鎳鍺矽金屬奈米點在非揮發性記憶體元件製作及研究

Abstract

傳統的非揮發性記憶體是利用複晶矽浮停閘(floating gate)作為載子儲存的單元，而在元件尺寸持續微縮下，此結構將面臨一些瓶頸。為了克服尺寸極限，近年來衍生出之奈米晶體非揮發性記憶體，即利用半導體或金屬奈米點作為電荷儲存的單元，可以減少穿隧氧化層的厚度，而不損失可靠性，進而降低操作電壓及操作速度增快。 在文獻中我們可知道目前已經有許多的材料已經成功的形成了奈米點，例如：Si、Ge、Ｃo and Ni. 找到合適的材料來形成奈米點來符合現今的非揮發性記憶體是相當重要的。 在不同的材料形成的奈米點時，各有明顯不同的優點，比如說半導體的奈米點，它的優點是在半導體工業中，是我們運用相當廣泛的，金屬奈米點的話，它有一個 相當高的功函數，而且在費米能階附近它有高能階密度，金屬有有著一個相當可靠的熱穩定性。 許多的文獻指出Ni-Si-Ge合金適合運用在SiGe元件連接上，根據這個文獻上所研究可知，NiSiGe合金有一個低的電阻性，它也有好的熱穩定性，在本篇論文中我們沉積了一層NiSiGe的薄膜利用熱聚積形成奈米點結構，使各自成為獨立的儲存單元。此外在NiSiGe快速升溫退火的過程中，我們通入氣體O2/N2來研究退火環境，還有溫度與是否先預蓋SiO2的影響。最後我們在與單純只有NiSi的奈米點做一個比較□入Ge的影響。

In a conventional nonvolatile memory (NVM), charge is stored in a ploy-silicon floating gate (FG) surrounded by dielectrics. But, it will suffer some limitations for continued scaling of the device structure. Therefore, the nanocrystal nonvolatile memory devices have been investigated to overcome the limit of the conventional floating gate NVM in recently years. Nanocrystal charge storage offers several advantages, the main one being the potential to use thinner tunnel oxide without sacrificing nonvolatility. This is a quite attractive proposition since reducing the tunnel oxide thickness is a key to lowering operating voltage and/or increasing operating speeds. Among the reported research, several kinds of nanodots have been studied such as Si, Ge, Co and Ni. Finding an adaptable material to satisfy the requirement is a major subject for current nonvolatile memory industry. Semiconductor nanodots are compatible material for the current semiconductor industry. However, metal nanodots are beneficial in variable work function, higher density of states around the Fermi level. Also, the metallic nanodots are considered as promising material due to the better thermal stability and the advantage of metal nanodots. Several reported researches indicate that nickel silicon germanium (Ni-Si-Ge) alloy has potential for the contact material of SiGe based devices. According the study, Ni-Si-Ge alloy can be formed steadily for the characteristics of low resistivity and well thermal stability. In this letter, using Ni-Si-Ge nanodots as distributed charge storage elements was investigated. Also, the carrier gas, such as O2 and N2, were also added as the Nickel Germanium silicide in RTA. The memory effect and the electrical reliability for NiSiGe nanocrystals surrounded in different dielectric were also investigated in this study. Temperature & pre-capped oxide are very important issue to accumulate our nanodots.