Characteristics of Nonvolatile Memory Effect with Ir Nanocrystals in Asymmetric Tunnel Barriers

• Main Authors: Chen, Chao-Jui, 陳昭睿
• Other Authors: Sheu, Jeng-Tzong
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/65419018067446582770

碩士 === 國立交通大學 === 奈米科技研究所 === 97 === Recently, nonvolatile memory with nanocrystals (NCs) has been widely studied to overcome limitations of conventional floating gate memory. The use of NCs as distributed floating gates minimized the problems of charge loss encountered in conventional floating-gate devices, allowing thinner tunnel oxide and, thereby, a lower operating voltage, better endurance and retention, and faster program/erase (P/E) speed. Compared to the semiconductor NCs, metallic NCs as floating gates possesses several advantages, such as larger change of electric capacity, stronger coupling with the conduction channel, a wide range of available work functions, higher density of states around the Fermi level, and a smaller energy perturbation due to carrier confinement. In this thesis, it used the difference between asymmetric tunnel barrier (ATB) and a single layer structure. Both compared operating voltage and endurance. It can take the better tradeoff between the programming/erasing and retention characteristic by ATB structure. And Iridium has high work function and good thermal stability, we can demonstrate Iridium nanocrystals embedded in different tunneling oxide layer for capacitor characteristic and find different nanocrystals’ diameter and density. At the same operating voltage(+/-5 V), ATB(SiO2/Si3N4) structure ΔVFB ≒4.2 V and single layer(SiO2) structure ΔVFB ≒1.5 V. Each Ir-NCs stored 4 electrons or holes in ATB structure decive and 2 electrons or holes in single-layer structure device. The charge remaining of ATB memory device was 50% at 104 s, and 55% for single-layer memory device. Although, there is no improvement in data retention ATB device do lower the operating voltage and increase higher P/E speed.