含碲化銻微粒之奈米複合薄膜應用於 非揮發性浮動閘極記憶體之研究

Abstract

本研究以貼靶濺鍍法在不同氮氣/氬氣流量比條件下沉積含有碲化銻（Sb2Te）相變化合金微粒之二氧化矽（SiO2）奈米複合薄膜，以此做為非揮發性浮動閘極記憶元件（Nonvolatile Floating Gate Memory，NFGM）之記憶層，並探討其電性質與微觀結構之關聯。電性量測結果顯示，含有在純氬氣環境下鍍成之奈米複合薄膜之NFGM元件經450□C、4分鐘之退火後，其耐電壓提升，正偏壓方向之漏電流則降低，經±7 V閘極電壓掃描測試之元件平帶電壓偏移量（Flatband Shift，□VFB Shift）為0.4 V，電荷密度為3.1×1011 cm□2。 在奈米複合薄膜之濺鍍製程中導入氮氣，當氮氣與氬氣流量比為0.1所製成之NFGM元件電性表現最佳，經±7 V閘極電壓掃描測試之最佳□VFB偏移值為4.41 V，電荷密度為4.21×1012 cm□2；經104秒、±5 V閘極電壓掃描之資料保存時間測試之元件的□VFB Shift值約1.8 V，電荷損失約為26.8%。此一優良元件電性與資料保存性質歸因於氮摻雜能抑制奈米複合薄膜中氧空缺與氧化銻相之形成，因而強化其電荷捕捉能力並降低漏電流特性，故Sb2Te-SiO2奈米複合薄膜具備應用於NFGM元件之潛力。

Nanocomposite thin films containing nano-scale Sb2Te chalcogenide particles embedded in SiO2 matrix were prepared by target-attachment sputtering method at various nitrogen/argon (N2/Ar) inlet gas flow ratios. Accordingly, the nanocomposite layers were implanted in the nonvolatile floating gate memory (NFGM) devices and the correlations of electrical properties to microstructures and chemical status of elements were investigated. As revealed by the C-V measurement, the N2-free NFGM samples subjected to a post-annealing at 450□C for 4 min exhibited a flatband voltage (ΔVFB) shift = 0.4 V at ±7 V gate voltage sweep and charge storage density = 3.1×1011 cm□2. As to the sample prepared at the condition of N2/Ar ratio = 0.1, it achieved a maximum ΔVFB shifts = 4.4 V and the charge density = 4.21×1012 cm□2 under ±7 V gate voltage sweep. The retention time analysis also observed a ΔVFB shift about 1.8 V and the charge loss about 26.8% under ±5 V voltage stress after 104 sec. The satisfied electrical and retention properties are ascribed to the suppression of oxygen vacancies and antimony oxides due to the N2 incorporation which leads to the enhancement of charge trapping capability on Sb2Te nanoparticles and low leakage current in the sample. Hence, the sole Sb2Te-SiO2 nanocomposite is a feasible programming layer for NFGM devices.