In Situ Synthesis of High Density sub-50 nm ZnO Nanopatterned Arrays Using Diblock Copolymer Templates

Abstract

Fabrication of high density (~155 Gbit in(-2)) ZnO nanopatterns through in situ decomposition of Zn precursors inside diblock copolymer templates and their application as charge storage centers in nonvolatile memory devices is described. The fabrication is performed in a highly controlled fashion with the resulting ZnO nanopatterned arrays exhibiting diameters of 38 nm and heights of 14 nm offering sub-50 nm feature resolutions. The ZnO nanopatterns are naturally n-type due to the presence of zinc interstitials and oxygen vacancies that act as defect levels in trapping charge carriers. Test capacitors (metal-oxide-semiconductor, MOS) constructed using nanopatterns formed on p-Si exhibited a large flatband voltage shift of about ~2.2 V for a low operating voltage of 10 V. A high charge trap density of 3.47 × 10(18) cm(-3) combined with a good retention capacity is observed with low tunneling oxide (thermally grown) thickness of 3 nm. This demonstrates the significant promise of the ZnO nanopatterned arrays to act as charge storage centers for potential application in nonvolatile flash memory devices. The charge trapping characteristics, the capacitance-voltage measurements, and the potential of ZnO nanopatterns as charge storage centers in fabricating nonvolatile memory devices are discussed.