Study on electron charging effect of quantum well of nano-particles for application of electrical device

Abstract

The nano-floating gate memory (NFGM) devices with In2O3, ZnO, SnO2, Au and SiC nano-particles on the p-type (100) silicon-on-insulator (SOI) wafers were fabricated and we analyzed the electrical characteristics such as subthreshold, threshold voltage shift and retention properties. The self-assembled metal-oxide nanoparticles such as In2O3, ZnO, and SnO2 were created by chemical reaction between the biphenyltertracarboxylic dianhydride-phenylene diamine (BPDA-PDA)-polyamic acid (PAA) layers and about 5-nm-thick In, Zn, and Sn films. Self-assembled In2O3 nanoparticles were formed inside the polyimide after curing at 400 oC for 1 hr. The average diameter and the particle density were 7 nm and 6x1011 cm− 2, respectively. The memory window of fabricated NFGM device due to the charging effect of In2O3 particles was larger than 4.4 V. The charge storage characteristics of NFGM devices with In2O3 nano-particles embedded in polyimide insulator were significantly improved by the post annealing in a 3% diluted hydrogen in N2 ambient. Also, NFGM devices with ZnO nano-particles embedded in polyimide insulators were fabricated. The size and the density of the ZnO nano-particles were about 10 nm and 2 x1011 cm-2, respectively. The threshold voltage shift (∆ VTH) of the NFGM with ZnO nano-particles was about 2.35 V at the initial stage of the program and the erase operations. The ∆ VTH decreased after 100 s from 2.35 V to 0.66 V at initial state of program and erase operations. The NFGM devices with SnO2 nano-particles on the p-type (100) SOI wafers were fabricated. After curing at 400 oC for 1 hr, the SnO2 nano-particles had spherical shape with an average diameter of 15 nm and the particle density was 2.4x 1011 cm-2. The electrons were charged into SnO2 nano-particles through 4.5-nm thick SiO2 tunnel layer from channel of NFGM by using Fowler-Nordheim tunneling method. The memory windows of the fabricated NFGM maintained at 0.5 V after 103 s. Additionally, a nano-floating gate capacitor and NFGM with double-layered Au nano-particles embedded in a SiO1.3N layer was fabricated and characterized to enhance the electrical performance of the NFGM based on metal nano-particles. The Au nano-particles were formed from Au thin film with a nominal thickness of 1 nm and their average size and density were about 4 nm and 2 x 1012cm-2, respectively. After the post-annealing process at 800 oC for 10 s, the at-band voltage shift of the nano-floating gate capacitor with double-layered Au nano-particles was about 9 V when the applied gate voltage was swept from -10 V to +10 V. Also, NFGM device with double-stacked Au nano-particles on p-type (100) SOI wafers were fabricated and the electrical characteristics, such as the subthreshold property, the threshold voltage shift and the retention property, were analyzed. The Au nano-particles, the SiO1.3N control and the tunnel oxides were deposited by reactive RF magnetron sputtering. The channel length and width of the NFGM, which contained the double-stacked Au nano-crystals, were 20 ?m. The memory window was about 1.23 V when the programming and erasing times of this memory device were approximately 500 ?s and 5 ms, respectively. However, the memory window increased up to about 6 V when initial programming/erasing conditions were 20 V for 200 ms and -20 V for 500 ms and it was maintained at 2.7 V after 103 s. A nonvolatile memory device with multilayered SiC nanocrystals for long-term data storage was fabricated, and its electrical properties were analyzed. The average size and density of the SiC nanocrystals, which were formed between the tunnel and control oxide layers, were approximately 5 nm and 2x1012 cm− 2, respectively. The memory window of nonvolatile memory with the multilayer of SiC nanocrystals was about 2.5 V after program and erase voltages of ?12 V were applied for 500 ms, and then it was maintained at about 1.1 V for 105 s at 75 ?C. The activation energy estimated from charge losses of 25% to 50% increased from 0.03 to 0.30 eV, respectively. The charge loss could be caused by a Pool?Frenkel current of holes and electrons between the SiC quantum dots and the carrier charge traps around the SiC nanocrystals embedded in SiO2 or the degradation effect of the tunnel oxide by stress induced leakage current.