 nm. The use of formic acid was an effective way to decrease the sintering temperature to 150 °C, at which temperature the resistivity was ∼72 μΩ cm. This low temperature sintering and microstructural densification was due to the decomposition of capping molecules and the reduction in Cu oxide by formic acid.