2, University of Science and Technology (UST), Daejeon, , Korea (the Republic of)
The properties of lateral Ni film etching by TFB etchant at room temperature were examined by using samples with patterned lamellae layers consist of Ni, Al2O3, and SiO2 for potential application of fabricating hierarchical structures. Lateral etching length was increased with increasing etching time, despite of the difficult passage through nanoscale gap in lamellae layers. However, higher etching rate (2.1 nm/s) was observed in lower Ni film, which has contact with SiO2 and Al2O3 layers, compared to that (1.6 nm/s) of upper Ni film, which has contact with only Al2O3, due to stronger wetting property of SiO2, inducing easier penetration of etchant into nanoscale passage between surrounding layers. The influence of the type of the contact material on the lateral Ni film etching was confirmed by the insertion of ~20 nm Al2O3 at the interface between the bottom SiO2 and lower Ni film, resulting in a similar lateral etching rate of both the upper and lower Ni films. In addition, the effect of Ni film thickness on the lateral etching characteristics was examined. Despite different contact materials on the upper and lower Ni films, almost no difference in the lateral etching lengths was founded in the sample with 150-nm-thick Ni films, which implies that the interface region affected by the contact materials is negligible.