Three-Dimensional Dielectric Capacitors Based on Si Nanopillar Arrays with Polystyrene Spheres as Patterning Template

In this work, self-assembled monolayer polystyrene spheres with reduced diameters by reactive ion etching (RIE) processing are used to serve as patterning masks for the formation of a Au mesh. Then, the metal-assisted chemical etching (MAE) process with Au mesh as the catalyst on Si substrates is carried on to generate Si nanopillar arrays. Finally, the Al₂O₃ dielectric layer and Al-doped ZnO electrode are successively grown on the Si nanopillar arrays by the atomic layer deposition process, thus forming the three-dimensional (3D) high-density dielectric capacitors. The diameter of the Si nanopillars can be controlled by selecting polystyrene spheres with the desired reduced diameter through the RIE process. The results indicate that Si nanopillars with an aspect ratio of 14 will be formed by a 4 min MAE process, and the corresponding capacitance density of the dielectric capacitors can be increased by five times compared to the planar ones. However, there is also a remarkable increase in the leakage current density, most likely related to the large electrode area of 3D dielectric capacitors and the local electric field enhancement at the corners and tops of the Si nanopillars.