後處理對於無鉛鈮酸鈉鉀薄膜特性之影響應用於非揮發性鐵電記憶體之研究

Study of the Effects of Post-Treatment on the Characteristics of (Na0.5K0.5)NbO3 –Based Films for the Applications of Nonvolatile Ferroelectric Random Access Memory

蘇志文(Chih-Wen Su)

指導教授 ： 朱聖緣

國立成功大學/電機資訊學院/電機工程學系/碩士(2016年)

摘要

本論文利用溶膠凝膠法在鍍有Pt下電極之矽基板上成長無鉛非當量鈮酸鈉鉀薄膜(NKN-based)，透過不同RTA退火溫度及高溫爐溫度調控，搭配XRD、XRR、SEM、XPS、J-E、εr、tanδ、室溫P-E及變溫P-E等量測，試圖找出較有利於鐵電記憶體的製程溫度條件，並且利用額外摻雜適量Li元素進入NKN結構的方式，改善薄膜之微結構並提升其電特性，進一部探討對於鐵電記憶體之影響。
從本研究可知，隨著RTA退火溫度逐漸提高，特性有所提升，主要是因為薄膜結晶性變好、緻密性變高，而當RTA溫度達 750 oC並利用高溫爐燒結800 oC後，可以獲得最佳的電特性如下，漏電流:7.64 × 10-10 A/cm2 (0 kV/cm)、4.30 × 10-8 A/cm2 (100 kV/cm)，介電常數:776 (100 kHz)，介電損耗:0.04 (100 kHz)；室溫電滯曲線量測之殘餘極化量最高達8.2 μC/cm2 (±400 kV/cm)，memory window最大為372 kV/cm (亦為3.72 V)，此外經過約108次循環量測都沒有明顯的特性損耗；疲勞特性量測發現在實際工作環境下(<100 oC)，NKN材料穩定性良好，仍可達約106次循環。
另外，藉著添加少量的Li，填補鈉鉀高溫下揮發的空缺，提升薄膜電特性如下，漏電流降低至1.24 × 10-10 A/cm2 (0 kV/cm)、3.90 × 10-8 A/cm2 (100 kV/cm)，100 kHz下之介電常數及介電損耗分別提升至786、降低至0.02；室溫下量測之電滯曲線殘餘極化量提升至11.8 μC/cm2 (±400 kV/cm)，memory window提升至393 kV/cm (亦為3.93 V)，循環量測次數也提升至約3×108次；疲勞特性量測相較於NKN，在<100 oC下之穩定性有提升，可達約107次循環。

關鍵字

鐵電記憶體 ； 無鉛 ； 鈮酸鈉鉀 ； 溶膠凝膠法 ； 後處理

並列摘要

In this research, lead-free (Na, K)NbO3-based (NKN-based) thin films were fabricated on Pt/TiO2/SiO2/Si substrates via a sol-gel processing method, and through the control of various RTA annealing temperature and high-temperature furnace temperature in process. With the measurement of XRD, XRR, SEM, XPS, J-E, εr, tanδ, room temperature P-E curve and variable temperature P-E curve, we tried to find more favorable conditions of the processing temperature for the ferroelectric memory. Others, it was found that the thin film microstructure improved and the electrical properties enhanced after adding the additional right amount of lithium element into NKN structure. In the optimum post-treatment temperature control, RTA:750 oC and furnace:800 oC, the leakage current was reduced to 1.24 × 10-10 A/cm2 (0 kV/cm), 3.90 × 10-8 A/cm2 (100 kV/cm), and the dielectric constant raised up to 786 and the dielectric loss decreased to 0.02, respectively under 100 kHz. The electrical measurements at room temperature hysteresis curve of residual polarization increased to 11.8 μC/cm2 (±400 kV/cm), memory window up to 393 kV/cm (also 3.93 V), the switching cycles also increased to about 3 × 108 times. The fatigue characteristics at <100 oC, the stability raised up to about 107 cycles compared to NKN.

並列關鍵字

FeRAM ； Lead free ； (Na, K)NbO3 ； Sol-gel ； Post-treatment

參考文獻

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