[13p-B13-1~12] 13.5 Semiconductor devices and related technologies

▲ [13p-B13-12] Passivation effects of 3D Array of Si-nanodisks Fabricated with Bio-template and Neutral Beam Etching Process for Photovoltaic Application

〇(P)MdZaman Molla¹, Shuichi Noda¹, Seiji Samukawa¹ (1.Tohoku University)

Keywords:Quantum dot superlattice, Bio-template, Neutral beam etching

We proposed and have been researching the formation of quantum nanodots of less than 10 nm in size by means of a top-down process using a low-energy neutral beam capable of defect-free processing. An advantage of the top-down process is that it can form nanostructures with an arrangement that can be uniformly controlled no matter what combination of materials is used. Instead of photolithography, we used a bio-template as an etching mask with dots of a few nm in size. The biological super-molecule (protein), ferritin has a diameter of 12 nm, and 7 nm iron core internal cavity. Ferritin molecules containing these iron cores are selectively placed in a two-dimensional arrangement on a silicon oxide film, and the protein is then removed by UV/ozone or heat processing, leaving behind the 7 nm iron cores on the substrate for use as an etching mask. Finally, Cl₂ based neutral beam that can anisotropically etch any kind of surface materials using the etching mask of 7 nm iron cores was used to etch the poly-Si followed by isotropic etching of surface SiO₂ by NF₃/hydrogen radical treatment. We are using this process to develop quantum-effect devices with a quantum nanodisc structure. A nanodisc is a nano-scale cylindrical structure whose height (thickness) is smaller than its diameter. The sub-10-nm quantum nanodiscs are formed in an array configuration with uniform spacing. Recently, the 3D array of Si-NDs consisting of 4 stack layers of 2~6 nm thick Si-ND layer and 2 nm SiC interlayer being deposited alternately onto P-type Si-substrate with the density of ~7×10¹¹ cm^-2. In this study, we passivated the side walls of the nano pillars by a thin layer (~2nm) of atomic layer deposited aluminum oxide (ALD-Al₂O₃) to eliminate the interface defects in between SiC interlayer and QD to minimize the carrier recombination that hampers the photovoltaic performance. Conductive atomic force microscopy (C-AFM) measurement was carried out to investigate the current leakage between QDSL and its substrate. From the current voltage relationship, it was clearly observed that the current leakage was drastically minimized to zero when the QDSL was passivated with ALD-ALD-Al₂O₃. Based on these results, size effects of 3D Si-NDs (2~6 nm) with SiC (2 nm) interlayer in QDSL structure will be discussed.