鈦奈米晶體應用於非揮發性記憶體

Abstract

摘要

非揮發性記憶體(NVM)目前在元件尺寸持續微縮下的需求為高密度記憶單元、低功率損耗、快速讀寫操作、以及良好的可靠度(Reliability)。傳統浮動閘極(floating gate)記憶體在操作過程中如果穿隧氧化層產生漏電路徑會造成所有儲存電荷流失回到矽基板，所以在資料保存時間(Retention)和耐操度(Endurance)的考量下，很難去微縮穿隧氧化層的厚度。非揮發性奈米點記憶體被提出希望可取代傳統浮動閘極記憶體，由於奈米點可視為電荷儲存層中彼此分離的儲存點，可以有效改善小尺寸記憶體元件多次操作下的資料儲存能力。近年來發展了許多方法來形成奈米點，一般而言，大多數的方法都需要長時間高溫的熱製程，這個步驟會影響現階段半導體製程中的熱預算和產能。 在本文中，一個簡單的製程方法用來形成鈦（Titanium）奈米點，並應用於非揮發性記憶體。室溫下，共濺鍍（co-sputter）靶材Ti和介電質(如:SiO2 、 Si、Ge)形成鈦系列相關奈米點的非揮發性記憶體結構，我們認為在退火過程中形成奈米點，可以簡單並均勻地形成高密度（∼1012）的奈米點。我們發現高密度的鈦矽氧奈米點與鍺奈米點交互作用有較佳的儲存能力。此外，這個應用在非揮發性記憶體的製程技術同時也是適用於現階段積體電路製程。

Abstract

Current requirements of nonvolatile memory (NVM) are the high density cells, low-power consumption, high-speed operation and good reliability for the scaling down devices. However, all of the charges stored in the floating gate will leak into the substrate if the tunnel oxide has a leakage path in the conventional NVM during endurance test. Therefore, the tunnel oxide thickness is difficult to scale down in terms of charge retention and endurance characteristics. The nonvolatile nanocrystal memories are one of promising candidates to substitute for conventional floating gate memory, because the discrete storage nodes as the charge storage media have been effectively improve data retention under endurance test for the scaling down device. Many methods have been developed recently for the formation of nanocrystal. Generally, most methods need thermal treatment with high temperature and long duration. This procedure will influence thermal budget and throughput in current manufacture technology of semiconductor industry. In this thesis, we provide a easy fabrication technique of titanium nanocrystals for nonvolatile memory. The nonvolatile memory structure of Titanium nanocrystals embedded in the SiO2 was fabricated by co-sputtering Titanium-Silicide and semiconductor material at room temperature. We consider that the nanocrystals formed in annealing process are simple and uniformly fabricated in our study. We found that TiSi2 add Ge to fabricate the nonvolatile memory can be obtained better storage effects. These fabrication techniques for the application of nanocrystal memory can be compatible with current manufacture process of the integrated circuit manufacture.